That good ol' keeping the 12V battery perky thread repeat.

DaevM

DaevM

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MG4 SE LR
Had the squeaky bum moment this morning with the 12V battery showing 12.2 after just 6 days of ownership. Due to trying to be proactive and not end up with windows inadvertently being left down when I'm not with the car, I'd got into the habit of using the power off button in safety to totally shut it down, as per windows down threads. Also thought this would stop any spurious drain of the 12V.
I'm having problems getting my Octopus IG OCPP going so trying various options with home charging. I don't do many miles and last run out was Sunday on an 80 mile round trip with dc charge in the middle, just to confirm it works ok.
Haven't managed a successful scheduled (2330-0530,) AC charge at home yet.
When checking MGismart this a.m. spotted 12.2V reading for battery. Read forum posts.
It would appear, according to the manual, that the vehicle needs to be in Ready mode for the HV battery to charge the 12V.
Put car in ready mode, voltage instantly showing as 14.2V, suggesting charging is occurring.
I'll leave it for an hour or so and see if it brings it back up to a more favourable state.
I'm thinking probably not a good idea to leave it powered off for days at a time 🤔.
Either / or, windows down or flat battery? Choices, choices
 
Last edited by a moderator:
DaevM said:
Had the squeaky bum moment this morning with the 12v battery showing 12.2 after just 6 days of ownership. Due to trying to be proactive and not end up with windows inadvertently being left down when I'm not with the car, I'd got into the habit of using the power off button in safety to totally shut it down, as per windows down threads. Also thought this would stop any spurious drain of the 12v.
I'm having problems getting my Octopus IG OCPP going so trying various options with home charging. I don't do many miles and last run out was Sunday on an 80 mile round trip with dc charge in the middle, just to confirm it works ok.
Haven't managed a successful scheduled (2330-0530,) AC charge at home yet.
When checking MGismart this a.m. spotted 12.2v reading for battery. Read forum posts.
It would appear, according to the manual, that the vehicle needs to be in Ready mode for the HV battery to charge the 12v.
Put car in ready mode, voltage instantly showing as 14.2v, suggesting charging is occurring.
I'll leave it for an hour or so and see if it brings it back up to a more favourable state.
I'm thinking probably not a good idea to leave it powered off for days at a time 🤔.
Either / or, windows down or flat battery? Choices, choices
Click to expand...

The Voltage shown in the app and in the car varies throughout the day without any charging taking place so I wouldn't worry to much.

The car should top up the 12V battery from the main battery as long as it's not connected to a charger.

Also, pre-heating the car will also top up the 12V battery which can be useful.

My 12V battery shows anything from 12.2 -12.7V when not charging.

Hope this helps
 
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Thanks for that.
Also, climbing out of the car drops it out of Ready mode 🤔, so no nipping in for a cuppa for half an hour while it goes through the Ready/charge cycle as per p.289 of the manual. Guess I'll just have to go for a drive then 😉👍
 
 
Jomarkh said:
What EVSE are you using to connect to IOG?
Click to expand...
Wallbox Pulsar Max. Has been running fine with Kia Soul for 18 months on Go and Intelligent Go. Octopus advised delete Soul and recreate with MG4. Getting as far as OCPP connected on Wallbox but Octopus claiming it can't detect device so can't test. Have been waiting 30 mins to allow it to be detected every time I've tweaked something - frustrating as hell.
It appears until it's completed the test it won't schedule.
Got a call in with Octopus so was trying just charging during cheap rate hours using either vehicle or Wallbox schedule.
 
Last edited:
pecker said:
The Voltage shown in the app and in the car varies throughout the day without any charging taking place so I wouldn't worry to much.

The car should top up the 12v battery from the main battery as long as it's not connected to a charger.

Also, pre-heating the car will also top up the 12v battery which can be useful.

My 12v battery shows anything from 12.2 -12.7v when not charging.

Hope this helps
Click to expand...
Exactly the same as mine. Anything between 12.2 - 12.7V.

Just checked it twice a few minutes apart & first it was 12.3V, then 12.5
 

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As I have posted elsewhere the main battery will charge the 12V battery without the car being in ready mode or charging.
Here is a screenshot showing mine being charged. The car hasn't been unlocked or put on charge for over 48 hours.
Screenshot_20240221-101126.jpg
 
Last edited by a moderator:
Ian Key said:
As I have posted elsewhere the main battery will charge the 12v battery without the car being in ready mode or charging.
Here is a screenshot showing mine being charged. The car hasn't been unlocked or put on charge for over 48 hours.
View attachment 24608
Click to expand...

Don't suppose you know what your car voltage was before the car started topping up the 12V battery.
 
Last edited by a moderator:
DaevM said:
Wallbox Pulsar Max. Has been running fine with Kia Soul for 18 months on Go and Intelligent Go. Octopus advised delete Soul and recreate with MG4. Getting as far as OCPP connected on Wallbox but Octopus claiming it can't detect device so can't test. Have been waiting 30 mins to allow it to be detected every time I've tweaked something - frustrating as hell.
It appears until it's completed the test it won't schedule.
Got a call in with Octopus so was trying just charging during cheap rate hours using either vehicle or Wallbox schedule.
Click to expand...
It took me a while to get my Wallbox Plus to connect via OCPP. I had to boost the wifi signal for it to work. I am now back using an Ohme (well testing until it is sold) then I will go back to using a Zappi.
 
You can check the car's read out of battery voltage by using a voktage tester across the terminals. Often the vehicle voltage display isn't very accurate. Alternatively, just go to an independent garage and ask them to quickly test the voltage, take 1-2 minutes, more time to open the hood of the car than do the test.
 
The 12V battery charges when the big battery is charging from the mains. It also charges when moving. It does not start when unplugged and turned off.

After 1 week away at an airport car park my mg4 12V battery was flat.
 
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nerfmg said:
The 12v battery charges when the big battery is charging from the mains. It also charges when moving. It does not start when unplugged and turned off.

After 1 week away at an airport car park my mg4 12v battery was flat.
Click to expand...
That's unlucky. You might need a software update as mine definitely does charge when switched off.
 

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