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26 minutes ago, nicknorman said:

This is one reason why I’d never want to live on a boat full time - not enough room for all my toys!

 

Ed is a top bloke, if anyone can sort out your electrics he can. Let us know what he says/does.

 

I'll definitely let you know what transpires. 

I also installed another 750 watts of solar over the last couple of days (I hijacked a friends visit to get my new panels brought unto me), and I have to say I only  did it because of information and advice gleaned from yourself and Peter, and a host of youtube videos. 

I only finished at 8pm, and I was too scared to connect the final bits just in case I'd overlooked something,  and the whole lot blew up.

Nobody needs an electrical disaster at 8pm on a bank holiday monday. 

No expense was spared. I even got a Victron mppt, instead of a cheapie as I usually do.

Its so grand that I would almost feel justified in organising an official switch-on ceremony for the new solar, in the manner of Blackpool illuminations, but my rather sparse crowd here at Whixall (mainly bird watchers and joggers) clearly do not share my enthusiasm, and they do not regard my installation with the same awe as I do myself. 

That will bring me up to 1.4kw, which means for about 8 months of the year I wont need any engine charging, provided I dont park in a tunnel.

Plans are in place to install a 3D printing factory to exploit all of the new electricity, using a dozen slave labourers press ganged from the HGV driver community. 

Great things lie ahead I feel.

 

 

Edited by Tony1
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On 30/08/2021 at 21:51, nicknorman said:

This is one reason why I’d never want to live on a boat full time - not enough room for all my toys!

 

Ed is a top bloke, if anyone can sort out your electrics he can. Let us know what he says/does.

 

Well, I had a very interesting day with Ed yesterday, and we now have a planned solution to deliver about 100-110 amps of charge, but are only halfway to completion at the moment. I'll try to describe his reasoning but much of it was expressed in 'electrical speak', and I only had the faintest grasp of its meaning or significance, so my sincere apologies to Ed if I misrepresent his words or actions: 

 

The first thing he did was to try Charles Sterling's suggestion of wiring both alternators to the starter battery, and he immediately saw that although the cable connections were still using some terminals on the A2B charger, the charger itself was not in action, and was purely decorative. 

 

He did carry out the second bit of the idea, which was to take the 'source' lead acid (knackered) out of the system, and wire the alternators directly to the starter battery, and then he physically removed the A2B charger unit which freed up some space, and simplified the wiring a lot. 

 

So despite being wired directly, the upper alternator wasn't delivering any useful charge. He did some quick tests and noticed that the voltage on the lower (100 amp) alternator was at least 14.8v most of the time, and on the smaller alternator it was I think 14.4. 

His deduction was that this voltage difference was the factor that was inhibiting the smaller alternator from doing its charging.  

 

He said normally you could change the regulator(s) in the alternator(s) so that the voltages were very close to each other, and this would probably result in both operating instead of one, but in the case of the canaline 38 he didn't know if the parts were available in the short term, or how easy they were to obtain, so that was put on the back burner as an idea. 

He used a long length of 16mm cable to reduce the voltage from the 100 amp alternator, and sure enough the smaller alternator did start to deliver some current, so at least we knew it would work if controlled correctly, and that one potential solution lay in this direction- better voltage control of the alternators. 

 

He had also spotted that the smaller alternator was only rated at 50 amps (according to a sticker on the unit), not the 70 amps advertised by the suppliers literature/websites etc, so a question arose as to whether it was worth even using it, as we could assume it was only capable of a continuous current of about 50% of its official rating, i.e. 25 amps. 

 

He then suggested that rather than consider an replacement for the 100 amp alternator (which had been our previous idea), that he instead replace the smaller alternator with a superior 90 amp unit he had the foresight to bring in his car, just in case. 

 

The problem I think is the crank is not really big enough to run say a 170 amp alternator properly- those generally require bigger cranks, poly V belt, and pulleys etc- so an alternator upgrade could also require spending on a poly V setup. crank etc- and that would get pretty expensive.

 

So he rapidly installed a brand new 90 amp alternator, thus bringing the total (safe) charging power of the two alternators up to 110-120 amps or so (which for me is enough), and at a much lower price than a single 150-170 amp alternator. 

Since I already had one B2B in place, he agreed that the most cost-effective solution would be to get another one, and use that to draw the additional charge that was now potentially available. 

 

So although we now had a decent level of charge potentially available, we still had the issue of controlling the voltages more closely so that both alternators worked, because the new unit was regulated./running at 14.4v, and so it had the same issue as its predecessor.

 

There is also an inherent risk in this setup that we were envisaging, which is that either alternator could potentially stop charging (due to voltage changes etc), and at that point you would have two B2Bs each drawing 50-55 amps, which was too much for one alternator alone to handle, as it would rapidly overheat and might well be badly damaged.

This risk was a concern for Ed, and as a solution he suggested that we set up two separate systems, such that each alternator would feed its own source battery, and that battery would feed its own B2B. This would mean the alternators would never be overstressed in the case of one stopping or failing in some way (as he has observed them doing several times in the past). 

 

So thats where we are now. I'm hoping Ed will return in 3 weeks, by which time I'll have a second B2B installed and with the red/black connections put in for the batteries/bus bars, and Ed will bring a source battery along, and he can then wire one alternator to that, feed the extra live cable into the cabin, and with an hour we should have the second B2B running, and he can look at some other issues I'm interested in resolving, e.g. fitting an immersion heater and switch so that in summer, I can use surplus solar to heat water.

 

But the folks who have been singing his praises are absolutely right- not only is he very easy to talk to and not at all arrogant, he will listen carefully to what you say you want, and then try to design a cost effective solution that fits your stated objectives- and he will tell you if thinks those objectives are a bit skewed or problematic. 

 

Not only that, but he's very ethical and fair.  

Because he had to drive off into Whitchurch to get a suitable belt, and because he personally felt he hadn't made as much progress as he wanted (although tbh I thought he'd done really well), he actually gave me a significant reduction on his hourly rate, so I think I only ended up paying about 60% of the labour costs that should have been due. 

 

Exactly as you said Nick, a top bloke, and a top professional too. 

