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Discussion Starter · #1 ·
Hi guys,

Iam new here, but old ev driver.

My fourth EV is MG ZS EV, I was hapy with it until last week when I realize that something isn't right, I have to charge it every night. If someone have the same problem or can help me to solve this one would be great.
I charge my car usually at home but last week I went to the shop and put the car on DC fast charger 50kw. SOC was 6%, after 1h and 5 min it shows 99% and it have deliver 26,412 KW from the grid, it was strange for me but on odometer it shows range 220km so I tought it is new charger and it doesnt mesure right. Two days ago I was at 20% so I went to another, old charger AC 22 kw, after 8 hours I came back and it shows 220km and on the charging station it shows delivered only 24 kw. Since car have battery pack off 44 kw that is strange to me. I was checking km during driving the car and in the start it is all ok, but yesterday in the morning it was 170km on odometer and wife take the car to get to hairdreser, pick up the kids and it shows 50km left, on totall odometer it went from 4.313 km to 4.380 km. When I check on wh/km it shows average 230wh/km last 1.500 km

Did any one off you have same problem?

Thanke you in advance!!!
 

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I would expect my eZS to take approximately 40kw to go from 6% to 99%.
I’m not sure on the European numbers but I would expect GOM to show 160m/260km on full charge.

It’s possible you have faulty bms because your numbers don’t sound good.
 

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Zoe Devotee
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Sounds very much like the dodgy BMS. At 100% charge (after balancing) what is the volts shown on the charging screen? Should be 455 if you've got the old good BMS. If its 440-ish then you've got the ropey BMS and need an update.
 

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Discussion Starter · #4 ·
Thanks for the help, will see the voltage soon. Iam almost finish with my job and will pick up the car.
 

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Discussion Starter · #5 ·
Charging finished, from 8% to 100% it take from the grid 27,212 kw. There is no voltage on charger but voltage on the car screen was 436V.
Based on yours posts iz looks like I have ropey BMS and need update😔
Does car have now full range or it have only 30kw battery? I supose that I need to go to service center to fix this??
Sorry Iam blond
 

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Zoe Devotee
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Charging finished, from 8% to 100% it take from the grid 27,212 kw. There is no voltage on charger but voltage on the car screen was 436V.
Based on yours posts iz looks like I have ropey BMS and need update😔
Does car have now full range or it have only 30kw battery? I supose that I need to go to service center to fix this??
Sorry Iam blond

Sounds like you've got the bad BMS. Needs an update, and it will take some time to restore the pack balance up from 436 to the new norm of 449 I believe. But you should see your range increase with every charge, and I don't believe you need to do full discharges, just 10-15% then balance and rinse and repeat for the next couple of months.
 

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Jeez I’d just give it back and get summat else.

Really liked my MG, but sounds like a real minefield with updates at the moment.
 

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Discussion Starter · #9 ·
Thanke for the help. I will contackt service center and charge car every night. Hope it will help to get battery balanced untill service center replays.
Thanke once more!!
 

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Thanke for the help. I will contackt service center and charge car every night. Hope it will help to get battery balanced untill service center replays.
Thanke once more!!
I think you need the update and then you can charge frequently to get the cells back in balance at the right voltage. The bad BMS is stopping the cells charging fully.
 

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Thanke for the help. I will contackt service center and charge car every night. Hope it will help to get battery balanced untill service center replays.
Thanke once more!!
The more you charge your car the worse it will get with the dodgy BMS. The more you rapid charge it the worse it will get.
Do not bother trying to equalise that battery either as that doesn’t work.

It’s going to take many hours of equalisation charging once you have had your car updated to get the car back to normal. Which is now 449V.

Get it updated ASAP.

Thete are so many threads on here, Facebook and MGEV’s website about this issue. Your dealer really should have contacted you to get it sorted ages ago. The update was released mid January 2021.

 

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Discussion Starter · #12 ·
Hi guys thanke you for all the help.
I have try over the weekend to balance the cells but nothing happened, voltage is still 436V. I have contact the seller for service, still no replay but the nearest service center is 350km away from me, it will be long way to there. How long that this update last, few hours or few days? Is it only software update or they will change the BMS?
 

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Hi guys thanke you for all the help.
I have try over the weekend to balance the cells but nothing happened, voltage is still 436V. I have contact the seller for service, still no replay but the nearest service center is 350km away from me, it will be long way to there. How long that this update last, few hours or few days? Is it only software update or they will change the BMS?
As above - it won't work until you get the update. It's a software change only. Shouldn't take more than a few hour s provided all goes well.
 

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Discussion Starter · #14 ·
Today I have received phone call from the service center, just need to see for the COVID-19 tests (there is no service center in my country, need to go to Austria) and I can come to service center for software update. How much this would be easier if there is ower the air software update...
 

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Discussion Starter · #15 ·
Lets bring this subyect alive. Last friday I finally went to the service center, last few days my avalible battery pack was around 22kw, range about 110km, average high way consumption 190w/km, fast charging speed 32kw, when is full voltage off battery was 431v.
Service center is 400km away, we have prepare for traweling and made 5 stops to come there.
Owner off the service center told me that now I can trust range on the car display, we allmost left on the road without off the power. Big change was that car now with new software shows consumption 150w/km at same terms, is that right??
I have question now how to bring this battery back to 44kw?
Yesterday I have charge it all the day at 220v and when it was full voltage was again 431v. Last night I made 17km run and come back, forgot to see what was consumption and when I start the car again it shows eror: Vehicle control system fault, and HV battery shut off.
After few minutes it started charging car?!?!?
This morning voltage is allso 431v.
How ti chargit to get back full battery capacity??
Empty battery to the bottom and charge it to 100% or make 20km and charge it to the 100%??
 

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I had a similar problem, my voltage when fully charged was 437 volts. As I had an OBD 2 dongle I was able to check the battery cell imbalance and found the cells to be badly unbalanced. I could also see that I had the bad BMS software version.

I took the car to my dealer. They updated the BMS software to the latest version. I requested they hold onto the car until they were able to balance the battery and achieve a fully charged voltage of 449 volts.

It took the dealer eight days of constantly charging, partially discharging and leaving the battery in balancing mode to balance the battery and achieve the required 449 volts.

A month later and my car is in good battery balance with a fully charged voltage of 449 volts.

My advice to anyone with low voltage at full charge is to return the car to the dealer.

The bad BMS was MG's fault and it is their responsibility to fix the problem they introduced. (See attached dealer information sheets on how they should properly balance a battery)

143833
143834
 

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Discussion Starter · #17 ·
Thanks dr Dave!! I have put it into ready mode and will leave it ower night, will see what will show tomorow. Ready mode is when you just pres start button without pressing break?? Am I right?
Witch OBD do you use???
I would like to buy my self one so I can monitor cell voltage.
Unfortunatlly I dont know how to fight for my rights, I have payed the trip and was happy when they sead they are finished, now it is big balancing period in front off me.
Did you noticed maybe after BMS update that it have lower consumption??
 

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No. Ready mode is when you hold down the brake. A green READY message appears on the instrument display, and the car is ready to drive off.
 

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Discussion Starter · #19 ·
No. Ready mode is when you hold down the brake. A green READY message appears on the instrument display, and the car is ready to drive off.
Thanks, that is mode when you can drive the car? When is in that mode I cant turn off the lights?
 

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Yes, Ready is the mode where you can drive the car.

You should be able to turn off the lights, as far as I know. Are yours set to Auto?
 
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