12V Battery Auto Charging Info

[MikeJS]

The manual states:
When the vehicle is powered OFF and the system detects that the 12V battery is running low, the vehicle will automatically charge the 12V battery under certain safety conditions to prevent the vehicle from failing to start due to low battery. This function will be automatically turned off upon completion of charging.
Note: When the system detects a fault/vehicle start/charging with an external device, it will automatically exit the 12V battery automatic charging function.

All fairly standard.

It then states:
Note: This function will be temporarily disabled when the high-voltage battery pack is running low. To avoid flat battery, it is recommended to charge the vehicle as soon as possible when the CLTC driving range is less than 70km.

Now given that the CLTC range estimate is supposed to be more optimistic than WLTP (around 15 to 25% more) so that should mean we need to keep the WLTP range to above about 50km…...

Pity they do not state a simple SOC % but then of course it seems we cannot see the SOC %!!

 

[evets]

The SOC% is available in My Car>Set

 

[Joningy]

The manual states:
When the vehicle is powered OFF and the system detects that the 12V battery is running low, the vehicle will automatically charge the 12V battery under certain safety conditions to prevent the vehicle from failing to start due to low battery. This function will be automatically turned off upon completion of charging.
Note: When the system detects a fault/vehicle start/charging with an external device, it will automatically exit the 12V battery automatic charging function.

All fairly standard.

It then states:
Note: This function will be temporarily disabled when the high-voltage battery pack is running low. To avoid flat battery, it is recommended to charge the vehicle as soon as possible when the CLTC driving range is less than 70km.

Now given that the CLTC range estimate is supposed to be more optimistic than WLTP (around 15 to 25% more) so that should mean we need to keep the WLTP range to above about 50km…...

Pity they do not state a simple SOC % but then of course it seems we cannot see the SOC %!!

Very interesting @MikeJS
Sadly Mike, my high voltage battery didn't seem to worry about the 12V battery going flat despite there being 74% remaining.
But I did use a smart charger which also didn't add anything to the 12V battery, maybe some sort of conflict with the HV battery, all a bit of a mystery, but all sorted by Penton MG in Salisbury, they even supplied us a taxi to get from the garage into city centre, brilliant service.
Seems OK again now!

 

[MikeJS]

Very interesting @MikeJS
Sadly Mike, my high voltage battery didn't seem to worry about the 12v battery going flat despite there being 74% remaining.
But I did use a smart charger which also didn't add anything to the 12v battery, maybe some sort of conflict with the HV battery, all a bit of a mystery, but all sorted by Penton MG in Salisbury, they even supplied us a taxi to get from the garage into city centre, brilliant service.
Seems OK again now!

What type of smart charger did you use? As the 12v is lithium I understand it needs a dedicated type of charger.

 

[Joningy]

What type of smart charger did you use? As the 12v is lithium I understand it needs a dedicated type of charger.

@MikeJS I wonder where you got the info that the 12v battery is lithium?
My info tells me my MGS5 is bog standard lead acid!

 

[MikeJS]

@MikeJS I wonder where you got the info that the 12v battery is lithium?
My info tells me my MGS5 is bog standard lead acid!

OK. The IM6 definitely has a lithium 12v battery. Is your IM5 the 100kwh or 75 kwh high voltage battery.

 

[MG Clive]

OK. The IM6 definitely has a lithium 12v battery. Is your IM5 the 100kwh or 75 kwh high voltage battery.

@Joningy has the MGS5, not an IM.

 

[MikeJS]

OK. The IM6 definitely has a lithium 12v battery. Is your IM5 the 100kwh or 75 kwh high voltage battery.

@MikeJS I wonder where you got the info that the 12v battery is lithium?
My info tells me my MGS5 is bog standard lead acid!

Seems you are on the wrong forum...

 

[Joningy]

Seems you are on the wrong forum...

Somehow I've slid into the wrong slot Mike, good job I'm not flying you home to the wrong airport!

 

[Joningy]

@Joningy has the MGS5, not an IM.

Apologies Clive!

 

[MikeJS]

Apologies Clive!

I have often clicked on the MGS5/6 links by mistake….

 

[NikLiverpool]

Apparently the IMs have a lithium ion 12V battery. There's a warning too to avoid jump starting it with standard 12V batteries.
I would like to think that being a lithium one we will avoid the typical problems EVs have with standard 12V ones.

