I posted this over at AEVA, but I thought it'd be interesting here too.
I was fortunate enough to get hold of a dismantled BMW iX Xdrive40 battery.
It's 330-350V in ten modules connected in series.
75kWh total.
Each module has a connector with 18+ wires, exposing all the individual cell voltages and temperature sensing.
They are all bussed together in a loom to a CSC module:
the CSC might be on a CANBus, but we couldn’t see any useful output directly. It turns out it’s transformer isolated, but didn’t investigate whether it can talk yet.
Inside the CSC is a bunch of microcontrollers and some isolation:
And some surface mount power resistors. It seems it does some balancing, but obviously the balance current is pretty low - small wire gauge and small resistors:
I’ve done some basic capacity testing of the batteries. At 75kWh and 330V quoted capacity they should be around 220Ah.
The top cover is just plastic and comes off easily. I didn’t need to cut the main power cables, I made some threaded connectors that mate to the orange screw terminals pretty well.
- 18 cells in a series/parallel arrangement in each module. 9S2P arrangement.
- one module weight about 40kg.
- Just bare cells with a connector that exposes each cell voltage and three temperature sensors
- no BMS or balancing circuit - because it’s in the CSC module
- initial voltages as I received it all 3.936V, all within about 1mV of each other - very good matching.
- charged them all to 4.05V (max nominal might be 4.1 or 4.2, depending on chemistry)
- discharged with an approx 60A load. Discharged to approx 3.05V, which is a common endpoint for lithium cells.
- main current carrying terminals are a TE connectivity thing with a conductive ring and an internal M4 thread.
Curve below:
Shows we got just about 200Ah between 4.05 and 3.05V at a ~4 hour discharge. That’s 27V to 36V for a module.
I think this is pretty typical, and we’d expect about 10% more capacity if we pushed it to the limits, so it seems bang on spec.
Internal resistance measured at about 3.5milliOhms(?) for the pack. Seems high, maybe - should check again.
For what it’s worth I bought one of these:
https://www.ebay.com.au/itm/353853522667?epid=1642437107&hash=item52635042eb:g:aVgAAOSwCk1h3omb:sc:AU_ExpressDelivery!3055!AU!-1&amdata=enc%3AAQAIAAAA8EZnobqGKNqnkJ914G4U6tiBcP509q%2FivcWanY4ljCYBuY%2Bo2luoMhC7T6UNFbwLUDIk6wNj9YFYzht5j8o%2BQUydeYeyNV5nW16R1BwF00dPe9hAZ4rVAuH51dMOzs90f2vODp6KJG72DEC%2BgnXBepAH3fnnx8jgijZvTZQ5wv9hOsRtmZsKypTIuMJUcAECYM92CU4GKE7y7nZEz3H%2BhoJrMQTRrfk13SQiQwJWkvU8WrzMwNhEqslwmYBJmZwK2b6QyEE2cahpBOtHi1AhBcVNbZblXQI0mL6pHQnIRnDhNy17RGfIhOjzaVpw%2B9vgZQ%3D%3D%7Ctkp%3ABFBMnPrIiLtiWhich happily runs off the pack and feeds a good 1200W into the grid.
I can supply more photos or measurements on request if anyone is interested. There's other parts that I didn't get good photos of; the parts that interface to the rest of the car and the charging subsystem and the safety cutout and so on. This is what I had, for what it's worth.
cheers, hope someone finds it entertaining,
cms