Flat 12v battery after 6 weeks

[dawson2099]

I called MG Assist and the AA were here within 45 minutes to get me going. No questions asked. Every cloud has a silver lining it seems. My radio was not working at all, but since the battery went flat and was recharged just started up again! No idea why but appreciative!

 

[siteguru]

The media system (as with most systems, other than the drive motor) relies on the 12V battery - if it's flat then it likely won't work.

 

[dawson2099]

The media system (as with most systems, other than the drive motor) relies on the 12V battery - if it's flat then it likely won't work.

Interesting - maybe that in effect forced a "factory" reset - sorted the problem anyway

 

[Gomev]

I went away for 6 weeks and on my return the car was dead. Doors would not open or anything I called MG support who sent the AA and they found the hidden manual key slot and opened the door and bonnet. I have to charge the 12v battery to recover the car even though the main battery was 57%

If at all, how many times while you were away did you poll the car to check it's wellbeing?

 

[dawson2099]

Is it possible to open the boot without the regular key?

 

[Lovemyev]

Is it possible to open the boot without the regular key?

Can you expand a little on your question please ?.
Are you referring to the key fob, the metal manual emergency key in the fob etc .

 

[dawson2099]

If the car won't open due to flat 12v battery I realise that I can open drivers door manually with emergency blade. If I keep my jump starter in the boot, could I get it out! I think there's an option for all doors to open with manual key but would this apply to boot too?

 

[WonkoTheSaneUK]

If the car won't open due to flat 12v battery I realise that I can open drivers door manually with emergency blade. If I keep my jump starter in the boot, could I get it out! I think there's an option for all doors to open with manual key but would this apply to boot too?

You can open the boot from the inside with the emergency blade.
Far easier to get into the cabin and drop the rear seat backs to access the boot.

 

[dawson2099]

Thanks. I'll keep the jump starter under my seat just in case.

 

[Lovemyev]

If the car won't open due to flat 12v battery I realise that I can open drivers door manually with emergency blade. If I keep my jump starter in the boot, could I get it out! I think there's an option for all doors to open with manual key but would this apply to boot too?

I use to keep my booster pack in the boot, until the same thing did cross my mind one day.
Yeah - You can get still get to it, but I thought is was a better idea just to store it under the drivers seat instead ?.

 

[Vingnut]

My plan is to get a frunk and store booster pack, type 2 cable and granny charger there. Meanhwile a booster pack would be stored under the seat, but first I have to buy a booster pack I guess.

 

[Lovemyev]

My plan is to get a frunk and store booster pack, type 2 cable and granny charger there. Meanhwile a booster pack would be stored under the seat, but first I have to buy a booster pack I guess.

Do it and you will be unlikely to need it, but if you don’t, you will !.
I bought one very soon after getting our ZS EV ( Gen 1 ) back in 2019.
Never used on the ZS but have used it about eight times to help out other people who have been caught out with a flat battery.
Strangely enough, they have ALL been either petrol ️ or diesels cars !.
Not sure what that suggests .
Every single person was totally convinced that a small ( ish ) booster pack would NOT turn over their cars.
So, I placed them a bet.
If this little box starts your car, you then donate £10 to my favourite children’s charity.
Of course they agree and 30 seconds later there wallets are £10 lighter and they fully intent to purchase one .
It could save you a lot of time waiting hours for the rescue people, for the same 30 seconds.

 

[Ian Key]

Quick tip: Put a note in your diary to charge the booster pack every two months.

I bought one and despite the instructions to charge it every 6 months when I came to do so the pack was totally discharged and wouldn't recharge. Luckily Amazon refunded me and I bought a different one.

 

[dawson2099]

Looking like I might either have a dud battery or the HV is not charging the 12v battery. Parked yesterday and battery showed 12.7v. This morning 12.2v and just now, out of curiosity, 12.1v. Heading slowly south. I do have a camera plugged into the 12v socket and AA Dongle in the USB but both are only powered up when car is Ready.

 

[Ian Key]

Looking like I might either have a dud battery or the HV is not charging the 12v battery. Parked yesterday and battery showed 12.7v. This morning 12.2v and just now, out of curiosity, 12.1v. Heading slowly south. I do have a camera plugged into the 12v socket and AA Dongle in the USB but both are only powered up when car is Ready.

Might be worth just unplugging the camera and the AA dongle overnight and see if the12v battery still drains.

 

[dawson2099]

I'm recharging now and will test overnight as suggested.

UPDATE for anyone interested - no solution but progress. Here is data noted since yesterday:

Day	Time	Voltage		Int Temp
Thursday	19.00	12.7	Parked up after a drive
Friday	10.00	12.2
	14.00	12.1
	16.30	12.7	14.30-16.30Mains charger
		13.0	APP	87C
		13.1	Car READY
		13.9	While driving
	21.00	12.6	Parked up after a drive
	22.00	12.5	Disconnected camera/AA
Saturday	9.00	12.3	APP	21C
		12.3	Tested with meter
		13.9	Car READY

All normal on Thursday night once parked. Car not on charge but dashcam connected to 12v socket and AA dongle to USB socket, both of which are OFF when car is locked. By Saturday PM battery voltage dropped to 12.1 so I recharged to 12.7 although the APP showed 13.0 and a wild internal temperature. Got car READY which showed 13.1 on the screen and 13.9 when driving.

Thinking that the battery drain might be the camera and/or AA dongle I parked up with battery showing 12.6 then disconnected both. Overnight the battery had drained to 12.3 (which I checked with a multimeter) as shown in the APP although when I put the car in READY mode the screen showed 13.9v.

Back to the dealer in a week but seems like a drain somewhere. The ready state voltage reading might be because the HV is starting to charge up the 12v battery? I haven't tested this while the car is on charge as yet.

Correction in first para Saturday should be Friday!

 

[tsedge]

I see regular changes in our battery voltage typically between 12.3V and 13.5-14V when it is being charged, yours look a little lower but a fluctation is normal.

Maybe there is a drain or maybe you have a weak 12V battery?

 

[siteguru]

My car is currently sat on my drive, having last driven it yesterday afternoon. I've just scanned with the app and the battery is reporting as 12.6V. (HV SoC is 76%).

 

[tsedge]

My car is currently sat on my drive, having last driven it yesterday afternoon. I've just scanned with the app and the battery is reporting as 12.6V. (HV SoC is 76%).

Mine is right now sitting at 12.5V and 77% SOC. Drove it this morning for a couple of short journeys.

 

[PeteC]

Mine is showing 12.4V and 58% SOC having just driven 350 miles.

A while back I came across an older video from Bjorn Nyland about the 12V battery. He used an MG ZS which showed similar variations in battery voltage and only charged when the car was 'woken up'. He was using pre heat from the app to wake the car and start the 12V battery charging.
If you're interested, this is the video: