12v battery

[Samg123]

Hi all. Just drove the mg4 25 reg. A couple of hours later, nothing works. I tried jumping the 12v battery and it started again but as it's less than 12 months old I was surprised thr 12v battery would die so quickly.

Does plugging in and charging help to recharge the 12v battery as well?

 

[siteguru]

On mine the 12V is charged when the HV is charging. In fact mine is charging right now and the app shows the voltage as 14.3V

 

[Samg123]

On mine the 12V is charged when the HV is charging. In fact mine is charging right now and the app shows the voltage as 14.3V

Thanks - is it safe to drive?

I'll need to jump it again to get home now. And then report to MG as I'd expect it last longer than 9 months?

 

[Martinonline]

What does the driver's display show as the battery voltage when you select the tyre folder or when you get a status update using the app?

Do you have any warning lights when the car is powered up?

 

[Samg123]

What does the driver's display show as the battery voltage when you select the tyre folder or when you get a status update using the app?

Do you have any warning lights when the car is powered up?

There were lots of systems off, but after about 10 mins of driving they all came back.

Just got home and plugged into charge at it turned off and won't start again.

 

[Samg123]

Oddly, no low battery warning

 

[Martinonline]

I've no idea what voltage triggers the low battery level warning, I've only had the low voltage battery charging circuit failure indication.

I would say you have a dodgy battery but have a check to see if the terminals are really tight; this has been reported as a problem previously.

Are you charging at the moment? If so what does the app say the battery voltage is?

 

[Samg123]

I've no idea what voltage triggers the low battery level warning, I've only had the low voltage battery charging circuit failure indication.

I would say you have a dodgy battery but have a check to see if the terminals are really tight; this has been reported as a problem previously.

Are you charging at the moment? If so what does the app say the battery voltage is?

Managed to get it charging after a couple of goes. It would lock while charging and cut out.

It now says 12v is at 14.4v

 

[siteguru]

14.4V means that the 12V charging circuit is active, without any other heavy load on the 12V battery (such as when the HVAC system is running).

 

[Samg123]

14.4V means that the 12V charging circuit is active, without any other heavy load on the 12V battery (such as when the HVAC system is running).

Thanks. So the battery is working. Just an odd drain on it then! Worth flagging to dealer as it's still in warranty?

 

[MickeySw]

The main function of the 12V aux is to get the car to start, once in READY (or charging) the DC/DC converts the HV battery voltage to around 14V. (You could actually disconnect the 12V battery, the car will keep running).

As long as the DC/DC is working, the 12V battery is charging.

Once you turn off the car, the 12V aux will take over again and power all systems (sleep mode) until you start it again. If the car doesn’t ‘wake up’ suspect a faulty 12V or parasitic drain.

IIRC, the Aux battery is only covered by MG warranty for 12 months, if it fails don’t bother with an OEM, just replace it with a well known brand.

 

[Kenno]

A common issue on new MG4s is that the battery clamps are not tight. Worth checking the tightness with a (I think) 10mm spanner

 

[decrep]

I think they are removed for shipping, then they aren't tightened properly before delivery.

 

[Samg123]

Following an overnight home charge, the app is reporting its at 12.6v which I think is where it should be when not charging. Still no idea why it died!

Thanks to everyone for relies.

 

[MickeySw]

Following an overnight home charge, the app is reporting its at 12.6v which I think is where it should be when not charging. Still no idea why it died!

Showing 12.6V after being charged is a good start, question though is how long will it last?

Common consensus is that ‘sulfation’ can cause irreversible damage to a 12V aux with just one deep discharge ( < 10.5V)?!

 

[Samg123]

Showing 12.6V after being charged is a good start, question though is how long will it last?

Common consensus is that ‘sulfation’ can cause irreversible damage to a 12V aux with just one deep discharge ( < 10.5V)?!

Not very long - I went to move it this morning, and it had enough power to unlock but then nothing! MG assist now called