Completely dead this morning

[andrew99]

So on my 5th day of being an MG4 owner I’ve had my first issue.
Doors wouldn’t open, car wouldn’t unlock. Battery had 74% charge last night.
AA came, opened the door with the physical key, tried charging the 12v battery. No joy, the occasional click and whir but no sign of life on the dash.
Booked a recovery vehicle, it’s on my drive so said they would get a specialist recovery vehicle.
Flatbed truck turned up but couldn’t do anything so now I’m waiting for another truck with no ETA.

 

[Cocijo]

It sounds like a 12v battery failure. Let’s hope that it is straightforward and that you get it sorted quickly.

 

[andrew99]

Tried to charge the 12v but didn’t make any difference.

 

[the briggie]

Not a great start. Hopefully only a faulty battery as that's the simplest remedy. Recovery needs to able to lift the rear wheels to avoid damage

 

[Cocijo]

It’s rear wheel drive.

 

[the briggie]

Apologies as you rightly point out rear not front..got confused with my Kia

 

[andrew99]

I do hope it’s something easily diagnosed and fixed. I bought a new car for reliability, not expecting no issues at all but this is disappointing.

 

[bowfer]

I do hope it’s something easily diagnosed and fixed. I bought a new car for reliability, not expecting no issues at all but this is disappointing.

Don’t let problems fester.
It’s dead easy to reject a car within the first 30 days, remember that.

 

[Cocijo]

I’m sure it will be ok. 12v issues are not uncommon on EV’s and a new battery should fix it If that is the problem.

 

[Alb]

The number of 12V battery failures we are seeing is way beyond what anyone might consider normal for a new car. I'm not sure if anyone ever bottomed out whether it was a parasitic drain issue or just a batch of bad batteries.

 

[Ian Key]

Mk3 Ford Mondeo's used to have dead battery syndrome where for no apparent reason the battery would totally discharge overnight. I don't think the reason why was ever fully explained and it didn't happen to every car, but the consensus of opinion was it was the blue-tooth module continuing to try and connect to the phone that had been paired with it even when the car was locked.

 

[WonkoTheSaneUK]

The number of 12V battery failures we are seeing is way beyond what anyone might consider normal for a new car. I'm not sure if anyone ever bottomed out whether it was a parasitic drain issue or just a batch of bad batteries.

We were told to expect 12V battery issues back in 2020, with freshly-built cars stuck in dockyards & factory storage yards for months.
3 years later, I have to wonder if manufacturers are still installing lockdown-era 12V batteries?

 

[stevegus]

Mk3 Ford Mondeo's used to have dead battery syndrome where for no apparent reason the battery would totally discharge overnight. I don't think the reason why was ever fully explained and it didn't happen to every car, but the consensus of opinion was it was the blue-tooth module continuing to try and connect to the phone that had been paired with it even when the car was locked.

Most cars would have a battery capacity of 40 amp hours. For a bluetooth to drain that overnight would seem a bit excessive UNLESS the battery was failing and having no where near original capacity

 

[bowfer]

Is it a reputable make 12v battery, or ‘cheapest supplier’ stuff?

 

[Cocijo]

The 12v batteries used in most EV’s were never designed for them. Once again an ICE design - for use when heavy discharge and cranking of an engine is needed. They don’t perform that great in EV’s by comparison- but they’re cheap. Some EV’s now use Lithium Ion 12v batteries.

 

[Alb]

For the likes of the ZSEV & MG5EV I'm pretty sure SAIC use the same battery that's fitted to the ICE version.

 

[stevegus]

The 12v batteries used in most EV’s were never designed for them. Once again an ICE design - for use when heavy discharge and cranking of an engine is needed. They don’t perform that great in EV’s by comparison- but they’re cheap. Some EV’s now use Lithium Ion 12v batteries.

If it’s anything like the cost comparison for a leisure battery in a motorhome you are looking at approx £500 for a lithium compared to £125 for a lead acid.

As an electronics design engineer the bean counters would have a fit at my company if i designed a 4x more expensive part into a product. Better is not always a requirement of the spec. It sucks.

 

[tsedge]

Is it a reputable make 12v battery, or ‘cheapest supplier’ stuff?

It is SAIC branded but I don't know if they make them or subcontract. Almost certainly cheapest of cheap and probably best to replace early if you want peace of mind.

The number of 12V battery failures we are seeing is way beyond what anyone might consider normal for a new car. I'm not sure if anyone ever bottomed out whether it was a parasitic drain issue or just a batch of bad batteries.

Tesla had a bad batch a few years back and that's partly why they switched to Lithium Ion 12V batteries.

Almost all 12V batteries come from China these days due to price.

 

[Cocijo]

The majority of 12v batteries in EV’s perform ok. There are issues but it’s important to note that although they are not ideal they work ok, most of the time.
One of the main areas that has caused excessive 12v drain on EV’s is not engaging the HV pack when sitting in the car and using accessories etc. Most users now know about this. With the MG4 setup (no start button) it’s not really an issue.

 

[WonkoTheSaneUK]

Tesla had a bad batch a few years back and that's partly why they switched to Lithium Ion 12V batteries.

Lately, Elon has been talking about skipping 24V "accessory" batteries, and jumping straight to 48V for the Cybertruck.