Posts: 1
Joined: Mon Apr 05, 2021 2:38 pm

Low 12v Battery on New Car

Mon Apr 05, 2021 2:54 pm


I have a 2020 Outlander PHEV. It was purchased in December and only has 1,600 miles on it. Was driving on the freeway last week, going 70/mph - out of nowhere lights start flashing “EV system service required, stop safely” and “RBS service required". It was terrifying as the car slowed to about 20/mph while on the freeway, and I had to quickly pull to the side of the road. I shut the car down, waited a few minutes and restarted it. It started fine, but the "service engine soon" light remained on. I was able to drive it the 25 miles to the dealership, and a few times during the drive the FCM system randomly was activated flashing "BRAKE". Really scary experience all around.

After sitting at the dealership for 5 days I was told they reset the computer because the 12v battery was low. When I inquired how it could be low on a brand new car, the tech said going forward I needed to start the car everyday and drive it around, and the battery was low because I must have let the car sit for a couple of days. How unreasonable is that?? Guess I can never go out of town or expect a dead 12v battery?

Looking back on it, in the days leading up to the incident, the FCM randomly kicked in a couple of times, but I assumed I was just too close to another car.

Anyone else have this happen? I'm kind of afraid to drive the car since it sounds like it's only a matter of time before it happens again. I owned a plug-in Prius hybrid for years and never had to drive it daily to keep the battery charged.

Posts: 8
Joined: Sun Aug 30, 2020 9:16 am

Re: Low 12v Battery on New Car

Tue Apr 06, 2021 4:13 pm

I had a similar set of symptoms (see my recent post) and the dealer initially thought it was the 12V battery as well. And they asked me if I didn't drive it much also. I responded we had just driven ~300 miles the day before. They cleared the codes and the symptoms returned after they hooked it up to their charger. A few days later, they did a deeper diagnostic and now believe it's a failed Body Control Module (previously I thought they told me it was the Engine Control Unit). They have to order this part but first have to get a Parts Warranty Authorization from Mitsubishi. It's looking likely that my car will be there for more than a couple weeks, maybe even a month. Mitsubishi is willing to cover a rental car for only *three* days. Needless to say I am very frustrated.

Posts: 8
Joined: Mon May 25, 2020 4:42 am

Re: Low 12v Battery on New Car

Mon Apr 12, 2021 12:02 am

It sounds like they are bullshitting you. The car should be able to stay unused for weeks, the 12V battery will not go down so quickly. Can you borrow a voltmeter to check it yourself?
If the 12V battery indeed discharges so quickly by itself then it is defective. You should change it, and for such a new car it should be covered by the warranty.

But anyway having a low battery doesn't really explain the problem you had on the freeway. When running the car supplies 14V to all the system through the DC/DC converter and there is no reason a low 12V battery would cause some problems when driving. At worst you'd have some problems when starting the car.

Posts: 111
Joined: Sat Oct 27, 2018 3:47 am

Re: Low 12v Battery on New Car

Mon Apr 12, 2021 2:57 am

We are in the UK and have a 2020 model, due the Covid19 lockdown the PHEV only get used 2 or three times a week at the most, on some occasion we have not used the PHEV for over a week, we are experiencing None of these problems
Mitsubishi Outlander 2.4 PHEV Design 2020 Towing a Swift Conqueror 480 2016 1500kg

Please be patient I suffered a brain injury several years ago and get confused at times

Posts: 223
Joined: Fri Jul 26, 2019 3:52 am

Re: Low 12v Battery on New Car

Tue Apr 13, 2021 2:31 am

I believe that a low 12V battery can cause these issues even when driving and the DC/DC converter should be supplying voltage and current for those Aux circuits, however unlikely that sounds. You shouldn't have issues with the 12V battery at that age, but it can happen. But it's certainly nonsense to expect you to drive it every day. Do you have the wifi module in the car for using the App? If so and you have it registered with a phone, that will cause the Aux battery to be recharged every day at 14:00 from the Drive battery and is a useful way of ensuring that the 12V battery stays topped up.

Get a new 12V battery, fully charge it before install and go from there. If you have no further problems then it probably was that.

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