Best alternator setup with lithiums?

[Tony1]

 

 

I'm sure its not essential but what I do is to start off with a lower draw (say 25-30amps) when the engine is cold, and keep it at tickover for say 10 mins.

So I'm not drawing a big current when the revs are still low.

Then when its all warmed up I switch on the other B2B and draw the full power, and at the same time I rev it up to 1300rpm to help keep the alternator cool. 

I'd be a tad uneasy about drawing the full 60 amps from my canaline 38 when the engine is at tickover revs, but then I also dont want to rev it up to 1300rpm as soon I switch it on, so I use this stepped approach. 

Its only a V belt, not a poly V, so I dont think high current at low revs (and with a cold engine) would be very good for it. 

 

Edited September 27, 2023 by Tony1

[Jen-in-Wellies]

1 minute ago, Tony1 said:

I'm sure its not essential but what I do is to start off with a lower draw (say 25-30amps) when the engine is cold, and keep it at tickover for say 10 mins.

So I'm not drawing a big current when the revs are still low.

Then when its all warmed up I switch on the other B2B and draw the full power, and at the same time I rev it up to 1300rpm to help keep the alternator cool. 

I'd be a tad uneasy about drawing the full 60 amps from my canaline 38 when the engine is at tickover revs, but then I also dont want to rev it up to 1300rpm as soon I switch it on, so I use this stepped approach. 

Its only a V belt, not a poly V, so I dont think high current at low revs would be very good for it. 

 

How do you switch in the second B2B? Just a suitably rated switch in the +ve wire in?

[nicknorman]

As you know my alternator controller limits maximum field current to maintain an acceptable alternator temperature (90C in my case). This obviously is an effective but complex solution.

But it has often occured to me that it would be quite simple (relatively simple!) to limit maximum field current by inserting a resistor in the field winding circuit, ie between the regulator and the rotor brush. Typical rotor resistance seems to be around 3 or 4 ohms, and max field current around 4 amps so adding say a 3 ohm resistor in series would reduce the maximum field current by around 1/2 to give around 2.5A max field current and a dissipation of 19 watts (so a decent high power wire wound resistor would be needed, maybe bolted to some steelwork acting as a heatsink).

Yes you would need to open up the alternator and intercept the connection between regulator and brush, but that shouldn't be too difficult to someone with basic competence on electromechanical things.

It would have some effect on the voltage profile, but it would reduce it somewhat which is probably not a bad thing.

2 minutes ago, Jen-in-Wellies said:

How do you switch in the second B2B? Just a suitably rated switch in the +ve wire in?

Usually they have a control input that is designed to be connected to an ignition switch, so you just supply (very low current) 12v to the control input to turn it on.

 

The bad thing about B2Bs is that they seem to be hideously inefficient (get very hot)

Edited September 27, 2023 by nicknorman

[Tony1]

30 minutes ago, Jen-in-Wellies said:

How do you switch in the second B2B? Just a suitably rated switch in the +ve wire in?

 

Mine are both victron and can be switched on and off by bluetooth, which is handy.

I leave the lower power 18 amp B2B permanently 'active', so it comes on as soon as the engine starts and the input voltage goes above the B2Bs trigger value (I think I use 13.3v). 

The 30 amp unit is left switched off after every charge, so what I do with that is just switch it on via bluetooth after a 10 minute warm up for the engine, and I up the revs a bit. 

If I'm cruising the boat and therefore I cant cant guarantee being able to keep the revs up at 1300 rpm, I will only use the 30 amp unit, and I'll  switch the 18 amp unit off. Thats the setup for the domestic alternator. 

 

I also use a further 30 amp victron B2B connected my starter alternator, so there is the option to get a bit more charge - again once the engine has warmed up a bit. 

So at full chat, I can get 30+30+18 amps, which means I can usually charge in a hour or so, if I get a bit of solar added in. 

When I was using the sterling units I could draw up to 90 amps when doing a static 1300rpm charge, but I realised it wasn't a great idea to push both the alternators (and their V belts) that hard, so I backed off a bit and settled on 75 amps. 

