40kWh module swap for 30kWh in original pack.

Hello all,

Has anyone done a module swap out within an existing 30kWh battery, replacing all the modules with newer 40kWh modules?

My understanding is they are physically matched in size and as my 30kWh battery needs a failing module replacing anyway, I am considering if it might be feasible to strip it out and upgrade to the larger modules, as I have the opportunity to buy a set of 24 "naked" modules.

As the terminal voltage of the 40's is slighly higher, surely this would work OK with existing management?, just giving a larger unused buffer at the top, no bad thing...

Now you can all tell me why it's a terrible idea and what I'm overlooking...

Thanks, Paul

Welcome. You would very, very likely also have to move the BMS modules.

favguy said:

Hello all,

Has anyone done a module swap out within an existing 30kWh battery, replacing all the modules with newer 40kWh modules?

My understanding is they are physically matched in size and as my 30kWh battery needs a failing module replacing anyway, I am considering if it might be feasible to strip it out and upgrade to the larger modules, as I have the opportunity to buy a set of 24 "naked" modules.

As the terminal voltage of the 40's is slighly higher, surely this would work OK with existing management?, just giving a larger unused buffer at the top, no bad thing...

Now you can all tell me why it's a terrible idea and what I'm overlooking...

Thanks, Paul

Click to expand...

Doesn't work that way; you have to swap the whole pack (if you're changing capacity/module types). I've done both a battery pack swap/upgrade (24->40 kWh) and a cell/module replacement (40 kWh module type).
I could swear there was another thread with this exact same question in the last month. I suggest you look for that thread.

I've seen the other thread, it's about mixing and matching modules within the same pack, this definitely wouldn't work as the chemistry and curves don't match.

I've now had a conversation with someone in the UK who has actually done this and it works fine apparently. The car treats the modules as 30kWh units though, so you don't get to access the full capacity, but it's like running a day one 30kWh pack as a result and even after allowing for considerable degradation on the 40 packs over time, the car will still get to use a full 30kWh. Also there's the advantage of having a much larger buffer top and bottom as a result of this, so regular charging to what the car sees as "100%" is really much lower.

So what you get is like a more bullet proof, strong 30kWh pack, so a costly option to get to that I suppose.