Fast charging and Low Voltage battery warning?

[Evgen K]

Hello guys. Sorry if this question was asked and answered earlier (please merge threads in such case or just delete). But i have one question.
I charge my MG4 Lux by fast charge stations and everything is OK with it, car gets 140kW (when the battery is warm enough). But when charge is finished (I stop charging at 80% level) driver screen shows two warning lamps.

These are "Low-voltage Battery Charging System Malfunction Warning Lamp" and "Power Battery Cut-off Indicator".
They are shown on screen when battery is charged and car is in "idle state" (not READY state). Lamps go away as soon as I step on brake pedal and car goes into READY state and do not come until the next fast charge.
The question: is it normal behaviour or I should visit dealer?

 

[ReintjeWA]

I see this when I fast charge too. Do you wait in the car while charging? I wonder if the car depends more on the 12V system because perhaps it can't charge and discharge the battery at the same time?

 

[Anon70]

I have seen similar warnings and put it down to the poor software not realising that certain systems have changed states and are showing as not ready or failed when they are checked.

Just powering up the HV system by pressing on the brake and driving off usually resets the warnings or if that fails a complete shutdown and reboot by locking the car, leaving it for 5 minutes and starting again.

 

[Martinonline]

I have seen this and considered it normal. I would say that the 'Low-battery Charging System' warning is a consequence of the HV battery being isolated during DC charging. I am open to correction.

 

[Rolfe]

I think you're right.

 

[Kithmo]

By fast I assume you mean rapid DC. The 12V is not charged up on a DC charger as it is on AC.
So if you're sat in the car with accessories on then you're draining the 12V. It shouldn't be a problem if your 12V is in good condition.
Those warning lights should go off if you get out, turn the car off (lock it), then unlock it and get back in (or simply press the brake pedal as mentioned above).

 

[kenneth104]

This usually occurs when you have stopped charging but haven't unplugged the charging gun yet

This is normal, all cars are designed like this

 

[pollenface]

They are shown on screen when battery is charged and car is in "idle state" (not READY state). Lamps go away as soon as I step on brake pedal and car goes into READY state and do not come until the next fast charge.

In non-ready state there is zero HV -> LV battery charging.

 

[Evgen K]

Thank you guys, so this is normal situation, but I would say it's weird.
And yes I'm waiting inside the car while fast DC charging.

 

[Kithmo]

In non-ready state there is zero HV -> LV battery charging.

Not true, as soon as you switch the car on (pre ready state) by sitting in the seat, the HV battery charges the 12V. Check the 12V voltage on the TPMS page, when it's charging it reads 13.9-14.2V.
When not charging the 12v reads 12.6V or less, as can be seen in the app.

 

[pollenface]

Not true, as soon as you switch the car on (pre ready state) by sitting in the seat, the HV battery charges the 12v. Check the 12v voltage on the TPMS page, when it's charging it reads 13.9-14.2v.
When not charging the 12v reads 12.6v or less, as can be seen in the app.

my apologies I'm speaking with regards to my MY22 ZS EV, my car doesn't switch on automatically when I sit in the seat. I would need to press the start button while holding my foot on the brake.

 

[siteguru]

It might help if you add your car to the Driving part of your forum profile, to avoid such confusion in future. This is the MG4 board so answers will naturally be swayed towards the MG4.

 

[Kithmo]

my apologies I'm speaking with regards to my MY22 ZS EV, my car doesn't switch on automatically when I sit in the seat. I would need to press the start button while holding my foot on the brake.

No problem, I was surprised as anybody when I found out the MG4 charged the 12V in ACC mode, having had a ZS before the 4 that didn't.

 

[siteguru]

ACC means Adaptive Cruise Control ... what you intending ACC to mean please?

 

[ReintjeWA]

My guess would be Accessorie-mode like the ICE cars when you turn the key one click.

Doesn’t the MG4 even activate the HV to charge up the LV whenever it detects a low voltage? I thought I read somewhere around here they introduced that in one of the updates to stop the 12V going flat?

 

[kenneth104]

My guess would be Accessorie-mode like the ICE cars when you turn the key one click.

Doesn’t the MG4 even activate the HV to charge up the LV whenever it detects a low voltage? I thought I read somewhere around here they introduced that in one of the updates to stop the 12V going flat?

It has this feature, but when plugged into a charger and not started, the system will not allow any high voltage power, so this feature will be temporarily turned off

 

[Coulomb]

The 12V is not charged up on a DC charger as it is on AC.
So if you're sat in the car with accessories on then you're draining the 12V.

It has this feature, but when plugged into a charger and not started, the system will not allow any high voltage power, so this feature will be temporarily turned off

I can't see why the car would not charge the 12 V when DC charging. The main contactors are on, so I'd expect the DC-DC converter be on, thus charging the 12 V battery.

I don't DC rapid charge often, but I'll have to watch the 12 V voltage next time. Others that rapid charge more often, can you confirm by observing the 12 V voltage?

 

[kenneth104]

I can't see why the car would not charge the 12 V when DC charging. The main contactors are on, so I'd expect the DC-DC converter be on, thus charging the 12 V battery.

I don't DC rapid charge often, but I'll have to watch the 12 V voltage next time. Others that rapid charge more often, can you confirm by observing the 12 V voltage?

Status：Before charging or after charging, NO , you only have 12V battery
Status：Charging, YES HVDC it's work, so you have a lot of 12V Power

 

[ReintjeWA]

Status：Before charging or after charging, NO , you only have 12V battery
Status：Charging, YES HVDC it's work, so you have a lot of 12V Power

Aha, so perhaps in a strange way the car is warning that now you have finished your charging, but you still have the plug fitted, you’re depleting your 12V system without the HV being able to top it up? In an ICE car the battery light comes on when in accessory mode for a similar reason.

 

[kenneth104]

Aha, so perhaps in a strange way the car is warning that now you have finished your charging, but you still have the plug fitted, you’re depleting your 12v system without the HV being able to top it up? In an ICE car the battery light comes on when in accessory mode for a similar reason.

It is mainly because the vehicle and the charging station adopt a "mutual distrust" design, so the high voltage is disconnected before and after charging.

Even if your 12V battery is dead, it will not recharge for you
Unplug the charging plug as soon as possible, especially if you are still in the car and turn on some daytime running lights, A/C fan, etc.