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

[Paulie68]

To add a little more about 12v lead acid batteries. If a lead acid battery is allowed to go completely flat and then left in this state for even a week or two, it will be permanently damaged. A simple recharge will give the illusion of it bieng fine, but it will have suffered sulphation and be permanently damaged.

The problem some are seeing with batteries is most likely from cars bieng left in standby mode during shipping. I used to work in automotive shipping and I observed a significant percentage turn up with flat batteries. They get jumper pack started to move from the ship to Dock storage. The next day they get jumped again to load onto a transporter. Once at the dealership, they get jumped once again to get them into the PDI workshop, where they will finally get properly charged to full. Too late for the batteries though that, sadly, will now fail typically within the year.

 

[Iain]

I totally agree - each to his or her own as to how you treat, wash or charge your car.
I would say that the HV lithium ion battery is probably better placed to withstand the rigours of the type of charging/discharging required to run our EVs.
The poor old 12v battery with its old lead acid technology is not so capable.
I also wonder how long our cars spent in storage, transit and dealer’s forecourts before we got the opportunity to love and cherish them.
I think the HV battery would be fine but if the 12v battery only got charged, along with the HV battery charge, before leaving the dealer I am not surprised it has failed on so many cars.
Dealers should ensure new ice cars have fully charged batteries before hand over to new owners but I suspect the same is not the case for the 12v battery in our EVs.
I gave my 12v battery an 8 hour trickle charge on getting home and have had no problems since.

 

[BigEVuser]

so if it seems to be a good idea to carry a battery pack in the car to get the car turned on if the 12v battery is flat...can anybody indicate how much current (amps) is required to do this ...so I can get the right size battery pack

 

[JodyS21]

so if it seems to be a good idea to carry a battery pack in the car to get the car turned on if the 12v battery is flat...can anybody indicate how much current (amps) is required to do this ...so I can get the right size battery pack

That is a very interesting question...
The whole point of the jump start battery packs, is to JUMP start the car, so give it a big jolt of power for a few seconds.
The one I've got has a really high output so it can jump start my diesel van easily.
But the EV doesn't need a jump start, it just needs a steady flow of power, not sure if they do this - certainly aren't designed for it ??
I guess it only needs a bit of 12v juice whilst it doing its initialisation stuff before it can engage the HV battery, which then starts topping up the 12v battery.

 

[Lovemyev]

I would imagine it only needs a very small amount of power just to wake up the car from a low 12 volt battery.
I would think that any small power pack would do this job.
Just something to raise the voltage in the 12 volt battery up to about 12.5 volts then the car will boot up.
From then, the traction battery will start charging the 12 volt battery.
Most small jumper packs are designed to supply enough punch to crank the starter motor as well for a very short amount of time.
I can not any difference between connecting a small power pack over using the standard method of connecting two 12 volt batteries with a pair of jumper cables ??.
Question :-
If you called out the rescue services out to your flat battery on your EV - What do you think they would use to bring your 12 volt battery back to life ?.
The same jumper pack that they would use on an ICE car I guess ?????.

 

[JodyS21]

It's a fair size 12v battery fitted, which I find strange that so many people have had them run flat. Looks the same physical size battery as in a mid-size IC car, people don't often run them flat by sitting with the radio on etc, I used to go weeks between using my old IC car sometimes and it was fine.
Is there a lot more load on the 12v battery in our EV car?
Is it just a learning lesson; that owners are thinking because they've got a massive battery in their car, they sit with it on standby longer than one would in the old IC days?

It really would make sense that the cars systems, automatically always sent power from the HV battery to the 12V battery if it was registering it as getting low. It's a bit pointless the software letting the car become unusable by letting the 12v battery go low yet having a HV battery with charge in it.

 

[Cocijo]

Lots of questions in my head. Why have a lead acid 12v battery at all? Why not a transformer if persisting with 12v electrics? Why have a 12v battery gauge? As you say why not automatically top up the 12v battery from HV if it really must be there? It all seems to date back to what Ice cars have. The start button is also completely unnecessary. Foot on brake starts car -
and go.

 

[Davemac278]

so if it seems to be a good idea to carry a battery pack in the car to get the car turned on if the 12v battery is flat...can anybody indicate how much current (amps) is required to do this ...so I can get the right size battery pack

I've not tried jump pack yet. Bought one on ebay which I have put in car. Feedback was good and that you connect and leave it connected to battery first 120 seconds to boost battery.

Partner wanted one as a back up for her car and to power her phone when out and about. Got cheaper one to try from amazon.

Screenshots attached

 

[Kithmo]

The difference with an ICE car is it has an alternator that puts out huge amperages typically 60-100A and EVs and Hybrids don't. They are designed to charge the 12v just enough to keep going.
I saw an interesting video on You Tube which said that even ICE cars now have a BMS computer to control the charging of the 12v so as to give better economy. It said that there is a little black box (sensor) attached to the -ve lead that controls the charge and if you jump started by connecting your jump started to the battery posts this would result in needing the BMS resetting via a diagnostic tool. But if you jumped it by connecting the -ve jump lead to the engine it wouldn't. It also said that if you changed the 12v battery then the 12v BMS would again need resetting.
It got me thinking as to whether the ZS has a 12v BMS and whether the ones who have had their 12v changed are the ones having trouble.
FYI, mine has the original SAIC battery and I've had no problems in the 7 months I've had it.

 

[mj224]

Just to add to the above posts, when my little Citroen Zero range was deteriorating, the dealer recommended a fast charge or two jizz up the battery. Whether he was right I don't know.

