My MG4 seems to be dead...

[Eddie A]

Hi, everyone

First post here - been driving my MG4 LR Trophy for a month or so, 450 miles covered as I don't get out much. All was fine yesterday - went out at 11am, came home at 2pm, put in the garage and locked with the keyfob. Went to unlock this evening to get something from the boot and no response - tried both fobs, and the phone app. Any clues? Got the AA coming round in the morning.

Eddie

 

[AndyL61]

Could be a loose battery connection. Quite common.

 

[MG 4 Phil]

12V battery connection or to low in power?

 

[Alb]

12V battery would be my first port of call.
If you have a meter, check the voltage.

 

[Jomarkh]

Have you got a 12V battery charger that you can connect to the car?

 

[siteguru]

If you can't unlock the car with the fob, you can manually unlock using the key hidden inside the fob. Check the manual. That way you'll be able to enter the car to open the bonnet (and so check the battery/tightness of connections).

 

[ncdlloyd]

We've just come out to our MG4 with the same problem this morning. We've had it for nine days...

AA have been called, we'll see what they say.

 

[Eddie A]

Mr AA tells me my battery is in good condition, but a bit drained. So parked up with a 12v charger tucked under the bonnet. That plus three days of 50 miles commuting should kick it back to life.

Until I got this car, I didn't realise there was a 12v battery alongside the motor battery, though it was one battery that did everything. Well, you live and learn. At least the battery booster I kept in my last petrol car will have a new home!

Thanks, all

Eddie

 

[tsedge]

Mr AA tells me my battery is in good condition, but a bit drained. So parked up with a 12v charger tucked under the bonnet. That plus three days of 50 miles commuting should kick it back to life.

Until I got this car, I didn't realise there was a 12v battery alongside the motor battery, though it was one battery that did everything. Well, you live and learn. At least the battery booster I kept in my last petrol car will have a new home!

Thanks, all

Eddie

The main battery is 400V (roughly) and runs the motors, it needs disconnecting from a load to charge it, so the car needs a second electrical system or you'd never be able to run anything in the car while charging (or lock it).

Car accessory electrics have been 12V since the 1950s (6V before that) and there's an enormous ecosystem of suppliers making systems for 12V.

Using a traditional lead-acid 12V battery is a cheap solution, but far from the best. Modern 12V lead-acid batteries are often poor quality (due to price wars) and they are ancient heavy and bulky technology.

Some EV makers are replacing them with 16V lithium batteries (16V with lithium fits with a 12V system electrical load) in a much more compact and lightweight form (eg Tesla), but these cost more to make, so many, like MG have not made that switch yet.

With the new Cybertruck and future products, Tesla are moving to a 48V accessories electrical system. This is much more efficient and cheaper than 12V (lower current equals low losses and much thinner cables). But it remains to be seen how many suppliers start making 48V accessories.

 

[solos]

Could be a loose battery connection. Quite common.

I'dd guess a flat keyfob battery

 

[Alex1985]

Mine went flat after being left for 8 days called the AA man who fitted his own 12v battery and followed me to the dealer. It was diagnosed with a software fault, they installed an upgraded software and whilst it has not been left standing for any length of time it seems ok but I am keeping an eye on the battery voltage via the app. Also the car unlocked itself as the battery became discharged, the Trophy does not seem to have any alternative method of opening the car (unless anybody knows different).

 

[AndyL61]

Mine went flat after being left for 8 days called the AA man who fitted his own 12v battery and followed me to the dealer. It was diagnosed with a software fault, they installed an upgraded software and whilst it has not been left standing for any length of time it seems ok but I am keeping an eye on the battery voltage via the app. Also the car unlocked itself as the battery became discharged, the Trophy does not seem to have any alternative method of opening the car (unless anybody knows different).

You can use the mechanical key inside the key fob , it's in the manual.

 

[Cathy]

You can use the mechanical key inside the key fob , it's in the manual.

Yes but unfortunately you cannot start the car if the battery is dead, but Mr AA sorted out my battery and so far so good.

 

[AndyL61]

Yes but unfortunately you cannot start the car if the battery is dead, but Mr AA sorted out my battery and so far so good.

Yes I know that, I was answering the statement that there was no other way to unlock the car.

 

[mkj0]

Yes but unfortunately you cannot start the car if the battery is dead, but Mr AA sorted out my battery and so far so good.

Yes you can, there’s sensor in the bottom of the storage bin under your elbow in the centre console. Drop the dead key on the bottom of that and the car will still detect it. Just tried it on my trophy, took the key apart and dropped the half with only the electronics and no battery in the bottom. Car could find the key.