Sudden battery loss on 2022 SR

[r0b1n68]

Hi everyone!

I received my Luxury SR model Monday afternoon.

I drove 130kms back home, it consumed 44% of battery.
Tuesday, I made my first commute trip to work.
It consumed 6% of battery.
The drive from work back home consumes 5% battery.

Yesterday night, I had 38% battery left.
I figured that I could drive until Thursday afternoon, I would have around 8 to 10% battery left.

But this morning, I went to work and something really strange happened.
I left home with 38%.
I didn’t paid attention to the battery percentage, until I got a warning chime « please charge vehicle »
I had 24% left.
So today, my commute consumed 14% of battery for 12kms driven.

Now my question : is this normal ?
Is it because the BMS is non-linear, and drop faster towards the end ?
Is there a hidden buffer, and MG wants us to charge our cars before it really reaches a low battery percentage, so 0% is not 0%, and my car, now at 24% battery, has more battery than that ?

I’m a little bit worried for my brand new car, I’m afraid the battery is faulty…

Any opinion on this ?

Thanks guys!

 

[Kithmo]

Was it colder and/or windy today maybe ?

 

[r0b1n68]

Was it colder and/or windy today maybe ?

Not at all. No wind, 10° outside, heating on 22° and fan speed at 1.
Also, I drove in eco mode, and never want more than 45% of power on the power gauge

 

[r0b1n68]

Title edited for clarity.

 

[N2STY]

Probably the lfp battery as has lower energy density think this is why tesla tell lfp owners to charge to 100%

 

[r0b1n68]

Probably the lfp battery as has lower energy density think this is why tesla tell lfp owners to charge to 100%

Yes I know that, but I don’t understand the loss of 14% of battery…
Is my battery really at 24%, or is it higher ?
I need an OBD dongle

 

[N2STY]

I would say 24% usable with some in reserve
The 14% loss is the lower density as battery was kept at under optimal charge the gauge was where you left it the night b4 and on your journey the gauge was playing catchup?

 

[r0b1n68]

I would say 24% usable with some in reserve
The 14% loss is the lower density as battery was kept at under optimal charge the gauge was where you left it the night b4 and on your journey the gauge was playing catchup?

Let me explain as best as I can (English is not my 1st language)

During my commutes, Tuesday, the battery was discharging in a normal manner (5 to 6% per commute)
I do 4 commutes per day
A commute (from home to work) is 12kms

Yesterday night, the battery was left at 38% in my garage at 16°
This morning, I started the car and it was still at 38%.
I drove a little bit and it went at 37% after 500 meters

Then I didn’t paid attention to the percentage, until I had a warning chime « please charge vehicle »
The car was at 25%.
Then it dropped at 24% when I parked at work.
The weird thing is, my commute uses only 5 to 6% battery, not 14!
That’s why I’m wondering if the BMS is not linear or, if something is wrong with the battery

I think the BMS is still learning the battery capacity, but this sudden loss worries me
The dealer is very far from my home

 

[N2STY]

I am sure is cos you keept the battery at 38% when it likes to be full the up to 100% I think density worsens if left at low soc

 

[drmcw]

My leaf is not linear because the voltage is lower when the SOC is lower so to maintain the same power then the current has to be increased and losses are squared for the current. I wouldn't expect the difference to be twice as bad though. Lots of little journeys hurt range due to having to re-heat the car each time I find. Since the car is new then I'd get it charged to 100% and let it do some balancing as that would be the first thing I'd do.

 

[r0b1n68]

My leaf is not linear because the voltage is lower when the SOC is lower so to maintain the same power then the current has to be increased and losses are squared for the current. I wouldn't expect the difference to be twice as bad though. Lots of little journeys hurt range due to having to re-heat the car each time I find. Since the car is new then I'd get it charged to 100% and let it do some balancing as that would be the first thing I'd do.

I will do it tonight
The original plan was to discharge it as low as I can, then charge it to 100% and let it balance the battery

I just went back home from work, and this time, it consumed 3% of battery, from 24% to 21%
I think the lower voltage thing is responsible of that, it was around 400volts this morning, now it’s as low as 370-375v if I remember correctly

 

[Mihir]

I drive a SR too but in my experience, the battery % drops for many or some of the following reasons:
1. Weather - if its cold or windy, it takes away some battery %
2. Drive mode - Did you check if you drove in eco/normal/sport mode
3. Battery balancing - Whenever I have charged at 100%, I get different range on different days anywhere between 158-186 miles. As suggested try charging to 100% and leave it on for a bit after that for battery balancing/equalisation
4. Make sure you turn the heating and/or demistifiers etc off before you stop the car. Try setting the trip counter to 0 before starting.

