MG ZS EV - 12v battery issue at start-up

[TinaH]

Hi, I’ve had to call MG Assist / AA out again because my 20 plate MG ZS EV won’t start (3rd time in 10 months). Main battery fully charged, its the 12V that keeps letting me down - not enough power to fire up all the start up checks, running lights etc that come on to get into ‘Ready’ mode. The car is booked in for first service in a few days, dealer is going to check the battery and the brake light switch, but has anyone else had this issue?? Otherwise, I love the car, but always worried every time I go to start it!

 

[Chrispydoc]

Worth checking if an interior light is on...or have you got a dash cam ?

 

[Davemac278]

Hi, I’ve had to call MG Assist / AA out again because my 20 plate MG ZS EV won’t start (3rd time in 10 months). Main battery fully charged, its the 12V that keeps letting me down - not enough power to fire up all the start up checks, running lights etc that come on to get into ‘Ready’ mode. The car is booked in for first service in a few days, dealer is going to check the battery and the brake light switch, but has anyone else had this issue?? Otherwise, I love the car, but always worried every time I go to start it!

I've had it happen twice in 2 weeks. Car is only a month old. Managed to stretch an extension lead to car as it was parked in street. Granny charged car overnight which charged up the 12v battery.

Learning to only sit in car in ready mode when radio and accessories on. Doesn't help that in lockdown car not being run enough to keep battery topped up.

I've just fitted a bluetooth battery monitor which will notify me on app on my phone if my battery drops below 70% and again at 20% charge.

 

[Cocijo]

do you use the car much in the accessories mode? - i.e. when not in ready mode. This will drain your 12v battery. Always have the car in ready mode if for example sitting in the car with heating on. Ready mode egages the high voltage battery pack. I never use the accessories mode - i find it pointless. Apologies if you already know this

 

[Cocijo]

Switching to ready mode will also top up the 12v battery. Not need to drive car.

 

[Davemac278]

I've had it happen twice in 2 weeks. Car is only a month old. Managed to stretch an extension lead to car as it was parked in street. Granny charged car overnight which charged up the 12v battery.

Learning to only sit in car in ready mode when radio and accessories on. Doesn't help that in lockdown car not being run enough to keep battery topped up.

I've just fitted a bluetooth battery monitor which will notify me on app on my phone if my battery drops below 70% and again at 20% charge.

I had dealer check battery this week and they gave me a print out showing 100% and good state of health. Must have been my dashcam, radio when sitting in car as no lights or doors left open. Only make that mistake once.

I have also bought a 12v car jump pack as a backup to get me started if it does happen again.

 

[TinaH]

do you use the car much in the accessories mode? - i.e. when not in ready mode. This will drain your 12v battery. Always have the car in ready mode if for example sitting in the car with heating on. Ready mode egages the high voltage battery pack. I never use the accessories mode - i find it pointless. Apologies if you already know this

No, I never use the accessories mode. Thanks for the tip though

 

[TinaH]

do you use the car much in the accessories mode? - i.e. when not in ready mode. This will drain your 12v battery. Always have the car in ready mode if for example sitting in the car with heating on. Ready mode egages the high voltage battery pack. I never use the accessories mode - i find it pointless. Apologies if you already know this

Worth checking if an interior light is on...or have you got a dash cam ?

No, I’m always really rally careful to switch everything off since the first time it happened - which was when the car was brand new, and I didn’t drive it for 3 weeks due to lockdown. The 12v was so flat we couldn’t even unlock the door - nightmare .

 

[Cocijo]

No, I’m always really rally careful to switch everything off since the first time it happened - which was when the car was brand new, and I didn’t drive it for 3 weeks due to lockdown. The 12v was so flat we couldn’t even unlock the door - nightmare .

If that happens again - I hope it doesnt - you can open the door using the physical key

 

[Davemac278]

Hi, I’ve had to call MG Assist / AA out again because my 20 plate MG ZS EV won’t start (3rd time in 10 months). Main battery fully charged, its the 12V that keeps letting me down - not enough power to fire up all the start up checks, running lights etc that come on to get into ‘Ready’ mode. The car is booked in for first service in a few days, dealer is going to check the battery and the brake light switch, but has anyone else had this issue?? Otherwise, I love the car, but always worried every time I go to start it!

