Low battery notice

[Gazzagaz]

Had my MG4 SR for a couple of weeks, very happy, but getting a warning on screen "Low battery do you wish to go into low battery mode? This is when the the main battery is at 80%. I imagine this is the 12v battery. Maybe im wrong, but i thought the 12v took its charge from the main battery. Any ideas would be appreciated

 

[Jomarkh]

If the HV is showing 80% then it sounds like an iffy 12v battery. Give your dealer a call.

 

[Alb]

Have you been doing anything that might be draining the 12V battery?

 

[Gazzagaz]

Have you been doing anything that might be draining the 12V battery?

No

If the HV is showing 80% then it sounds like an iffy 12v battery. Give your dealer a call.

Thanks. Think i will

 

[Cocijo]

Had my MG4 SR for a couple of weeks, very happy, but getting a warning on screen "Low battery do you wish to go into low battery mode? This is when the the main battery is at 80%. I imagine this is the 12v battery. Maybe im wrong, but i thought the 12v took its charge from the main battery. Any ideas would be appreciated

Presumably you have the option to respond yes or no? Have you tried responding? What’s low battery mode?

 

[Gazzagaz]

Have a look at this:

 

[Ayoull]

Have View attachment 14586a look at this

This occurs when the HV battery is low on power so there's something not right here, when did you last do a balance charge?

 

[Gazzagaz]

This occurs when the HV battery is low on power so there's something not right here, when did you last do a balance charge?

View attachment 14587

Cars only 2 weeks old, no idea what a balance charge is, how do i do one?

 

[Ayoull]

Cars only 2 weeks old, no idea what a balance charge is, how do i do one?

Basically the SR model has an LFP battery that needs charging to 100% ideally once a week and then left to charge until the charge port goes out completely basically to balance the cells in the battery pack.

The reason this is to be done so regular on an LFP battery is due to how the voltage curve is pretty flat the battery management system (BMS) can't accurately keep track if you do alot of top up charges without balancing the pack.

 

[Gazzagaz]

Basically the SR model has an LFP battery that needs charging to 100% ideally once a week and then left to charge until the charge port goes out completely basically to balance the cells in the battery pack.

The reason this is to be done so regular on an LFP battery is due to how the voltage curve is pretty flat the battery management system (BMS) can't accurately keep track if you do alot of top up charges without balancing the pack.

Thanks, thats a great help. Im using a granny charger atm, untill my 7kw charger gets fitted. Would that make a difference?

 

[Ayoull]

Thanks, thats a great help. Im using a granny charger atm, untill my 7kw charger gets fitted. Would that make a difference?

Not at all, as long as it's an AC charger you're using which a granny and 7kW one are, they can be used to balance the battery pack it'll just take longer to do.

 

[PristDean]

Basically the SR model has an LFP battery that needs charging to 100% ideally once a week and then left to charge until the charge port goes out completely basically to balance the cells in the battery pack.

The reason this is to be done so regular on an LFP battery is due to how the voltage curve is pretty flat the battery management system (BMS) can't accurately keep track if you do alot of top up charges without balancing the pack.

Is this true for long range NMC batteries too ?

 

[Deleted member 10041]

Is this true for long range NMC batteries too ?

NMC should really only routinely be charged to 80% then about once a month as a balance charge to 100%. Also don't like being left at 100% for any length of time.
Stageshoot is the only member that I'm aware of that charges his lr to 100% everyday but he needs the range and only keeps the car for a year.

 

[Ayoull]

Is this true for long range NMC batteries too ?

NMC still need balancing but more for cell health and integrity but they only recommend every month or so.

But NMC has a more predictable and consistent drop in voltage so you can top-up the battery and the BMS will maintain an accurate idea of the state of charge to around 1-3% degree of error where as LFP has between a 10-20% degree of error when not balanced and you just keep topping up

 

[Jomarkh]

Thanks, thats a great help. Im using a granny charger atm, untill my 7kw charger gets fitted. Would that make a difference?

Once the car reaches 100% the charge rate drops and the cells get balanced just leave it powered up over night, it will do it automatically and then stop drawing power.

 

[Alb]

Balanced or not, the car shouldn't be reporting the main battery low at 80%.

 

[Ayoull]

Balanced or not, the car shouldn't be reporting the main battery low at 80%.

If all it has done is top up yes it could seen it happen on a 200MWh storage battery, BMS reported 40% half hour later dead with only a 10kW draw on it for testing.

Once fully charged and balanced was fine.

 

[Gazzagaz]

Balanced or not, the car shouldn't be reporting the main battery low at 80%.

Thats what i was thinking

 

[Gazzagaz]

If all it has done is top up yes it could seen it happen on a 200MWh storage battery, BMS reported 40% half hour later dead with only a 10kW draw on it for testing.

Once fully charged and balanced was fine.

Will do, thanks again

 

[Ayoull]

Will do, thanks again

If you can charge to 100% allow it to complete a balance and see how low you can run it before the low battery warning comes up