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Cheap LiFePO4 BMS?


jetzi

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17 minutes ago, redwing said:

Dr Bob has two B2Bs in parallel I think. His wiring diag. is somewhere back in this thread.

 

(Nick, do you know how Bob is doing ?)

Yes, I found it. It just shows the 2 B2Bs in parallel for both inputs and outputs with an isolator to allow one to be disconnected (to avoid overloading the alternators I think). No not heard from him. It does seem odd that such a prolific poster should suddenly cease. Something about Li battery safety upset him IIRC, but I think there must have been more to it than met the eye.

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1 minute ago, nicknorman said:

Yes, I found it. It just shows the 2 B2Bs in parallel for both inputs and outputs with an isolator to allow one to be disconnected (to avoid overloading the alternators I think). No not heard from him. It does seem odd that such a prolific poster should suddenly cease. Something about Li battery safety upset him IIRC, but I think there must have been more to it than met the eye.

 

I unwittingly helped him through a lock back in the summer July I think. I only found out it was Dr Bob an hour later, from another member here. His Bobbiness didn't know it was me, either! 

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10 minutes ago, nicknorman said:

Yes, I found it. It just shows the 2 B2Bs in parallel for both inputs and outputs with an isolator to allow one to be disconnected (to avoid overloading the alternators I think). No not heard from him. It does seem odd that such a prolific poster should suddenly cease. Something about Li battery safety upset him IIRC, but I think there must have been more to it than met the eye.

It was the shits that did for him istr 

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3 minutes ago, MtB said:

Yes I too thought it was something to do with the separating toilet he fitted in his new boat, and the torrent of criticism they get on here.

Ah yes I'd forgotten about that. Dog poo in bins actually. However it seems a bit odd to permanently leave the forum as a result of just one thread, in which participation is not mandatory.

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2 hours ago, nicknorman said:

Take 2 wires from each of battery positive and negative, one to each B2B. 

 

OK.... so splitting the existing positive should not cause a problem, in the sense that 2 separate wires are not really different to one wire being split in half...

 

Subject to the split wire being OK to carry the current produced for 2 B2Bs, and all that :) 

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48 minutes ago, redwing said:

Tony, on the Marinehowto site they suggest you might overheat your alternator doing what you intend. I don't know how right they are.

 

https://marinehowto.com/understanding-the-sterling-power-pro-batt-ultra-battery-to-battery-charger/

 

 

I think he simply says that your "charge sources" should be 30% larger, (he actually suggests that an alternator should be double the size of the B2B, earlier in the article), than your total B2B "size.

 

i.e. for paralleled 60A B2Bs, the alternator should be 240A, or paralleled 30A B2Bs the alternator should be 120A.

 

I have a Victron 30A B2B charging my Lithiums, and I believe my alternator is 55A. Having said that, I've never seen more than about 34A into my LA bank from it.

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4 minutes ago, Richard10002 said:

 

I think he simply says that your "charge sources" should be 30% larger, (he actually suggests that an alternator should be double the size of the B2B, earlier in the article), than your total B2B "size.

 

i.e. for paralleled 60A B2Bs, the alternator should be 240A, or paralleled 30A B2Bs the alternator should be 120A.

 

I have a Victron 30A B2B charging my Lithiums, and I believe my alternator is 55A. Having said that, I've never seen more than about 34A into my LA bank from it.

I'm not sure he is recommending that much, but I think Tony wants to run 90a B2B from his 100a alternator 

 

LiFePO4 Alternator Sizing – If you intend to feed a LiFePO4 battery bank with a ProBatt Ultra, and many do, then Sterling’s suggestion of 30% over-sized, for the alternator, we find to be rather inadequate. We recommend at least double the alternator rating, or larger for the B2B charger. So, if you want to use a 30A B2B on LiFePO4 then you would need an alternator rated at a bare minimum of 60A but preferably one sized for 80A would be much better. Each engine bay, and its heat characteristics, will be different, so predicting how much larger is impossible to really say. In our experiments with stock alternators we find double the B2B input rating for the alternator is a bare minimum.