 

Edited by Tony1
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2 hours ago, Tony1 said:

 

Well, I had a very interesting day with Ed yesterday, and we now have a planned solution to deliver about 100-110 amps of charge, but are only halfway to completion at the moment. I'll try to describe his reasoning but much of it was expressed in 'electrical speak', and I only had the faintest grasp of its meaning or significance, so my sincere apologies to Ed if I misrepresent his words or actions: 

 

The first thing he did was to try Charles Sterling's suggestion of wiring both alternators to the starter battery, and he immediately saw that although the cable connections were still using some terminals on the A2B charger, the charger itself was not in action, and was purely decorative. 

 

He did carry out the second bit of the idea, which was to take the 'source' lead acid (knackered) out of the system, and wire the alternators directly to the starter battery, and then he physically removed the A2B charger unit which freed up some space, and simplified the wiring a lot. 

 

So despite being wired directly, the upper alternator wasn't delivering any useful charge. He did some quick tests and noticed that the voltage on the lower (100 amp) alternator was at least 14.8v most of the time, and on the smaller alternator it was I think 14.4. 

His deduction was that this voltage difference was the factor that was inhibiting the smaller alternator from doing its charging.  

 

He said normally you could change the regulator(s) in the alternator(s) so that the voltages were very close to each other, and this would probably result in both operating instead of one, but in the case of the canaline 38 he didn't know if the parts were available in the short term, or how easy they were to obtain, so that was put on the back burner as an idea. 

He used a long length of 16mm cable to reduce the voltage from the 100 amp alternator, and sure enough the smaller alternator did start to deliver some current, so at least we knew it would work if controlled correctly, and that one potential solution lay in this direction- better voltage control of the alternators. 

 

He had also spotted that the smaller alternator was only rated at 50 amps (according to a sticker on the unit), not the 70 amps advertised by the suppliers literature/websites etc, so a question arose as to whether it was worth even using it, as we could assume it was only capable of a continuous current of about 50% of its official rating, i.e. 25 amps. 

 

He then suggested that rather than consider an replacement for the 100 amp alternator (which had been our previous idea), that he instead replace the smaller alternator with a superior 90 amp unit he had the foresight to bring in his car, just in case. 

 

The problem I think is the crank is not really big enough to run say a 170 amp alternator properly- those generally require bigger cranks, poly V belt, and pulleys etc- so an alternator upgrade could also require spending on a poly V setup. crank etc- and that would get pretty expensive.

 

So he rapidly installed a brand new 90 amp alternator, thus bringing the total (safe) charging power of the two alternators up to 110-120 amps or so (which for me is enough), and at a much lower price than a single 150-170 amp alternator. 

Since I already had one B2B in place, he agreed that the most cost-effective solution would be to get another one, and use that to draw the additional charge that was now potentially available. 

 

So although we now had a decent level of charge potentially available, we still had the issue of controlling the voltages more closely so that both alternators worked, because the new unit was regulated./running at 14.4v, and so it had the same issue as its predecessor.

 

There is also an inherent risk in this setup that we were envisaging, which is that either alternator could potentially stop charging (due to voltage changes etc), and at that point you would have two B2Bs each drawing 50-55 amps, which was too much for one alternator alone to handle, as it would rapidly overheat and might well be badly damaged.

This risk was a concern for Ed, and as a solution he suggested that we set up two separate systems, such that each alternator would feed its own source battery, and that battery would feed its own B2B. This would mean the alternators would never be overstressed in the case of one stopping or failing in some way (as he has observed them doing several times in the past). 

 

So thats where we are now. I'm hoping Ed will return in 3 weeks, by which time I'll have a second B2B installed and with the red/black connections put in for the batteries/bus bars, and Ed will bring a source battery along, and he can then wire one alternator to that, feed the extra live cable into the cabin, and with an hour we should have the second B2B running, and he can look at some other issues I'm interested in resolving, e.g. fitting an immersion heater and switch so that in summer, I can use surplus solar to heat water.

 

But the folks who have been singing his praises are absolutely right- not only is he very easy to talk to and not at all arrogant, he will listen carefully to what you say you want, and then try to design a cost effective solution that fits your stated objectives- and he will tell you if thinks those objectives are a bit skewed or problematic. 

 

Not only that, but he's very ethical and fair.  

Because he had to drive off into Whitchurch to get a suitable belt, and because he personally felt he hadn't made as much progress as he wanted (although tbh I thought he'd done really well), he actually gave me a significant reduction on his hourly rate, so I think I only ended up paying about 60% of the labour costs that should have been due. 

 

Exactly as you said Nick, a top bloke, and a top professional too. 

 

Well there you go, he is the yardstick by which to judge the other numpties you foolishly allowed onto your boat😱!

 

Anyway for what it’s worth I fully agree with his thoughts, the best solution under the circumstances is 2 alternators, 2 separate batteries and 2 B2B2s, which will get around the problem of the different regulated voltages and be fault tolerant. I’d also suggest using the ignition input to the B2Bs which will allow you to manually switch them off to avoid too high a SoC when you need to cruise for a long day despite solar having well-charged the batteries already.

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6 minutes ago, nicknorman said:

Well there you go, he is the yardstick by which to judge the other numpties you foolishly allowed onto your boat😱!

 

Anyway for what it’s worth I fully agree with his thoughts, the best solution under the circumstances is 2 alternators, 2 separate batteries and 2 B2B2s, which will get around the problem of the different regulated voltages and be fault tolerant. I’d also suggest using the ignition input to the B2Bs which will allow you to manually switch them off to avoid too high a SoC when you need to cruise for a long day despite solar having well-charged the batteries already.

 

Thanks Nick, and one of the other things I didnt have time to mention was he expressed concern about the way the B2B would burst into life shortly after the engine started, but if it sensed a lower voltage at any time in the source battery, it would instantly switch itself off.

These cut-off voltages are configurable, but he said this abrupt disconnection of the B2B (which happens two or three times in the first few minutes of running, and again occasionally later) might be a bit stressful and risky for the alternator (which is something I think I've seen you mention before as well).

So the idea of using the engine ignition connection to start and stop the B2B came up, and he'll do that on his next visit too. 