 

[evets]

Apparently the IMs have a lithium ion 12V battery. There's a warning too to avoid jump starting it with standard 12V batteries.
I would like to think that being a lithium one we will avoid the typical problems EVs have with standard 12V ones.

Hope springs eternal

 

[MikeJS]

I had a reply from MG Customer Services about the 12v battery charging question.

They have stated -The driving range is 55km for UK vehicles. 20% SOC is the actual cut off for the function.
Good to have a definitive answer. However, 20% is ridiculously high (approx 20kw). The Hyundai used to do this at 20% but they reduced it to 10% at that was with a much smaller HV battery. The 12v can only take a very small percentage of the main battery so really no need to protect it at such a SOC.

 

[Giller]

I've fitted a battery monitor to the "conventional" battery in my S6, just to keep an eye on it as you can set an alert if it drops below a selected SOC, but also to answer the question of how much power does a dash cam wired to the OBD port with a permanent live feed use, but this morning I saw it was being charged automatically from the main battery, yes I know that's what's meant to happen but nice to see it happening.

 

[MikeJS]

I've fitted a battery monitor to the "conventional" battery in my S6, just to keep an eye on it as you can set an alert if it drops below a selected SOC, but also to answer the question of how much power does a dash cam wired to the OBD port with a permanent live feed use, but this morning I saw it was being charged automatically from the main battery, yes I know that's what's meant to happen but nice to see it happening.

View attachment 43276

Did you mean to post this in the IM6 forum?

 

[Giller]

Did you mean to post this in the IM6 forum?

Yeah because it was related to a specific question concerning charging in the IM6 forum.

 

[321mutley]

Got my IM6 launch edition two weeks ago and it died over the weekend. Pressed the brake pedal and selected drive and it juddered from the front wheels and came up with "drive motor fault". Turned it off and on again and it cleared and drove to work and home now issues. Monday went to leave for work and put it in drive, loud clock and "drive unit fault# and "system fault". Wouldn't reset and couldn't drive it. Called MG assist and they came out in 20 minutes. Plugged in to OBD reader and 15 faults found. Arranged for collection next day to take to dealer. Next day got in it to try and get handbrake off to load on low loader, still had the same faults but now was also coming up with 12v battery low, instrument panel dimmed and then shut down.

I'm still waiting for diagnostics on the fault but have looked on Google and found that there have been a few reports of drive motor faults and one suspect is a low 12v battery voltage. This apparantly causes issues with sensors.

I have looked into the 12v charging and as stated in the original post, the system should charge the 12v battery when low. However the manual says the facility turns off when the battery charge is low or when plugged in to an external charger.

So when I first got the car I could only charge it for a few hours each night due to working 14 hrs with commuting each day, and I was running a charge deficit resulting in me getting home on the final day with just 3% charge remaining.

I then fully charged it over the next couple of days. However my charger doesn't start charging until the cheap rate kicks in at midnight. I plugged the car in around midday and it was plugged in but not charging until midnight.

My question is, does anyone know if the 12v battery charging stops when the lead is plugged in or when a charge is detected. I thought that if it was plugged in to the mains it would be the perfect time to top up the 12v battery but the line in the manual suggests that's when it actually prevents charging. And given I ran the car until it was almost completely flat, it wouldn't have charged the 12v battery until it was over 20%, but the car was still plugged in. I had been driving with the heated seat and steering wheel, lights and heater so that's not going to help. Schoolboy error.

 

[MikeJS]

The 12v does not get charged is the HV battery is less than 20%. Not sure it matters if the car is plugged in or not as the 20% is the key figure. Hope the rest is sorted out quickly.

 

[321mutley]

Yes I didn’t realise this and to be fair I don’t think this is how it should be. Everything runs off the 12v battery, what’s the point of having 20% SOC if you can’t turn the lights on to see where you’re going

It was the line from the manual you quoted that I was trying to get my head round.

“Note: When the system detects a fault/vehicle start/charging with an external device, it will automatically exit the 12V battery automatic charging function.”

The bit that says charging with an external device is not particularly clear. Is it referring to the HV system and does that mean whilst charging, or does simply plugging the cable in waiting to charge count. Or does it mean an external 12v charger on the LV system so it’s not charging from two sources.

I think in my case it’s just me not realising the limitation of the system and being forced to push it to the limit due to my shifts. Hopefully a charge by the dealer will get it back and then I’ll fit a monitor that I’ve got sitting in the garage that sends me a message when the voltage drops, and just keep on top of it.