Can you post an update when dealer has checked your car out. Be interested to know if its a faulty 12v battery, faulty brake light switch or as another owner has reported that there may be a software update to HV controller. (He commented that the dealer said that MG was aware of this issue)

 

[Frank]

No, I’m always really rally careful to switch everything off since the first time it happened - which was when the car was brand new, and I didn’t drive it for 3 weeks due to lockdown. The 12v was so flat we couldn’t even unlock the door - nightmare .

Hi TinaH,

I would hope (assuming you have a home charger) that during the three weeks you were not using the car that you left it plugged in. If you did you would NOT have had this problem.

A lot of EV Owners in my opinion have this fixation of not using their home chargers until the think they need a charge, well guess what your car especially if left immobile for a long time does need a charge. Just keep it plugged in , it does NOT harm the car.

Regards

Frank

PS Before you ask, in the 18 months I have had my EV(s) I plug it in EVERY night when finished with it no matter what the SOC is and I have NEVER had problems with the 12 V battery.

 

[Cocijo]

Hi TinaH,

I would hope (assuming you have a home charger) that during the three weeks you were not using the car that you left it plugged in. If you did you would NOT have had this problem.

A lot of EV Owners in my opinion have this fixation of not using their home chargers until the think they need a charge, well guess what your car especially if left immobile for a long time does need a charge. Just keep it plugged in , it does NOT harm the car.

Regards

Frank

PS Before you ask, in the 18 months I have had my EV(s) I plug it in EVERY night when finished with it no matter what the SOC is and I have NEVER had problems with the 12 V battery.

Hmm - not sure if having your high voltage battery sitting on full for long periods is best practice

 

[Chrispydoc]

If I've driven THE MG for more than 10 miles, I plug the car in when I get home. Once it is fully charged up, I normally unplug it. That has been my routine for the 13 months.

I've been doing this for the last 4 years with my PHEV and have had no problems, other than recently, I had not used it for over a month...and its 12 volt went flat! I charged it up again and now make a point of using that (instead of the MG) at least once a week.

 

[Frank]

Hmm - not sure if having your high voltage battery sitting on full for long periods is best practice

Who gives a shit, you have a 7 year warranty, and most likely have got a new/different car by 3/4 years. Did you ado

don't know what happened to my reply ,there was a lot more than above. The short bit posted above looks a bit abrupt, sorry . My longer post put my feelings/reasoning in a nicer way, sorry if it upset anyone.

 

[Paulie68]

Who gives a sh*t, you have a 7 year warranty, and most likely have got a new/different car by 3/4 years. Did you ado

don't know what happened to my reply ,there was a lot more than above. The short bit posted above looks a bit abrupt, sorry . My longer post put my feelings/reasoning in a nicer way, sorry if it upset anyone.

If you care about sustainability, you want the car to have a long life, despite the fact it may not be your problem. Having most EV's scrapped at under 10 years old due to needing new batteries that will cost far in excess of their then current value is a very bad situation for the world.

Charging to 100% every night whether needed or not is a pretty good way to ensure less than 70% capacity left shortly after the warranty runs out! In fact SAIC\MG are probably a bit nervous some cars might not get to 7 years at 70%, hence shifting the upper voltage down by 5v at the last update!

 

[Paulie68]

If I've driven THE MG for more than 10 miles, I plug the car in when I get home. Once it is fully charged up, I normally unplug it. That has been my routine for the 13 months.

I've been doing this for the last 4 years with my PHEV and have had no problems, other than recently, I had not used it for over a month...and its 12 volt went flat! I charged it up again and now make a point of using that (instead of the MG) at least once a week.

The Outlander PHEV is using a different battery setup that keeps parameters much further away from the top and bottom of the batteries limits, so you don't see degradation (apart from the software issue that reduces capacity over time on some Outlanders)

What you're doing to the ZS, is the worst possible thing for its battery, unnecessarily daily cycling a lithium battery right at the top few percent! It's even worse for your car with it still running the pre update higher voltage too! I pity its next owner...