 

The B2B charger can also be switched off/on manually via a rather clumsy process of holding down both major buttons for between 5-9 seconds- not ideal, but it can be done at least, if the SoC gets too high for too long. 

 

So the charging control is all very manual at the moment, with manual disconnects for each set of solar panels, and a fiddly disconnect for the B2Bs, but it is a workable solution for the time being. 

 

My long term ideal would be a control mechanism to automatically disconnect all the charging if the SoC reaches say 90%, but I'll need another BMV 712, plus a relay or another BEP, so thats a task to think about once I've got the second B2B installed. 

If I start researching it too early, I'll forget the detail be the time I come to try it.

 

 

 

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On 02/09/2021 at 11:16, nicknorman said:

Well there you go, he is the yardstick by which to judge the other numpties you foolishly allowed onto your boat😱!

 

Anyway for what it’s worth I fully agree with his thoughts, the best solution under the circumstances is 2 alternators, 2 separate batteries and 2 B2B2s, which will get around the problem of the different regulated voltages and be fault tolerant. I’d also suggest using the ignition input to the B2Bs which will allow you to manually switch them off to avoid too high a SoC when you need to cruise for a long day despite solar having well-charged the batteries already.

 

Hi Nick, I know you take an interest in these sorts of control systems, so I thought i would run my thoughts past you, and hopefully get your comments on it all, if/when you have time. 

 

 When I mentioned the idea of a high SoC disconnect between the B2Bs and the batteries, by means of a BMV712 plus BEP switch, Ed pointed out that the B2Bs have sockets labelled BMS1 and BMS2, that act to stop the charging. In the manual it says this about them: 

 

"Use BMS 1 - if your BMS trips and provides a 0V (ground signal), then use BMS 1. This shall result in the BBC turning off. Once the BMS removes this trip status, i.e. the 0V signal goes back to a +ve signal, the BBC shall start charging again.

 

Use BMS 2 - if your BMS trips to a +ve voltage (2V-17V), then use BMS 2. This shall result in the BBC turning off when this voltage is received. Once the BMS removes this trip status, i.e. the +ve signal goes back to 0V signal, the BBC shall start charging again"

 

As usual I have only the vaguest idea what that really means, but it does at least suggest that it might be possible to use either the BMS1 or BMS2 socket to switch off the B2Bs, using a signal from the BMV712. 

Can I ask- if this is the case, would I use BMS1 or BMS2 to work with a BMV712?

 

 

But now the plot thickens. 

Ed also pointed out that my victron MPPT can be remotely switched by the BMV712 using this cable: 

 

https://www.victronenergy.com/accessories/ve-direct-non-inverting-remote-on-off-cable

 

What all of this seems to mean is that I can automatically disconnect all four of the charging systems (the two B2Bs plus the two MPPTs), all via the BMV712.

I guess this assumes that you can split the BMV 'trigger' signal into four, so that it goes to the four different charging units - do you know if that's feasible?

 

If it is, my new plan is to use my existing BMV712 as low voltage and low SoC disconnect, and install a second BMV712 to handle the high voltage and high SoC disconnect.  

The reason I'm thinking this way is because the current BMV and BEP setup completely isolates the batteries- from both charge and load. 

 

So am I right in thinking that I need to rewire things such that the load cables will bypass the high-voltage disconnect in some way, and the charging cables need to bypass the low voltage/SoC disconnect part of the system? 

I.e. a high voltage event does not disconnect the loads from the batteries, as I think it does now, and a low voltage event does not disconnect the charging unit (as I think it does now). 

 

I don't really know how that would all be done in practice and where all the cables would go, but before I think about that detail, do you think it is in principle the correct approach? Is it even feasible? 

 

 

Edited by Tony1
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52 minutes ago, Tony1 said:

"Use BMS 1 - if your BMS trips and provides a 0V (ground signal), then use BMS 1. This shall result in the BBC turning off. Once the BMS removes this trip status, i.e. the 0V signal goes back to a +ve signal, the BBC shall start charging again.

 

I am no longer au fait with the fast changing lithium technology and acronyms. What does BBC stand for in this context, please?

 

 

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27 minutes ago, MtB said:

 

I am no longer au fait with the fast changing lithium technology and acronyms. What does BBC stand for in this context, please?

 

 

 

That Sir, is a very good question- and one to which I have no certain answer, which is why I rely so often on the help and advice of Mr Norman and others. 

My sincere hope is that BBC actually means B2B, although the model is referred to as BB1260 by Sterling themselves. 

 

I am encouraged in this theory by the fact that the first two letters of BBC are the same as BB1260, and that perhaps the C stands for 'charger'. 

But in truth I am as ignorant as a early mediaeval peasant contemplating the workings of a jet aircraft. I'm still not entirely convinced that my inverter isn't powered by lots of tiny electrical pixies. 

 

How else can I explain the sparks earlier when I replaced the red inverter cable?

Clearly the pixies were angry at being temporarily disconnected from their beloved 240v system. 

 

Edited by Tony1
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The electrical pixies all went off to the aerospace world.  Some became lift pixies and others metamorphosed into drag daemons.  There is a NASA paper on this.  Author was Mary Schafer.

 

BBC - Charles Sterling's spillchucker on B2B?

 

N

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3 minutes ago, nb Innisfree said:

British Broadcasting Corporation? 

 

Given the text I quoted, and I'll quote part of it again for your benefit, I don't think Tony1's BMS tripping is likely to result in that BBC turning off. Do you?

 

Hence my request for the meaning of BBC "in this context"

 

"Use BMS 1 - if your BMS trips and provides a 0V (ground signal), then use BMS 1. This shall result in the BBC turning off."

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11 minutes ago, Tony1 said:

That Sir, is a very good question- and one to which I have no certain answer, which is why I rely so often on the help and advice of Mr Norman and others. 

 

Curiously, I find Mr Norman's lithium project no help at all as I'm not into programming stuff, Empirbuses and all that. Most opaque to feek plummers like me.

 

I subscribe to the KISS principle. The simpler and more transparent, the better in my view. If one can figure out what is going on by looking at it, all the better. This is the pinnacle of KISS, in my opinion.