 

 

Edited September 27, 2023 by Tony1

[Jen-in-Wellies]

What about a resettable thermal fuse attached to the alternator case, to disable the second B2B if the alternator is getting a bit hot and flustered?

https://uk.rs-online.com/web/p/thermal-fuses/1769097?gb=b

What would be a suitable alternator case temperature limit to avoid overheating the active electrical bits? A Victron video, where they abuse an alternator by dumping huge currents in to a Lithium battery suggests around 50C for the case perhaps.

 

[Tony1]

Just a thought on the bilge blower/fan cooling idea:

I was looking at fans that might do this, but I was concerned that the power they would use in blowing air over the alternator would have to be offset against how much extra current they would allow the alternator to give out.

After trying this out (on a freezing january day and thus using very cold air) I found that with my cheapo alternators, a cooling fan only allows them to safely give out maybe an additional 10 amps, at most. And the fan itself would probably draw 5 amps, so the benefit from such fans might not be as much as you would hope. 

A fan could be a help if your B2B is drawing say 5 amps too much for the alternator to stay cool, but if the alternator internals are putting out that kind of heat, maybe your fan is only cooling the outer parts of it, and perhaps some innards are still too hot? 

And there is the question around what temp actually constitutes overheating that might damage an alternator.

I've seen some people suggest 150 degrees is ok, but given that my alternators normally run at about 50-55 degrees, I decided I didnt want them to go over 100 degrees, so that's how I personally decided on the 'safe' current limits, and that's how I selected the right B2Bs to match them.

 

20 minutes ago, Jen-in-Wellies said:

What about a resettable thermal fuse attached to the alternator case, to disable the second B2B if the alternator is getting a bit hot and flustered?

https://uk.rs-online.com/web/p/thermal-fuses/1769097?gb=b

What would be a suitable alternator case temperature limit to avoid overheating the active electrical bits? A Victron video, where they abuse an alternator by dumping huge currents in to a Lithium battery suggests around 50C for the case perhaps.

 

 

To be honest, having used these kind of setups for a few years, I think the simpler approach is to select B2Bs of the right size so the alternator never gets too hot. Too hot in my case is over 100 degrees, but that's an individual think. Nick says he uses 90 degrees, which is probably wiser. 

 

They behave very predictably in practice. In other words, if I switch on both my 30 amp and 18 amp B2Bs and the engine is only idling, the alternator will always go above 100 degrees within 10 minutes or less. 

So in my case I could just leave both B2Bs permanently in the active state (so they both come on when the snegine starts), but as soon as I got to a lock say,  and went into tickover, the alternator will get too hot within minutes, and so I'd be resetting that fuse several times a day. 

I do know those B2Bs have a small wire input that does allow them to be remotely switched on and off, and I used that function to switch off the B2Bs when the SoC got to 85%, using the relay function on a BMV712. 

The BMV712 also monitors temp, so in theory I think you could put a victron temp probe on the alternator, attach it to a BMV712, and then you can configure it to send a 12v signal that will switch off one or both of the B2Bs when the alternator gets too hot. 

 

But a BMV costs around £150, so if budget is an issue that's not ideal....

I would ask whether automation is really needed, or you could just manage the B2B manually, but maybe stick a temp probe on the alternator as fall back warning?

 

 

Edited September 27, 2023 by Tony1

[nicknorman]

15 minutes ago, Jen-in-Wellies said:

What about a resettable thermal fuse attached to the alternator case, to disable the second B2B if the alternator is getting a bit hot and flustered?

https://uk.rs-online.com/web/p/thermal-fuses/1769097?gb=b

What would be a suitable alternator case temperature limit to avoid overheating the active electrical bits? A Victron video, where they abuse an alternator by dumping huge currents in to a Lithium battery suggests around 50C for the case perhaps.