PS, what you're doing would be perfect for keeping a 12v lead acid battery in perfect condition forever, I think quite a few people mistakenly think this is also best practice for lithium.

 

[Cocijo]

How you charge your car is after all is said and done up to you. I just think that it a shame if you aren’t aware of how best to manage your high voltage battery and prolong it’s usable life. You can then make an informed choice. Charging on the basis that you always want to have a full charge (perhaps because you’re used to having a full tank of fuel) even if you don’t intend to use the car much is again your call - but not best practice for Lithium-ion battery packs. They prefer to sit between about 30% and 80% and don’t respond well over time to being fully charged or fully discharged for long periods. Of course the smaller the battery pack size the harder this may be in practice, but the rules still apply. What tends to happen is when relatively new the battery performs adequately, but in later life performance can dip quite dramatically. Battery packs do also have buffers top and bottom to protect them further from the impacts on the cells of these two extremes, but if it suits your lifestyle and you are bothered about prolonging battery life it’s not that difficult to apply these recommendations sensibly.

 

[Cocijo]

As far as the 12v battery is concerned - this uses different cell technology and likes to sit charged up if possible - with the MG in ready mode this gets a charge. So if you’re not using the car and want to keep the 12v topped up either trickle charge it or switch to ready for a while and charge it that way if you are able (you don’t need to drive the car) - it will soon read c14v. A common issue with the MG ZS EV is draining the 12v battery by using accessories when not in ready mode.

 

[Paul225]

Hi, I’ve had to call MG Assist / AA out again because my 20 plate MG ZS EV won’t start (3rd time in 10 months). Main battery fully charged, its the 12V that keeps letting me down - not enough power to fire up all the start up checks, running lights etc that come on to get into ‘Ready’ mode. The car is booked in for first service in a few days, dealer is going to check the battery and the brake light switch, but has anyone else had this issue?? Otherwise, I love the car, but always worried every time I go to start it!

I had same problem before Christmas and my car was 10 months old - garage replaced 12v battery

 

[Lovemyev]

You know what, I just wonder how many 12 volt batteries in EV's get switched out just because they have just gone flat ?.
Of course, if the battery is faulty internally then YES of course it needs replacing.
Replacing it may be seen as the correct thing to do for the customers piece of mind, but the same thing will happen again if it is down to bad practice and a misunderstanding of how and when the 12 volt battery receives it charge in normal use.
I know the debate of how you should charge / treat your HV battery will go on and on forever.
But it's simple really, if you are leasing the car or intend to hand back the car in a limited time scale then to be totally honest, you don't give a dame what harm ( or not ) it does to the HV pack to be quite frank.
In the same way that you stick it through the rotary car wash at the super market once a month and think it's a great job to be fair.
If on the over hand you intend to keep your EV a number of years, and given the battery makes up a large percentage of the cost of the entire car, you just may want to treat it a little differently.
This is no way intended to be a criticism of how people choose to look after ( or not ) of their cars.
Each to their own I say !.
It's a similar mind set to plugging in your mobile phone and computer every single day when it still has 90% of the battery remaining - why ???.
I think they call it :- "Force Of Habit".
ONLY - speaking for myself here, I will be keeping my SOC between about 50 and 100 ( ish ) miles of range in the current C19 situation.
If I was allowed to make a longer journey, then yes I would fully charge and then use the car that very same day.
It will only be receiving a rapid charge as and when it needs it in emergency use.
We are both retired and have owned the ZS EV for over 12 months.
Covered almost 9,000 miles and been through two lock downs.
I am sure we would have covered even more miles without C19 preventing travel in Wales.
99.9% of our charging has all been done from our home wall box.
The car has been attached to a rapid twice, once to ensure that the car would work okay.
And on the second occasion when we decided to make an unexpected trip one day and I had not bothered to charge.
We could have used my wife's ICE car, but we paid a visit to a local Polar rapid about 2 miles from our home address and picked up about 100 miles in about 35 mins ( ish ).
I do what I consider is the best policy for looking after my battery pack.