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On 20/02/2023 at 11:25, Tony1 said:

 

Nick knows my setup pretty well because he very kindly advised me on how to wire it all. 

It got to the point of 'where do I connect that red wire?' .....

 

 

 

Speaking of the red wire, do I need to put a fuse in the control cable between the Victron MPPT and the Victron BMV-712? I'd like to set it up like yours, cycling between 2 states of charge. If so, what fuse rating would it require?

 

Another question I have: is it OK to cycle my batteries between quite high SOC? For instance, between 60% and 90%. I'd like to always have a large reserve pool, if it doesn't damage the batteries.

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9 minutes ago, 170968 said:

 

Speaking of the red wire, do I need to put a fuse in the control cable between the Victron MPPT and the Victron BMV-712? I'd like to set it up like yours, cycling between 2 states of charge. If so, what fuse rating would it require?

 

Another question I have: is it OK to cycle my batteries between quite high SOC? For instance, between 60% and 90%. I'd like to always have a large reserve pool, if it doesn't damage the batteries.

Yes 🙂

 

Some suppliers (e.g. BYD, second largest LFP manufacturer in the world?) no longer quote lifetime in cycles, they quote it in accumulated MWh (e.g. 45MWh for 15kWh battery). So long as you don't go below 0% or 100% (or spend long periods there) they don't care whether you cycle 3000x 0%-100% or 1500x 0%-50% or 1500x 50%-100% or 10000x 60%-90% -- and they guarantee lifetime using the MWh figure (using data logging), it's not just a data sheet/publicity number.

 

Of course what their inbuilt BMS calls "0%" and "100%" is their definition, it's possible they have intentionally built some margin in (e.g. "0%" is actually 5%, "100%" is actually 95%), but the principle is clear -- so long as you stay away from the low-voltage (11.6V=2.9V/cell on discharge?) and high-voltage (13.8V=3.45V/cell on charge?) knees, LFP don't really care what you do in between.

 

If you mostly stay between 10% and 90% SoC limits according to your BMS (even with occasional excursions to 0% and 100%), you shouldn't have to worry about anything else 🙂

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35 minutes ago, 170968 said:

 

Speaking of the red wire, do I need to put a fuse in the control cable between the Victron MPPT and the Victron BMV-712? I'd like to set it up like yours, cycling between 2 states of charge. If so, what fuse rating would it require?

 

Another question I have: is it OK to cycle my batteries between quite high SOC? For instance, between 60% and 90%. I'd like to always have a large reserve pool, if it doesn't damage the batteries.

 

Apologies, we will need Nick's expertise to answer this properly, but I'll give it try for now:  The control wire I used was black, I think it was 18AWG. But no fuse is needed on that control wire. 

I'll see if I can get a pic of the back of the BMV712 later, showing the wires.

The pic shows how I configured the BMV712, with Nicks help:

I'm using the low SoC relay function to monitor the SoC, but I'm using it 'in reverse' as a high SoC monitor, as you'll see from the SoC settings. 

 

In terms of cycling the batteries in a way that will prolong their life, again there are many more people far more knowledgeable than me about this topic, but there are a few things I've picked up from the contributors here:  

They need regular runs down to lower SoC (ie lower than 10 or 20%). In my case I do that about once each week.

Its awkward to arrange as a liveaboard because you need the batteries to be running down low during the day- you dont want a low voltage alarm at 4am. 

So you need to set things up so that you run them down to a low SoC, but you still have enough time to get some charge back into them before it gets too late. Its no use getting down to 5% SoC at 9pm, for example, as its too late too recharge in order to get your fridge through the night. 

So there are practical constraints, but the general principle seems to be that they need regular 'exercise', and they need to be pushed to their capacity limits periodically. 

 

One key thing to bear in mind is not to hold them at an extreme SoC for very long. In my case as soon as the BMV712 is synchronised to 100% I stop all the charging, and put the kettle on in order to draw some charge from them a bit quicker. 

 

Its more awkward in winter, because for example today we have a bit of solar, but we wont get much tomorrow.

So today I've adjusted the SoC limit up to 90% to take advantage of what solar we have.

It costs money (in diesel) to replace charge in winter, so you always have a bit of reluctance to switch off your MPPTs and let the batteries SoC go down, when there is some perfectly good solar available.  

