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Multiple 12v chargers on 48v series bank

pops106

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Aug 24, 2020
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141
Hello,

Quick question around charging options.

I have access to pretty cheap second hand batteries quite often so I am constantly adding batteries and moving them around my different solar setups. I currently have in series 3 x 55ah batteries on my main grid tie but just managed to get some more batteries so going to upgrade this to 8 x 55ah 4s2p so 48v meaning I need a new charger as the current one is 36v.

I also have in my shed 2 x 55ah in series which I would like to be able to charge if I need, couple of 12v systems but I have a charger for them if need to charge them.

So the question is, instead of going out and buying a 48v charger for my grid tie which could change again at some point could I instead just use multiple 12v chargers whilst leaving them in series.

Roughly something like below

Blank diagram (1).jpeg
I then have everything tied into my Home Assistant so I can monitor a smart plug which would detect when the chargers have dropped the amps down to pretty much nothing before switching off the chargers and switching on the solar.

Thanks for any opinions guys, cheers.
 
I think the chargers setup this way could work, but it wouldn’t be reliable...

just get an MPPT multiple voltage controller.
It will autosense the bank voltage, and charge accordingly.
 
I think the chargers setup this way could work, but it wouldn’t be reliable...

just get an MPPT multiple voltage controller.
It will autosense the bank voltage, and charge accordingly.

The charge controller i have is fine on the solar side, it does the usual 12 to 48v it is the ac chargers I am worried about.
 
That is an example of why I like autonomous switching solar setups over true grid tie. Not dissing folks who select that, they know what they need.

I’m a cheap yankee and the idea of ‘beating the system’ is just plain appealing. Then AC charging isn’t really a thing. The solar (and batteries) run until they run out of power for a given set of loads, while anything high-draw just lives on the grid. Often easy to configure things so if the grid is down YOU aren’t.

But that’s just me and what I’d do. (I have no grid power anyway, so...)
 
OMG! Could someone just answer the poster's question? The root of the question is asking if you can charge 12V batteries individually while they are in series. Obviously you shouldn't just charge one because that will cause them to become out of balance and lessen their lifespan. But can you charge them all individually while in series? I will use my situation as an example. I currently have 3 x 12V AGM batteries. I plan on putting 2 in series for my solar setup whilst leaving one for the starting battery for my boat. I currently have a 3 x 12V Promariner Pronautic 30amp charger. Can I still use it to charge those three batteries even though two are now in series? For the love of GOD, someone please answer the actual question, not tell me what you would do. A definitive yes or know and why.
 
OMG! Could someone just answer the poster's question? The root of the question is asking if you can charge 12V batteries individually while they are in series. Obviously you shouldn't just charge one because that will cause them to become out of balance and lessen their lifespan. But can you charge them all individually while in series? I will use my situation as an example. I currently have 3 x 12V AGM batteries. I plan on putting 2 in series for my solar setup whilst leaving one for the starting battery for my boat. I currently have a 3 x 12V Promariner Pronautic 30amp charger. Can I still use it to charge those three batteries even though two are now in series? For the love of GOD, someone please answer the actual question, not tell me what you would do. A definitive yes or know and why.
See post #2...
 
OMG! Could someone just answer the poster's question? The root of the question is asking if you can charge 12V batteries individually while they are in series. Obviously you shouldn't just charge one because that will cause them to become out of balance and lessen their lifespan. But can you charge them all individually while in series? I will use my situation as an example. I currently have 3 x 12V AGM batteries. I plan on putting 2 in series for my solar setup whilst leaving one for the starting battery for my boat. I currently have a 3 x 12V Promariner Pronautic 30amp charger. Can I still use it to charge those three batteries even though two are now in series? For the love of GOD, someone please answer the actual question, not tell me what you would do. A definitive yes or know and why.

The answer to your situation is ...... that is the way multi-bank chargers are used on a boat all the time. The charger doesn't care if they are all individual or any combination of series / parallel .... just keep with the AGM setting and don't accidentally select FLA.

The example the OP posted seems possible to me .... but is well beyond the scope of any experience I have had with batteries.
 
