[RE-wrenches] Different LFP Batteries in Parallel

[Jason Szumlanski]

They are Lithionics.


Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Mon, Jul 14, 2025, 9:33 AM jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> 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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