 

I'm planning on a post describing a lithium installation for a boat, which will be the antithesis of Nick's creation. I'll probably title it "Lithium for Idiots" or something along those lines, if I can ever figure out how to design a system simple enough for that description. I'm reminded of that bloke who wrote a long letter to a friend and finished it with the epithet "Sorry this is such a long letter, I didn't have time to write a short one.".

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17 minutes ago, MtB said:

 

Given the text I quoted, and I'll quote part of it again for your benefit, I don't think Tony1's BMS tripping is likely to result in that BBC turning off. Do you?

 

Hence my request for the meaning of BBC "in this context"

 

"Use BMS 1 - if your BMS trips and provides a 0V (ground signal), then use BMS 1. This shall result in the BBC turning off."

Only joking... 

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11 minutes ago, MtB said:

 

 

 

Curiously, I find Mr Norman's lithium project no help at all as I'm not into programming stuff, Empirbuses and all that. Most opaque to feek plummers like me.

 

I subscribe to the KISS principle. The simpler and more transparent, the better in my view. If one can figure out what is going on by looking at it, all the better. This is the pinnacle of KISS, in my opinion.

 

I'm planning on a post describing a lithium installation for a boat, which will be the antithesis of Nick's creation. I'll probably title it "Lithium for Idiots" or something along those lines, if I can ever figure out how to design a system simple enough for that description. I'm reminded of that bloke who wrote a long letter to a friend and finished it with the epithet "Sorry this is such a long letter, I didn't have time to write a short one.".

 

Knowing very little about electrics, I absolutely identify with the objective and the design principle of 'keep it simple'- but in this case I would suggest 'as simple as possible'. 

 

I went through a whole evolution process with my lithium install- initially really trying to keep it  all simple, but gradually realising that if I wanted it to be safe, and also simple to operate, there would have to be some complexity. 

 

I initially tried a drop-in replacement approach, but immediately found that my A2B charger was pushing the voltage way too high at the end of the charge cycle, and also there was no control over the charging current either, so the alternator was seriously overheating. 

 

Using a B2B was a simplistic approach to resolving these problems. It kept the current and voltage under much better control, and even the cabling and the concept of it was simple (ish). An alternator regulator is probably better, but I had no-one around who could do that work.

 

But I think the battery installation is the simple part with lithiums.

The inevitable complexity crept in when I started to realise how vulnerable lithiums are to high and low voltages, and I got on to the arrangements for protecting them from extreme voltages.

 

Most lithiums do come with a BMS that has extreme voltage protection cut offs set already (as I'm sure you'll know), but the values they use are pretty extreme, and by the time the internal BMS cuts in, the battery might be at risk of serious damage. 

My batteries came without a BMS (the Valence type), so I had no option but to set something up to protect them, which was how I got into the whole Victron BMV712 thing, with a motorised relay switch to do the disconnecting if the voltage got too high/low, or if the SoC got too low, etc. 

  

If you feel you can rely on the built-in BMS systems, then things can potentially be kept pretty simple. 

The most important thing I've found is the monthly ritual sacrifice of a small mammal to the great spirits of lithium. 

 

 

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4 minutes ago, Tony1 said:

If you feel you can rely on the built-in BMS systems, then things can potentially be kept pretty simple. 

 

I think not, but like you, my view is the simpler the better, but not to the point where essential functionality is missed out.

 

All decent branded drop-in replacements come with a built in BMS that disconnects at high and low voltage, but also here we need a charge disconnect on low temperature too, and cell balancing. The SOK offering according the the Will Prowse review does all this internally. https://www.amazon.co.uk/SOK-Battery-Rechargeable-Temperature-Disconnect/dp/B0922WZCJG/ref=sr_1_3?crid=1GVSP0FWYJCHE&dchild=1&keywords=sok+lifepo4+battery&qid=1630857205&sprefix=SOK+lifepo4+%2Caps%2C165&sr=8-3

 

But in addition, as you point out I would be wary of relying on the internal BMS, so I would also want my own external high and low SoC disconnects too. The simplest way to do this is not yet clear to me. Two BMV712s, perhaps.

 

And then there is monitoring. I don't want to find myself sitting in the dark if a low SoC disconnect operates, so I want to be able to see at a glance the SoC of each cell. Some sort of display on the wall seems simplest. 

 

And finally, the alternator needs protecting when the high SoC disconnect operates, if that is what is charging at the time. Simplest seems to be to connect a gash LA batt in parallel with one's SOK. 

 

Or another approach, cheaper than a so-called drop-in SOK or similar, is to build the installation using bare cells. Four x 280ah cells can be had for about £800, but then one needs to select a BMS and all the wiring, sensors, mounting etc to go with it. https://www.amazon.co.uk/dp/B093BS5BWY/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B093BS5BWY&pd_rd_w=kn3Dm&pf_rd_p=828203ef-618e-4303-a028-460d6b615038&pd_rd_wg=RPl2N&pf_rd_r=F8RGNCAKTR49GQ95RTR9&pd_rd_r=7e0e5048-cf25-414b-89f8-6213557d8130&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzVDA0WDJVVFhBS1JCJmVuY3J5cHRlZElkPUEwNzg0MjUwM1FKVzVDT04yS1VOQiZlbmNyeXB0ZWRBZElkPUEwNDE1NzE0S0lTNjFRT0tGWEhPJndpZGdldE5hbWU9c3BfZGV0YWlsJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

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14 minutes ago, MtB said:

 

I think not, but like you, my view is the simpler the better, but not to the point where essential functionality is missed out.

 

All decent branded drop-in replacements come with a built in BMS that disconnects at high and low voltage, but also here we need a charge disconnect on low temperature too, and cell balancing. The SOK offering according the the Will Prowse review does all this internally. https://www.amazon.co.uk/SOK-Battery-Rechargeable-Temperature-Disconnect/dp/B0922WZCJG/ref=sr_1_3?crid=1GVSP0FWYJCHE&dchild=1&keywords=sok+lifepo4+battery&qid=1630857205&sprefix=SOK+lifepo4+%2Caps%2C165&sr=8-3

 

But in addition, as you point out I would be wary of relying on the internal BMS, so I would also want my own external high and low SoC disconnects too. The simplest way to do this is not yet clear to me. Two BMV712s, perhaps.

