OBD Data

ari197 said:

My almost 2 years MG4 SE SR (so LFP model) is at 92% SoH..

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Have you done a deep discharge and full AC recharge recently?

ari197 said:

My almost 2 years MG4 SE SR (so LFP model) is at 92% SoH..

Click to expand...

My just over 2 years old SE SR is at 92.65% after 8800 miles. (I'm retired so low mileage now). It has also had regular deep discharge and full charge and balance cycles (the latest just this week ... 2% to 100% and balance), so I've looked after the battery pack as well as I can. Degradation in the MG4 LFP pack is largely time-biased over the first couple of years or so, so I'd anticipate most SE SR owners will follow the same deg curve.

Hi,
As a simpleton I cannot even pretend I understand all of the above - a few principals yes but beyond that it is a word salad. So perhaps you could shed a light on my problem which is as follows:

In July when my MG4 Trophy (NMC battery) was 18 months old approx 18k miles, I did my first SOH reading (the dealer's figures were non-sensical) and it showed 99.5%.

On 1 October following an update, the car wouldn't go into Park and so would always charge to 100% so I had to limit charging time to cut off early. When I needed to charge to 100%, the charge always ended abruptly (no balancing).

The car was due into the dealer on 16 Dec to be fixed and before that I carried out a car scanner diagnostic and the SOH had dropped to 97.4%. When it went in I asked the dealer to give me the SOH figures they read and it came back as 100%! (as was the SOC which the dashboard was showing as 51%).

Having had the update, I did a 100% charge on the Zappi and it was balancing for well over an hour (see pic) however the SOH remained at 97.4%.

I tried a 100% charge with the granny charger and then three cycles of discharging 1% or so and then recharging (1.7 - 2kW to add the last 1%) but still the SOH remains at 97.4% and the delta shows as 675.61 volts (see attached).

Have I lost that 2% capacity forever or what can I do to get it back and is the high Delta a problem?

Any thoughts/advice appreciated.

It might be an unpopular opinion but I do think people need to stop obsessing about SOH because:

- We don't know how it is calculated or what it means, it is absolutely not a direct measure of the health of the battery. It certainly isn't comparable across models / makes with different batteries.

- It can change due to changes in calculation methods by MG which you can experience by having software updates on your car.

- It is far better to have a repeatable route on which to test your car's range in similar weather conditions.

All that really matters is: Do you get enough range for your regular needs?

tsedge said:

It might be an unpopular opinion but I do think people need to stop obsessing about SOH because:

- We don't know how it is calculated or what it means, it is absolutely not a direct measure of the health of the battery. It certainly isn't comparable across models / makes with different batteries.

- It can change due to changes in calculation methods by MG which you can experience by having software updates on your car.

- It is far better to have a repeatable route on which to test your car's range in similar weather conditions.

All that really matters is: Do you get enough range for your regular needs?

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I agree, I like seeing people being so enthusiastic about things, but realistically SOH shouldn’t matter so much. I doubt any of us ever worried about the loss in engine power our ICE cars suffered over the years?

I think part of it is that now you can get a number on a screen and it feels relatable because it’s on a 0-100 scale, but like you said, as longs as you get the same mileage on a similar drive, than that’s all you really need to know right?

EV convert said:

Have I lost that 2% capacity forever or what can I do to get it back

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My guess is that you have had bad BMS firmware for a while. It's quite possible that the BMS will eventually (in 1-6 months) come up with a higher SoH figure. So you may effectively get some of that health back.

EV convert said:

and is the high Delta a problem?

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I think that >600 V figure must be nonsense, wrong PID used in part of the calculation.

Thanks for your feedback folks and here is my rationale for it being of concern:

It is true that we didn't make similar comparisons for ICE cars but range was not the limiting factor with 700 miles range on a full tank and I do undertake 200+ mile trips. Refuelling an ICE takes 5 mins not 20 (once on a charger) and there are some 8,300 petrol stations nearly all of which take cash, contactless payments, cheques etc.

I do understand that the SOH, and therefore range, will decrease over time but if the 'not going into park' problem has caused premature degradation then I should flag that up to the dealer as it happened within the 2 yr warranty period.

If, on the other hand, Coulomb guess is correct and the charging system sort itself out over the following weeks/months, then all will be well. Ultimately, only time will tell.

Thanks again for all your responses - much appreciated.

wattmatters said:

Have you done a deep discharge and full AC recharge recently?

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Hi Wattmatters. I am interested in your home assistant dashboard for my MG4. Can you please let me know more details as I also want the same solution for my MG4? Thanks in advance.

Razvan said:

Hi wattmatters. I am interested in your home assistant dashboard for my mg4. Can you please let me know more details as i also want the same solution for my MG4? Thanks in advance.

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See here:

I've just got the VLink OBDII dongle and plugged it into my MG4 - I have the OBD Auto Doctor app on my android phone but only seem to get the coolant temperature displayed - tried to add other sensors but all seem to want Premium version - is this right or should I use an alternative App??

Car Scanner app. As it happens I paid for the premium upgrade, but in the free version you can still see all the relevant data. Just make sure to select the MG4 (Beta?) configuration.