Sorry Richard, overlooked your "paralleled"

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All this talk of paralleling B2Bs is reminding me that the days are getting shorter and my solar is not going to cut it for much longer. It's time I start figuring out how I'm going to add my 40A starter alternator into my lithium charging regimen. Currently I'm sitting with just one 75A-rated domestic alternator which left me with more engine running than I'd have liked last winter, and this winter I've got my new Eberspacher hydronic based central heating system in the mix as well, so I could really use the extra current from the 40A if I can make it work.

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13 minutes ago, jetzi said:

All this talk of paralleling B2Bs is reminding me that the days are getting shorter and my solar is not going to cut it for much longer. It's time I start figuring out how I'm going to add my 40A starter alternator into my lithium charging regimen. Currently I'm sitting with just one 75A-rated domestic alternator which left me with more engine running than I'd have liked last winter, and this winter I've got my new Eberspacher hydronic based central heating system in the mix as well, so I could really use the extra current from the 40A if I can make it work.

 

LPG powered genny + 240V charger? or petrol powered genny if you can store it, (and fuel), ashore, or somewhere on the boat that is as safe as a gas locker.

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4 hours ago, nicknorman said:

I would not daisy chain. You don’t want the voltage drop from the first device affecting the second. Take 2 wires from each of battery positive and negative, one to each B2B. Same for the B2B outputs, separate wires to the distribution bus bars.

 

Thanks Nick, I didnt daisy chain in the end, and both units started up ok, but I think they have overheating issues. 

 

They started off great guns, giving most of the expected charge current, but after about 5 minutes I heard the B2B cooling fans kick in (which seemed pretty early), and at exactly that moment I watched the total output charge fall dramatically, from a total of 65 amps to about 40 amps. 

 

That's two BB1260s, one at half power and one at full power, and all I was getting was 41 amps. 

I switched the half power unit to full power and it made no difference at all, the total out put stayed around 40 amps.

Personally, I'm convinced the units internal temp management is throttling them back to very low output levels after what seems like a very short time at a modest output.

The voltages may be interacting in such a way as to prevent both running at a decent output level, but they were using the same profile and were in the same phase of charging. 

 

Tbh, I'm starting to regret going down the route of using B2Bs. There is still an outside chance that it is not the B2Bs but rather the alternator that is somehow limiting its output because it is getting a bit hot, but there are no visible controls in place to make that happen. 

I have a feeling that the victron B2Bs would work better, in the sense that their Orion 30 amp B2B unit actually outputs the 30 amps in its title, whereas the Sterling 60 amp units will output anything between 30 amps and 55, but certainly not 60.

I feel misled and disappointed in the Sterling products, but in hindsight the better route would have been an 170 amp alternator upgrade, a poly V crank and pulley, and an alternator regulator. 

I guess you live and learn. 

 

 

 

Edited by Tony1
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2 hours ago, Richard10002 said:

LPG powered genny + 240V charger? or petrol powered genny if you can store it, (and fuel), ashore, or somewhere on the boat that is as safe as a gas locker.

 

I'm absolutely not putting petrol anywhere near my boat! I'm a CCer so I don't have any ashore to speak of. One day I'll commission an electric boat constructed entirely out of solar panels, and with a super silent cocooned diesel generator that is hooked up to my BMS to automatically start during the right hours and alert me when I need to top up with diesel, so that can just be part of the fire and forget BMS. Along with a heat store like @peterboat's. This is the dream, for when my ship comes in.

For now though I plan to make do with what I have, which is a Beta 38 with a 75A domestic alternator, and a 40A starter alternator. The starter alternator is currently not attached to anything at all (starter battery is charged with a VSR) so I'm getting an extra up to 40A for free if I can parallel them. I'm not sure if the 40A alternator currently installed is actually working but I have a new, spare unit. I also have a plan in my back pocket to increase the output of the alternators while using ducting and fans to better cool them as per @Dr Bob's set up. In any event it makes no sense to not use the 40A, even if I just reconnect it to the starter battery and chuck the VSR away. I also have a spare domestic alternator - at some point I'm going to try my hand at the alternator surgery @nicknorman performed, but despite his name, he's really the Dr Hibbert whereas I'm Dr Nick. But the alternators I'm using are cheap as chips and I'm having fun, so it's really just a case of finding the time to play.

