HV Battery Contactor Actuation

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Active member
Feb 6, 2022
I am trying to manually actuate the HV battery contactors in order to manually charge the batteries. I have a high voltage, low amperage power supply that I would like to connect to the HV charge cabling but I need to actuate the contactor in order to charge. I want to avoid dropping the battery pack to do this. Does anyone know of a way to do this? The current condition of my RAV4 EV is this.

1) The battery charge is very low, 262V +/-.
2) The original onboard charger stopped working a few month ago. I replaced the 50A fuses but it still would not charge.
3) I replaced the onboard charger with a Tesla Model S charger and that charger will not communicate to the ECU gateway which, I assume, is due to firmware incompatibility.
4) I would like to recover the battery now, just to get myself out of this deep discharge state before the battery gets damaged (if it is not already, though we do not think it is). Hence the call for help.

Also, if anyone has more information about why the Model S charger will not communicate with the ECU and suggestions on how to fix that, I would appreciate it. My next step will be to pull the Model S charger and switch boards from my original RAV4 charger to see if that fixes the communication problem. Any help on this so I am not working in complete darkness is appreciated.

Thank you,
The BMS controls the contactors, so likely it's choosing not to do so based on the pack voltage being too low. However since you've done a bit of work on the car, it could be possible that something else is causing the contactors not to close, like a break in the high voltage interlock circuit.

Step 1 should be checking for current error codes on the Tesla side using the powertrain software, to understand why the contactors won't close. I'm assuming you still have your system setup for remote diagnostics with Vlad (@alflash).

Step 2 would be to re-flash the firmware in the Model S charger. While it is the exact same part # used in the RAV4, the Model S firmware is not compatible. The programming is done through the powertrain software, and I'm assuming Vlad should be able to help you remotely if you want to go that route.

If after addressing both these steps the car still won't charge, then you're probably looking at having to drop the battery pack to manually connect to the HV battery. If you're still on the original contactors, it would be a great time to proactively replace them, as the failure rate seems to be increasing with age.
Dear Sirs, let me remind you the following.
If there was a "native" charger in the vehicle, it was known that
a) it was visible in the system with "Ign ON" Mode

But the Tesla system in Charge mode fixed the code CHG_f002 Charger internal problem detected,

b) at the same time it is known for sure that this charger has the correct software
[*]Firmware updater SVN: 70832
9/23/2015 17:15:40 UTC
updateTime 1443028540
Crc check...succeeded.
Update manifest succeeded.
Update chgcpld.hex 10 => 10 - skipping - succeeded.
Update chg.hex 0.21.24 => 0.21.24 - skipping - succeeded.
Overall result: succeeded.
c) when installing a Tesla charger, it is not visible in the system, that is, there is no connection with it..

IMO. In this situation, it was possible to recharge the HV battery using towing due to the recovery mode ...

Note. If the firmware version of the charger does not match, the codes GTW_f016 / GTW_f056 and, probably, GTW_d001 Firmware version mismatch appear.
But since the Tesla charger is not visible in the system (point c), its ID is unknown and there is no way to try to reprogram it.

I assume only two reasons for this situation - a malfunction of the "donor" charger or an error during its installation.

Reference. System status in Ready mode immediately after changing charger fuses :

p.s. If a break in the high voltage interlock circuit, fault code BMS_f008 and/or BMS_f036 appears in the system:
So 262V / 92S = 2.85Vpc (*average* Volt per cell) [1]. But what is the *minimum* cell voltage? And what is the lowest "safe" voltage? This voltage is well in the "knee" of the discharge curve. I assume the RAV4 EV is bottom balanced, so the deviation should be no are than, say, 0.050V, so you should be safe. But can you verify this somehow? Can the "Tesla Powertrain Diagnostics" show the individual cell (per "brick" as tesla calls them) voltages?

[1] TMC
[2] diysolarforum
The BMS voltages are available on the Tesla CANbus. This is one of the screens on the OVMS.


I also put another misc. info screen of RAV4-EV specific parameters available from the Tesla bus. I have not dug into the Toyota bus yet.


The BMS will protect the battery pack by opening the contactors when any cell reaches 2.50VDC.
Thank you Miimura and Johan. With Alflash and Davio's help, I was able to get the On-Board Charger working and the car immediately started charging. I am now driving it daily and it is running perfectly. There was no damage to the battery fortunately so the discharge level was not enough to damage it. I am writing up a story of my experience and will post it to the forum soon.
Since the topic contains the word “contactor” in the title, I would venture to offer you a photo of the condition of the contacts of a faulty RAV4EV contactor with a mileage of 141,000 km.
The moving contact (plate/yoke) was itself welded to one of the fixed contacts.