"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

 

[TreeBadger]

Updated Link for that Starter Device

Thank you, I'll check it out.

 

[Gomev]

I bought the smallest Noco, the GB20 as it was on offer at the time. It works fine.

 

[TreeBadger]

I bought the smallest Noco, the GB20 as it was on offer at the time. It works fine.

Brilliant, thank you

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.

I disconnected the 12V, left it for a few minutes and then reconnected it. This has solved the issue and the SoC is now back up to 100%. All is working fine now. Thank you very much for your help.

 

[Area808]

I am leasing a new MG5 since December. We started getting these messages every day after 6 months. The 12V battery was replaced under warranty about a month ago. Now the same warning messages are coming back on a new battery. We use the car normally, don’t let it sit for long periods. I think it’s just a very very poor design. Something is draining the 12V but we’ve no idea what it is. I suppose we just need to keep a jump start with us and ignore it I guess.

 

[SimonomiS]

I am leasing a new MG5 since December. We started getting these messages every day after 6 months. The 12V battery was replaced under warranty about a month ago. Now the same warning messages are coming back on a new battery. We use the car normally, don’t let it sit for long periods. I think it’s just a very very poor design. Something is draining the 12V but we’ve no idea what it is. I suppose we just need to keep a jump start with us and ignore it I guess.

That's not normal behaviour and you shouldn't have to carry a jump start device to use on a regular basis. Have you disconnected the 12V battery to see if that resets things? You'll need to do a short drive afterwards for the error lights to clear.

 

[Area808]

That's not normal behaviour and you shouldn't have to carry a jump start device to use on a regular basis. Have you disconnected the 12v battery to see if that resets things? You'll need to do a short drive afterwards for the error lights to clear.

We don’t carry a jump lead as yet and It’s never actually died on us. Just given us warning messages. I have a hunch that a 3rd party energy app is slowly draining the 12V as we switched to a smart EV tariff and the car is logged in on that. It trickle charges the car over long hours and we have been having problems since linking the car to that app. I’ve logged out of it this morning to see if the problems might go away.

I haven’t disconnected the 12V but it was replaced a month ago, so it was disconnected then. Constantly disconnecting the battery doesn’t seem like a good solution either.

Failing that, I suppose we go back to the lease company. As I say, replacing the 12V battery has seemingly not solved this problem.

 

[SimonomiS]

Good luck with your troubleshooting!

 

[5teep]

Seems to be a fact of life with EVs and 12v batteries. I'm booked in to get mine replaced next week as it's not holding a charge properly, meantime I unplug everything when I switch off the car at night to try and avoid drain.

 

[Area808]

Seems to be a fact of life with EVs and 12v batteries. I'm booked in to get mine replaced next week as it's not holding a charge properly, meantime I unplug everything when I switch off the car at night to try and avoid drain.

It may well be the case that’s it’s actually nothing to do with the 12v battery at all, like in my case.

I have read about a few cases of apps constantly communicating with EVs and causing them to always be awake, sending and receiving messages, and I have a working theory that this may be my problem. At one point I was logged in on 3 different apps all talking to my flipping car. I’m logging out of all of them, and we shall see if that improves things.

It might be the case that’s that this is all too smart for its own good and the 12V is the thing that suffers. We shall see.

 

[5teep]

It may well be the case that’s it’s actually nothing to do with the 12v battery at all, like in my case.

I have read about a few cases of apps constantly communicating with EVs and causing them to always be awake, sending and receiving messages, and I have a working theory that this may be my problem. At one point I was logged in on 3 different apps all talking to my flipping car. I’m logging out of all of them, and we shall see if that improves things.

It might be the case that’s that this is all too smart for its own good and the 12V is the thing that suffers. We shall see.

Possibly but in my case the car is not connected to any devices, no AA, no bluetooth at all, simply because I hate the clunky way the car and AA interact. This is my second MG5 and I've had 12v issues with both of them. Thankfuly it's a company car and I don't have to pay