I got through the winter last year with my piddly 75A alternator (set up to only produce about 40A consistently) so it can be done at a push. I was just running my engine more than I liked for someone with LiFePOs. I was doing very little cruising last winter due to Covid restrictions, so I hope that this will all just encourage me to keep boating throughout the shorter days! I must admit the last 7 months of solar has kind of spoiled me, I have all but forgotten about my batteries.

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28 minutes ago, Tony1 said:

 

Thanks Nick, I didnt daisy chain in the end, and both units started up ok, but I think they have overheating issues. 

 

They started off great guns, giving most of the expected charge current, but after about 5 minutes I heard the B2B cooling fans kick in (which seemed pretty early), and at exactly that moment I watched the total output charge fall dramatically, from a total of 65 amps to about 40 amps. 

 

That's two BB1260s, one at half power and one at full power, and all I was getting was 41 amps. 

I switched the half power unit to full power and it made no difference at all, the total out put stayed around 40 amps.

Personally, I'm convinced the units internal temp management is throttling them back to very low output levels after what seems like a very short time at a modest output.

The voltages may be interacting in such a way as to prevent both running at a decent output level, but they were using the same profile and were in the same phase of charging. 

 

Tbh, I'm starting to regret going down the route of using B2Bs. There is still an outside chance that it is not the B2Bs but rather the alternator that is somehow limiting its output because it is getting a bit hot, but there are no visible controls in place to make that happen. 

I have a feeling that the victron B2Bs would work better, in the sense that their Orion 30 amp B2B unit actually outputs the 30 amps in its title, whereas the Sterling 60 amp units will output anything between 30 amps and 55, but certainly not 60.

I feel misled and disappointed in the Sterling products, but in hindsight the better route would have been an 170 amp alternator upgrade, a poly V crank and pulley, and an alternator regulator. 

I guess you live and learn. 

 


is it just because you have the same cupboard, but twice as much heat generated? Something seems not quite right!

9 minutes ago, jetzi said:

 

I'm absolutely not putting petrol anywhere near my boat! I'm a CCer so I don't have any ashore to speak of. One day I'll commission an electric boat constructed entirely out of solar panels, and with a super silent cocooned diesel generator that is hooked up to my BMS to automatically start during the right hours and alert me when I need to top up with diesel, so that can just be part of the fire and forget BMS. Along with a heat store like @peterboat's. This is the dream, for when my ship comes in.

For now though I plan to make do with what I have, which is a Beta 38 with a 75A domestic alternator, and a 40A starter alternator. The starter alternator is currently not attached to anything at all (starter battery is charged with a VSR) so I'm getting an extra up to 40A for free if I can parallel them. I'm not sure if the 40A alternator currently installed is actually working but I have a new, spare unit. I also have a plan in my back pocket to increase the output of the alternators while using ducting and fans to better cool them as per @Dr Bob's set up. In any event it makes no sense to not use the 40A, even if I just reconnect it to the starter battery and chuck the VSR away. I also have a spare domestic alternator - at some point I'm going to try my hand at the alternator surgery @nicknorman performed, but despite his name, he's really the Dr Hibbert whereas I'm Dr Nick. But the alternators I'm using are cheap as chips and I'm having fun, so it's really just a case of finding the time to play.

I got through the winter last year with my piddly 75A alternator (set up to only produce about 40A consistently) so it can be done at a push. I was just running my engine more than I liked for someone with LiFePOs. I was doing very little cruising last winter due to Covid restrictions, so I hope that this will all just encourage me to keep boating throughout the shorter days! I must admit the last 7 months of solar has kind of spoiled me, I have all but forgotten about my batteries.


You should just be able to connect both alternator outputs in parallel. If they have the same or similar regulated voltage they should share the output in proportion to their respective sizes.