In winter I do tend to cycle between 60 and 85% more often, as you have a natural tendency to want more charge in reserve in colder/darker weather, but I have to force myself to let them run down the SoC once every couple of weeks at most, as I know that will give them a longer life.

 

 

 

Screenshot_2023-03-08-10-40-00-001_com.victronenergy.victronconnect.jpg

Edited by Tony1
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42 minutes ago, 170968 said:

 

Speaking of the red wire, do I need to put a fuse in the control cable between the Victron MPPT and the Victron BMV-712? I'd like to set it up like yours, cycling between 2 states of charge. If so, what fuse rating would it require?

 

Another question I have: is it OK to cycle my batteries between quite high SOC? For instance, between 60% and 90%. I'd like to always have a large reserve pool, if it doesn't damage the batteries.


I think the Victron MPPT remote on off has to be pulled up to battery voltage to turn on, left floating or at battery negative to turn off. In that case you need a wire from battery + to the BMV relay com, and a wire from BMV relay NC (or NO, depending on what you are trying to achieve) to the MPPT.

 

Any connection to battery + needs to be fused, so it would go battery+ to fuse to BMV relay Com, with the fuse close to the battery+. The aim being to not have any length of wire that could short to hull etc that is not protected by a fuse.

 

Yes 0% is 10v but I try to avoid going below 12v. There is very little Ah between 12v and 10v

 

As IanD says, just stay away from the voltage knees. We do tend to store our boat in the marina at 50% SoC but that is just because we can! When out and about I tend to charge to 80% but that could just as well be 90 or 95% I think. Voltage only goes above 13.6v (3.4v/cell) after that

Edited by nicknorman
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24 minutes ago, nicknorman said:


I think the Victron MPPT remote on off has to be pulled up to battery voltage to turn on, left floating or at battery negative to turn off. In that case you need a wire from battery + to the BMV relay com, and a wire from BMV relay NC (or NO, depending on what you are trying to achieve) to the MPPT.

 

Any connection to battery + needs to be fused, so it would go battery+ to fuse to BMV relay Com, with the fuse close to the battery+. The aim being to not have any length of wire that could short to hull etc that is not protected by a fuse.

 

Just to add that the way mine is set up, the relay is normally closed, and it is not inverted.

 

 

Screenshot_20230308_113238.jpg

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37 minutes ago, Tony1 said:

 

Apologies, we will need Nick's expertise to answer this properly, but I'll give it try for now:  The control wire I used was black, I think it was 18AWG. But no fuse is needed on that control wire. 

I'll see if I can get a pic of the back of the BMV712 later, showing the wires.

The pic shows how I configured the BMV712, with Nicks help:

I'm using the low SoC relay function to monitor the SoC, but I'm using it 'in reverse' as a high SoC monitor, as you'll see from the SoC settings. 

 

In terms of cycling the batteries in a way that will prolong their life, again there are many more people far more knowledgeable than me about this topic, but there are a few things I've picked up from the contributors here:  

They need regular runs down to lower SoC (ie lower than 10 or 20%). In my case I do that about once each week.

Its awkward to arrange as a liveaboard because you need the batteries to be running down low during the day- you dont want a low voltage alarm at 4am. 

So you need to set things up so that you run them down to a low SoC, but you still have enough time to get some charge back into them before it gets too late. Its no use getting down to 5% SoC at 9pm, for example, as its too late too recharge in order to get your fridge through the night. 

So there are practical constraints, but the general principle seems to be that they need regular 'exercise', and they need to be pushed to their capacity limits periodically. 

 

 

 

Thanks for the help Tony, much appreciated.

 

Just to be sure, does your charger come on at 60% and turn off at 90%? If you could let me know later whether your control cable is connected to NO or NC, that would be great.

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42 minutes ago, 170968 said:

 

Thank you Ian, that's very helpful. Just to check, 0% is 10V right? Not that I intend going down that low.

0% may be 10V according to some suppliers but it's *way* down the voltage knee, as Nick says you shouldn't ever go there in normal operation, and there's no point below 2.8V/cell because there's naff-all extra energy going that low. It's OK as an emergency disconnect voltage to stop the batteries being damaged. All these voltages depend on charge/discharge rates anyway, here's a plot for the Winston cells:

 

 

LFP.png

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38 minutes ago, nicknorman said:


I think the Victron MPPT remote on off has to be pulled up to battery voltage to turn on, left floating or at battery negative to turn off. In that case you need a wire from battery + to the BMV relay com, and a wire from BMV relay NC (or NO, depending on what you are trying to achieve) to the MPPT.

