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gnsa14 avatar image
gnsa14 asked

BMS setup for 32x 3,2v Lifepo4 280Ah & Multiplus II

Hi all,

New to the forum, I have scanned for similar posts, but can't find any same answers.

Sorry if i have missed previous answer.

I'm looking to build home battery, with a grid-tie Multiplus-II 5000VA and 32x 280Ah Lifepo4 3.2v cells (16s2p making up the 48V, 28kWh). Battery Link here

My existing setup includes 8kW PV on a Fronius Primo, and will be optimised for self consumption, whilst incorporating EV charging.

My question is currently around the BMS setup. I am looking to use the Daly 16s BMS, but unsure if there is any benefit in using 2x BMS's, 1 for each 16s string, or only use 1 BMS with 2 cells wired as pairs into single 16s string). Obviously with this arrangement I will loose the monitoring of difference in voltage between the cells in each pair, but not sure if there is any other benifit / downfall.

Thanks in advance.

battery charging
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gnsa14 avatar image gnsa14 commented ·

I found this video on YouTube, which explains this in a little detail.

https://www.youtube.com/watch?v=zStEtH9Le-w&feature=youtu.be

And, one of the comments posted was...

Q: I was curious how each separate cell balances?

A: (By Author) BMS manages balance of cells in series, and for cells in parallel, they cycle together and balance each other. Cells MUST be matched to do this properly. My cell supplier does this. If using used cells, not a good idea to parallel. LiFePO4 super easy to parallel though, compared to other chemistries.

Anyone have thoughts about this?

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Justin Cook avatar image Justin Cook ♦♦ commented ·

Hi @gnsa14, welcome to the Community!

DIY battery packs are not Victron approved or supported, but I will move this question into the Modifications Space so that users of other non-supported systems that may be similar or have relevant insight might be able to assist.

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Joe avatar image
Joe answered ·

@gnsa14 , seems you have built what I am planning to do My existing PV has almost the size of yours as well. Would you be open for a 1:1 exchange about your project?

Assuming we're both German we eben could change to local :)

Regards,

Jochen

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gnsa14 avatar image gnsa14 commented ·
no, sorry...

I'm in Australia. I have had this up and running well for some time now, and it is rock solid!

1x BMS i think is better than 2 strings with 2x BMS.

will try the VenusOS driver mentioned below to bring BMS details into Cerbo also.

I run all this back into my Home assistant which does charge control, dynamic EV charging rate control, and all sorts of other bits.

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David avatar image
David answered ·

REC BMS. Much better than Daly - and communicates with the GX unit.

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pau1phi11ips avatar image pau1phi11ips commented ·

My Daly shows up in Venus OS: https://github.com/Louisvdw/dbus-serialbattery


REC BMS is superior but a lot more expensive.

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gnsa14 avatar image gnsa14 pau1phi11ips commented ·
Thanks for this driver link, that looks interesting. will investigate!
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Joe avatar image
Joe answered ·

Any nice Web access / UI possible for REC BMS as well?

What if you have a 32S pack? Does it need 2x16 REC BMS or can I do it like gnsa14 described it (two batteries are one cell)

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hjohnson avatar image hjohnson commented ·
I would do 2p16s rather than 16s2p. If you do the former, you can do it with a single BMS (such as the REC BMS) whereas the latter requires two. Given the way the victron ecosystem works, you’re better off with a single bms communicating with it. The official victron batteries communicate with their bms and present as a single battery. Same with the various rackmount solutions.
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gnsa14 avatar image gnsa14 hjohnson commented ·
agree
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