The manufacturers of the Citroen (actually a Mitsibushi) claimed a 93 mile range. After 10 years the real world range was about 40 winter miles and 50 summers ones. Accepting the manufacturers range is optimum (certainly optimistic), in 10 years the battery range was down by about 2/3rds or so. And we buy any car gave me quite a good price for it I have to add...

I have read that the Lithium batteries like to be charged little and often.

 

[Simondi]

Just out of interest , I use a CTEK mxs 3.8 charger on my other cars, is this suitable for the 12v battery on the ZSEV?

 

[Iain]

I think the CTEK would be good for occasional trickle charge of 12v battery. I would also suggest connecting the 12v charger as described on page 243 of manual to avoid any unwanted spikes.
Due to less car use, due to current travel restrictions, and the present cold weather I think it is good practice to keep 12v battery in good condition same as I have always done with previous ICE cars.
An occasional trickle charge is better than a failure on the road.

 

[Stuart74]

I had this same problem on Wednesday
Car was still plugged into my 7kw Wallbox charger. High voltage battery fully charged.
System control fault and HV battery fault.
Car will not go into ready mode.
Called AA and they took one look at it and said they would take it back to the dealer in Glasgow.
Taken away on Thursday 9 am.
Dealer said still waiting for MG to check all readings and allow me to get cat back.
Only allowed hire car through Enterprise for 2 days.
Really poor.
I have no idea when I’m getting car back.
I live on outskirts of Edinburgh and work in Glasgow.
Not happy with dealer or MG.
dealer stated no courtesy card till end of March.
MG saying you only get 2 days car hire!
So you buy new car it has faults and you don’t get a car.
Fingers crossed I get car back Monday
I will post Dealers findings.

 

[Lovemyev]

I think the CTEK would be good for occasional trickle charge of 12v battery. I would also suggest connecting the 12v charger as described on page 243 of manual to avoid any unwanted spikes.
Due to less car use, due to current travel restrictions, and the present cold weather I think it is good practice to keep 12v battery in good condition same as I have always done with previous ICE cars.
An occasional trickle charge is better than a failure on the road.

I have a CTEK GO unit, very similar to the other units really.
I also purchased the option quick connect kit.
This gives you the ability to hard wire the red positive lead of the quick connect kit to the battery via an eyelet and then attach the black negative lead to a an earthing point on the body shell of the car.
Not the negative terminal of the 12 volt battery.
The short quick connect lead can then be left ready and waiting for when you are ready to charge your battery.
The quick connect cable just snaps into place on the twin lead into the CTEK unit and your ready to charge.
No "Faffing" about with them crocodile clamps than can jump off the battery terminals.
I have tried mine a few times over the last 12 months and it is really quick to set up and getting charging.
The CTEK charger will run through a quick evaluation of the current state of the battery, then set the charge status to suit.
If it detects that the charge in the battery is pretty high, it will reduce the charge rate down right down to a slow trickle / maintenance battery mode automatically.
Just another one of then "Nice To Have / Just In Case" back up plans.

 

[Simondi]

With the EV being new I hadn't thought to use my CTEk but on reading this threatyi think I may well do so

 

[Lovemyev]

With the EV being new I hadn't thought to use my CTEk but on reading this threatyi think I may well do so

Like I said, I have offered up mine to the car twice over the last 12 months.
On both occasions it reported the battery at full ready state in about 1 hour.
So, that would indicate that the 12 Volt battery did not require much additional charging to be fair.

 

[Kithmo]

I'm a bit disillusioned by this 12v battery conditioning.
After 4 years of religiously sticking my CTek on the Prius every 4-6 weeks to keep the 12v battery conditioned, it let me down last week after not being used for just 3 weeks.
I got in andwhen I tried to start it, my plug-in battery monitor was flickering between 6-8v, the Auto headlights were flashing on and off (it was dark) and it wouldn't engage the HV battery.
It jumped ok with my little jump pack and when I returned home later I put the Ctek on and it's been fine since, SWMBO's using it daily.
I now am wondering if it's worth sticking the CTek on it at all if the battery is going to fail after 4 years anyway or if I should just stick the CTek on when it's been stood a week or two. I don't really want to buy a new 12v battery as I'm thinking of trading it in in a couple of months for a MG5.

 

[Iain]

How Long Do Car Batteries Last

There is no simple answer, but based on decades of industry experience, we know that three key factors affect the life of a car battery: time, heat and vibration.

www.aaa.com

Although the above link provides information on 12v batteries for ICE cars there is good advice that is pertinent to EVs including expected lifespan. Hope this is helpful.

 

[Iain]

I'm a bit disillusioned by this 12v battery conditioning.
After 4 years of religiously sticking my CTek on the Prius every 4-6 weeks to keep the 12v battery conditioned, it let me down last week after not being used for just 3 weeks.
I got in andwhen I tried to start it, my plug-in battery monitor was flickering between 6-8v, the Auto headlights were flashing on and off (it was dark) and it wouldn't engage the HV battery.
It jumped ok with my little jump pack and when I returned home later I put the Ctek on and it's been fine since, SWMBO's using it daily.
I now am wondering if it's worth sticking the CTek on it at all if the battery is going to fail after 4 years anyway or if I should just stick the CTek on when it's been stood a week or two. I don't really want to buy a new 12v battery as I'm thinking of trading it in in a couple of months for a MG5.

Hi Kithmo,
I hope your 12v battery will last until you trade in the car.
You have not said what type of battery it is but if it is not ”maintainance free” might be worth checking electrolyte levels and if necessary topping up with distilled water.

 

[Exdro]

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

I am having Dash Cams fitted on Tuesday! Is this likely to cause a problem?