IMO do the battery balancing and see if that makes any difference.

 

[r0b1n68]

I drive a SR too but in my experience, the battery % drops for many or some of the following reasons:
1. Weather - if its cold or windy, it takes away some battery %
2. Drive mode - Did you check if you drove in eco/normal/sport mode
3. Battery balancing - Whenever I have charged at 100%, I get different range on different days anywhere between 158-186 miles. As suggested try charging to 100% and leave it on for a bit after that for battery balancing/equalisation
4. Make sure you turn the heating and/or demistifiers etc off before you stop the car. Try setting the trip counter to 0 before starting.

IMO do the battery balancing and see if that makes any difference.

At the moment I didn’t charge my car since I received it
The dealer gave it to me with 100% battery, and I want to discharge it around 10% and then charge it up to 100% and let it balance

This morning there was no wind, 10° exterior temp, I was in Eco mode, heating at 22° & fan speed at 1
That’s why I really don’t understand the consumption

 

[Mihir]

At the moment I didn’t charge my car since I received it
The dealer gave it to me with 100% battery, and I want to discharge it around 10% and then charge it up to 100% and let it balance

This morning there was no wind, 10° exterior temp, I was in Eco mode, heating at 22° & fan speed at 1
That’s why I really don’t understand the consumption

Try the 100% charge today and see if it makes any difference. Keep us all posted on how it goes.

 

[Mihir]

Have a look at EV Watchdog Android monitoring App if you are looking for a ODB adapter/app. The app developer is a member on this site and is on one of the threads under General Resources and seems to be very helpful.

 

[John G]

The default for MG is to show a please recharge message at 25%. This is to give you plenty of notice, not scare you. When you start the vehicle The GOM will show its best estimate based on your previous recent driving and adjust it according to the temperature. This why you might get home with a warm battery showing , for example, 75km but in the morning it shows 60km. Getting the car warm or cool uses quite a bit of energy but keeping at the required temperature uses a lot less.
It's quite normal to be a bit worried about it all for a couple of months but you will soon get used to it and know when to charge and understand the systems better. I was worried like you two years ago but now I just know what it all means and know what to do in all weather's.

 

[r0b1n68]

Have a look at EV Watchdog Android monitoring App if you are looking for a ODB adapter/app. The app developer is a member on this site and is on one of the threads under General Resources and seems to be very helpful.

I tried 4 different apps, but none of them can show anything apart TPMS sensors, 12v battery voltage, and total mileage since new
I think the newer models are not supported at the moment

 

[r0b1n68]

The default for MG is to show a please recharge message at 25%. This is to give you plenty of notice, not scare you. When you start the vehicle The GOM will show its best estimate based on your previous recent driving and adjust it according to the temperature. This why you might get home with a warm battery showing , for example, 75km but in the morning it shows 60km. Getting the car warm or cool uses quite a bit of energy but keeping at the required temperature uses a lot less.
It's quite normal to be a bit worried about it all for a couple of months but you will soon get used to it and know when to charge and understand the systems better. I was worried like you two years ago but now I just know what it all means and know what to do in all weather's.

I totally agree with you, and I’m not worried about the range, I had an e-208 before so I know electric cars pretty well

My concern is the sudden loss of battery, from 38 to 24%, because this commute should have taken 5 to 6%, not 14, that’s the only thing I’m worried about

I connected an OBD adapter to see the real battery capacity and percentage, but none of the 4 apps I used could see the informations I needed
Maybe an update is required for the new 2022 models

 

[r0b1n68]

Try the 100% charge today and see if it makes any difference. Keep us all posted on how it goes.

I will charge my car tonight after work, and tomorrow I will see how much Kw my wallbox put into the car
I know the ZS have approximately 10 to 12% of charge loss when charged on 7kw
Then I will calculate approximately how much is into the battery

 

[Mihir]

I tried 4 different apps, but none of them can show anything apart TPMS sensors, 12v battery voltage, and total mileage since new
I think the newer models are not supported at the moment

I've asked the question to Daniel, the app developer of EV Watchdog if newer cars are supported - EV Watchdog for MG EV. He seems pretty proactive. Lets see what he says!