communication with BMS

[Zwerius]

Hello all,

I have a 2014 i3-Rex. This one still has the 22 kWh battery.
I would like to upgrade to the larger (almost double capacity) battery and use the old 22 kWh battery as a storage system in my house.
In that case the BMS would need to communicate with a SMA Home Manager.
The SMA Home manager communicates over a CAN-Bus.
Does anyone here know what the communication system of the i3 BMS is?

 

[jadnashuanh]

Back near the release of the i3, BMW showed a prototype i3 battery installed as a home battery backup device. I don't know if they ever actually marketed it anywhere, but they have also done some demonstration utility battery backup systems using those battery packs. You probably won't get anything out of them, but it wouldn't hurt to call and ask.

 

[eXodus]

so there are two options.

1. You take the pack apart and add your own BMS to each cell. soldering any aftermarket BMS to the existing balance leads.
2. You get one of these: https://www.secondlife-evbatteries.com/collections/accessories/products/simp-bms


Yet, you home system does not necessary need to talk to the BMS - it just needs the correct charging and discharging parameters.
As long as you get the correct voltages setup you should be fine.

BMW is using old battery packs as backup power in their manufacturing plants. The home energy storage market idea was dropped.
The 60ah i3 cells don't like sitting a high level of charge without degrading fast. That's why you can not access all the capacity in your car. (17kwh out of 22kwh)

So think very hard how your home system will be used. Is it a pure backup - so sitting at full all the time? Or are you using it for load balancing every day?

If it's a backup, just set it so that it only goes up to 80% of what the car allows you. So basically - to be safe half the capacity. 11-12kwh
And then you are at the point where it starts making less sense financially. You can get Tesla Model S cells with 5kwh - which like sitting at 90% for less then $1000 a piece.

When you cycle you can go higher - since the battery is not sitting a higher capacity for long intervals.