Expanding a 304AH 16S with a 280AH 16S

drbytes

Solar Enthusiast
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Oct 21, 2021
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Hi

I currently run a 304AH 16S battery bank. It's nearly always full at the end of the day but I can't quite get trough the night with it's stored capacity due to electrical heating eating a ton of energy.
So I decided to add another bank to the setup albeit being slightly smaller in AH due to shortages -> 280AH


What are my options with this ? Do I create a complete new 16S battery+ bms and place those in parallel ?
Or can I perhaps pair a 304 and a 280 cell in parallel and then place those pairs into a 16S?
 

drbytes

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Oct 21, 2021
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Another pack then.

I'm wondering if I now should just get a Seplos BMS for each pack so that they can communicate with each other and with the inverters
 

Pyrofx

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I did that with rec bms's. 6 of them so far. Has been wory free for a year now
 

drbytes

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REC BMS? Gonna google that. Do they speak Growatt/Pylontech ? I guess I could google that too
 

Pyrofx

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So far Sma and victron.
You might have to check with them.
They are in slovania
 

drbytes

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Yeh they just told me that for the time being they won't be taking on any new orders. With the whole supply chain being in pieces and all.
 

MisterSandals

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If you decide to pair them 2P16S, you will have better results if you make each pair as similar as possible to the other pairs.

To do this, I think pairing strongest 304 to weakest 280, second strongest. 304 with second weakest 280,…weakest 304 with strongest 280 will be best (or at least a very good starting point).

FWIW, I did my 2P4S this way. They were all 206Ah “rated”. I did not test for capacity numbers, just ranked by relative strength thru daily use, monitoring and data gathering.
 

Bvillebob

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Oct 21, 2021
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I have two batteries with 16 of the 304's and two with 16 of the 280K's, all operated in parallel and working great. The difference in real capacity is minimal, the batteries all charge and discharge in unison, no problems.
 

drbytes

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Ok, so better to build two distinct batteries and parallel them.

I'm thinking of getting that Seplos BMS for the 280 pack and keep the JBD on the 304 pack. Then I'll parallel the packs and connect the Seplos to my Growatt inverters via S485 so it can report the SOC.

Would that work ?
 

Mandy Chou (Deligreen)

Deligreen- Make DIY Battery Easier
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Ok, so better to build two distinct batteries and parallel them.

I'm thinking of getting that Seplos BMS for the 280 pack and keep the JBD on the 304 pack. Then I'll parallel the packs and connect the Seplos to my Growatt inverters via S485 so it can report the SOC.

Would that work ?
i think you need to build another battery pack with the same cells, if the current pack is 304AH, the other one also use 304AH rather than 280AH cells. Parallel them. and also you need to make sure the two packs voltage are balanced and make sure the BMS is working in this way which support parallel.
 
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