 

I would say 50C is far too cool. Engine bay may easily be say 35C and the alternator is bolted onto a hot engine. One problem is that it depends which bit of the alternator you are going to measure. Case, windings, diodes, regulator are all at different temperatures. Our alternator is a double fan version and I decided to position the temperature sensor in the airflow on the outlet from the diode area, since the diodes and regulator are probably the most likely things to suffer from high temperatures. I limit at 90C as I mentioned.
Alternators do run very hot, the Iskra alternator we have quotes a maximum ambient temperature of 110c . That is ambient temperature, the alternator temperature will of course be a lot more!

 

 

[Jen-in-Wellies]

The thermostats I have in mind should reset themselves, so no manual resets required. Would put my mind at rest, knowing that disabling one of the B2B's, would allow the alternator to cool without intervention. 90, or 100C maximum case temperature sounds more like it.

[Tony1]

1 hour ago, Jen-in-Wellies said:

The thermostats I have in mind should reset themselves, so no manual resets required. Would put my mind at rest, knowing that disabling one of the B2B's, would allow the alternator to cool without intervention. 90, or 100C maximum case temperature sounds more like it.

 

If you do go down the 'twin B2B' route, I think part of the testing phase will be to establish what rpm is needed for the optimum cooling.

It might be 1300rpm like mine, or maybe a bit more, or even less.

I found that my alternator doesn't cool very well even at 1200rpm- it seems that 1300rpm is needed to keep the  alternator temp down when I am drawing more than 35 amps from it. 

So you'll find that if you go above a certain current output from the alternator, no amount of rpm will keep it cool. And tbh you dont want to be running the engine at high rpm in neutral anyway, I would guess. 

So you need to find out how much the alternator can safely put out when it has some rpm to cool it (maybe 1200-1300rpm). That will be for the static charging during winter, when you're moored and you know the rpm (and the cooling) will be maintained.

The second thing you need to find out is how much the alternator can safely put out when at tickover rpm. 

In my case, when at tickover, my 100 amp cheapo domestic alternator can put out about 35 amps whilst staying below 100 degrees. If I up the output even by 5 amps, the temp goes up to about 115 or 120 degrees, which I wasnt happy with.

So if your friend's 110 amp alternator is of a similar type or quality to mine, the reality is that it might not give out more than 40 amps anyway. Maybe even a bit lower. 

 

I can see why you would want to keep both B2Bs switched on as the default, and rely on the thermostat to manage switching them on and off. I wouldn't mind a bit more automation in my B2B management tbh.

And as I said, most B2Bs do have inputs for a remote BMS control wire, and a 12v signal into that port will switch them on and off. 

 

If you do take that approach, I think you will still need one of the B2Bs to able to run at tickover without overheating the alternator, otherwise it will be switching on and off all day if you go cruising. Really, you want one B2B that you know will carry on charging as you cruise with no complications. And tbh the current 30 amp victron might be just about right for that role. My 100 amp alternator will run a 30 amp victron B2B all day long with no overheating.

The way I see it working when out on a cruise is this: You start the engine in the morning, and both B2Bs fire up, so you're drawing maybe 50 amps total, and the engine is warming up at tickover (and remember, its not ideal to work an alternator hard at tickover rpm.

Within 10 minutes the 50 amp draw will cause the alternator to go above 100 degrees, and the second B2B will be automatically switched off. 

It will probably take 20 mins to get back below 100 degrees, at which point it gets automatically switched on again.

Now if you are keeping up enough revs to keep it cool (say 1300), then you'll have no problems and you'll get the full 50 amps. But if you stop and tie up the boat at a lock landing, say, then the boat is at tickover and before you've even prepared the lock, the alternator has gone over temp again and the second B2B is switched off. 

Or lets say you go past one of those lines of moored boats about a mile long. The alternator will be constantly held at around 100 degrees the whole time, because as soon as it goes below 100 the second B2B will switch back on, the current output will increase, and a few minutes later the alternator is over temp again. 

And so over most of the day, even out cruising, the second B2B will probably spend most of its time switched off anyway, because the alternator is going over temp (because the revs are not going high enough to cool the alternator).