 

Any connection to battery + needs to be fused, so it would go battery+ to fuse to BMV relay Com, with the fuse close to the battery+. The aim being to not have any length of wire that could short to hull etc that is not protected by a fuse.

 

Yes 0% is 10v but I try to avoid going below 12v. There is very little Ah between 12v and 10v

 

As IanD says, just stay away from the voltage knees. We do tend to store our boat in the marina at 50% SoC but that is just because we can! When out and about I tend to charge to 80% but that could just as well be 90 or 95% I think. Voltage only goes above 13.6v (3.4v/cell) after that

 

The remote port needs to be brought to 2.9V. There's another port next to it which has a positive current. They ship with a small link cable between the two. I'm not sure what voltage is at the terminal and I'm not sure where to poke my negative probe to find out! It does however say in the instructions that you can use a switch between these two to turn it on and off.

 

What size fuse would I require if I used the battery positive as you suggested?

 

There seems to be a disagreement on whether you need to fully charge/discharge the bank now and then. Do you?

 

Thanks for the help Nick.

 

2 minutes ago, IanD said:

0% may be 10V according to some suppliers but it's *way* down the voltage knee, as Nick says you shouldn't ever go there in normal operation, and there's no point below 2.8V/cell because there's naff-all extra energy going that low. It's OK as an emergency disconnect voltage to stop the batteries being damaged. All these voltages depend on charge/discharge rates anyway, here's a plot for the Winston cells:

 

 

LFP.png

 

Yes, I was looking at the charts for mine earlier because I noticed when using the kettle, the voltage didn't recover to the level I expected. Apparently this is normal and voltage isn't always the same for a given SOC. I don't know how many times I've thought I understood these batteries, only to find some new information which sends me into confusion again. I do believe I'm getting there...again.

49 minutes ago, nicknorman said:


I think the Victron MPPT remote on off has to be pulled up to battery voltage to turn on, left floating or at battery negative to turn off. In that case you need a wire from battery + to the BMV relay com, and a wire from BMV relay NC (or NO, depending on what you are trying to achieve) to the MPPT.

 

I'm trying to achieve the BMV starting the solar charge at 60% and turning it off at 90%. Hopefully Ive understood the thing and this is achievable?

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17 minutes ago, 170968 said:

Thanks for the help Tony, much appreciated.

 

Just to be sure, does your charger come on at 60% and turn off at 90%? If you could let me know later whether your control cable is connected to NO or NC, that would be great.

 

 

Yes, with those settings the MPPTs (and B2Bs) will switch off once the SoC rises above 90%, and they will switch back on when the SoC falls below 60%. 

In winter I tend to fiddle around with the settings every few days to get the most out of the limited solar. 

But in the high summer- with a steady 80 or 90 amps available all day long- I'll probably set 75% as the daily max for the SoC. 

When you know that there is never going to be a shortage of power you can be a bit more liberal with the settings, and on some days in summer the batteries are so full that the MPPTs dont even come on.

To be honest it was all down to Nick helping me. Once I realised that most MPPTs and chargers now come with a remote BMS control input, I asked about how a BMV712 could be set up to switch them on and off based on SoC, and Nick explained that I could use the low SoC function to do it, but in reverse.  

 

One thing to bear in mind is that SoC accuracy can obviously drift over time, so the bulk charging voltage on the MPPTs doesnt want to be too high, as that is the backup to stop the MPPTs charging at an appropriate point. 

 

Edited by Tony1
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3 minutes ago, Tony1 said:

 

 

Yes, with those settings the MPPTs (and B2Bs) will switch off once the SoC rises above 90%, and they will switch back on when the SoC falls below 60%. 

In winter I tend to fiddle around with the settings every few days to get the most out of the limited solar. 

But in the high summer- with a steady 80 or 90 amps available all day long- I'll probably set 75% as the daily max for the SoC. 

