Diy lifepo4 using 3s config for 12v systems

[Ckbeale]

I am ordering a large group of cells and have been exploring options for 12v configurations. I'm considering using 3s 5p which would yield 10.8 - 12.6 voltage at a nice 300 AH. This seems like a very safe config for 12v systems as the 3s cutoff would put the min voltage at 3.3 rather than 2.5 in a 4s configuration. I'm just wondering if anyone has any experience in this config and if they can share some pros and cons. Thanks.

 

[MisterSandals]

Why are you doing 3S? We need the story because it seems you are doing this for a reason.
Do you only have 3 cells to work with?
Above 3.3v (13.2v) quite a bit of the power resides here so you got that going for your idea.

 

[Ckbeale]

Looking at 3s because of the cell deal I found, 15 cells @ 60 ah. Utilizing 3s I can use all 15 cells to make 300 AH battery and the voltage range is much closer to that of lead acid. Using 4s I'd have 3 cells unused.

 

[MisterSandals]

Fair enough.
I wonder which actually has more capacity?
I think you are on the bleeding edge, please post your results!

 

[Sophie]

Why not configure 4s 6p if there is enough space for cells LFP 3.2v 50ah, we usually pack by 4s. Maybe you have some new threads.

 

[Sophie]

cells 50ah LFP

 

[Knighthawk]

I am ordering a large group of cells and have been exploring options for 12v configurations. I'm considering using 3s 5p which would yield 10.8 - 12.6 voltage at a nice 300 AH. This seems like a very safe config for 12v systems as the 3s cutoff would put the min voltage at 3.3 rather than 2.5 in a 4s configuration. I'm just wondering if anyone has any experience in this config and if they can share some pros and cons. Thanks.

I'm running all my diy solar generators with 21700 cells in a 3s configuration. Only reason is the cut off voltage on my inverters match the battery low voltage pretty well. Just an extra layer of low voltage protection. Never tried 4s with them. 12.5 is my max charge voltage. Would love to know if the 4s configuration would be worth the effort. I'd guess it would be. Not sure though.

 

[jnyer27]

KnightHawk, I want to do the same with some used cells but the problem I am having is the Charge Controller. I am trying to avoid a complete retrofit of my new travel trailer. Victron has a IP67 Charger that looks promising. What is the easy way to go to reduce the charging voltage with a existing system built for Sealed Lead Acid. I'm considering DC to DC or the IP67 like solution.

WFCO’s three-stage battery charging results in longer battery life and is totally automatic. Nominal voltage output modes are a 13.2 VDC range “float” mode, 13.6 VDC range “absorption” charge mode, and a 14.4 VDC range “bulk” charge mode. Short-circuit and reverse polarity protectionIt's a https://wfcoelectronics.com/product/wf-8735-35-amp/

Thanks!