 

And then there is monitoring. I don't want to find myself sitting in the dark if a low SoC disconnect operates, so I want to be able to see at a glance the SoC of each cell. Some sort of display on the wall seems simplest. 

 

And finally, the alternator needs protecting when the high SoC disconnect operates, if that is what is charging at the time. Simplest seems to be to connect a gash LA batt in parallel with one's SOK. 

 

Or another approach, cheaper than a so-called drop-in SOK or similar, is to build the installation using bare cells. Four x 280ah cells can be had for about £800, but then one needs to select a BMS and all the wiring, sensors, mounting etc to go with it. https://www.amazon.co.uk/dp/B093BS5BWY/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B093BS5BWY&pd_rd_w=kn3Dm&pf_rd_p=828203ef-618e-4303-a028-460d6b615038&pd_rd_wg=RPl2N&pf_rd_r=F8RGNCAKTR49GQ95RTR9&pd_rd_r=7e0e5048-cf25-414b-89f8-6213557d8130&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzVDA0WDJVVFhBS1JCJmVuY3J5cHRlZElkPUEwNzg0MjUwM1FKVzVDT04yS1VOQiZlbmNyeXB0ZWRBZElkPUEwNDE1NzE0S0lTNjFRT0tGWEhPJndpZGdldE5hbWU9c3BfZGV0YWlsJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

One advantage of the B2B approach is that the lead acid battery does provide a degree of protection for the alternator if the charging system instantly disconnects, and it also acts as an absolute limit on the current that will be taken from the alternator.

 

But my system has ended up being complex, despite my early efforts to avoid that. I now have two MPPTs feeding in charge, and soon I will have two B2Bs as well, so the cabling is becoming a bit of a mess. 

 

I consider scenarios when thinking of the designs. For example, how can I make the battery management simple enough that a family member could be trusted to cruise the boat for a few days, whilst I go on a trip? A BMV712 to keep the SoC below 90% could be really useful in that case. 

 

Or, when I feel safe travelling abroad for a few weeks the boat will be left unattended in a marina. I cant leave the solar panels connected and charging the whole time, as the batteries will be kept at 100% for several weeks, which is pretty stressful and will shorten their life expectancy. 

So ideally, any system you design should take account of managing the charge from an MMPT as well as the engine, and should protect the batteries from being kept at 100% for too long. Its not that it'll kill them, the way a high voltage would, but instead of lasting a decade, they might be struggling after 5 years say- so ideally you want to avoid that situation.

 

I feel that with lithiums I have moved from the idea of Battery management into the sphere of battery coddling. But they are worth  it.  

Edited by Tony1
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4 hours ago, Tony1 said:

 

Hi Nick, I know you take an interest in these sorts of control systems, so I thought i would run my thoughts past you, and hopefully get your comments on it all, if/when you have time. 

 

 When I mentioned the idea of a high SoC disconnect between the B2Bs and the batteries, by means of a BMV712 plus BEP switch, Ed pointed out that the B2Bs have sockets labelled BMS1 and BMS2, that act to stop the charging. In the manual it says this about them: 

 

"Use BMS 1 - if your BMS trips and provides a 0V (ground signal), then use BMS 1. This shall result in the BBC turning off. Once the BMS removes this trip status, i.e. the 0V signal goes back to a +ve signal, the BBC shall start charging again.

 

Use BMS 2 - if your BMS trips to a +ve voltage (2V-17V), then use BMS 2. This shall result in the BBC turning off when this voltage is received. Once the BMS removes this trip status, i.e. the +ve signal goes back to 0V signal, the BBC shall start charging again"

 

As usual I have only the vaguest idea what that really means, but it does at least suggest that it might be possible to use either the BMS1 or BMS2 socket to switch off the B2Bs, using a signal from the BMV712. 

Can I ask- if this is the case, would I use BMS1 or BMS2 to work with a BMV712?

 

 

But now the plot thickens. 

Ed also pointed out that my victron MPPT can be remotely switched by the BMV712 using this cable: 

 

https://www.victronenergy.com/accessories/ve-direct-non-inverting-remote-on-off-cable

 

What all of this seems to mean is that I can automatically disconnect all four of the charging systems (the two B2Bs plus the two MPPTs), all via the BMV712.

I guess this assumes that you can split the BMV 'trigger' signal into four, so that it goes to the four different charging units - do you know if that's feasible?

 

If it is, my new plan is to use my existing BMV712 as low voltage and low SoC disconnect, and install a second BMV712 to handle the high voltage and high SoC disconnect.  

The reason I'm thinking this way is because the current BMV and BEP setup completely isolates the batteries- from both charge and load. 

 

So am I right in thinking that I need to rewire things such that the load cables will bypass the high-voltage disconnect in some way, and the charging cables need to bypass the low voltage/SoC disconnect part of the system? 

I.e. a high voltage event does not disconnect the loads from the batteries, as I think it does now, and a low voltage event does not disconnect the charging unit (as I think it does now). 

 

I don't really know how that would all be done in practice and where all the cables would go, but before I think about that detail, do you think it is in principle the correct approach? Is it even feasible? 

 


That’s a good steer from Ed about the MPPTs. Yes you should be able to use one BMV712 to switch off the 4 charge sources at a specified SoC. The MPPT requires 12v to switch on and 0v (or floating) to switch off. The B2B BMS1 input also requires 12v to switch on and 0v to switch off, so it should just be a matter of taking one wire from the BMV relay and splitting it into 4 wires to each of the MPPTs and B2Bs. It might require a little bit of experimentation but I would start of with these wires going to the COM relay terminal, and the NO relay terminal connected to 12v.

 

If this doesn’t work it might be necessary to connect the NC terminal to 0v and hope the relay is break before make (i’m sure it will be).

 

The only thing to bear in mind is that the BMVs progressively lose accuracy and need to be synchronised at 100% SoC from time to time. It therefore will be necessary to override the high SoC shut off, so in the above mentioned wire to the B2Bs/MPPTs there should be a changeover switch (SPDT) that allows a manual selection of +12v onto these wires to force a continued charge until the batteries are actually at or very near 100%. Once the synchronisation conditions are met (some specified charge voltage with the current having fallen to say 5% of capacity) the BMVs will reset to 100% and be good for a few weeks.