When you know that there is never going to be a shortage of power you can be a bit more liberal with the settings, and on some days in summer the batteries are so full that the MPPTs dont even come on.

To be honest it was all down to Nick helping me. Once I realised that most MPPTs and chargers now come with a remote BMS control input, I asked about how a BMV712 could be set up to switch them on and off based on SoC, and Nick explained that I could use the low SoC function to do it, but in reverse.  

 

One thing to bear in mind is that SoC accuracy can obviously drift over time, so the bulk charging voltage on the MPPTs doesnt want to be too high, as that is the backup to stop the MPPTs charging at an appropriate point. 

 

 

I'm the same with the fiddling. I want to set up all this automation but I'll never leave it alone to do it's thing! Like you say though, a lot of it won't be necessary once spring comes <looks out window at a blizzard>.

 

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12 minutes ago, 170968 said:

 

Yes, I was looking at the charts for mine earlier because I noticed when using the kettle, the voltage didn't recover to the level I expected. Apparently this is normal and voltage isn't always the same for a given SOC. I don't know how many times I've thought I understood these batteries, only to find some new information which sends me into confusion again. I do believe I'm getting there...again.

 

 

I find that for a liveaboard the batteries are never truly at rest, because there is always a charge or a load of some sort happening if you liveaboard. Even the BMV712 unit draws a tiny but constant current.  So you never really see the true resting voltage, which is what the charts use. 

 

But to get an idea of what the resting voltage would be, I've estimated that for every 2amps of load, the resting battery voltage seems to be reduced by about  0.01v. But that only works up to loads of about 10 or 15 amps, and after that its not a reliable method. 

 

So I sort of estimate my resting voltage by taking account of the load at the time, and adding on 0.01v for every 2 amps of load. 

I can then assess that 'compensated' voltage against the SoC, and make sure that voltage and SoC are broadly consistent with each other. I never just look at SoC on its own.

 

For charging, it seems that for every amp of charge, the resting voltage increases by 0.01v, so the effect of charging on the resting voltage seems to be roughly twice the effect of a load.

I've also noticed that at more extreme states of charge, a 2 amp load will produce a slightly different amount of change in battery voltage (as you might expect). 

All this behaviour may vary from battery to battery, of course- this is only my own set. 

 

 

 

 

9 minutes ago, 170968 said:

 

I'm the same with the fiddling. I want to set up all this automation but I'll never leave it alone to do it's thing! Like you say though, a lot of it won't be necessary once spring comes <looks out window at a blizzard>.

 

 

Exactly the same for me- I had automation in mind when setting it up, but I never stop fiddling with the values! 

That said, at least I know that if I have a fridge full of food that I dont want to waste (eg by simply switching off all the electrics), and if I need to leave the boat for a few days, I have the option of setting up the SoC monitor so that the batteries wont be roughly treated, and the fridge/electrics will still work ok from the panels. 

It was also done with the idea of a guest being able to use my boat for a few days without having to worry about managing MPPTs and batteries.

All I need to do is show them the SoC monitor, so they can keep an eye on how much charge they have. In summer there is so much solar that there is nothing they can really do to run it down other than switching on the immersion heater, but I'll ask them not to do that! 

 

 

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25 minutes ago, Tony1 said:

It was also done with the idea of a guest being able to use my boat for a few days without having to worry about managing MPPTs and batteries.

All I need to do is show them the SoC monitor, so they can keep an eye on how much charge they have. In summer there is so much solar that there is nothing they can really do to run it down other than switching on the immersion heater, but I'll ask them not to do that!

Wow you're brave 😄

 

OK I connected it all up and fiddled with the settings and it works! The only thing missing for now is a fuse. If anyone knows the fuse size required that would be great. Otherwise I'll stick in a <1a and see how it goes!

 

Thank you all again for the help and advice. I'd be lost without it.

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1 hour ago, 170968 said:

 

The remote port needs to be brought to 2.9V. There's another port next to it which has a positive current. They ship with a small link cable between the two. I'm not sure what voltage is at the terminal and I'm not sure where to poke my negative probe to find out! It does however say in the instructions that you can use a switch between these two to turn it on and off.


I think it depends on which model of MPPT you have. I was thinking of the ones that used the Ve.direct port but it sounds like yours has a dedicated on-off input. I would thus simply pass the wires from the 2 ports that are currently linked, via the BMV relay contacts. (And remove the link of course). No need for a fuse. If the input is designed to work on 2.9v, don’t connect it to 12v!

