ZS EV 12v battery issue

[KrispiiDuck]

Hi folks,

Interested in your opinions please.

My 74 plate ZS EV Trophy turned into a large blue paperweight yesterday. None of the keys worked for unlocking and eventually I made it into the cabin using the emergency blade key. The dashboard was dead - no light, not able to start. I called upon MG Assist. AA were out within the hour and diagnosed the 12v battery being shot - he said that it was only taking 5 rather than up to 65 amps? (image from the AA breakdown report attached) So the patrol guy used a booster pack to get the car started and told me to take it to the garage as the car is under warranty - he also hooked me up with a hire car.

I drove to the dealer and booked the car in, sent them the battery report and left the car with them, expecting to get the battery replaced.

This afternoon I got a call to say that it started fine this morning and they are blaming my dashcam (which incidentally was fitted months ago and we left it home alone for 3 weeks in April and no issues when we returned. They are going to test it again tomorrow, but it sounds as though they are saying that there is no fault and they will not be replacing the battery.

 

[KrispiiDuck]

Today's update is that they say it's fine today, within MG specifications, without the dashcam connected, so they won't be changing the battery

 

[Gadget Geek]

The 12V battery has a 12 month warranty on it, so I suppose see how it goes and at the slightest sign of not holding its charge, get it swapped out.

 

[elektro]

Recently did a bit of research on dash cams. Are you using the parking mode (meaning the dash cam stays on even when the car is off and parked), assuming it is hardwired and supports that? If so the hardwire kit should have a safety cutoff at a certain voltage, usually there are a few different options. Mind telling us which dash cam it is?

From what (little) I understand, lead acid batteries do NOT like being deeply discharged and can take damage from it, especially if done repeatedly. Could be that the low charge rate the AA guy saw had something to do with the 0% SOC of the battery and that the amps would increase once it has charged a bit. I suspect the dealership charged the battery overnight so it looks ok on a quick test - doesn't mean the battery is actually healthy though.

Also if someone can explain this "74 plate" thing to me I'd appreciate it. Seen different variants of it on this forum and it only seems to be a thing in the UK?

 

[KrispiiDuck]

Recently did a bit of research on dash cams. Are you using the parking mode (meaning the dash cam stays on even when the car is off and parked), assuming it is hardwired and supports that? If so the hardwire kit should have a safety cutoff at a certain voltage, usually there are a few different options. Mind telling us which dash cam it is?

From what (little) I understand, lead acid batteries do NOT like being deeply discharged and can take damage from it, especially if done repeatedly. Could be that the low charge rate the AA guy saw had something to do with the 0% SOC of the battery and that the amps would increase once it has charged a bit. I suspect the dealership charged the battery overnight so it looks ok on a quick test - doesn't mean the battery is actually healthy though.

Also if someone can explain this "74 plate" thing to me I'd appreciate it. Seen different variants of it on this forum and it only seems to be a thing in the UK?

It is a Thinkware F200, hardwired and does support recording when the car is turned off, set at the lowest reording level, but the car was only standing over a weekend - previously I had left it for 3 weeks when we were away earlier this year with no issues on our return. I've had to collect the car as is and will keep an eye on it, but they said to get it recovered to them without jumpstarting it if it happens again.

74 plate refers to when the car was registered in the UK - we have two registration periods in a year.
March to August 2025 would be a 25 plate, mine was registered in September 2024, so it is a 74 plate. Hope that helps!

 

[elektro]

It is a Thinkware F200, hardwired and does support recording when the car is turned off, set at the lowest reording level, but the car was only standing over a weekend - previously I had left it for 3 weeks when we were away earlier this year with no issues on our return. I've had to collect the car as is and will keep an eye on it, but they said to get it recovered to them without jumpstarting it if it happens again.

74 plate refers to when the car was registered in the UK - we have two registration periods in a year.
March to August 2025 would be a 25 plate, mine was registered in September 2024, so it is a 74 plate. Hope that helps!

Ok I haven't heard of that dash cam, but I would check if the hardwire kit has that safety cutoff and what it's set to. Basically the lower voltage settings are not recommended to preserve battery health. If it doesn't have that cutoff feature then your dash cam might have caused damage to your battery over the long term and it's just become noticeable now that the battery health has degraded.

Thanks for explaining the plate thing and sorry if I'm being daft, but how does September 24 translate to the number 74? Edit: Is Sep-Feb just always 7 and Mar-Aug 2 and then the second digit is the year? Guess I could Google this, sorry .

 

[KrispiiDuck]

I'll have a chat with my auto-electrician regarding the dashcam.

As far as the registration dates go, I think it was an arbitrary decision to offset the later registrations by 50, way back in 2000.

More info:

Registration plates in the United Kingdom follow a specific format and set of rules, which makes it simple to work out the age of a car or van.

Standard UK car number plates consist of a combination of letters and numbers, typically in the format of two letters, followed by two numbers, a space, and then three more letters or numbers (for example, AB12 CDU).

What do the letters and numbers on a UK registration plate mean?

• The first two letters represent the region where the vehicle was registered and are assigned by the Driver and Vehicle Licensing Agency (DVLA)
• The two numbers in the middle are the ‘age identifier’. The second number indicates the year of registration, and the first number indicates the specific six-month period within that year (usually March to August or September to February).
• The last three letters on the plate are generally random and do not carry any specific information

 

[fred12345]

Thanks for explaining the plate thing and sorry if I'm being daft, but how does September 24 translate to the number 74? Edit: Is Sep-Feb just always 7 and Mar-Aug 2 and then the second digit is the year? Guess I could Google this, sorry .

Google says:
"In the UK, new car registration plates are released twice a year, in March and September. The two numbers in the middle of the plate indicate the age of the vehicle and change with each release. For example, in March 2025, the age identifier will be "25", and in September 2025, it will be "75".

so for 2025 registered cars you will have 74 until March, then 25 until September when it turns 75

 

[elektro]

Google says:
"In the UK, new car registration plates are released twice a year, in March and September. The two numbers in the middle of the plate indicate the age of the vehicle and change with each release. For example, in March 2025, the age identifier will be "25", and in September 2025, it will be "75".

so for 2025 registered cars you will have 74 until March, then 25 until September when it turns 75

Odd. Especially as you can't tell the decades apart, so what's the point? Maybe there are more magic numbers I don't know about. Anyway, at least I have an idea now, thanks. I think I must just stop trying to understand it fully and/or blame my current COVID infection...