The 12v auxiliary battery completely failed...

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Skylander

Member
Joined
Jan 6, 2023
Messages
10
Recently got a 2015 GX4hs with 80K miles so I decided to schedule it for a complete check at the dealership (as mentioned in my other post, they did a big software update).

One of the (written) requests I had was to check the EV battery and also the 12v Aux battery (when I had the BMW i3, lots of issues were caused by the 12v aux batt).

So the reports came back that both batteries are healthy, no issues and they gave me some print outs. :D

Knowing that I'd be away for a week, I didn't want to leave the EV battery flat so when I drove it last time I used the Charge mode quite often getting the EV range up to 5 miles.

Back a week later, unlock the car but it goes completely dead, dashboard dark yet I could still hear the AVAS sound!? not even the door locks were responsive, locked the car with the key and went to find a neighbour to lend me an extension so I can charge it.

Accessed the boot from the inside via the little flap, left the EV charger plugged in for 2 hours but nothing.
I then removed the boot cover to access the 12v battery and connected a smart charger - it showed 3.6v charge!!

Ultimately I had to remove the 12v battery and leave it in the garage to charge... couldn't use the car for almost 2 days.
Calling the dealer they said it's normal because the ICE doesn't charge the 12v battery.. :shock:

So I still don't understand how the report came completely fine and the auxiliary battery was healthy and then reached such a low charge - did I do something wrong? what could've caused this in just a week?
 
Most likely something drawing power continuously during the time you were away.

Typically heating/cooling turning on and off on a timer.

Other culprits would include after market accessories like alarms, dashcams, CB radio, etc.

Wifi turns off after two days if you don't use it, but if you have a device at home that communicates with the car, that could keep the wifi running for a week.
 
Cheers Andy, still puzzled as the car doesn't have any accessories and I haven't left anything connected, not even the USB charger..
Remote climate was always completely off, WiFi only linked to my phone which wasn't nearby.
 
It is a bad 12V battery, was it good during checkup or they didn't really do it will remain a mystery.

On that note, one can't charge the vehicle while 12V battery is dead.
 
Make sure that you get the right kind, i.e. Absorbent Glass Mat (AGM) .

The 12v battery is charged by the traction battery when the car is turned on.

If you have a model with a working 'Remote Module' the battery is also charged every day at 2pm, from the traction battery, while the car is turned off.

The 'Remote Module' is the device that lets owners connect to the car via the app.

(It may also provide the blue tooth connection, but I'm not sure about that.)
 
Skylander said:
I am looking to find a replacement auxiliary battery..

How does the car charge the 12v battery?

Hi
Did you ever manage to source a replacement Auxiliary battery at a decent price, as I’m looking into replacing mine before I have any problems as it’s coming up to 8 years old next month
 
I have bought from Tayna batteries several times before.

The little YUASA HJ-S46B24L(S) AUXILIARY BATTERY 12V 45AH is quite pricey though....

£190.89 + delivery.... ;)
 
MrPastry said:
I have bought from Tayna batteries several times before.

The little YUASA HJ-S46B24L(S) AUXILIARY BATTERY 12V 45AH is quite pricey though....

£190.89 + delivery.... ;)

Hi
Yes that is a little pricey 😱 but better than the inconvenience of not being able to start my car because my 8 year old battery had let me down I guess.
Am I right in thinking at coming up for 8 years old my original battery must now be reaching the end of its serviceable life. I understand the location of auxiliary battery in my outlander but is it just a straightforward swap, so remove floor tray undo securing bar then remove battery terminals off the old battery.
Then fit and connect up the new battery, will I lose any information by disconnecting the auxiliary battery like radio codes and or vehicle settings or will it retain all said information for the couple of minutes the battery will be disconnected before the new battery is fitted ?
 
Recently got a 2015 GX4hs with 80K miles so I decided to schedule it for a complete check at the dealership (as mentioned in my other post, they did a big software update).

One of the (written) requests I had was to check the EV battery and also the 12v Aux battery (when I had the BMW i3, lots of issues were caused by the 12v aux batt).

So the reports came back that both batteries are healthy, no issues and they gave me some print outs. :D

Knowing that I'd be away for a week, I didn't want to leave the EV battery flat so when I drove it last time I used the Charge mode quite often getting the EV range up to 5 miles.

Back a week later, unlock the car but it goes completely dead, dashboard dark yet I could still hear the AVAS sound!? not even the door locks were responsive, locked the car with the key and went to find a neighbour to lend me an extension so I can charge it.

Accessed the boot from the inside via the little flap, left the EV charger plugged in for 2 hours but nothing.
I then removed the boot cover to access the 12v battery and connected a smart charger - it showed 3.6v charge!!

Ultimately I had to remove the 12v battery and leave it in the garage to charge... couldn't use the car for almost 2 days.
Calling the dealer they said it's normal because the ICE doesn't charge the 12v battery.. :shock:

So I still don't understand how the report came completely fine and the auxiliary battery was healthy and then reached such a low charge - did I do something wrong? what could've caused this in just a week?
I was on holiday for 2.5 months and when I came back my 12v battery was completely flat. You don't need to take the battery out to charge it. You can charge it from the engine compartment. Connect the charger to batterie's + port and connect the negative end to the body of the car. Mine charged overnight and had no issues.
 
I have bought from Tayna batteries several times before.

The little YUASA HJ-S46B24L(S) AUXILIARY BATTERY 12V 45AH is quite pricey though....

£190.89 + delivery.... ;)

Yeah, if you think that is pricey, go check it with the dealer, they will ask for it between £500 and £1000!
 
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