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32 minutes ago, Tony1 said:

 

 

Tbh, I'm starting to regret going down the route of using B2Bs. There is still an outside chance that it is not the B2Bs but rather the alternator that is somehow limiting its output because it is getting a bit hot, but there are no visible controls in place to make that happen. 

My 70A alternator reduces to a 60A alternator as it reaches operating temperature. I don't think there's an explicit control path, it's just that the rotor current reduces as the windings get hot and their resistance increases.

 

MP

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3 minutes ago, MoominPapa said:

My 70A alternator reduces to a 60A alternator as it reaches operating temperature. I don't think there's an explicit control path, it's just that the rotor current reduces as the windings get hot and their resistance increases.

 

MP

 

I think this is definitely a factor, but I dont believe it alone can explain the drop off I'm seeing at the moment. 

My main alternator is rated at 100 amps, so on that basis I would very roughly assume that it might be capable of maintaining 80-85 amps once the rotor current issue has come into play.

 

But what I'm actually seeing is  40 amps total output (although to be fair, this was measured out of the B2Bs, not directly out of the alternator.

 

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21 minutes ago, nicknorman said:


is it just because you have the same cupboard, but twice as much heat generated? Something seems not quite right!

 

 

No, the cupboard door is wide and it is always left open during charging, so no ventilation issues.

Ambient temp at the batteries is usually below 20 degrees, even in the heatwaves. 

 

I'll test the BB 1230 units tomorrow, but this time I'll direct a fan at the B2Bs and see if that delays the onset of their cooling fans kicking into action. Currently they start running  at between 5-10mins into the charge.

 

 

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23 minutes ago, MoominPapa said:

My 70A alternator reduces to a 60A alternator as it reaches operating temperature. I don't think there's an explicit control path, it's just that the rotor current reduces as the windings get hot and their resistance increases.

 

MP

Yes. My alternator controller displays field current. When I have it set to “fast charge” the maximum field current is not limited by the regulator. It is around 4.25A to start with. As the alternator gets hot it decreases to about 3.7A with the same voltage across it.

12 minutes ago, Tony1 said:

 

I think this is definitely a factor, but I dont believe it alone can explain the drop off I'm seeing at the moment. 

My main alternator is rated at 100 amps, so on that basis I would very roughly assume that it might be capable of maintaining 80-85 amps once the rotor current issue has come into play.

 

But what I'm actually seeing is  40 amps total output (although to be fair, this was measured out of the B2Bs, not directly out of the alternator.

 

The clue will surely be to measure the input voltage to the B2Bs. If the alternator is keeping up, the input voltage will be up around mid to high 13s. If the alternator can’t keep up then surely the B2B will just shut down due to low voltage at the input. It then takes 5 seconds to restart again. So you would see large slow fluctuations in the charge current on the BMV.

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17 minutes ago, Tony1 said:

 

I think this is definitely a factor, but I dont believe it alone can explain the drop off I'm seeing at the moment. 

My main alternator is rated at 100 amps, so on that basis I would very roughly assume that it might be capable of maintaining 80-85 amps once the rotor current issue has come into play.

 

But what I'm actually seeing is  40 amps total output (although to be fair, this was measured out of the B2Bs, not directly out of the alternator.

 

The clue will surely be to measure the input voltage to the B2Bs. If the alternator is keeping up, the input voltage will be up around mid to high 13s. If the alternator can’t keep up then surely the B2B will just shut down due to low voltage at the input. It then takes 5 seconds to restart again. So you would see large slow fluctuations in the charge current on the BMV.

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11 hours ago, jetzi said:

 

I'm absolutely not putting petrol anywhere near my boat! I'm a CCer so I don't have any ashore to speak of. One day I'll commission an electric boat constructed entirely out of solar panels, and with a super silent cocooned diesel generator that is hooked up to my BMS to automatically start during the right hours and alert me when I need to top up with diesel, so that can just be part of the fire and forget BMS. Along with a heat store like @peterboat's. This is the dream, for when my ship comes in.