If you were to set the temp threshold at say 80 or 90 degrees that would be better- but if its at 100 degrees, you are repeatedly pushing that alternator over a comfortable operating temp, and they do take a while to cool down again. Personally, I dont know if I'd want my alternator spending a significant part of the day around 100 degrees. 

If its a cruising day, then you're probably going to get 4 or 5 hours of charge done anyway, so a 30 amp B2B isn't so bad in that context. You'll have gotten around 130 Ah of charge by the time you moor up. 

I can see pros and cons in the automation, but in this scenario, I think maybe on the whole my preference would be to only use the 30 amp B2B when out cruising, and it'll have the benefit of keeping the average temp of the alternator down. 

For me, the second B2B would only be used for static charging- or maybe when I know I'll be able to keep up the revs when cruising- which I find I usually cant do unless I'm on a river.  

 

ETA- if your friend has a second alternator, a better alternative would be to hook that one up to a 30 amp B2B as well, so even at tickover you get 60 amps of charge. 

An older lead acid battery will do the job for these things, it doesnt need a new one. 

Edited September 27, 2023 by Tony1

[nicknorman]

13 minutes ago, Tony1 said:

 

If you do go down the 'twin B2B' route, I think part of the testing phase will be to establish what rpm is needed for the optimum cooling.

It might be 1300rpm like mine, or maybe a bit more, or even less.

I found that my alternator doesn't cool very well even at 1200rpm- it seems that 1300rpm is needed to keep the  alternator temp down when I am drawing more than 35 amps from it. 

So you'll find that if you go above a certain current output from the alternator, no amount of rpm will keep it cool. And tbh you dont want to be running the engine at high rpm in neutral anyway, I would guess. 

So you need to find out how much the alternator can safely put out when it has some rpm to cool it (maybe 1200-1300rpm). That will be for the static charging during winter, when you're moored and you know the rpm (and the cooling) will be maintained.

The second thing you need to find out is how much the alternator can safely put out when at tickover rpm. 

In my case, when at tickover, my 100 amp cheapo domestic alternator can put out about 35 amps whilst staying below 100 degrees. If I up the output even by 5 amps, the temp goes up to about 115 or 120 degrees, which I wasnt happy with.

So if your friend's 110 amp alternator is of a similar type or quality to mine, the reality is that it might not give out more than 40 amps anyway. Maybe even a bit lower. 

 

I can see why you would want to keep both B2Bs switched on as the default, and rely on the thermostat to manage switching them on and off. I wouldn't mind a bit more automation in my B2B management tbh.

And as I said, most B2Bs do have inputs for a remote BMS control wire, and a 12v signal into that port will switch them on and off. 

 

If you do take that approach, I think you will still need one of the B2Bs to able to run at tickover without overheating the alternator, otherwise it will be switching on and off all day if you go cruising. Really, you want one B2B that you know will carry on charging as you cruise with no complications. And tbh the current 30 amp victron might be just about right for that role. My 100 amp alternator will run a 30 amp victron B2B all day long with no overheating.

The way I see it working when out on a cruise is this: You start the engine in the morning, and both B2Bs fire up, so you're drawing maybe 50 amps total, and the engine is warming up at tickover (and remember, its not ideal to work an alternator hard at tickover rpm.

Within 10 minutes the 50 amp draw will cause the alternator to go above 100 degrees, and the second B2B will be automatically switched off. 

It will probably take 20 mins to get back below 100 degrees, at which point it gets automatically switched on again.

Now if you are keeping up enough revs to keep it cool (say 1300), then you'll have no problems and you'll get the full 50 amps. But if you stop and tie up the boat at a lock landing, say, then the boat is at tickover and before you've even prepared the lock, the alternator has gone over temp again and the second B2B is switched off. 

Or lets say you go past one of those lines of moored boats about a mile long. The alternator will be constantly held at around 100 degrees the whole time, because as soon as it goes below 100 the second B2B will switch back on, the current output will increase, and a few minutes later the alternator is over temp again. 

