Battery balancing and battery life - fast or slow charging?

[Colin E]

I have always used the granny charger to do a battery balance (every 2 months approx.) Now I'm on time-of-use electricity tariff, I would prefer to use the home AC charger to get the job done during the lowest electricity rate (9am to 3 pm). Any views on speed of charging and battery life?

 

[fred12345]

I have always used the granny charger to do a battery balance (every 2 months approx.) Now I'm on time-of-use electricity tariff, I would prefer to use the home AC charger to get the job done during the lowest electricity rate (9am to 3 pm). Any views on speed of charging and battery life?

There are tons of posts on this question, maybe best to move this post to one of those posts where people would reply more readily?
Admin?

From memory, all home chargers are "slow". Can't remember seeing any figures in the manual but 7kW was considered slow charging. The screen in the car will confirm. On mine it does say slow or fast charging

 

[decrep]

As I understand it.
Balancing should be done regularly, maybe once a fortnight? But it doesn't matter how much charge you start from it just has to go to 100% and be left on charge until it says charging finished, it will stay on 100% while it balances.

Calibration charging can be done 6 monthly, and that requires the charge to start from under 10%.
a rate of 7kW isn't too fast, the car can slow the charge down towards the end if it gets too fast anyway.

 

[Colin E]

Thanks for the information. My QUBEV home charger has switching available for 6, 13, 16 and 32 amp charge rates. I've been using the 16amp (3.68 kW at 230 volts) for regular charging; looks like it will be OK for a full balancing charge.

 

[Corindikev]

Anything below 11 kW is considered slow charging. Only vehicles with 3 phase AC charge ports can achieve 11kW. Other than the 77 kWh battery all MG 4s and probably ZS models have single phase internal chargers. An EVSE drawing 32 amps or about 7.4kW AC will charge the car with a maximum of 6.6 kW DC. It will do this right up to 100%. Only fast DC chargers slow down from about 80% and above.

Balancing only occurs when charging via AC slow chargers. Any maximum charge setting from 60% to 100% will automatically go in to balance mode when it reaches the target %.

For example if you set the maximum to 80% for a NMC battery (as in the 64kWh MG4 battery which is "Battery health mode") when 80% capacity is reached the charger will continue for a while at up to 6.6 kW DC, then reduce to around 4 kW and eventually to a trickle which is displayed on the iSmart app as 0.00 kW and then it will disconnect when balancing is complete.

 

[Steve Kaye]

As I understand it.
Balancing should be done regularly, maybe once a fortnight? But it doesn't matter how much charge you start from it just has to go to 100% and be left on charge until it says charging finished, it will stay on 100% while it balances.

Calibration charging can be done 6 monthly, and that requires the charge to start from under 10%.
a rate of 7kW isn't too fast, the car can slow the charge down towards the end if it gets too fast anyway.

Whats the difference between balance and calibration charging?

 

[decrep]

Hi Steve, balancing is where all the individual cells are adjusted to the same voltage.
Calibrating is so the computer can work out your range.

I'm no expert on this, but apparently there are a few different methods of battery balancing. The thought seems to be that the MG discharges the highest voltage cells to the lowest voltage, then recharges the whole bank to the max level.

Calibrating lets the computer know how much charge goes into the battery from less than 10% to 100%

 

[Corindikev]

The battery will go in to balance mode (at least for the MG4) at whatever you set the maximum to charge to from 60% to 100% on an AC charging point. As it is recommended to charge to 80% for normal day to day use for NMC batteries most owners set the level at 80% unless planning a long trip & then you set the level to 100%.

7kW or 32 amps is slow charging and the car will charge at this level from 0 to 100%. Fast charging is direct current (DC) charging. The single phase car charger will only charge at 6.6kW from a 7.4kW AC power supply (EVSE)

Fast chargers are from 25 to 50 kW & rapid chargers are above 50kW up to 350kW. These are often called Super Chargers and all are DC chargers and use the 2 bottom pins of the CCS 2 socket. The maximum charge rate for the MG4 is 140kW & 94kW for the ZS EV.

 

[aleks57]

Whats the difference between balance and calibration charging?

there is no calibration charge, there is balancing of elements in a group. it all depends on the BMS version and the battery condition.

 

[decrep]

there is no calibration charge, there is balancing of elements in a group. it all depends on the BMS version and the battery condition.