For now though I plan to make do with what I have, which is a Beta 38 with a 75A domestic alternator, and a 40A starter alternator. The starter alternator is currently not attached to anything at all (starter battery is charged with a VSR) so I'm getting an extra up to 40A for free if I can parallel them. I'm not sure if the 40A alternator currently installed is actually working but I have a new, spare unit. I also have a plan in my back pocket to increase the output of the alternators while using ducting and fans to better cool them as per @Dr Bob's set up. In any event it makes no sense to not use the 40A, even if I just reconnect it to the starter battery and chuck the VSR away. I also have a spare domestic alternator - at some point I'm going to try my hand at the alternator surgery @nicknorman performed, but despite his name, he's really the Dr Hibbert whereas I'm Dr Nick. But the alternators I'm using are cheap as chips and I'm having fun, so it's really just a case of finding the time to play.

I got through the winter last year with my piddly 75A alternator (set up to only produce about 40A consistently) so it can be done at a push. I was just running my engine more than I liked for someone with LiFePOs. I was doing very little cruising last winter due to Covid restrictions, so I hope that this will all just encourage me to keep boating throughout the shorter days! I must admit the last 7 months of solar has kind of spoiled me, I have all but forgotten about my batteries.

 

An electrician was looking at why only one of my alternators was doing any actual charging, and he reckoned it was because the non-active alternator was regulated at a lower voltage than the active unit (I think they were 14.5v and 14.8v), and the result was that the smaller unit never kicked into life. 

He inserted about 5 or 6 metres of 16mm cable in front of the working alternator as a quick way of lowering the voltage, and sure enough, the smaller alternator started to produce some charge. Its not really a workable solution because the cable length required would have been very long, but it indicated his guess was probably correct.

For beta alternators, it might be possible to get a replacement regulator for one of the units to bring them both to same voltage, and then in theory they will work together more readily. But I got the impression it is not always an exact science, and sometimes one of the alternators can spontaneously stop charging, and thus leave all of the charging to the other unit, which in turn might introduce the risk of overheating- but I guess that risk depends on how the rest of your system is set up.

 

 

 

Edited by Tony1
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My mate has had his alternators parallel for years and both still but they are identical 70 amp models.  Because you can only get one poly v pulley on the engine and 70 is what he likes on the single v belt.  You maybe better fitting one 150+ otherwise.  He has measured 100 amps into a big inverter load for a long time without alternator problems.

 

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On 16/09/2021 at 09:06, Tony1 said:

 

An electrician was looking at why only one of my alternators was doing any actual charging, and he reckoned it was because the non-active alternator was regulated at a lower voltage than the active unit (I think they were 14.5v and 14.8v), and the result was that the smaller unit never kicked into life. 

He inserted about 5 or 6 metres of 16mm cable in front of the working alternator as a quick way of lowering the voltage, and sure enough, the smaller alternator started to produce some charge. Its not really a workable solution because the cable length required would have been very long, but it indicated his guess was probably correct.

For beta alternators, it might be possible to get a replacement regulator for one of the units to bring them both to same voltage, and then in theory they will work together more readily. But I got the impression it is not always an exact science, and sometimes one of the alternators can spontaneously stop charging, and thus leave all of the charging to the other unit, which in turn might introduce the risk of overheating- but I guess that risk depends on how the rest of your system is set up.

 

 

 

 

 

The Beta 38 has a V-belt for the 40A and a poly-V for the secondary alternator, which nowadays is 100A so he could fit one of these -- IIRC they're not that expensive from Beta, and they're standard Iskra models which might be available cheaper elsewhere. Current sharing between two non-identical alternators is unlikely to work properly especially as they heat up, the current vs. voltage curves for the internal regulators are never going to match.

 

43 minutes ago, Detling said:

My mate has had his alternators parallel for years and both still but they are identical 70 amp models.  Because you can only get one poly v pulley on the engine and 70 is what he likes on the single v belt.  You maybe better fitting one 150+ otherwise.  He has measured 100 amps into a big inverter load for a long time without alternator problems.

