Posts: 3
Joined: Sun Jun 07, 2015 12:43 pm

Issues following 12v Aux Battery replacement.

Morning everyone,

I have been searching the forum in the hope that someone else has had the same issue as myself following replacing the 12v Aux battery…

Having owned our 2014 4hs since new, we have never had any issues. But, this weekend, on start up, the car started behaving very strangely. The wouldn’t start and we had multiple warnings on the dash (Eva system service, FCM system service, etc). After finding a thread on here, it was evident that the 12v battery was dead. No real understanding as to why though. Perhaps the battery was just too old?

The recovery service arrived and swiftly attached a jump pack and we were on our way again. No further warnings or faults. The following day, I replaced the 12v battery to prevent it happening again and everything was fine until the next time we drove the car further than the drive battery range…

We were driving along and, once the drive battery was depleted, we lost all drive to the wheels. Foot flat to the floor to try and spark the engine into life to provide drive, no joy. We quickly pushed the ‘charge’ button to force the engine to start and drive then returned. This is now happening every time the drive battery’s are depleted.

I’ve done some reading online and have learnt that the BMU gets reset when you disconnect the 12v battery and I’m wondering if this would also produce the same fault we’re having?

If anyone can shed some light or experience then I would be extremely grateful! We currently live out in Cyprus and the language barrier with the Mitsubishi representative out here is making me feel like we’ll never get to the bottom of the issue!
Posts: 26
Joined: Mon May 25, 2020 4:42 am

Re: Issues following 12v Aux Battery replacement.

Did you notice a significance increase of the EV range indicated by the car since you replaced the battery? In that case it's possible that the BMU was reset and it thinks that the battery has a higher capacity than it actually has. The battery gets depleted and disconnects because of low cell voltage.
The only way to fix it is to take it to your dealer and have them do a DBCAM to have the BMU relearn the battery capacity. See Richie's FAQ question A.2 for a description. He gives a reference to the procedure in the workshop manual, hopefully it can help you point the local mechanic to the correct procedure.
In the mean time, remember to force the car in charge mode when the battery level gets too low to prevent this from happening to you.
Last edited by Daixiwen on Tue Sep 27, 2022 12:35 am, edited 1 time in total.
Posts: 3
Joined: Sun Jun 07, 2015 12:43 pm

Re: Issues following 12v Aux Battery replacement.

I have noticed that the range has increased significantly so it sounds like you’re bang on the money.

Thanks for the link to the description and outlining what the dealer needs to do.

Fingers crossed for when the car goes in next week…

Return to “Technical Discussions”