BMW i3 battery and Fronius inverter

Topics concerning storage of renewable energy e.g. home battery systems
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Joined: Thu Dec 28, 2023 9:42 pm

BMW i3 battery and Fronius inverter

Post by odlg »

I am new here, and I am trying to connect a BMW i3 battery to my Fronius solar inverter. The plan is to use Dalas lilygo based system to connect them.
Currently, I have CAN communication with the battery and I can fetch needed information from the BMW i3 BMS which BMW calls SME. I would prefer to use the BMS that is already in the battery enclosure.
Dala has recorded communication on PT-CAN2 (from another car) which is the bus that the battery is connected to and replaying it does not make the contactors close. Currently, I am not sending the CAN message IDs that the battery sends.
I have connected the battery as stated here: ... i3-battery

I have a number of questions that I hope someone can answer :) :
1. Regarding precharge. When powering the battery 12V the precharge contactors close for a brief moment. I have tried to add a 470 uF capacitor, but that does not make much difference. Does anybody know what the expected load is? Or perhaps have a voltage curve from a successful precharge?
2. Is the actual precharge done when the battery get WUP signal or is CAN communication also needed?
3. Regarding CAN communication - is it possible to make contactors close by using pre-recorded CAN communication? Or is it a sequence of events and responses to certain events? Or is there some handshake?

Has anybody been using the existing BMS in BMW i3 batteries?

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