 

 

I doubt that the Beta 38 would be happy with a second alternator above 100A due to pulley size/loading -- Beta support up to 175A on the Beta 43 upwards (actually, even 2 of these if you ask them) so I'm sure they'd offer this on the Beta 38 if it could support it.

 

https://betamarine.co.uk/inland-alternator-options/

 

BTW I just looked back into my emails about alternators with Beta and found the attached -- at normal charging rpm (1200rpm engine/3250rpm alternator with the pulleys Beta use) the 100A one produces little more output than the lower current ones...

Iskra.png

Edited by IanD
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12 minutes ago, IanD said:

Alternators from Beta are quite cheap (and usually standard Iskra models which might be cheaper elsewhere), maybe he can just replace the 40A alternator with a 75A one identical to the one he already has and then parallel them up?

If he's got two V-belts then a single 150A alternator is a no-go, this needs a poly-V bely which needs a new crank pulley etc...

 

The electrician who helped me fitted a 90 amp alternator in place of the cheap 50 amp unit that was in place, and testing so far indicates it can put out about 40-42 amps continuously before starting to overheat- it does partly depend how much overheating you are prepared to tolerate. 

 

My other alternator is rated at 100 amps, but I'm finding it can give out about 45 amps without overheating. If I set it up to put out 50 amps, it go up to about 100 degrees, but that doesnt seem too dangerous really. 

 

So at the moment, although my two alternators are rated at 190 amps in total, I'm not comfortable allowing them to put out any more than 85-90 amps. 

I think the more expensive alternators might do better, and in fact if I could start the whole upgrade over again I would go for a single big alternator, new crank thing, poly V belt etc, and a regulator, instead of the B2B approach that I took. 

 

In my case I think the total cost to get a big alternator plus all the supporting bits installed, plus a regulator, would have been about £1400, but it would have eventually paid for itself in fuel saved (over say 8 years), by doing a lot less engine running. 

 

 

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29 minutes ago, Tony1 said:

 

The electrician who helped me fitted a 90 amp alternator in place of the cheap 50 amp unit that was in place, and testing so far indicates it can put out about 40-42 amps continuously before starting to overheat- it does partly depend how much overheating you are prepared to tolerate. 

 

My other alternator is rated at 100 amps, but I'm finding it can give out about 45 amps without overheating. If I set it up to put out 50 amps, it go up to about 100 degrees, but that doesnt seem too dangerous really. 

 

So at the moment, although my two alternators are rated at 190 amps in total, I'm not comfortable allowing them to put out any more than 85-90 amps. 

I think the more expensive alternators might do better, and in fact if I could start the whole upgrade over again I would go for a single big alternator, new crank thing, poly V belt etc, and a regulator, instead of the B2B approach that I took. 

 

In my case I think the total cost to get a big alternator plus all the supporting bits installed, plus a regulator, would have been about £1400, but it would have eventually paid for itself in fuel saved (over say 8 years), by doing a lot less engine running. 

 

 

I looked at this last year and talked to Beta at some length about it. It turned out that the solution with lowest cost and least worry about belt loading was to use 2 of the standard Beta alternators (external controller optional and expensive), not one of the really big non-standard jobbies like Balmar (external controller required) -- I was looking at 2 24V alternators in series to generate 48V, but I expect the same will apply to 2 12V ones in parallel.

 

Also note that a lot of the high-power alternators/Travelpower need higher revs than normal to achieve their headline rating -- you can even see this with the Iskra 80A/100A alternators, unless you rev the engine the 100A one doesn't give any more current than the 80A one.

 

For any of these cases, providing cool air to the alternators (fan plus ducting?) is a very good idea to try and prevent overheating, especially if you're drawing a lot of current at low rpm. Even so they're going to get pretty hot, they like being spun faster so the internal cooling fan is more effective.

 

These figures are for a Beta 43, you can also see that there's a pretty heavy torque loading at low rpm which will pull the engine revs down, so an external controller which can dial back current at idle would help -- the Wakespeed is the best at this but cost about £700 in the UK last time I looked... 😞

 

alternators.png

Edited by IanD
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