Bad day. Battery drop from 13% to 1%.

[LZA]

Drove my ZS TLR 200miles to pick up my son. Arrived with 13% remaining. Went for a lunch. Came back the car after 3 hours, 1% left. Car was definitely locked. And nothing was on.
Eventually I had to call MG Assistant to get it to the nearest charger.

Did anybody have similar experience? I knew GOM is only an estimate. But 13% and 1% was a massive difference. ZS either guessed it wrong or lost 12% in 3 hours. Either way, I am deeply worried.

 

[Gadget Geek]

In 3 hours, the traction battery would cool down, thus changing all the readings. It happened to me once, but I was at home when I noticed it.

 

[LZA]

In 3 hours, the traction battery would cool down, thus changing all the readings. It happened to me once, but I was at home when I noticed it.

Thank you for the explanation. I visit my son regularly. This has never happened before even during the winter time. Now the worry is how do we know the shown battery percentage is "Real"? Or is it alright to leave the car with 10% battery after a long journey?

 

[drmcw]

Surely after a long journey you'd expect to be at a charger? Not a great idea to leave it at a low SOC.

 

[LZA]

Surely after a long journey you'd expect to be at a charger? Not a great idea to leave it at a low SOC.

We normally have a coffee/lunch after arriving. Then charge on our way back (there are 300 kW chargers just 2miles away).
But after today's incident, we may need to change our routine.

 

[drmcw]

We normally have a coffee/lunch after arriving. Then charge on our way back (there are 300 kW chargers just 2miles away).
But after today's incident, we may need to change our routine.

If you're going to rapid charge then doing it while the battery is warm should save you time in the long run as you'll get a much higher charge rate with a warm battery too.

 

[LZA]

If you're going to rapid charge then doing it while the battery is warm should save you time in the long run as you'll get a much higher charge rate with a warm battery too.

To be hoest, the ZS charge rate is pretty good even with a cold battery. Yesterday, AA tow me to the nearest rapid charger. The charge rate reached 75kW within a few seconds.

 

[drmcw]

But 94 kW with it warm

Edit: BTW is yours a SR or LR? If SR then would explain the 75 kW charge and also the big drop when left for a while.

Edit2: Just seen your original post says TLR so the LR! So it is the cold then.

 

[LZA]

But 94 kW with it warm

Edit: BTW is yours a SR or LR? If SR then would explain the 75 kW charge and also the big drop when left for a while.

Edit2: Just seen your original post says TLR so the LR! So it is the cold then.

I got about 84kw with a warm battery.

I can understand the range drop due to warious factors. After all, it's an estimation. But battery percentage? The car should know how much electrons are in the tank.

 

[drmcw]

I believe the SOC is worked out from the voltage and was why I thought you might have the SR with the LFP battery. That battery type has a very flat voltage curve and so is subject to a much larger error in estimating the SOC.

 

[Coulomb]

I believe the SOC is worked out from the voltage and was why I thought you might have the SR with the LFP...

I believe that with LFP, they have to count coulombs (amp•seconds, current multiplied by time) as well as use some hints from voltage and adjustments for temperature. And of course the count goes backwards for regen.

 

[drmcw]

I believe that with LFP, they have to count coulombs (amp•seconds, current multiplied by time) as well as use some hints from voltage and adjustments for temperature. And of course the count goes backwards for regen.

I think Tesla tried that but don't think MG resorted to that. OP has LR anyway.

 

[MGLuckyMe]

I only have SR… received car end of June this year… I don’t do many miles probably 8k per year hence the reason I went for a SR. Did my usual round trip yesterday to my unit and back typically about 15 miles when checking the range but yesterday it went down close to 30 miles… was driving normally, didn’t drive aggressively. Nothing different to my normal routine.

Not happy with what I experienced…. I know it’s beginning to get cold but its still pretty mild too…

I’ve had a couple of these experiences now and I’m not getting really worried but I’m starting to notice things already.

What’s more concerning is that if I’ve only had the car under 6 months what’s the state of the battery going to be like in a couple of years time. I barely do 8k miles per year and I’m not confident in the longevity of the battery already.

Not sure if this info helps anyone, whether anyone can help educate me on anything relatable but simply putting down my experience.

Thanks

 

[Tangoed Man]

I only have SR… received car end of June this year… I don’t do many miles probably 8k per year hence the reason I went for a SR. Did my usual round trip yesterday to my unit and back typically about 15 miles when checking the range but yesterday it went down close to 30 miles… was driving normally, didn’t drive aggressively. Nothing different to my normal routine.

Not happy with what I experienced…. I know it’s beginning to get cold but its still pretty mild too…

I’ve had a couple of these experiences now and I’m not getting really worried but I’m starting to notice things already.

What’s more concerning is that if I’ve only had the car under 6 months what’s the state of the battery going to be like in a couple of years time. I barely do 8k miles per year and I’m not confident in the longevity of the battery already.

Not sure if this info helps anyone, whether anyone can help educate me on anything relatable but simply putting down my experience.

Thanks

My friend’s Tesla's range is awful in the colder weather, and also has LFP batteries.

