The EoS tester can be rented from some places, a great i3 expert is available in CZ, https://www.i3upgrade.cz/ Another alternative when dealing with a locked battery, is to open up the battery and bypass the contactors. Nobody has reported if this works yet (feel free to edit this wiki!), worst case you could also replace the i3 BMS with an RJXZS

An indicator if the battery is not in lock state is the range indicator of the crashed car. If it displays battery range/percentage, the battery is probably not in lock state even if a few airbags have gone off.

Crashed BMW i3 battery being reset with an EoS tester:

The HV connector needs to be plugged in for the battery to be able to turn on (Interlock detection)

• Pin 1 = HV+
• Pin 2 = HV-

• Pin 1 HVIL (loop to 2)
• Pin 2 HVIL (loop to 1)

The bmw I3 uses a 35mm² high voltage cable. To connect it to a terminal block and go down in size to a more manageable 10mm² you need ferrules for these stranded wires to not damage them. This can be done by cutting off the old connector and using a ferrule and crimping them. These tools are not so common for consumers. An alternative for this is modifying the connector and use the current connector as ferrule so you don't have to buy or rent tools to achieve a non-stranded wire for the thermal block with size 35mm²

Click on Details ⬇

The LV connector is located on the back of the battery pack, next to the A/C cooling port. A/C connector is not required for operation.

It has the following pinout:

Connect the wiring as follow:

• Pin 1 30C - Connect to to 12V, 10A fuse optional
• Pin 9 15WUP-Signal (Green/GreenRed) - Connect to 12V, 5A fuse optional. Control this pin with ASR-10DD relay or a Pololu Power Switch controlled by PIN 25 in the LilyGo.
• Pin 7 (Red) - Connect to to 12V, 5A fuse optional
• Pin 2 Ground (BrownBlack) - Connect to Ground
• Pin 4 CAN-H (WhiteYellow) - Connect to LilyGo CAN-H - twist with CAN-L cable and put a 120Ω resistor across to CAN-L.
• PIN 10 CAN-L (WhiteBlue) - Connect to LilyGo CAN-L
• Pin 6 I_LOCK (BlueRed) (connect to Pin 12 with a 33Ω resistor in between)
• Pin 12 I_LOCK (BlueRed) (connect to Pin 6 with a 33Ω resistor in between)
• Pin 3 Refrigerant valve (NOT USED)
• Pin 8 Refrigerant valve (NOT USED)

The wakeup signal needs to be actuated by the Battery-Emulator, and as soon as messages start to come through from the battery we reply. This ensures a reliable startup. Same goes for rebooting/shutting down the battery. The Battery-Emulator sets WUP to low incase we need to command the BMS off.

Since the LilyGo board has 3.3V logic on the GPIO pins, we need to use a solid state relay in order to boost the 3.3V -> 12V. Example connection using 1x ASR-10DD solid state relay:

Below an example wiring diagram

• BMW i3 battery
  • 60Ah
    • 61252353679 / 140116 / 7625051 / ​2353644 / ​728838
  • 94Ah
    • 61252412020 / 72883817 / 8647909 / 14191812
  • 120Ah
    • 2412116 / 2412117 / 7933745 / 7933746 / 7933747
• BMW HV cable
  • 61129346573
  • 61126809274
  • 761978102
• BMW HVIL bridge
  • 12527630408
• BMW Connector
  • 61139165781 (also known as 9165781).
  • Note: equivalent part from Kostal is # 9411204.
  • Link to Alibaba, You can order a sample instead of multiple connectors
    • This includes MQS bushing contacts, no wires attached
  • Search suggestion "12 Pin 9165781-01/76616-9"
• 8x BMW Bushing contact MQS with cable
  • 61130030859 / 61130005197 (they are all the same color though, recommend to mark them)
  • Or get a free wiring harness from your scrap dealer and reuse the cables
• HV Capacitor 470µF or higher and more than 500V.
  • Consider a capacitor with screw connection to avoid the need of soldering iron
• 33Ω resistor, ¼ watt or similar is fine.
• 12V power supply (When Grid-backup is not available)
  • with UPS to avoid welded contacts)
    • E.G: Mean Well DRC-40A with a 12v 1.2ah battery

Capacitors are high voltage, so they need to be inside an IP enclosure to prevent anyone from touching or water getting onto it and shorting it out. Most either mount the capacitor next to the battery, or next to the inverter, at either end of the HV bus. The most popular solution is to install fuses and the capacitor right at the start where HV comes out of the battery, sort of an add-on box that gets mounted on the original HV cable coming out of the battery. This is also a good place to step down the batteries thick DC cabling (35mm² in case of the i3), down to a more manageable 10mm². To avoid the need for 35mm² crimping tools you could consider this solution

Example of capacitor integrated at point where wire gauge is reduced, inside exclosure:

Problem	Suggested fix
Contactors not closing	Check that the capacitor is seated between HV+ and HV-. Check that negative and positive are not accidentally shorted together
Event "Error: Battery interlock loop broken. Check that high voltage / low voltage connectors are seated"	Check that both interlocks are OK. 1. The High Voltage needs to have the two small HVIL wires joined together near the orange connector. 2. The Low Voltage connector also needs to have pin 6 and 12 connected via a 33 Ohm resistor. If you are doing the pins yourself, make sure they are seated all the way.

Fronius Gen24 with 2x BMW i3 batteries in double battery mode

i3 94Ah with Sofar inverter