Battery Balancer with two 24v batteries in parallel

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nobodyspecial asked Feb 19 2021 at 10:14 PM

Battery Balancer with two 24v batteries in parallel

I'm not readily finding the answer to my question. I've got two 24v 200AH LiFePO4 in parallel. The diagrams I'm seeing are looking for a center tap point between two 12v batteries in series which is not an option for me. Any suggestions would be appreciated. Thank you.

Battery Balancer

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Answer 1 · 2021-02-19T22:23:39Z

seb71 answered · Feb 19 2021 at 10:23 PM

You don't need Battery Balancers for your batteries.

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nobodyspecial commented · Feb 20 2021 at 2:04 PM

Thank you for your response. This tends to be my opinion as well but research reveals conflicting answers. Of course most of that if from YouTubers unpacking the batteries they just got from Alibaba. Oy vey. I'm new to the Lithium family of batteries so I'm still learning a lot here.

Please check my thinking out: Each of my 24v batteries has their own BMS so they should be "managing" themselves, right? Within some reason both batteries are seeing the same voltage since they are hooked up to the same 24v buss. They should be at the same state of charge so they don't particularly need to be "talking" to each other.

But when you two 12v wire batteries in series the voltage only has to add up to 24v so one battery could be 13v and the other could be 11v which would indicate substantially different states of charge. Albeit that's an extreme example but it just for rough illustration purposes. This is where the Battery Balancer does the most good.

Am I on the right track?

Thanks!

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seb71 nobodyspecial commented · Feb 20 2021 at 2:18 PM

Victron Battery Balancers are meant for lead-acid batteries (connected in series). For situations like you describe in the last paragraph.

LiFePO4 batteries usually have a BMS with monitoring at cell level. So much finer monitoring and control.

Do you have Victron LiFePO4 batteries or from some other manufacturer?

Besides the BMS thing, before connecting the batteries in parallel, make sure they have very close battery voltage (and ideally very close state of charge).

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nobodyspecial seb71 commented · Feb 21 2021 at 11:43 PM

Correct these have their own individual BMS. Preferred Energy. If you care to check them out. https://www.electriccarpartscompany.com/24v-200ah-preferred-lifepo4-lithium-battery-pack They used to have detailed paralleling instructions on that above link that mentioned a very special paralleling cable including instructions down to the pin outs. now that is gone and is replaced with instructions that make a lot more sense . The old document is what started me down the road of thinking I needed a battery balancer.

The individual cell monitoring is just fascinating. I've spent days with a hydrometer or refractometer desulfating and equalizing large (~2000AH @ 48V) off grid lead acid battery packs so I'm familiar with the problems of individual cells being out of sync.

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Battery Balancer with two 24v batteries in parallel

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