MGS5 12V battery dead

[Shwd mae]

Has anyone else had a problem with the 12V battery becoming drained overnight? I returned my first MGS5 due to this problem and today I have had exactly the same problem with my replacement MGS5, arghhhhh.

 

[Ian Key]

Check the battery terminals are tight.

 

[Rei]

Funny you would have two with the same problem. Mine has been great, and I've got a dashcam that goes into parking mode for 6 hours after I turn it off.

 

[decrep]

hmm, evidence is starting to point to the user.
Do you have something plugged in?
The OBD dongle draws power even when car is off.

 

[bilbo]

Has anyone else had a problem with the 12v battery becoming drained overnight? I returned my first mgs5 due to this problem and today I have had exactly the same problem with my replacement mgs5, arghhhhh.

Yes, mine did this again yesterday morning. It's preceded by the "USB Recognition Failed" message on the centre screen on start up, then the radio getting stuck on one station, then eventually a battery drain. I have the car booked in for tomorrow for an investigation, but since everything has rebooted now, it's all OK. I'll have to contact the garage to see if it's still worth taking the car in, or just wait till I get the error again and the doom loop begins again.

 

[Shwd mae]

Thanks for the replies. If it's 'the user' I would like to know how? Car is locked, full charge, not connected to charger. Why on earth should the battery become drained?

 

[decrep]

something is draining it,
you have nothing plugged in to USB ports, OBD dongle and every thing else is turned off?
Needs a sparky with a meter to see where the current is going.

 

[Shwd mae]

Nothing plugged in. There was an annoying problem with the tailgate not opening high enough, but no dashcam/cables etc plugged in.

 

[Shwd mae]

Problem has been identified as a drain from the T box.

I also mentioned that my MG app would often log me out and say 'account change, your account is logged in on another device' and this may be connected to the problem.

 

[emmrecs]

I also mentioned that my MG app would often log me out and say 'account change, your account is logged in on another device' and this may be connected to the problem.

Ditto here with that very annoying message but, at least at the moment, I'm not seeing any parasitic 12v drain so the issues may not be related.

 

[cargocare]

Has anyone else had a problem with the 12V battery becoming drained overnight? I returned my first MGS5 due to this problem and today I have had exactly the same problem with my replacement MGS5, arghhhhh.

MG Garage have checked my MG5 for this problem (twice) the problem has reoccurred several times, today they advise there is a switch (part of the foot brake mechanism for turning the car on) which has an intermittent fault, the switch may on occasion not switch off when you leave/ lock the car. They have tested the switch and found it may be the culprit (nothing is 100%) MG Garage are ordering a new switch and discussing which warrantee to charge - my warrantee or MG's, hope this helps

 

[Rob Leijsen]

As I posted in another thread, I'm having a problem too. Nothing attached, still my battery is draining rather fast. The car wil probably not start after 48 hours. I sometimes see the message "connecting" on the dashboard if I walk by, I hear things (relays?) if I sit in the car without it being turned on. The MG garage here in Breda (Netherlands) looked into it twice, still no solution.
Deleted the app, made my charger not clever, no change.

 

[emmrecs]

I sometimes see the message "connecting" on the dashboard if I walk by

That should occur only if the car is plugged into a charger, I think. If it is happening for you without your car being connected to a charger this is something you need to point out to your dealer.

I've also heard these "relay" sounds but usually for only a few minutes immediately after the car has been powered down, i.e., turned off. Again, if you hear them at other times, this is something for the dealer to resolve.

 

[decrep]

sounds like the sensor in the charger socket, is activating with no plug in.

 

[dx4100]

I have woken up to a dead MG this morning. Waiting on the AA but its going to be 12v battery for sure. Its crazy considering the size of the battery underneath the car with a 70% charge....

The MG not so "Smart" app says it was awake around 3:39am

I noticed the boot had that issue where it was too low yesterday so I pushed it up to resolve. It was opening and closing correctly I felt afterwards but can't rule out its related. I was also in the car fitting a screen protector yesterday to the infotainment system when it said it was switching off due to a low v12 issue and I thought here we go.

Tested the battery with a battery tester and it was showing as 85% SOC and 100% SOH. Which shouldn't have resulted in a dead car this morning. Will see what the AA say when they get here soon.

 

[dx4100]

Dead battery. AA got it going again and its currently on the drive in ready mode to top up the 12 v. it seems to top up just being turned on. Thoughts ?

Don't think this will sort it to be honest but lets see in the morning.

 

[TimothyN]

Forgive me, I may be talking bollix, because I have only read this in the manual, but isn't there a relatively straightforward way to jump start with a dead battery? pp283 and 284 of the manual?

Presumably you can also trickle charge the battery?

Or have I missed the point again?

 

[dx4100]

AA have jumped started it. It's back to life. AA guy advised to leave it charging from main battery for a few hours. I'm not a car expert by any means but seen to make sense what he was saying.

After the f1 I will go see what the state of charge is. I do have battery tester so will see what it says.

 

[dx4100]

Battery looking good now. Will give it a bit longer to try and try and hit 100% and then see how it goes.

 

[Ian Key]

I noticed the boot had that issue where it was too low yesterday so I pushed it up to resolve. It was opening and closing correctly I felt afterwards but can't rule out its related. I was also in the car fitting a screen protector yesterday to the infotainment system when it said it was switching off due to a low v12 issue and I thought here we go.

When you were in the car fitting the screen protector did you press the brake pedal to turn the car on?

If not then while you were sorting the tailgate out and fitting the screen protector the car's auxiliary systems would be powered from the 12V battery which wouldn't be being topped up by the main traction battery.

I'm not saying that you haven't got a defective 12V battery or that the one fitted isn't up to the job but that could be the reason. It might be worth investing in a jump starter power pack. It doesn't have to be that powerful as all it has to do is provide enough power to get the main battery relays to operate.