1 hour ago, 170968 said:

 

There seems to be a disagreement on whether you need to fully charge/discharge the bank now and then. Do you?

 


No I don’t think it’s necessary. Worst case scenario is that some capacity is lost, but that is reversed by a full discharge/charge cycle so it’s not a big deal. Haven’t noticed any such thing yet, but then we have 600Ah and generally it cycles between about 80% and 50%. I think the occasional full charge up to 100% (to synchronise the BMV) tends to wake the batteries up and delete any “memory effect”, but I can’t prove that! I aim to do that once a month.

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8 minutes ago, nicknorman said:


I think it depends on which model of MPPT you have. I was thinking of the ones that used the Ve.direct port but it sounds like yours has a dedicated on-off input. I would thus simply pass the wires from the 2 ports that are currently linked, via the BMV relay contacts. (And remove the link of course). No need for a fuse. If the input is designed to work on 2.9v, don’t connect it to 12v!


No I don’t think it’s necessary. Worst case scenario is that some capacity is lost, but that is reversed by a full discharge/charge cycle so it’s not a big deal. Haven’t noticed any such thing yet, but then we have 600Ah and generally it cycles between about 80% and 50%. I think the occasional full charge up to 100% (to synchronise the BMV) tends to wake the batteries up and delete any “memory effect”, but I can’t prove that! I aim to do that once a month.

 

 

Great, my job is done in that case. 👍

 

I will probably do the same as you and do a monthly (or maybe every other month) full charge.

 

By the way, the input contact is rated at "2.9V and up to battery voltage", so would have been fine. I read a thread on the diysolar forum quoting an older manual which stated the output is 3.5V.

 

 

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53 minutes ago, 170968 said:

Wow you're brave 😄

 

OK I connected it all up and fiddled with the settings and it works! The only thing missing for now is a fuse. If anyone knows the fuse size required that would be great. Otherwise I'll stick in a <1a and see how it goes!

 

Thank you all again for the help and advice. I'd be lost without it.

 

Somehow with the victron kit I had a spare red wire with a fuse and holder already within it, so I just used that. 

Maybe you could unscrew the fuse holder in the BMV712 pos wire that you already have, and see what size that fuse is? 

 

PS - since SoC is a derived value and can drift, I would advise always checking both SoC and voltage together. 

You can guesstimate the resting voltage by adjusting the observed voltage (to take account of any loads or charges),  as per above. 

 

And I cant say I'd be over the moon about letting someone used my boat, even for a few days.

There is always that risk of a newbie sinking it in a lock, but of course there is other damage that can be done to boat systems by careless use or abuse.  

But the person is a long term waterways enthusiast, and may never be able to purchase their own boat- and might even struggle to fund a canal holiday at the moment- so it would be a nice gesture, and an experience they would really love. 

 

 

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4 minutes ago, Tony1 said:

PS - since SoC is a derived value and can drift, I would advise always checking both SoC and voltage together. 

You can guesstimate the resting voltage by adjusting the observed voltage (to take account of any loads or charges),  as per above.

 

Good idea. I'll do exactly that.

4 minutes ago, Tony1 said:

 

Somehow with the victron kit I had a spare red wire with a fuse and holder already within it, so I just used that.

 

That's to include the starter battery voltage in the app.

Edited by 170968
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1 minute ago, 170968 said:

 

Good idea. I'll do exactly that.

 

And congrats, you are now only the second person on the entire waterway system to set up an automated SoC control thingy with a BMV unit. 

Now I only feel half as barmy as I did before. 

 

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5 minutes ago, Tony1 said:

 

And congrats, you are now only the second person on the entire waterway system to set up an automated SoC control thingy with a BMV unit. 

Now I only feel half as barmy as I did before. 

 

 

I feel like it's a great way to do things. I didn't realise the MPPT had a remote on/off until recently. Now I just want something programmable so that I can have the solar put in slightly less current than what I'm using. Then at 60% go full charge. Like this I can slow down the cycling. Im doing it manually atm but it's getting old already.

I dont think such a thing exists.

