Dead Battery and Won’t Charge!

[Sam S]

Hi, I got my car in February last year and have been loving it until today!

I set it to charge last night as it was just over 30% and this morning it is frozen up, stopped charging in the night at some point and is not responding. I assume the battery is now dead due to the cold, or needs to warm up before it can respond. I managed to unlock it and got in but the screen won’t come on so I can’t tell it to start charging and my charger won’t start again until the car responds……

Has anyone got any tips please on how I can get it charging? This has got me quite worried as it has been fantastic till now, but this is the first really cold spell since I got it and fortunately I don’t have to go anywhere this morning, but it should be ready any time to get in and go.

Thank you .

 

[Ian Key]

Its possible that the 12V battery has gone flat. If you can't or don't want to charge it yourself give MG Assist a call.

 

[Sam S]

Thank you very much for your reply. I have been reading around and was not aware the 12V battery is the power house, as I have never had any issues. Very naive, but I will learn from this. I will pop to Halfords and see if I can get a suitable booster as I need the car later!

 

[Jomarkh]

The car needs the 12V battery to turn on the computer that then kicks the HV battery into life and that charges the 12V battery. You only need a booster pack connected to the 12V battery to get the car back on in Ready mode.

 

[Sam S]

Thanks

 

[Ian Key]

Thank you very much for your reply. I have been reading around and was not aware the 12v battery is the power house, as I have never had any issues. Very naive, but I will learn from this. I will pop to Halfords and see if I can get a suitable booster as I need the car later!

You don't need a powerful one as you aren't turning an engine over just powering up a few relays etc.

Your car will have full AA breakdown cover including home start provided through MG Assist (0800 072 3338)

 

[Paulussie]

Hi, I got my car in February last year and have been loving it until today!

I set it to charge last night as it was just over 30% and this morning it is frozen up, stopped charging in the night at some point and is not responding. I assume the battery is now dead due to the cold, or needs to warm up before it can respond. I managed to unlock it and got in but the screen won’t come on so I can’t tell it to start charging and my charger won’t start again until the car responds……

Has anyone got any tips please on how I can get it charging? This has got me quite worried as it has been fantastic till now, but this is the first really cold spell since I got it and fortunately I don’t have to go anywhere this morning, but it should be ready any time to get in and go.

Thank you .

 

[Martinonline]

And whilst you're dealing with the battery check the terminal leads are tight. Some have reported them loose causing the 12V battery not to charge correctly and not supplying the current needed.

 

[JonnyG]

Anyone know the CCA figure for the standard MG4 12V battery ?

I know someone who has a 12V car battery tester and I think it needs this figure entering to estimate the battery % SoH. Thought I'd give mine a check after reading this and after the freezing weather

Note : I am just talking about the 12V battery under the bonnet !

 

[Alb]

I think it's 570A at -18°C

 

[ReintjeWA]

Mine is 450A (Aussie Trophy LR) with a Jan 2024 build date

 

[Alb]

Interesting, my figure is for the 63AH battery.

 

[JonnyG]

Mine is 450A (Aussie Trophy LR) with a Jan 2024 build date

Thanks, that makes sense as this battery was suggested as a straight replacement (by an MG dealer I think) in another thread :-

EA472 Exide Premium Car Battery 063TE

EA472 Exide Premium Car Battery 063TE Exide are one of the leading battery manufacturers companies in the world and have been delivering quality in the automotive and infrastructure sectors for more than 130 years! Exide EA472 premium car batteries are Exide's leading wet lead acid battery...

www.tayna.co.uk

 

[ReintjeWA]

Interesting, my figure is for the 63AH battery.

Surely CCA don’t really matter for an EV? Not to the extend it meant something for ICE cars anyway? It is interesting they apparently ship with different AH figures, maybe just chucked in what was available haha

 

[JonnyG]

It's just a figure that the battery tester needs to output SoH I think. I'll doublecheck the side of mine before I test ..... too lazy and cold outside to check at the moment

 

[T1 Terry]

Ah, CCA and RC are all tested differently. CCA as it suggests, are cold cranking amps and have a temp reference as well. RC, Reserve capacity is a how many mins a brand new fully charge battery can supply 25 amps before it drops to 10.5v.
Ah, amp hrs, is one of those magical numbers that mean nothing with a number of other references. The C rating is the number of hrs the battery can supply the load, that load is the capacity divided by the number of hrs, this all has to happen at 25*C and the battery must be fully charged and virtually new, and it needs an end of discharge voltage. As an example, the 63Ah rating needs the C number, common is C20 for lead acid batteries, so 63/20 = 3.15 amps for 20 hrs down to 10.5v, but some resellers on the likes of evilbay might use C100, 63/100 = 0.63 amps for 100 hrs down to ...... the point you can no longer get 0.63 amps out of it ....... an absolutely useless measurement in that case.

