MG5 won't balance charge (2020 pfl exclusive)

[MickeySw]

Remember also that this estimated SoH may rebound slightly in summer.

Your HV battery's capacity is increasing as temperatures rise, however the SoH algorithm will most likely take that into account and is therefore unlikely to go up..

 

[Coulomb]

Your HV battery's capacity is increasing as temperatures rise, however the SoH algorithm will most likely take that into account and is therefore unlikely to go up..

If your BMS recently did the full calculation, as opposed to the "not enough data, assume linear degradation for now", and it does a competent job, then yes, temperature should have been taken into account, and yes, no rebound should be expected.

But my impression is that the BMS only does the full calculation about twice a year, and if it doesn’t see a low enough state of charge, it may never do it.

 

[MickeySw]

But my impression is that the BMS only does the full calculation about twice a year, and if it doesn’t see a low enough state of charge, it may never do it.

True, in order to start a battery capacity calibration SoC has to be below 10%, then AC charge all the way to 100% and leave it connected until balancing has finished.

There is a (badly translated) suggestion in the battery maintenance section of the MG5 manual to do this at least twice a year

 

[Gomev]

True, in order to start a battery capacity calibration SoC has to be below 10%, then AC charge all the way to 100% and leave it connected until balancing has finished.

There is a (badly translated) suggestion in the battery maintenance section of the MG5 manual to do this at least twice a year
View attachment 34380

I wonder how many have ever done this ? To achieve 90%+ charging in one go, on AC, requires a long time on charge, longer than most, if not all periods of off-peak available on any tariff.

 

[crispyjay]

I wonder how many have ever done this ? To achieve 90%+ charging in one go, on AC, requires a long time on charge, longer than most, if not all periods of off-peak available on any tariff.

I do this quite often. Get to the office and 7kW charge all day. Does that count?

 

[emmrecs]

I do this quite often. Get to the office and 7kW charge all day. Does that count?

As I understand it, it depends whether your battery SOC is at or below 10% when you plug in.

 

[crispyjay]

It is. Free charging at work so try to arrive as empty as l dare. Best is 6%.

 

[Gomev]

I do this quite often. Get to the office and 7kW charge all day. Does that count?

As a rough calculation from 10% of actual size (rounded - 61kWh or should it be 57 usable ?) would need approx 55kWh (51kWh).
Onboard charger is 6.6kW so would require over 9 (8.5) hours plus balancing time to go 10-100%. - Just about a full at work
Can't remember if the 5 Trophy has 11kW charging, if so times obviously reduce a fair chunk.

All rough guesstimations.

 

[kevin ellard]

As a rough calculation from 10% of actual size (rounded - 61kWh or should it be 57 usable ?) would need approx 55kWh (51kWh).
Onboard charger is 6.6kW so would require over 9 (8.5) hours plus balancing time to go 10-100%. - Just about a full at work
Can't remember if the 5 Trophy has 11kW charging, if so times obviously reduce a fair chunk.

All rough guesstimations.

The trophy does have 11kW charging but the park and ride at York is the only place in the UK where I have been able to use it. In France they seemed more common.

 

[Petriix]

Well, panic over, it balanced last night.

I bought an OBD dongle and was able to get some info from Car Scanner. The cells didn't seem out of balance at all at 50% SOC but I wanted to see what was happening at '100%". I noticed that one of the PWM line contacts was a bit corroded so cleaned the green stuff off with a cocktail stick so that might have made a difference.

Looking at the Myenergi app this morning showed the familiar long tail of balancing. Car was at 405V and cell min/max from car scanner was 3.22V on all but 2 modules where the min was 3.21 so nothing major.

The one concern 8s that SOH was showing at 94%. I doubt it's lost 4% in 2 months so suspect the dealer made up the 98% number at the last service. Not too alarming but worse than I was led to believe.

 

[SimonomiS]

Well, panic over, it balanced last night.

I bought an OBD dongle and was able to get some info from Car Scanner. The cells didn't seem out of balance at all at 50% SOC but I wanted to see what was happening at '100%". I noticed that one of the PWM line contacts was a bit corroded so cleaned the green stuff off with a cocktail stick so that might have made a difference.

Looking at the Myenergi app this morning showed the familiar long tail of balancing. Car was at 405V and cell min/max from car scanner was 3.22V on all but 2 modules where the min was 3.21 so nothing major.

The one concern 8s that SOH was showing at 94%. I doubt it's lost 4% in 2 months so suspect the dealer made up the 98% number at the last service. Not too alarming but worse than I was led to believe.

View attachment 34418

Very interesting. What make is your OBD dongle? I have a PFL Exclusive 70 plate and would like to do the same. Pardon my ignorance, but what's a PWM line contact?! My last service showed 96% SOH but from 68k miles

 

[Coulomb]

I noticed that one of the PWM line contacts was a bit corroded so cleaned the green stuff off with a cocktail stick so that might have made a difference.

Was this in the car's OBD-II socket? I doubt that the PWM pins are used, only CAN bus and power.

It may have been that your battery was balanced enough not to need low power balancing the last few charges.

The cells didn't seem out of balance at all at 50% SOC but I wanted to see what was happening at '100%".

An LFP battery always appears to be really well balanced at medium SoC; the battery has to be at very high or very low SoC to notice any imbalance. Since the battery is top balanced, you only care about cell voltage differences at 95-100% SoC.

 

[Petriix]

Very interesting. What make is your OBD dongle? I have a PFL Exclusive 70 plate and would like to do the same. Pardon my ignorance, but what's a PWM line contact?! My last service showed 96% SOH but from 68k miles

One of these: https://www.amazon.co.uk/Vgate-Blue...c7c-4cc6-bf51-0e710119a9de&pd_rd_i=B06XGB4873

@Coulomb I mean the CP line on my Zappi's tethered cable. It's an NCM battery.

 

[MickeySw]

The one concern 8s that SOH was showing at 94%. I doubt it's lost 4% in 2 months so suspect the dealer made up the 98% number at the last service. Not too alarming but worse than I was led to believe.

Maybe it just needs a battery capacity calibration, might be worth a try…

 

[Coulomb]

I mean the CP line on my Zappi's tethered cable.

Ah, the Control Pilot signal, of course. That's a good thing to have clean.

It's an NCM battery.

Oh. 3.21 V seems very low for an NCM cell. Was the battery at a very low state of charge when you read this value?

Actually, it's pretty low for an LFP cell too. I'm wondering if your OBD-II app is misinterpreting the cell voltage values.

 

[MickeySw]

Oh. 3.21 V seems very low for an NCM cell. Was the battery at a very low state of charge when you read this value?

Actually, it's pretty low for an LFP cell too. I'm wondering if your OBD-II app is misinterpreting the cell voltage values.

Well spotted, it’s a 96S pack therefore 405V total is around 4.21V/cell?

 

[Coulomb]

it’s a 96S pack

I don't know, various models have different pack configurations. But yes, 96 and 104 cell configurations have been discussed.

 

[MickeySw]

I don't know, various models have different pack configurations. But yes, 96 and 104 cell configurations have been discussed.

According to the MG5 manual (I gather type 2 is LFP while 1&3 seem NMC)...

 

[Coulomb]

According to the MG5 manual

Thanks. The 104 cell pack was probably for the MG4.

They run both types of cells to very low voltages. Way lower than I'd be comfortable with.

 

[Pebblefeline]

My module voltage at 100 percent soc is around 3.27V according to Car Scanner.