Edited by nicknorman
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3 hours ago, MtB said:

 

 

 

Curiously, I find Mr Norman's lithium project no help at all as I'm not into programming stuff, Empirbuses and all that. Most opaque to feek plummers like me.

 

I subscribe to the KISS principle. The simpler and more transparent, the better in my view. If one can figure out what is going on by looking at it, all the better. This is the pinnacle of KISS, in my opinion.

 

I'm planning on a post describing a lithium installation for a boat, which will be the antithesis of Nick's creation. I'll probably title it "Lithium for Idiots" or something along those lines, if I can ever figure out how to design a system simple enough for that description. I'm reminded of that bloke who wrote a long letter to a friend and finished it with the epithet "Sorry this is such a long letter, I didn't have time to write a short one.".

Clearly my system is very complicated. But the main design criteria was to have it simple and foolproof to use. And when you mix lithium batteries with a mandate to be user-transparent, there has to be technical complexity hidden in the mix. In my opinion, anyway! But will read your “Lithium installations for dummies” with interest! If you ever write it!

 

I think Tony’s approach and my approach are interesting opposites. Tony has spent quite a lot of money on his B2Bs, BEP motorised switch etc etc. They sort of hang together adequately by means of a couple of BMVs. In other words pushing £1k of kit not quite intended for the purpose, repurposed into doing more or less what is needed.

Whereas I started from scratch, built an alternator controller purpose designed for my alternator and my lithiums. Component cost is perhaps £50 and it does exactly what it needs to do and no more. I did likewise for the BMS which also cost around £50 for the hardware. It does exactly what it needs to do and no more (including operating the tyco emergency disconnect bistable relay, and controlling the Combi charging).

 

Plus of course a huge amount of time. But it was lockdown time, and therefore free!

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1 hour ago, nicknorman said:


That’s a good steer from Ed about the MPPTs. Yes you should be able to use one BMV712 to switch off the 4 charge sources at a specified SoC. The MPPT requires 12v to switch on and 0v (or floating) to switch off. The B2B BMS1 input also requires 12v to switch on and 0v to switch off, so it should just be a matter of taking one wire from the BMV relay and splitting it into 4 wires to each of the MPPTs and B2Bs. It might require a little bit of experimentation but I would start of with these wires going to the COM relay terminal, and the NO relay terminal connected to 12v.

 

If this doesn’t work it might be necessary to connect the NC terminal to 0v and hope the relay is break before make (i’m sure it will be).

 

The only thing to bear in mind is that the BMVs progressively lose accuracy and need to be synchronised at 100% SoC from time to time. It therefore will be necessary to override the high SoC shut off, so in the above mentioned wire to the B2Bs/MPPTs there should be a changeover switch (SPDT) that allows a manual selection of +12v onto these wires to force a continued charge until the batteries are actually at or very near 100%. Once the synchronisation conditions are met (some specified charge voltage with the current having fallen to say 5% of capacity) the BMVs will reset to 100% and be good for a few weeks.

 

Thanks a lot Nick, that is really encouraging information.

Just to check something- when you say to take one wire from the BMV relay, what do you mean?

There will be a BMV712 shunt and the display unit- is that the relay?

 

To facilitate the automated disconnection feature, I've ordered a second victron MPPT 100-50, which will replace the existing EPever Tracer AN series unit, which had no remote disconnect function. I'm very impressed with the victron unit I already have- you can even switch it off via the phone app (as well as configuring it). 

 

And since you can manually disable the MPPT via the app, I'm also wondering now if you can use victron's VE local networking functionality to do the automatic high-SoC switch off of the MPPT, instead of hard wiring it.... There doesnt seem to be any options on the app that do this,  but they are very clever things...

 

Unusually for me, I had actually thought about how to override the automatic disconnect feature when I want to synchronise, and my thinking was to use the software - i.e. to edit the parameters using the app- maybe lower the high-SoC cutoff value to say 20% temporarily, so that it will not disconnect when I calibrate the units? 

I prefer a hard wired switch if I'm honest, but I feel Ed would have to do that, and its a technical step I can take after I get the high SoC cut off sorted out.

 

ETA- I think I'm confusing myself here, because there was an earlier suggestion of using the low SoC parameter as the 'trigger' (with a BEP switch), but setting the trigger value at 85% (instead of a more normal 20% say). 

The original idea was to NOT invert the relay, so the BEP switch stayed closed below 85%, but then opened above 85% and thus performed the disconnection function. 

But without the BEP, and with a direct switch off link from the BMV712 to the MPPT, will the idea still work of using 85% as the switch off or trigger value? 

The VE cable (that Ed sent me link for) is  described as non-inverting. So for the MPPT to be switched off, you said that it needs the voltage to drop to zero. 

Is that what the BMV712 will do if I set it to use a low SoC switch as a high-SoC switch? 

 

 

Edited by Tony1
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36 minutes ago, Tony1 said:

 

Thanks a lot Nick, that is really encouraging information.

Just to check something- when you say to take one wire from the BMV relay, what do you mean?

There will be a BMV712 shunt and the display unit- is that the relay?

 

To facilitate the automated disconnection feature, I've ordered a second victron MPPT 100-50, which will replace the existing EPever Tracer AN series unit, which had no remote disconnect function. I'm very impressed with the victron unit I already have- you can even switch it off via the phone app (as well as configuring it). 

 

And since you can manually disable the MPPT via the app, I'm also wondering now if you can use victron's VE local networking functionality to do the automatic high-SoC switch off of the MPPT, instead of hard wiring it.... There doesnt seem to be any options on the app that do this,  but they are very clever things...

 

Unusually for me, I had actually thought about how to override the automatic disconnect feature when I want to synchronise, and my thinking was to use the software - i.e. to edit the parameters using the app- maybe lower the high-SoC cutoff value to say 20% temporarily, so that it will not disconnect when I calibrate the units? 

I prefer a hard wired switch if I'm honest, but I feel Ed would have to do that, and its a technical step I can take after I get the high SoC cut off sorted out.

