[RE-wrenches] Different LFP Batteries in Parallel

[jay]

Hi Jason,

can you let us know what the old battery is so we can dig up the specs and see if there would be any issues.  

There are a few odd ball like simpliphi which while a 51.2v has a very narrow window for operation compared to most other prismatic cells.

jay





> On Jul 14, 2025, at 5:07 AM, Jason Szumlanski via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:
> 
> There are never-ending videos on YouTube showing different brands and capacities of LFP batteries working in parallel. I have never tried it myself, and every instinct says don't do it, but I have a situation where it would be very helpful. 
> 
> I have a client with an older 60 kWh battery that is discontinued and incompatible with any other battery from the same manufacturer. It has a BMS with a 51.2 volt nominal rating. They need another 20 kWh of capacity. It is too costly to scrap the existing battery and start over, and the existing battery has been tested and confirmed to hold very close to its rated capacity.
> 
> What is the real deal on mixing and matching? Is anyone doing this safely and successfully? I wonder what the battery manufacturers say about it. 
> 
> Jason Szumlanski 
> Florida Solar Design Group 
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