And so over most of the day, even out cruising, the second B2B will probably spend most of its time switched off anyway, because the alternator is going over temp (because the revs are not going high enough to cool the alternator).

If you were to set the temp threshold at say 80 or 90 degrees that would be better- but if its at 100 degrees, you are repeatedly pushing that alternator over a comfortable operating temp, and they do take a while to cool down again. Personally, I dont know if I'd want my alternator spending a significant part of the day around 100 degrees. 

If its a cruising day, then you're probably going to get 4 or 5 hours of charge done anyway, so a 30 amp B2B isn't so bad in that context. You'll have gotten around 130 Ah of charge by the time you moor up. 

I can see pros and cons in the automation, but in this scenario, I think maybe on the whole my preference would be to only use the 30 amp B2B when out cruising, and it'll have the benefit of keeping the average temp of the alternator down. 

For me, the second B2B would only be used for static charging- or maybe when I know I'll be able to keep up the revs when cruising- which I find I usually cant do unless I'm on a river.  

 

 

I don't think 100C is particularly hot for an alternator (depending on which bit of it we are talking about). Diodes are rated up to around 170C, although that is the junction temperature, the case temperature would have to be a fair bit less but let's say 150C is probably the max limit. Of course the alternator is designed to take in air and first pass it through the diodes and regulator, before going on to the windings. So even if the air outlet and case temperature might be well over 100, the electronic bits will be a lot cooler. 100C is only a trigger point if you are made of water, which the electronics aren't!

 

While I am on can I mention that I think your approach to starting the engine from cold isn't what I would do. A cold diesel engine is best warmed up at an rpm above idle to hasten the warming process, and I think that to more or less go straight to 1300rpm is kinder to the engine than letting it idle for a while. If you look at the starting instructions for these engines, it typically says to set the throttle quite a bit open and I doubt it says to revert to idle as soon as it fires up.

Edited September 27, 2023 by nicknorman

[Tony1]

42 minutes ago, nicknorman said:

While I am on can I mention that I think your approach to starting the engine from cold isn't what I would do. A cold diesel engine is best warmed up at an rpm above idle to hasten the warming process, and I think that to more or less go straight to 1300rpm is kinder to the engine than letting it idle for a while. If you look at the starting instructions for these engines, it typically says to set the throttle quite a bit open and I doubt it says to revert to idle as soon as it fires up.

 

Cheers Nick, yes I do recall puzzling over why they would want you to start putting revs on any engine as you start it up.

I've always had a sort of instinctive (but incorrect) feeling that it was best to let a boat engine spend ten minutes warming up at tickover revs before going any higher.

Thanks for the advice. 

 

[Sea Dog]

1 hour ago, Tony1 said:

 

Cheers Nick, yes I do recall puzzling over why they would want you to start putting revs on any engine as you start it up.

I've always had a sort of instinctive (but incorrect) feeling that it was best to let a boat engine spend ten minutes warming up at tickover revs before going any higher.

Thanks for the advice. 

 

Plus, on first start up it's likely your alternator(s) will be presenting quite a load as the depleted batteries draw their heaviest current of the charging cycle. Mine typically starts first thing with a draw of around 100 amps. Whilst this drops away fairly quickly with lead acids, a few revs is needed to cope comfortably with that initial heavy load.

[peterboat]

2 hours ago, nicknorman said:

 

I don't think 100C is particularly hot for an alternator (depending on which bit of it we are talking about). Diodes are rated up to around 170C, although that is the junction temperature, the case temperature would have to be a fair bit less but let's say 150C is probably the max limit. Of course the alternator is designed to take in air and first pass it through the diodes and regulator, before going on to the windings. So even if the air outlet and case temperature might be well over 100, the electronic bits will be a lot cooler. 100C is only a trigger point if you are made of water, which the electronics aren't!