 

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10 minutes ago, 170968 said:

 

I feel like it's a great way to do things. I didn't realise the MPPT had a remote on/off until recently. Now I just want something programmable so that I can have the solar put in slightly less current than what I'm using. Then at 60% go full charge. Like this I can slow down the cycling. Im doing it manually atm but it's getting old already.

I dont think such a thing exists.

 

 

Apologies, I've not picked up on what you're aiming for there.

Are you saying that when the SoC is between 60 and 90, you would like to have the MPPT charge the battery, but not at its full rate?

You want the charging to be done at a rate that is slightly lower than the load/consumption, which would have the effect of gradually reducing the SoC? 

Then when the SoC has fallen to 60%, the MPPT would change so that it was charging at its full rate, and that would result in the SoC going up again?

And the reason you want to do that is to slow down the charge/discharge cycling process? 

Have I got that right? 

 

 

Edited by Tony1
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2 minutes ago, Tony1 said:

 

Apologies, I've not picked up on what you're aiming for there.

Are you saying that when the SoC is between 60 and 90, you would like to have the MPPT charge the battery, but not at its full rate?

You want the charging to be done at a rate that is slightly lower than the load/consumption, which would have the effect of gradually reducing the SoC? 

Then when the SoC has fallen to 60%, the MPPT would change so that it was charging at its full rate, and that would result in the SoC going up again?

And the reason you want to do that is to slow down the charge/discharge cycling process? 

Have I got that right? 

 

 

 

Yes you got it right. Thinking more about it I realised it's really not worth bothering.  I think I just hate wasting the tiny bit of power available at the moment as Im currently on the discharge part of the cycle. Once spring comes I doubt I'll care at all.

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22 minutes ago, 170968 said:

 

Yes you got it right. Thinking more about it I realised it's really not worth bothering.  I think I just hate wasting the tiny bit of power available at the moment as Im currently on the discharge part of the cycle. Once spring comes I doubt I'll care at all.

 

I can totally understand not wanting to waste the limited solar power that we get in the winter, but I suspect a complex charge controller device might not pay for itself.

What happens in reality is that the solar never actually gets your batteries up to 90% anyway during the poor months (or not often). 

In Dec and Jan the panels spend the limited daylight hours putting in a few amps, and quite often not even keeping up with what your fridge and laptop are using, so overall the batteries are usually discharging all the time, until you start running the engine.

 

Where its more of a thing to consider is in say late Feb, or early Nov, when there is some half decent solar. 

But all you have to do is manually adjust your upper SoC limit from 80 or 85% up to say 90 or 95%, so the panels wont get switched off by the BMV712.

I find that scenario doesnt happen on enough days to be worth an automated solution- ultimately there are so few amps on offer in those periods it doesnt make a massive difference to your batteries- you are mostly relying on the engine/genny anyway. 

 

But yes, come late March it becomes irrelevant anyway- in my case with 1.4kw of panels, you have to start switching off the panels in mid afternoon as the batteries are already full by then. But it does depend how much solar you have. 

Even despite the snow and cloud today, I've had 950 Wh of solar so far.

I got my panels in autumn 2020 before the prices went up, but its still worth getting- of all the changes I've made, the extra solar panels is the only thing that will more than pay for itself with the next year or two, in terms of saving on diesel etc.

You gotta love solar panels! 

 

 

 

 

Screenshot_20230308_142559.jpg

Edited by Tony1
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1 hour ago, Tony1 said:

 

I can totally understand not wanting to waste the limited solar power that we get in the winter, but I suspect a complex charge controller device might not pay for itself.

What happens in reality is that the solar never actually gets your batteries up to 90% anyway during the poor months (or not often). 

In Dec and Jan the panels spend the limited daylight hours putting in a few amps, and quite often not even keeping up with what your fridge and laptop are using, so overall the batteries are usually discharging all the time, until you start running the engine.

 

Where its more of a thing to consider is in say late Feb, or early Nov, when there is some half decent solar. 

But all you have to do is manually adjust your upper SoC limit from 80 or 85% up to say 90 or 95%, so the panels wont get switched off by the BMV712.

I find that scenario doesnt happen on enough days to be worth an automated solution- ultimately there are so few amps on offer in those periods it doesnt make a massive difference to your batteries- you are mostly relying on the engine/genny anyway. 