 

[drmcw]

I only have SR… received car end of June this year… I don’t do many miles probably 8k per year hence the reason I went for a SR. Did my usual round trip yesterday to my unit and back typically about 15 miles when checking the range but yesterday it went down close to 30 miles… was driving normally, didn’t drive aggressively. Nothing different to my normal routine.

Not happy with what I experienced…. I know it’s beginning to get cold but its still pretty mild too…

I’ve had a couple of these experiences now and I’m not getting really worried but I’m starting to notice things already.

What’s more concerning is that if I’ve only had the car under 6 months what’s the state of the battery going to be like in a couple of years time. I barely do 8k miles per year and I’m not confident in the longevity of the battery already.

Not sure if this info helps anyone, whether anyone can help educate me on anything relatable but simply putting down my experience.

Thanks

The state of the battery will be fine. You just need to learn how the car behaves in various conditions and that range is a guess. Buying the SR because you do 8k a year is not the reason to go for an SR. If you did 30k per year but all journeys were 100 miles or less then it would still be perfectly good but if you do 8k per year but most journeys are over 200 miles then you've made a bad choice.

 

[frb123]

Drove my ZS TLR 200miles to pick up my son. Arrived with 13% remaining. Went for a lunch. Came back the car after 3 hours, 1% left. Car was definitely locked. And nothing was on.
Eventually I had to call MG Assistant to get it to the nearest charger.

Did anybody have similar experience? I knew GOM is only an estimate. But 13% and 1% was a massive difference. ZS either guessed it wrong or lost 12% in 3 hours. Either way, I am deeply worried.

Hi LZA

I had a similar experience to this some time ago and posted separately, I will try and dig out the thread. It has actually happened to me on more than one occasion, that is to say having arrived somewhere after a long journey (200+ miles) with the battery circa 10%, then having left it for a few hours/overnight, it has then, alarmingly, displayed 1 or 2%. I share(d) your alarm in this occuring. It does make confidence in the % reading quite difficult. I also have had the opposite "issue" whereby the % stays static over a similar journey, which at other times will drop by circa 10%. There are obviously the temp/weather/batt temp variables to consider but I find the % to just be a bit unreliable generally.

I would also say however that I am not concerned about the overall battery health or that there is any problem that needs fixing, it's just another limitation of the vehicle that requires some experience and understanding to have confidence in. It still goes as far as it should etc. I should also note that this massive drop off only occurs at the bottom end of a cycle, that is to say as per your/my experience when the car is stopped for a period of time at around the 10% mark.

The only behavioural adjustment I have really made is to not run it that low unless I know there is 100% a reliable charger at my destination, in which case I'll happily run down to 5% or lower. If not I would fast charge en route to arrive with say, 20% at least.

Edit: My similar thread from before:

Thread 'Battery drain (10%-3% overnight) ?' Battery drain (10%-3% overnight) ?

 

[LZA]

@frb123 Thank you for sharing your experience. Your reply of confirming witness similar issure is very helpful. I am really appreciate all the information and explanation. I also read your previous threat finding it's very useful. This is my first EV. I am still learning its behaviour. As you said, maybe it's just another limitation of the vehicle that needs experience and understanding.

Anyway, I have booked in with my local dealer to run some diagnoses. Will see what they say and report back.

Many thanks.

 

[STMDUK]

Thank you for the explanation. I visit my son regularly. This has never happened before even during the winter time. Now the worry is how do we know the shown battery percentage is "Real"? Or is it alright to leave the car with 10% battery after a long journey?

This has happened to me in the E2008 and my old Polestar. Parked with a low, but not critical battery and came back to it being 1% or so. I think this is a technical quirk of current battery tech rather than anything particular with the car itself, especially with liquid cooled battery cars; as when the battery is warm, it holds more power and can release it in a more linear fashion, when the warm coolant stops circulating and the battery cools down, it will become less efficient. Despite the drawbacks, liquid cooled battery's are more stable, reliable, and do not degrade as fast as air cooled.

I always try and charge the car when I arrive or put it on a charger while I'm there to kind of bounce off any possible debacles, either that or I try to arrive with 50% plus by charging on the way, so I can jump in and drive towards home. Not a particularly useful thing, but it at it avoids the problem.

 

[Lovemyev]

What’s more concerning is that if I’ve only had the car under 6 months what’s the state of the battery going to be like in a couple of years time. I barely do 8k miles per year and I’m not confident in the longevity of the battery already.

If you are really concerned about the longevity of your traction battery and want to help with avoiding any serious battery degradation in the future, then it maybe a good idea not to run the SOC into the low teen’s on a regular basis.
This is typically proven not to be good practice.
With a remaining range of only 13 miles the car would have been shouting for a recharge for a good number of miles before this TBH.
I think I would be looking to charge when it hits about 20 miles remaining myself ?.
You have to be 110% confident that the charger you will be using is fully operational and not blocked when running that low, otherwise if you have find a different charger, you may not make it !.

 

[JCFlippen]

After picking up tips from this forum amonst others I make all charging judgements based on % not range. I run my TCLR typically between 20% and 80% and start thinking of charging when down to 30% either by actual running info or ABRP predictions. Just done 2000miles through France with this policy and avoided range or charger anxiety.