 

While I am on can I mention that I think your approach to starting the engine from cold isn't what I would do. A cold diesel engine is best warmed up at an rpm above idle to hasten the warming process, and I think that to more or less go straight to 1300rpm is kinder to the engine than letting it idle for a while. If you look at the starting instructions for these engines, it typically says to set the throttle quite a bit open and I doubt it says to revert to idle as soon as it fires up.

My engine used to have fast idle when it was cold, which nicely took care of warming up. However I wouldn't advise over revving a cold engine as oil is thick, as whilst oil pressure is good, flow is non existent! So a sudden bang is a possibility?

[nicknorman]

48 minutes ago, peterboat said:

My engine used to have fast idle when it was cold, which nicely took care of warming up. However I wouldn't advise over revving a cold engine as oil is thick, as whilst oil pressure is good, flow is non existent! So a sudden bang is a possibility?

Yes however there are a couple of considerations, one being that modern multigrade oils are not that thick when cold. But mainly, 1300rpm out of a max of 2700 or so is not particularly fast.

[MtB]

1 hour ago, Sea Dog said:

Plus, on first start up it's likely your alternator(s) will be presenting quite a load as the depleted batteries draw their heaviest current of the charging cycle. Mine typically starts first thing with a draw of around 100 amps. Whilst this drops away fairly quickly with lead acids, a few revs is needed to cope comfortably with that initial heavy load.

 

Yes when I first started the K1, it wouldn't rev any higher than about 200rpm for the first minute or so due to this effect! 

 

After ten minutes though, one could rev the nuts off it up to about 500rpm...

[TheBiscuits]

On 23/09/2022 at 12:51, nicknorman said:

My bad, the Renology DC DC is 60A not 120A, so that will be fine with the 2x 80A alternators and at £170 is much better value than the Sterling … IF it does what it says on the tin. (No reason to suspect it doesn’t).

 

Importantly, the Sterling 60A B2B takes max 60A from the alternator/start battery, delivering around 45A to the domestic bank (or 30A/23A at half power) 

 

The Renogy 60A takes around 90A from the starter/alternator, delivering 60A to the domestics (or 45A/30A at half power) 

 

All figures are taken from the relevant manufacturers manuals, and there's a reason I opted for the Sterling version ...

 

 

 

 

[Tony1]

9 hours ago, nicknorman said:

Yes however there are a couple of considerations, one being that modern multigrade oils are not that thick when cold. But mainly, 1300rpm out of a max of 2700 or so is not particularly fast.

 

The Canaline UK distributor (engines plus) recommend 15w-40 mineral oil (API CC), and I recall someone saying that is quite a thick oil, an 'old fashioned' kind of oil.

That said, the manual does say that when starting up, the throttle should be pushed forward (I think they even specify an approximate angle)- so it seems maybe they aren't overly concerned about the oil thickness when cold. 

I think their instructions result in about 1100rpm at start up, which does feel like plenty for the rather agricultural canaline 38.. 

[peterboat]

On 27/09/2023 at 22:50, nicknorman said:

Yes however there are a couple of considerations, one being that modern multigrade oils are not that thick when cold. But mainly, 1300rpm out of a max of 2700 or so is not particularly fast.

Most boats are still running on 15/40 which isnt thin, I put 5/30 in mine fully synthetic as it's what we used at work.

[Jen-in-Wellies]

On 27/09/2023 at 18:23, Jen-in-Wellies said:

The thermostats I have in mind should reset themselves, so no manual resets required. Would put my mind at rest, knowing that disabling one of the B2B's, would allow the alternator to cool without intervention. 90, or 100C maximum case temperature sounds more like it.

An update. We fitted a second Victron 30A batt2batt charger in the end. The second batt2batt can be disabled  with a toggle switch by the steerers position and also by a thermostat, attached to the alternator that opens at 100C and closes again at 85C. Some thermal grease improves contact to the alternator case. The idea being that the second batt2batt can be manually switched off when the engine is idling, or automagically, if it is causing the alternator to overheat.