So does that mean that the GOM in the ZS really has no idea???

 

[Data]

As I understand it from my dealer, balancing & calibration charges are one & the same thing. A proper balance charge won't be able take place until you get the low battery warning usually at 20% charge or below. It's best to charge the vehicle slowly (Granny or 7kw) & continuously all the way to 100%. Balancing the battery automatically tells the car (BMS) exactly how much charge is stored (& where 100% is) & allows more accurate calculation of the miles the car is capable of covering based upon how it was last driven. The range may of course change once driving begins. It may increase or may go down, all dependant on traffic & road conditions & driving style. Just like an ice car. However, generally after a balancing charge you may get more range & more accuracy from the car & GOM.

 

[decrep]

I wouldn't trust a dealers understanding.
Yes a calibration charge from less than 10% to 100% will also do a balance.
However a balance charge can be done from almost any level, it doesn't have to be under 10%
Well that's the case with my MG4, maybe the ZS is different?

 

[Data]

Hi decrep, yes dealer explained LFP batteries are a little different, as in the MG4. But similar rules apply. I have NMC which doesn't need to go to 100% very often to calibrate the cars BMS. The slow voltage drop in use allows the car to see where the state of charge actually is at anyone time. Yours does require 100% more often to calibrate the BMS as the voltage doesn't drop down evenly as in an NMC battery. But as far as I can determine, there is no real difference between a calibration charge where the purpose is to tell the car where 100% is & a balance charge. Both of those really do the same thing & will equalise the battery cells & tell the BMS where 100% is. My dealer is a premium dealership with years of experience with EV's. He has some of the very best techs in the country winning all the national tech awards.

On a technical point, you cannot properly balance an NMC battery or an LFP battery by charging to 80% only. Only at 100% can the BMS see the full battery markers & begin leveling the battery cells. This may or may not take sometime to do. This is as told to me by MG technical staff. The cars own BMS software has to be in control & is only triggered by allowing the battery low warning to be issued during driving. In the ZS MK2 this is at 20% charge. Once the low battery warning has been issued, next time you plug in to charge, the BMS takes full control & will level the battery cells voltage at 100%. Just leave the car charging until the trickle charge stops. That apparently is how a proper full battery balance is done as told to me by MG. I suspect any battery balancing you experience at 80% isn't actually much of a balance if at all.

So if anyone has further facts on this stuff, do tell.
PS. Just to add. It's a good idea to take the battery charge down a bit more after getting the low battery warning. That ensures that ALL the battery cells are below the threshold required to trigger the BMS balancing charge software. I took mine down to 17% charge & it balanced perfectly taking just 12 mins.

 

[decrep]

As you say, I think it's the difference between the LFP and NMC batteries, they need slightly different charging schedules

 

[Data]

Yes, but you might want to actually check if yours is actually balancing at 80%. My colleague has an new MG 5. His is also LFP. But he doesn't experience a balancing of any kind at 80% charge. He can only balance at 100% after a low charge warning. So not too sure about your MG4.

 

[decrep]

Somebody earlier posted that the 80% charge had to be timed, and it may only be with the NMC batteries. I don't have the ability to time a charge finish, so I can't test that.
I have to let it go to 100%

 

[siteguru]

7kW or 32 amps is slow charging and the car will charge at this level from 0 to 100%. Fast charging is direct current (DC) charging. The single phase car charger will only charge at 6.6kW from a 7.4kW AC power supply (EVSE)

Fast chargers are from 25 to 50 kW & rapid chargers are above 50kW up to 350kW. These are often called Super Chargers and all are DC chargers and use the 2 bottom pins of the CCS 2 socket. The maximum charge rate for the MG4 is 140kW & 94kW for the ZS EV.

In the UK it is slightly different.

Slow = Granny charging
Fast = 7kW up to about 30kW AC (typically 22kW AC being the fastest)
Rapid = 50kW+ DC
Ultra-Rapid = 150kW+ DC

 

[Data]

In the UK it is slightly different.

Slow = Granny charging
Fast = 7kW up to about 30kW AC (typically 22kW AC being the fastest)
Rapid = 50kW+ DC
Ultra-Rapid = 150kW+ DC

What he says!

 

[Corindikev]

Weird. My information is based on what is printed in the MG4 Owners manual.

 

[Data]

Don't forget that everything is upside down in Oz compared to here! That must make a difference...