A quality LFP 12v battery, like a Winston Batteries brand, is tested at C2 down to 12v while under load, e.g. 100Ah battery discharged @ 50 amps for 2 hrs and holds better than 12v while still delivering the 50 amp load .....
Thus ends todays sermon on battery terminology

T1 Terry

 

[ReintjeWA]

Ah, CCA and RC are all tested differently. CCA as it suggests, are cold cranking amps and have a temp reference as well. RC, Reserve capacity is a how many mins a brand new fully charge battery can supply 25 amps before it drops to 10.5v.
Ah, amp hrs, is one of those magical numbers that mean nothing with a number of other references. The C rating is the number of hrs the battery can supply the load, that load is the capacity divided by the number of hrs, this all has to happen at 25*C and the battery must be fully charged and virtually new, and it needs an end of discharge voltage. As an example, the 63Ah rating needs the C number, common is C20 for lead acid batteries, so 63/20 = 3.15 amps for 20 hrs down to 10.5v, but some resellers on the likes of evilbay might use C100, 63/100 = 0.63 amps for 100 hrs down to ...... the point you can no longer get 0.63 amps out of it ....... an absolutely useless measurement in that case.

A quality LFP 12v battery, like a Winston Batteries brand, is tested at C2 down to 12v while under load, e.g. 100Ah battery discharged @ 50 amps for 2 hrs and holds better than 12v while still delivering the 50 amp load .....
Thus ends todays sermon on battery terminology

T1 Terry

As always it was a pleasure coming to your TED-talk

 

[Sam S]

Anyone know the CCA figure for the standard MG4 12V battery ?

I know someone who has a 12V car battery tester and I think it needs this figure entering to estimate the battery % SoH. Thought I'd give mine a check after reading this and after the freezing weather

Note : I am just talking about the 12V battery under the bonnet !

Sounds like a good idea after my experience. I got a battery booster to charge the battery up and waited……..I ended up getting the AA out in the end and the battery was reading at 4V! It was boosted quickly back to 14.1V and then I took the car for a run, as suggested by AA, and went to MG about 12 miles away to make sure the battery was charging and keeping the charge.

Due to the snow, hail and ice, I managed to also damage my windscreen wipers along the way, as they must’ve still been stuck in the ice and got strained when I turned them on. My fault for rushing. These issues have knocked my confidence in the car though, as I haven’t had these problems with any of my other (ICE) cars .

 

[tsedge]

MG EVs are supplied with cheap small car ICE 12V batteries. All part of the cost cutting and they don't last well.

The CCA is pretty irrelevant. Leisure batteries cost a lot more but last a lot longer and are more reliable in cold weather.

My own view is that it is worth changing the 12V battery every 2 years with an EV, unless it is supplied/replaced by a lithium battery or something else that is a better fit for the long term (eg decent leisure battery).

General advice is to carry:

• 12V battery booster in cabin (small one, top up regularly).
• 10mm spanner (in case you need to disconnect and reconnect the 12V supply to reboot the car).
• MG key with the emergency key in it (not everyone has the emergency key supplied inside both keys: I only have it in one key).
• Trim tool to remove the charger flap cover and T45 Star bit to open the charging door once cover is removed if it fails.
• Familiarise yourself with the emergency charger socket release cable access in the boot.
• Familiarise yourself with the emergency boot release procedure from inside the car - think this may be easier with a screwdriver.

Oh and change your key batteries every year (yes part of the 2 years service but they won't necessarily last that long - mine did not).

 

[Lizibee]

This has happened to me. I couldn’t get into my MG4 today. My son opened the car using the spare key. Need to jump start the car now after reading this post.