When first switched on at around 1300rpm engine speed, we got a lot of belt squeal, but the alternator drive belt was very badly worn. With a new drive belt, all is well. So far, the thermostat hasn't tripped, to our knowledge, while monitoring the batt2batt status with the Victron phone app. You notice the extra load on the engine when the second batt2batt is switched in and anecdotally, the engine room seems hotter with both batt2batts doing their thing.

Thanks every one for your thoughts and experiences.

[Tony1]

2 hours ago, Jen-in-Wellies said:

An update. We fitted a second Victron 30A batt2batt charger in the end. The second batt2batt can be disabled  with a toggle switch by the steerers position and also by a thermostat, attached to the alternator that opens at 100C and closes again at 85C. Some thermal grease improves contact to the alternator case. The idea being that the second batt2batt can be manually switched off when the engine is idling, or automagically, if it is causing the alternator to overheat.

When first switched on at around 1300rpm engine speed, we got a lot of belt squeal, but the alternator drive belt was very badly worn. With a new drive belt, all is well. So far, the thermostat hasn't tripped, to our knowledge, while monitoring the batt2batt status with the Victron phone app. You notice the extra load on the engine when the second batt2batt is switched in and anecdotally, the engine room seems hotter with both batt2batts doing their thing.

Thanks every one for your thoughts and experiences.

 

I love that thermostat with the 100-85 degree range, I'm going to give some thought to incorporating that into my B2B setup- maybe even one of them on each alternator.

I think that will be a really good additional safeguard to protect the alternators.

I'm guessing the thermostat gives a 12v signal down a small wire, into the BMS port of the B2B?

 

So would this one work in the same way, do you think?

https://uk.rs-online.com/web/p/thermostatic-switches/2532773

I like the idea of allowing the alternator to cool down a bit lower than 85 degrees- maybe even down to its normal operating temp of 55 degrees- before it starts working hard again.

That might work better at keeping the alternator closer to its normal operating temp for more of the time, e.g. if I'm in tickover for 20 minutes near a lock or something. 

 

 

 

 

 

If I'm out cruising I could use that to control my third B2B switching on and off, rather than me do it manually.

My normal cold start routine is to only have one B2B in an ON state by default. My thinking is to give the engine a few minutes at a normal tickover 

I have one of those 30A B2Bs on each alternator, and my new plan is set a delay 

 

[Jen-in-Wellies]

42 minutes ago, Tony1 said:

 

I love that thermostat with the 100-85 degree range, I'm going to give some thought to incorporating that into my B2B setup- maybe even one of them on each alternator.

I think that will be a really good additional safeguard to protect the alternators.

I'm guessing the thermostat gives a 12v signal down a small wire, into the BMS port of the B2B?

 

So would this one work in the same way, do you think?

https://uk.rs-online.com/web/p/thermostatic-switches/2532773

I like the idea of allowing the alternator to cool down a bit lower than 85 degrees- maybe even down to its normal operating temp of 55 degrees- before it starts working hard again.

That might work better at keeping the alternator closer to its normal operating temp for more of the time, e.g. if I'm in tickover for 20 minutes near a lock or something. 

 

 

 

 

 

If I'm out cruising I could use that to control my third B2B switching on and off, rather than me do it manually.

My normal cold start routine is to only have one B2B in an ON state by default. My thinking is to give the engine a few minutes at a normal tickover 

I have one of those 30A B2Bs on each alternator, and my new plan is set a delay 

 

The Victron B2B's have a two pin socket and green plug on them for remote control that comes with a small loop of wire. See video below. Connect the two pins together enables the B2B, as default. Connecting either one pin to +12V, or the other pin to ground will also enable the B2B,  so there are a variety of options available. In this case, we replaced the short loop with an 8m long one of 0.5mm2 wire from one pin to the other, with a toggle switch and the thermostat in series, breaking the loop. If either the toggle switch is off, or the thermostat goes over 100C, the B2B is disabled.

The thermostat you linked to looks like it should work. It isn't as robust as the one I used, which takes standard 1/4" blade connectors, so you'd need to look at some strain relief on the wires going to the pins and have some heat shrink sleeving on them too.