The answer to your situation is ...... that is the way multi-bank chargers are used on a boat all the time. The charger doesn't care if they are all individual or any combination of series / parallel .... just keep with the AGM setting and don't accidentally select FLA.

The example the OP posted seems possible to me .... but is well beyond the scope of any experience I have had with batteries.
I think it comes down to what the charger see's the voltage of the individual cells while they are in series with a load applied. I haven't actually tried this myself. I'm looking for an answer to this question just like the original poster.
 
I think it comes down to what the charger see's the voltage of the individual cells while they are in series with a load applied. I haven't actually tried this myself. I'm looking for an answer to this question just like the original poster.
I gave you an answer.

Seems like the OP should be the one commenting on the answers to his thread .... You should have started your own thread instead of confusing this one.
 
But can you charge them all individually while in series?
Yes you can charge them individually in series. The trick is keeping them balanced.
When you have batteries in series, if they are not nearly identical in every way, then the stronger batteries will cannibalize the weaker batteries.

If you can manage the charging (and discharging) so that the batteries remain equal in charge and capacity, it should work fine.
 
Post #2 doesn't definitively answer anything. Saying something could work but wouldn't be reliable without any explanation or evidence to support it is merely conjecture, not an answer.
True…
But without knowing the capabilities of his 12V chargers, and the monitoring he will put into his bank, any other answer is a mere guess.
 
OMG! Could someone just answer the poster's question? The root of the question is asking if you can charge 12V batteries individually while they are in series. Obviously you shouldn't just charge one because that will cause them to become out of balance and lessen their lifespan. But can you charge them all individually while in series? I will use my situation as an example. I currently have 3 x 12V AGM batteries. I plan on putting 2 in series for my solar setup whilst leaving one for the starting battery for my boat. I currently have a 3 x 12V Promariner Pronautic 30amp charger. Can I still use it to charge those three batteries even though two are now in series? For the love of GOD, someone please answer the actual question, not tell me what you would do. A definitive yes or know and why.

OP Here just saw an email notification come in.

Good to see some more responses, I did go ahead and buy 4 x 12v chargers and running them as described in the first post with no issues at all. They are cheap chargers but 7 stage so they all reach float at 13.8v. Stupid thing is the LCD on them measures differently on all 4 but almost identical when you measure with a pair of meters.

It actually works really well because it brings the batteries in balance each night.

I have a cheap electric tariff 20:30 till 01:30 now so I switch off the solar and charge the batteries each night.

It has highlighted that all the second hand batteries are not exactly equal so I have stuck some cheap balancers on as well which are working well, I don't get one of the batteries running away up over 15v whilst one is 14.1v for example now, seems to work well both charging and discharging.

Thanks for the responses guys
 
Yes you can charge them individually in series. The trick is keeping them balanced.
When you have batteries in series, if they are not nearly identical in every way, then the stronger batteries will cannibalize the weaker batteries.

If you can manage the charging (and discharging) so that the batteries remain equal in charge and capacity, it should work fine.
This is a much better answer than the first reputed answer (post #2) which explained little if anything.

The thing not mentioned is that with a heterogeneous mix of chargers, balancing the currents between chargers is probably the most difficult to counter.
 
Well my saga continues... own doing buying second hand batteries.

Started a thread about my batteries

I basically finally bought a battery capacity tester so I can get to the bottom of which are good and bad batteries, good news my 12v chargers do what they say they do.

batt.PNG

It is something like, test, desulfur, soft start, bulk, absorb, test again, top up, float

The above is 2 of my second hand 55ah batteries out of the 10 (8 in use) 4s2p and you can clearly see one of them has way less capacity remaining, the above is charge that went back in after the capacity test, below is the results from the capacity test.

Battery 55AHAHTimeCharge StartCharge EndCharge TimeCharge WH StartCharge WH FinishWH InPeukert
B1
23.38​
02:20:16​
14:33:07​
20:45:07​
06:12:00​
4​
543​
539​
1.07​
B2
9.39​
00:56:20​
20:48:52​
23:47:52​
02:59:00​
543​
778​
235​
1.45​

So in about 9 days time of testing I should have all the results.
 
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