12v battery drained, cant get recharged

[Smokeysworld]

Hello all.

So, I have read a couple of threads on this forum but can't seem to find the resolution I need.

I left my lights on my mk1 MG ZS EV overnight and the 12v battery is completely dead.

I have a full sized booster (the 8in1 type from Halfords) which I have tried to use.

I got into my car with the key, popped the bonnet and connected/turned on the booster.

The car came to life (along with a million errors)

I left it 20 mins and by this time the booster was almost drained. I turned the booster off and the car immediately died and would not start up.

It was as if the car was bipassing the 12v battery and using the booster but not charging.

I then recharged the booster to full, hooked it up/turned it on again and left it for an hour.

Same outcome.

The car has a full HV battery (albeit one of the errors is that its not powering on) but I'm now stuck with a dead car and no way to charge it.

Advice would be handy as I'm not sure what I'm doing wrong with my first EV!

Thank you.

 

[Gadget Geek]

I would guess your 12V battery is completely dead and not holding its charge. You could try an overnight charge on a 12V charger/conditioner first. If that doesn't work, I'm afraid its a new battery you need.

 

[Smokeysworld]

Is it likely if it's been perfectly healthy until this moment?

 

[johnb80]

Recharge your booster pack and attach it to the car, turn the ignition on and disconnect the booster pack. The DC to DC converter should now try to charge the 12v battery from the HV battery. Your battery may recover over time but it may take a while to charge, you need the car in its ready state for the charger to work.

 

[Smokeysworld]

Recharge your booster pack and attach it to the car, turn the ignition on and disconnect the booster pack. The DC to DC converter should now try to charge the 12v battery from the HV battery. Your battery may recover over time but it may take a while to charge, you need the car in its ready state for the charger to work.

This is the problem I come up against...
Booster has full charge.
Attach to car.
Turn on ignition (Start is green).
Disconnect booster.
Car shuts off immediately.

If I leave the booster attached and wait, 5 mins or so, all the errors start coming including HV battery shutdown and the start/stop button and keyfob recognition.

 

[Verdigris]

Total discharge can be the coup de gras for a flaky lead-acid battery but it is worth trying what johb80 said, before buying a new one.

 

[Gadget Geek]

Is it likely if it's been perfectly healthy until this moment?

Yes. Totally draining a battery can render it useless.

 

[Smokeysworld]

I have disconnected the battery and am currently charging it with the booster. Hopefully it takes a charge and all will be normal. I have very little faith at this point!

 

[Jomarkh]

My battery went flat in my MG5. I put the pack on but didn't put the car in ready mode so it went off again. Tried again but put in full ready mode took off the pack and drove off.
Try boosting again and putting it in full ready mode. Would connecting it to an EVSE help?

 

[Smokeysworld]

My battery went flat in my MG5. I put the pack on but didn't put the car in ready mode so it went off again. Tried again but put in full ready mode took off the pack and drove off.
Try boosting again and putting it in full ready mode. Would connecting it to an EVSE help?

This seems to be part of the issue. When the car turns on, it doesn't go to ready mode. I pressed the start stop button and nothing happens other than the power tunring off.

 

[Jomarkh]

This seems to be part of the issue. When the car turns on, it doesn't go to ready mode. I pressed the start stop buttin and nothing happens other that the power tunring off.

Is your foot on the brakes?

 

[Smokeysworld]

Yeah, tried it both ways. Will give it another go when the battery has some charge.

 

[Lovemyev]

The 12 volt battery has degraded that far, it is in an unrecoverable condition I think.
It’s new battery time unfortunately !.

 

[Smokeysworld]

So thought I'd provide an update for anyone with similar issues.
Seems that because of all the errors, the HV batteries were disabled, the start/stop button too. So the solution was to disconnect the battery completely and recharge it independently.
Once I hikked it back up with a full charge, no issues, no warnings etc.
So we are all good now!

 

[Lovemyev]

So the solution was to disconnect the battery completely and recharge it independently.

Just for clarification, you removed the 12 volt battery from the car, then independently charged it away from the car, then refitted it and all was fine, correct ?.