 

The BMV relay is contained within the display unit. If you look at the back of it there are 3 connections, COM, NO and NC (common, normally open and normally closed. It’s a changeover aka SPDT relay.)

 

The BMV does broadcast all its parameters over the VE.direct port, but whether the MPPTs can use that data I don’t know, you’d have to read the manual! I do know that the MPPT on off function we mentioned earlier, uses the VE.direct port rendering unavailable to receive VE.direct data. So you can have one or the other, not both.

 

No you can’t fix the full charge issue by lowering the high SoC cutoff, that will just cut off the charging sooner! If you set the high SoC cutoff to 100% that won’t fix the problem either because the accumulated error in SoC might mean an indicated 100% is reached well before actual 100%. You need the switch as I mentioned. It’s not a big deal, toggle switch with 3 terminals, centre one to the B2Bs etc, one outer to the BMV relay and the other outer to 12v.

Edited by nicknorman
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7 minutes ago, nicknorman said:

The BMV relay is contained within the display unit. If you look at the back of it there are 3 connections, COM, NO and NC (common, normally open and normally closed. It’s a changeover aka SPDT relay.)

 

The BMV does broadcast all its parameters over the VE.direct port, but whether the MPPTs can use that data I don’t know, you’d have to read the manual! I do know that the MPPT on off function we mentioned earlier, uses the VE.direct port rendering unavailable to receive VE.direct data. So you can have one or the other, not both.

 

No you can’t fix the full charge issue by lowering the high SoC cutoff, that will just cut off the charging sooner! If you set the high SoC cutoff to 100% that won’t fix the problem either because the accumulated error in SoC might mean it’s reached well before actual 100%. You need the switch as I mentioned. It’s not a big deal, toggle switch with 3 terminals, centre one to the B2Bs etc, one outer to the BMV relay and the other outer to 12v.

 

Thanks again Nick, I will explain the switch thing to Ed, he will have a clearer idea of the type of switch needed.

I'm off to read the MPPT manual.

I may be gone for some time.

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6 hours ago, MtB said:

 

I think not, but like you, my view is the simpler the better, but not to the point where essential functionality is missed out.

 

All decent branded drop-in replacements come with a built in BMS that disconnects at high and low voltage, but also here we need a charge disconnect on low temperature too, and cell balancing. The SOK offering according the the Will Prowse review does all this internally. https://www.amazon.co.uk/SOK-Battery-Rechargeable-Temperature-Disconnect/dp/B0922WZCJG/ref=sr_1_3?crid=1GVSP0FWYJCHE&dchild=1&keywords=sok+lifepo4+battery&qid=1630857205&sprefix=SOK+lifepo4+%2Caps%2C165&sr=8-3

 

But in addition, as you point out I would be wary of relying on the internal BMS, so I would also want my own external high and low SoC disconnects too. The simplest way to do this is not yet clear to me. Two BMV712s, perhaps.

 

And then there is monitoring. I don't want to find myself sitting in the dark if a low SoC disconnect operates, so I want to be able to see at a glance the SoC of each cell. Some sort of display on the wall seems simplest. 

 

And finally, the alternator needs protecting when the high SoC disconnect operates, if that is what is charging at the time. Simplest seems to be to connect a gash LA batt in parallel with one's SOK. 

 

Or another approach, cheaper than a so-called drop-in SOK or similar, is to build the installation using bare cells. Four x 280ah cells can be had for about £800, but then one needs to select a BMS and all the wiring, sensors, mounting etc to go with it. https://www.amazon.co.uk/dp/B093BS5BWY/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B093BS5BWY&pd_rd_w=kn3Dm&pf_rd_p=828203ef-618e-4303-a028-460d6b615038&pd_rd_wg=RPl2N&pf_rd_r=F8RGNCAKTR49GQ95RTR9&pd_rd_r=7e0e5048-cf25-414b-89f8-6213557d8130&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzVDA0WDJVVFhBS1JCJmVuY3J5cHRlZElkPUEwNzg0MjUwM1FKVzVDT04yS1VOQiZlbmNyeXB0ZWRBZElkPUEwNDE1NzE0S0lTNjFRT0tGWEhPJndpZGdldE5hbWU9c3BfZGV0YWlsJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

I thought you wanted kiss? My system is kiss  solar panels batteries job done for last 4 years! Quality mppt controller required that you know really does go into float and I am going to make it more complicated when I change the genny alternator to a 24 volt one to charge LifePo4s directly rather than a charger of the 240 volts provided by the genny, I am thinking through a mppt controller or long thinish cable direct to batteries to bring on some voltage drop

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Just picking up on the edit, the BMV relay is pretty flexible as you can set its function to normal or inverted. But anyway, it is a changeover switch so the com is connected either to NO or NC depending on the relay’s state. So if you connect the devices to be controlled to com, you can connect 12v to either NO or NC depending on whether you chose to use the relay in normal or inverted mode.

 

So yes you set the high SoC to say 85% and the low SoC to a bit less, maybe just 84% and that should work. Charging stops at 85% and restarts at 84%.

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1 hour ago, nicknorman said:

Just picking up on the edit, the BMV relay is pretty flexible as you can set its function to normal or inverted. But anyway, it is a changeover switch so the com is connected either to NO or NC depending on the relay’s state. So if you connect the devices to be controlled to com, you can connect 12v to either NO or NC depending on whether you chose to use the relay in normal or inverted mode.

 

So yes you set the high SoC to say 85% and the low SoC to a bit less, maybe just 84% and that should work. Charging stops at 85% and restarts at 84%.

 

Fab, thanks a lot Nick. 

If you dont mind, I'd just like to express it again to make sure I understand it correctly:

So the way I'm planning to use the BMV712 means it will be in an 'alarm status' mode for most of the time, since it will spend most of the time below its low SoC cut off 85%. 

To do this, I think I want to initially try connecting 12v to the Normally Open port, which will mean the relay will open (and switch off the MPPT) when the SoC rises above what it regards as its low limit of 85%, right? 