 

[Tony1]

28 minutes ago, Jen-in-Wellies said:

The Victron B2B's have a two pin socket and green plug on them for remote control that comes with a small loop of wire. See video below. Connect the two pins together enables the B2B, as default. Connecting either one pin to +12V, or the other pin to ground will also enable the B2B,  so there are a variety of options available. In this case, we replaced the short loop with an 8m long one of 0.5mm2 wire from one pin to the other, with a toggle switch and the thermostat in series, breaking the loop. If either the toggle switch is off, or the thermostat goes over 100C, the B2B is disabled.

The thermostat you linked to looks like it should work. It isn't as robust as the one I used, which takes standard 1/4" blade connectors, so you'd need to look at some strain relief on the wires going to the pins and have some heat shrink sleeving on them too.

 

 

Fab, thanks Jen. 

I have used this port before for switching the B2Bs on and off, but I used a one-way length of cable running from a victron BMV712 to send a +12v signal into one of those two sockets- I cant remember which one, but it was the second control method you described above.

But your method is very simple and very cheap, and would give me a great fallback safety mechanism for the domestic alternator. 

 

I recall when I did my temp testing, I measured the hottest point on the alternator.

But if the fittings force me to attach the thermostat to a slightly cooler position on the alternator, I may actually look at using 90 degrees as the high temp 'trigger' point to switch off the B2B. 

 

 

 

 

 

 

5 hours ago, Jen-in-Wellies said:

An update. We fitted a second Victron 30A batt2batt charger in the end. The second batt2batt can be disabled  with a toggle switch by the steerers position and also by a thermostat, attached to the alternator that opens at 100C and closes again at 85C. Some thermal grease improves contact to the alternator case. The idea being that the second batt2batt can be manually switched off when the engine is idling, or automagically, if it is causing the alternator to overheat.

When first switched on at around 1300rpm engine speed, we got a lot of belt squeal, but the alternator drive belt was very badly worn. With a new drive belt, all is well. So far, the thermostat hasn't tripped, to our knowledge, while monitoring the batt2batt status with the Victron phone app. You notice the extra load on the engine when the second batt2batt is switched in and anecdotally, the engine room seems hotter with both batt2batts doing their thing.

Thanks every one for your thoughts and experiences.

 

Just another thought- this same sort of idea could presumably be used to disable the B2Bs when the temp is too low to safely charge the lithiums, as long as you can find a thermostat that opens at say 0 degrees, and closes at +1 degrees (for example). 

I made the mistake of moving the batteries into the engine bay to minimise criticism during my impending BSS inspection.

But the BSS inspector thought the engine bay was a less safe location than indoors, so at some point my prodigal sheep will be coming back into the fold, if I can muster the required motivation. 

 

 

[nicknorman]

All very good but sorry I’m going to be an a…hole and say that all this is beating around the problem. The solution is proper alternator /charge control.
We have been pootling around Tamworth this last few days, not really cruising because Jeff has a deadline to meet on his OU MA and has been glued to his Mac. So unusually, we are charging the battery whilst tied up. This is a screenshot from today.

 

 

An hour 45 to fully charged. Not that we need to fully charge. Standing by to receive incoming hate…

Edited November 3, 2023 by nicknorman

[Jen-in-Wellies]

7 minutes ago, nicknorman said:

All very good but sorry I’m going to be an a…hole and say that all this is beating around the problem. The solution is proper alternator /charge control.

A proper alternator charge controller is nice. We looked in to it, but didn't have the budget for Wakespeed. The first BMS was already there, so adding a second was the cheaper solution. Still a step up in sophistication from a resistive charging wire.

[nicknorman]

2 minutes ago, Jen-in-Wellies said:

A proper alternator charge controller is nice. We looked in to it, but didn't have the budget for Wakespeed. The first BMS was already there, so adding a second was the cheaper solution, but still a step up in sophistication from a resistive charging wire.

As an engineer I think I am morally offended by B2Bs because they are so horrendously inefficient. But just ignore me!