Inexorabilis
Standard Member
Hello everyone,
I posted this as a reply in a thread previously, but I feel it deserves it's own thread so that anyone googling this problem will find a good resource with steps to take to resolve the issue.
Background: I bought my MG ZS EV in November 2022 and in the following year the 12V battery died on at least 5 or 6 different occasions. Once at the airport when I was picking it up after a longer trip away. However, it also sometimes died even when I had recently driven it (e.g. the day before). I couldn't make head nor tails of it, since I wasn't leaving lights on overnight or "wasting" energy.
How to fix the immediate flat 12v:
The Longterm fix for the flat 12v (background):
I brought my Car to the dealer twice specifically for this issue.
The Longterm fix for the flat 12v (What do):
- In short: If you're experiencing the same issue, take it to the dealer and ask them to do the same troubleshooting as described above.
I posted this as a reply in a thread previously, but I feel it deserves it's own thread so that anyone googling this problem will find a good resource with steps to take to resolve the issue.
Background: I bought my MG ZS EV in November 2022 and in the following year the 12V battery died on at least 5 or 6 different occasions. Once at the airport when I was picking it up after a longer trip away. However, it also sometimes died even when I had recently driven it (e.g. the day before). I couldn't make head nor tails of it, since I wasn't leaving lights on overnight or "wasting" energy.
How to fix the immediate flat 12v:
- With the 12v dead, your car will be unresponsive and wont respond to your remote key.
- On your MG ZS EV key, press in the little silver button on the side that pops up the clip and allows you to remove the physical key blade. Flip open the blade handle.
- Underneath your Car Door handle is a small slit - push your key blade into this, then "lever" it upwards to pop off the small plastic cover. This will uncover a regular key slot.
- Use your key blade to unlock the car by inserting it into the key slot and turning like a normal key.
- Once inside, pull the Hood-pop lever, which is located near your right-side knee when you're normally sat in the car. This will pop the hood.
- Standing in front of the car, slide the hood lock lever (located roughly in the centre) and lift the hood up and secure it like a normal hood.
- Your 12V battery is located on the right side of the engine compartment. You can identify it by the large + and - symbols.
- Use another car (AA, neighbors, friends or family) to connect jump-cables to the 12V.
- Use a 12V jump starter pack to jump-start the 12V. I bought this one on Amazon and found it to be its weight in gold while I had the issue as I kept it in the glovebox.
- Either way, you will attach clamps to the + and - metal bolts, then turn on the [other car][jump starter pack]
- Turn on your car as normal by pressing the power button and pushing the brake down.
- The car will start and the alarm will go off and scare the beejeezus out of you.
- Use your key to "unlock" your car to stop the alarm going off.
- Remember to pop the plastic cover back onto the handle. To do this, you will need to hold the handle grip in the "opening" position, then pop on the cover.
The Longterm fix for the flat 12v (background):
I brought my Car to the dealer twice specifically for this issue.
- The first time (Mid 2023) they couldn't identify the issue as the 12v battery seemed healthy. They applied all software updates but nothing seemed to resolve the issue.
- During my annual check up (November 2023), the engineer told me (as an aside, unrelated to my annual check) that they had identified a very likely fix for the 12v battery and that I should bring the car back into them the next time it went flat. Apparently, and I quote: "the issue was affecting virtually all MG ZS EVs in the country".
- My car's 12v died again in December and I called the dealer to get it booked in for the "known issue" with the battery we had talked about. - The engineer's tone greatly changed at this point "I never said there was a widespread issue. MG have not admitted to any battery faults."
- My assumption is that there is a known fault, but MG don't want to admit it since it would be hugely expensive for them to resolve it.
The Longterm fix for the flat 12v (What do):
- In February 2024 I brought my car into the dealership and left it there for 3 or 4 days.
- Monitoring equipment indicated that the idle 12V battery use was "near the high end of the acceptable spectrum". (BAD!) The idle use didn't go into a place where it would trigger an alert, but it was unusually high.
- They fully unplugged the 12v battery and left it for a few hours. It's possible that they also manually unplugged individual components (radio etc.).
- They plugged the 12v battery back in and monitored it for the next few days
- At this time, the idle 12V battery use went down to the "bottom end of the acceptable spectrum" (GOOD!)
- Since then, my MG ZS EVs 12V battery has not died once even though the engineer said that this was a "likely, but not a definite" fix.
- Again, my assumption is that they can't say its a definite fix, because to say that would be to admit that there is a known widespread issue with a definite fix. Staying vague and pretending that cars must just have an individual issue is more likely to keep legal happy I'm guessing.
- It's the dumbest "turn it off and on again" ever, but apparently it resolved the issue. The root cause it likely related to a part of the software being overactive and drawing just a little too much juice when idling. Restarting that software through a hard-reset was enough to stop the draw.
- In short: If you're experiencing the same issue, take it to the dealer and ask them to do the same troubleshooting as described above.
