# Prius battery upgrade with lithium



## Tom (Mar 26, 2008)

We sell Priuses. We also refurbish Gen 2 battery packs.
As I work through a donor pack for replacement cells, I am looking at the remaining chassis and contemplating replacing the OEM NiMH cells with V41 lithium cells that we have been selling. The V41 are about 3.7v @ 41ah.
Two of them in series would be about the same as one OEM module.
Seems like an interesting project to see how they might respond with the OEM BMS.
Or might be a great way to start a fire.
We would need a new battery chassis and cooling shroud.
I am not sure that just having a larger storage capacity is going to do anything without an onboard charger.

Would appreciate any thoughts. I have enough projects with customers cars and cars we are prepping for resale, but these empty chassis' are taunting me.

Having about 30x more capacity is interesting for not much more weight.

tom in maine


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## astrand (May 12, 2012)

Tom said:


> We sell Priuses. We also refurbish Gen 2 battery packs.
> As I work through a donor pack for replacement cells, I am looking at the remaining chassis and contemplating replacing the OEM NiMH cells with V41 lithium cells that we have been selling. The V41 are about 3.7v @ 41ah.
> Two of them in series would be about the same as one OEM module.
> Seems like an interesting project to see how they might respond with the OEM BMS.
> ...


The OEM Battery ECU will still think that the battery has 6.5 Ah, so unless you do something about that, there will not be much of a difference. You could use BMSplus/BMS2 from the now gone http://hybridinterfaces.ca/ or some similar solution (for example, I have a complete PHEV system with BMSplus-like functionality built on the https://www.ttcontrol.com/products/electronic-control-units/general-purpose-controllers/hy-ttc-60/).

Also note that Lithium typically requires cell level balancing and monitoring, which you will not get with the OEM Battery ECU.

Br,
Peter


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