For most of its life it will not be in what it regards as a normal state- it will be below its minimum SoC value, and therefore will keep the relay closed. As far is its concerned it will be in a alarm situation, but as far as I'm concerned its working as planned. Doing this in reverse is hurting my head trying to think it through!

 

Also, how about this idea:

After a solar charge up to 85% (which might be completed by 10am on a summer day), I wouldn't want the MPPT to start charging again as soon as it fell to 84%- because with the fridge etc running, that fall to 84% could happen within half an hour. So the MPPTs would be on and off all day, and hovering around 85%- not a major problem, but not ideal. 

Ideally, I would rather consume some of the battery charge, and maybe let it get down to 50% or so, before it starts charging again. 

 

So I could leave the boat alone for a month, say, knowing that the batteries will cycle between 50% and 85% (albeit very slowly, as the fridge will be left off).

 

So there are two values in the relay settings for the low SoC.

One is the bell icon that is struck through by a line (which I would set to 60%), and the other is the normal bell icon (which I would set to 85%). 

From reading the manual I initially got the impression that the normal bell icon is the value at which the 'change' would be triggered (in my case this would be the SoC reaching 85%), and the struck through icon is the value at which the 'normal' situation would be restored. Normally, this value is higher than the other one, as you want the SoC to rise a bit before reconnecting loads and other things to the batteries.

 

But in my case, the value for the 'struck through' bell icon would want to be lower, right?

It shows the SoC value at which I want to re-close the relay and start charging again, so I would set that to 60% - do I have that right? 

 

I ask because I've seen another explanation from which I got the impression that it works as follows:

at any time when the SoC value lies somewhere between the two set trigger values, the alarm/switch condition is triggered. 

If that were true, I'd want to use 85% and 100% I guess, but I'm not sure which of those  two descriptions correctly outlines the operation of the SoC relay settings. 

I think I've already lost several much needed IQ points in the month since I retired!

 

  

Edited by Tony1
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19 minutes ago, Tony1 said:

 

Fab, thanks a lot Nick. 

If you dont mind, I'd just like to express it again to make sure I understand it correctly:

So the way I'm planning to use the BMV712 means it will be in an 'alarm status' mode for most of the time, since it will spend most of the time below its low SoC cut off 85%. 

To do this, I think I want to initially try connecting 12v to the Normally Open port, which will mean the relay will open (and switch off the MPPT) when the SoC rises above what it regards as its low limit of 85%, right? 

For most of its life it will not be in what it regards as a normal state- it will be below its minimum SoC value, and therefore will keep the relay closed. As far is its concerned it will be in a alarm situation, but as far as I'm concerned its working as planned. Doing this in reverse is hurting my head trying to think it through!

 

Also, how about this idea:

After a solar charge up to 85% (which might be completed by 10am on a summer day), I wouldn't want the MPPT to start charging again as soon as it fell to 84%- because with the fridge etc running, that fall to 84% could happen within half an hour. So the MPPTs would be on and off all day, and hovering around 85%- not a major problem, but not ideal. 

Ideally, I would rather consume some of the battery charge, and maybe let it get down to 50% or so, before it starts charging again. 

 

So I could leave the boat alone for a month, say, knowing that the batteries will cycle between 50% and 85% (albeit very slowly, as the fridge will be left off).

 

So there are two values in the relay settings for the low SoC.

One is the bell icon that is struck through by a line (which I would set to 60%), and the other is the normal bell icon (which I would set to 85%). 

From reading the manual I initially got the impression that the normal bell icon is the value at which the 'change' would be triggered (in my case this would be the SoC reaching 85%), and the struck through icon is the value at which the 'normal' situation would be restored. Normally, this value is higher than the other one, as you want the SoC to rise a bit before reconnecting loads and other things to the batteries.

 

But in my case, the value for the 'struck through' bell icon would want to be lower, right?

It shows the SoC value at which I want to re-close the relay and start charging again, so I would set that to 60% - do I have that right? 

 

I ask because I've seen another explanation from which I got the impression that it works as follows:

at any time when the SoC value lies somewhere between the two set trigger values, the alarm/switch condition is triggered. 

If that were true, I'd want to use 85% and 100% I guess, but I'm not sure which of those  two descriptions correctly outlines the operation of the SoC relay settings. 

I think I've already lost several much needed IQ points in the month since I retired!

 

You are getting confused between the alarm settings and the relay settings. They are entirely different! You don’t want to configure the alarm settings otherwise the bloody thing will be beeping all the time! Well maybe you want to configure the alarm for a very low SoC to warn of impending low voltage disconnect, up to you.


You need to configure items 16 and 17 (SoC relay and clear SoC relay). 17 is set to your 85% or whatever, 16 is set for when you want charging to restart. I suggest that more life is used up from the battery by cycling between say 85% and 50%, than by keeping the SoC near 85%. Battery life is generally measured in terms of cycles and 85% to 50% to 85% is a third of a cycle. There is no point in having the battery supply load when it could easily be supplied by the engine or the solar.

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13 minutes ago, nicknorman said:

You are getting confused between the alarm settings and the relay settings. They are entirely different! You don’t want to configure the alarm settings otherwise the bloody thing will be beeping all the time! Well maybe you want to configure the alarm for a very low SoC to warn of impending low voltage disconnect, up to you.


You need to configure items 16 and 17 (SoC relay and clear SoC relay). 17 is set to your 85% or whatever, 16 is set for when you want charging to restart. I suggest that more life is used up from the battery by cycling between say 85% and 50%, than by keeping the SoC near 85%. Battery life is generally measured in terms of cycles and 85% to 50% to 85% is a third of a cycle. There is no point in having the battery supply load when it could easily be supplied by the engine or the solar.

 

Thanks for that clarification Nick, much appreciated. 

When talking about those icons, I was referring to the 'low SoC relay' settings that are displayed on the app- not sure where I got all the references to alarms....

I had misunderstood as well- I had thought setting 16 was my 85% value, so that is really helpful.

I'll have the control lead next week, so I might try some experiments with one of the MPPTs in advance of Ed's visit.

 

Can I ask a favour- could you possibly recommend some sort of cable junction thing to split the BMV712 control signal up and send it down four separate wires? 

I'm not seeing anything that acts like a sort of micro bus bar...

 

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