 

But yes, come late March it becomes irrelevant anyway- in my case with 1.4kw of panels, you have to start switching off the panels in mid afternoon as the batteries are already full by then. But it does depend how much solar you have. 

Even despite the snow and cloud today, I've had 950 Wh of solar so far.

I got my panels in autumn 2020 before the prices went up, but its still worth getting- of all the changes I've made, the extra solar panels is the only thing that will more than pay for itself with the next year or two, in terms of saving on diesel etc.

You gotta love solar panels! 

 

 

 

 

 

 

That all makes good sense. I've only had the boat for a few months and spent the winter in a marina, so this is my first week off-grid with the lithium bank. Hence the micro managing. I think I'm about ready to just "set and forget" it. It'll be interesting to see how things improve over the next month or so.

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25 minutes ago, 170968 said:

 

That all makes good sense. I've only had the boat for a few months and spent the winter in a marina, so this is my first week off-grid with the lithium bank. Hence the micro managing. I think I'm about ready to just "set and forget" it. It'll be interesting to see how things improve over the next month or so.

 

I thought I would set and forget two years ago, and I'm still fiddling around with the settings almost daily, although as you say that wont be the case in summer.

There comes a time in Spring or summer where there is so much solar power that you can set it and forget about electricity until October, but I still find myself checking the voltage and SoC on my phone app at least every hour, just out of habit! 

How early in the year the solar will supply all your daily power does depend on how many panels you have, as you'll know. In my case its been supplying 60-70% of what I need since mid Feb. Even today, in the snow and drizzle, I've had 1140Wh (and counting), although I wont get much more now. 

So I'm almost self sufficient for electricity already, even on the poor days- but the price of that is having your roof covered in panels.

 

In case you haven't considered it, I would have a look at using solar to heat the immersion and thus get hot water in the summer. If you only cruise one day per week or so, the solar hot water can be a real bonus, as it saves you running the engine for hot water, and less engine hours means less diesel etc. And you really need some hot water to shower on those awful sweaty summer days. 

 

I know its childish but I still get a surprise when I look at the MPPTs on a summer day giving 45-48 amps each for most of the day.   

If I had any space I'd get an aircon unit tbh, there's certainly enough solar power to run one in the oppressively hot days of June-August. 

 

 

Edited by Tony1
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On 08/03/2023 at 16:08, Tony1 said:

 

I thought I would set and forget two years ago, and I'm still fiddling around with the settings almost daily...

 

Nice sunny day. Getting lots of free power.

 

Would you (or anyone else) mind sharing your settings for absorbtion voltage and length? I am trying to achieve 85% with a lowish voltage setting. I tried it at 13.6v absorbtion and for only 15 minutes. It went into float whilst the SOC is down at 81%, so that's no good. Should I leave the voltage and increase the absorbtion time so that it stays at 13.6V while getting to 85%, or what do you suggest?

 

 

On 08/03/2023 at 16:08, Tony1 said:

 

I thought I would set and forget two years ago, and I'm still fiddling around with the settings almost daily, although as you say that wont be the case in summer.

There comes a time in Spring or summer where there is so much solar power that you can set it and forget about electricity until October, but I still find myself checking the voltage and SoC on my phone app at least every hour, just out of habit! 

How early in the year the solar will supply all your daily power does depend on how many panels you have, as you'll know. In my case its been supplying 60-70% of what I need since mid Feb. Even today, in the snow and drizzle, I've had 1140Wh (and counting), although I wont get much more now. 

So I'm almost self sufficient for electricity already, even on the poor days- but the price of that is having your roof covered in panels.

 

In case you haven't considered it, I would have a look at using solar to heat the immersion and thus get hot water in the summer. If you only cruise one day per week or so, the solar hot water can be a real bonus, as it saves you running the engine for hot water, and less engine hours means less diesel etc. And you really need some hot water to shower on those awful sweaty summer days. 

 

I know its childish but I still get a surprise when I look at the MPPTs on a summer day giving 45-48 amps each for most of the day.   

If I had any space I'd get an aircon unit tbh, there's certainly enough solar power to run one in the oppressively hot days of June-August. 

 

 

 

I have thought about using the excess to heat water, but not an air-conditioner. It's a great idea and I do have space. Only thing I don't like is the amount of noise the bloody things make.

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