"12 volt battery charge low avoid parking for more than 3 days" message

[TreeBadger]

I have a 23 reg MG5 Trophy SW Long Range and it recently started showing the "12 volt battery charge low avoid parking for more than 3 days" message when I stop the car and open the door. It first happened a few days ago when I brought it home from being serviced. I was hoping the error would clear after I had charged the car as I understand charging the HV battery also charges the LV battery, but it hasn't made any difference. I've also taken it for a good drive.
If I unlock the car and don't put it into ready straight away, eg if I'm loading things into the car, it comes up with "12 volt battery charge low, please start the vehicle features may be limited" or something similar. I've checked the 12V battery status on the dashboard when the car is running and it shows 14.7 volts and State of Health appears to be about 50% (it did briefly drop to about 25%, but went back up to 50% when I drove the car for twenty minutes or so). With the car not running, the 12V battery currently shows 12.1V on the MG app.
Another possible factor is that I was away for a few days prior to the service and let the range go down lower than the usual 20% (probably about 15%) before charging it and also charged it up to 100%. I remember reading something about how going below 20% can sometimes cause the HV battery to stop charging the LV battery. I don't usually let it get below 20% and only charge up to 80% for my normal driving).
I'm planning to contact MG about it over the next day or two, but wanted to see if anybody else has experienced this before I do so that I'm best prepared to explain it to them.
Any help or suggestions are much appreciated. Thank you.

 

[kevin ellard]

12.1V on the app is a bit low but not too worrying but regularly getting the "avoid parking" message would worry me. It is possible that the 12V battery has a fault and, as fault finding procedures go, replacing the 12V is cheaper than a lot of other things you could do.

One possibility is that you have the weird radio problem that can drain the 12V even when the car is turned off. Has the radio been behaving oddly? If so then a real reset (disconnecting the 12V far a few minutes) may fix it. My trophy has had that problem once about a year ago and has been fine since.

 

[MickeySw]

I was hoping the error would clear after I had charged the car as I understand charging the HV battery also charges the LV battery, but it hasn't made any difference. I've also taken it for a good drive.

The CCU will charge the 12V battery every time the car is READY or charging, no need to take her for a spin.

With the car not running, the 12V battery currently shows 12.1V on the MG app.

This is about 50% charged.

Another possible factor is that I was away for a few days prior to the service and let the range go down lower than the usual 20% (probably about 15%) before charging it and also charged it up to 100%.

By the time the HV battery is reaching 100%, the 12V aux should also be fully charged.

I remember reading something about how going below 20% can sometimes cause the HV battery to stop charging the LV battery.

Your memory is playing tricks with you, there is no such limit.

I'm planning to contact MG about it over the next day or two, but wanted to see if anybody else has experienced this before I do so that I'm best prepared to explain it to them.
Any help or suggestions are much appreciated. Thank you.

The 12V aux battery warranty is only one year therefore go with @kevin ellard ‘s advice; if a hard reset doesn’t improve the situation, replace the 12V battery.

 

[TreeBadger]

Thank you all for your help. I haven't noticed any weird behaviour from the radio lately. However, I will try the reset. If that doesn't solve it, I'll go with replacing the 12V battery. Thank you also for confirming the warranty on it. Much appreciated.

 

[jackois]

I had something similar last week... A year ago, my 22 plate 5LR wouldn't unlock, due to a low 12v battery, diagnosed by the AA who I called out. He 'jump-started' thhe car and said to monitor it and call him if it played up again. He alos recommended buying a jump pack to keep in the glove box. The battery has been fine, reading generally 14.1V when running.

Fast forward to last week, and after charging at a Gridserve, I got a HV battery alarm when I tried to start the car, noticing that the12V was showing 12.1V. Luckily, I'd taken his advice and my year old Noco jump pack was in the glove box, which got the car going again.

Since then, the car has been fine, and is back to 14.1V on the 12V battery when in use. I suspect, I'd ran the battery down when switching it on to check the progress of the charging...

All back to normal, but monitoring the 12V battery again...

 

[TreeBadger]

Thank you for all the info, much appreciated. I may well invest in a jump pack just in case. Out of interest, which model of Noco did you go for?

 

[Archev]

Thank you for all the info, much appreciated. I may well invest in a jump pack just in case. Out of interest, which model of Noco did you go for?

I don’t think it matters - they’ll all start an ev with its relatively low power requirements.

 

[jackois]

I bought this one:

https://www.amazon.co.uk/NOCO-GB40-UltraSafe-Lithium-Starter

It has an usb outlet for phone charging and so on and recharges via usb. There are loads, but this is the one the AA chap recommended.

 

[Eddie99]

Updated Link for that Starter Device

 

[MickeySw]

. The battery has been fine, reading generally 14.1V when running.

This isn’t the battery voltage, it’s what the CCU supplies when READY/charging

I got a HV battery alarm when I tried to start the car, noticing that the12V was showing 12.1V.

That’s about half full

Luckily, I'd taken his advice and my year old Noco jump pack was in the glove box, which got the car going again.

Probably just a coincidence, but better look at it than for it…

. I suspect, I'd ran the battery down when switching it on to check the progress of the charging...

12V battery is also charging when you top up the HV battery