Lithium battery bank reliability

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wally01 asked Jan 6, '22

Lithium battery bank reliability

I am looking to replace 16x 240ah AGM batteries with a lithium battery bank. This is configured as a 48v bank, with 3x Victron battery balancers across each series string of batteries (a total of 4x series strings connected in parallel).

Does anyone have thoughts on reliability issues between replacing these AGMs with 12v lithium batteries using the same battery balancers and connection as the current setup, versus using multiple 48v lithium batteries in parallel? Would the 48v batteries do a better job at cell balancing compared to 4x series connected 12v lithiums with external battery balancers?

Lithium Battery

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Answer 1 · 2022-01-07T05:00:04Z

Alexandra answered · Jan 07, 2022 at 05:00 AM

@wally01

It largely depends on if the 12V lithium batteries you choose can be connected like that and the kinds of loads you are running. For example with battle born you have to tell them when you order them that that is the config you are wanting to do, then they match up battery bms or series.

And yes the 48V system does work with the balancers. Infact it is recommended. I have done a setup like that it worked ok. There were a few tweaks for reliability. Sometimes solar overshoot when a big load droppped off at 100% SOC caused the bms to shut down. But you can work around that with voltage tweaking. I have seen also a few bms blown in one 12v from this kind of setup.

When building a bank that is really is just easier and more reliable to get 48V batteries when using lithium.

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Answer 2 · 2022-01-07T09:11:56Z

ejrossouw answered · Jan 07, 2022 at 09:11 AM

@wally01 It really depends where you will be installing the batteries as some 48V units are typically best suited to domestic installs given their different shapes and warranty terms of use. Victron Lithium Smart can max have 5 batteries parallel and 4 in series to e.g. with 300Ah batteries give a max of 1500Ah. Of course with greater DOD you can opt for a smaller bank. Modern LifePO4 batteries typically all have integral cell balancing and monitoring so even having balancers will be lost on me.

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Alexandra ♦ commented · Jan 07, 2022 at 08:00 PM

The Victron ones are different in this regard.

We have run a few different brand 12v in a 48v bank. In each setup, the individual battery (takes care of itself) balances its own cells but you will have voltage differences between each 12v battery. Ohms law in a bank still exists. And each battery (much like lead acid) also have slight internal resistance differences. Hence the need is still there for built bank to use balancers. In any case already owns them so not an extra expense.

Not all batteries can be used in this way and some brands specifically say not to. So if @wally01 decides to do this then will have to choose brands wisely.

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Answer 3 · 2022-01-08T05:21:33Z

wally01 answered · Jan 08, 2022 at 05:21 AM

Thanks for the replies so far. Alexandra, your comment of the single BMS blowing up in this type of battery bank is the type of things I am looking for.

I have seen a number of different batteries that mention all types of restrictions on number of batteries that can be run in series and parallel.

I mainly was looking at the 12v battery option as I have the system set up with large cables and balancing, but if the 48v batteries will be more reliable long term then that’s what I will go with.

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kevgermany ♦♦ commented · Jan 08, 2022 at 05:42 AM

You can still use the large cables with higher voltage batteries. No need to replace.

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