Loss of range and warning light 'please slow charge high voltage battery' coming on 4-5 times per day

[JillianW]

I have owned my MG EV since December 2020. Had no problems until this month. I am using at least 2k of battery to every 1 km travelled with no air con, heating on etc. I have had a total breakdown where every warning light was on and unable to move car after starting. Had to be towed to nearest dealer.
Car started on arrival to drive off tow truck! ???? . They said they did a battery reset and software upgrade but when I picked the car up the " please charge high voltage battery' came on before I had left the dealer. I have done an equalisation charge last night and it completed the task and charging lamp was off this morning.
I now have 271kms on Eco mode on the display I have only ever had max 231 on Eco mode, however still used 5kms of battery to 1.5km travel and 'please slow charge high voltage battery" warning light still coming on today. Also have had 'brake regeneration limited' warning light on twice this week.
Any ideas????

 

[Davemac278]

It sounds like you had the faulty BMS update which degraded your battery voltage and therefore range capacity. I had same issue when I bought my car in Dec 20. MG released a new software update on 15th January and again in February 21. If the dealer has just updated the software but not helped your car charge and balance to get you to a new fully charged voltage of 449/450v then it will take a good month or so of constant charge/balance cycles to get your car back to normal voltage and actual range.

Your regen warning is because car battery is fully charged and has no space to put regen charge. This is normal but you will find your regen will kick in quicker now with new BMS as new buffer added to capacity.

Also your slow charge warnings will go once you get battery back and balance/equalisied charged.

Useful video on topic here

 

[Davemac278]

MG uk have even issued guidance to dealers to get car to a voltage range minimum before giving customers car back to them.

 

[Davemac278]

Loads on here about BMS

Check this link to help you find your voltage screen to check

Post in thread 'Voltage reading' Voltage reading

 

[JillianW]

I have owned my MG EV since December 2020. Had no problems until this month. I am using at least 2k of battery to every 1 km travelled with no air con, heating on etc. I have had a total breakdown where every warning light was on and unable to move car after starting. Had to be towed to nearest dealer.
Car started on arrival to drive off tow truck! ???? . They said they did a battery reset and software upgrade but when I picked the car up the " please charge high voltage battery' came on before I had left the dealer. I have done an equalisation charge last night and it completed the task and charging lamp was off this morning.
I now have 271kms on Eco mode on the display I have only ever had max 231 on Eco mode, however still used 5kms of battery to 1.5km travel and 'please slow charge high voltage battery" warning light still coming on today. Also have had 'brake regeneration limited' warning light on twice this week.
Any ideas????

Thanks so much! I have not had any help from the dealer/service! I am not sure they know anything about MG EVs. Thankyou for the podcast it was great, but can you tell me how I see the voltage screen on the dash?

 

[Davemac278]

Scroll up down buttons on right hand side of steering wheel.

 

[JillianW]

Scroll up down buttons on right hand side of steering wheel.

Thanks!

 

[Davemac278]

I ran my car down one blob and then charged (MG badge pulsing) and left to balance (MG light on whilst balancing and off when complete)

Found it took from over 10 hours to balance and now after a month of constant charge cycles it's on around 2 hours to complete and at 449v with an improving variance of cell balance between lowest cell and highest.

Use AC home 7kw or granny charger so it does a balance at end of top up charge from about 85% (one blob on dash)

Worth getting a OBD dongle and one of the Apps such as car scanner torque Pro or Thai free app on this site.

 

[Davemac278]

This is some of the info I can get from an App connected to a bluetooth OBD dongle.

 

[JillianW]

Loads on here about BMS

Check this link to help you find your voltage screen to check

Post in thread 'Voltage reading' Voltage reading

Hi thanks for all the info! Next question on my journey to understand my car- what should the low voltage battery reading be on the dash when big voltage battery fully charged?
I have done two equalization charges now and car reads 425volts- I assume I keep equalize charges going as still using heaps of battery to drive not far?

 

[JillianW]

I ran my car down one blob and then charged (MG badge pulsing) and left to balance (MG light on whilst balancing and off when complete)

Found it took from over 10 hours to balance and now after a month of constant charge cycles it's on around 2 hours to complete and at 449v with an improving variance of cell balance between lowest cell and highest.

Use AC home 7kw or granny charger so it does a balance at end of top up charge from about 85% (one blob on dash)

Worth getting a OBD dongle and one of the Apps such as car scanner torque Pro or Thai free app on this site.

Thanks again! This is making it so easy to understand and ask for help from dealer

 

[Davemac278]

Hi thanks for all the info! Next question on my journey to understand my car- what should the low voltage battery reading be on the dash when big voltage battery fully charged?
I have done two equalization charges now and car reads 425volts- I assume I keep equalize charges going as still using heaps of battery to drive not far?

It is going to take you a long time to recover 24v from your current 425 to the new BMS maximum for your car which is 449v.

You will need to force your car to complete a full balance. I wasn't using my car much during lockdown but ran it down one blob on dash to around 83-85%. That way when I charged the car overnight it would fully charge and then automatically complete a balance/equalization to try and recover the cells to the same level.

You are probably only going to see a 1v rise every charge cycle so plan on getting 24 charges completed before seeing a range improvement. You may also find balance times take a long time to complete but in time they will improve to a more reasonable 2 hours from what you may be experiencing at the moment.

Search BMS on this site for more background and you will have an understanding of everyone's frustration with the faulty BMS of Late Oct-Dec 20.

MG accepted it was their fault and dealers were asked to give customers a free service for their inconvenience.

Worth asking your dealer for loan car whilst they charge it and resolve range issues as per my last screenshot of guidance issued by MG UK.

 

[JillianW]

Thankyou! Am starting the long journey of trying to explain all this to my dealer /service dept
I am slowly getting higher voltage readings the more equalization charges I do but it’s only at 431v - still along way to go ..

 

[Jamlam]

Great info on this thread. I was getting the annoying "slow charge" message and red battery sign to. I also noted I was struggling to get even 85 miles on a full charge in E mode and I was get 4+miles p/Kw some times too. I don't use the heating/Fans but only in extreme situations.
This range was also during the mild weather in spring (before the constant rain!). I only have a granny charger and i've always charged on this but i've just checked my cars volts now and it reads 402V!!!!!!!! and the slow charge message popped up again and i only have 64 mile range!

I've just come back from the MG dealer today as they recalled it for the new BMS update and they said it will take 350 HOURS (yes 350 hours ) of charging to stabilize the batteries. The dealership said driving the car also counts as the re-gen brake also counts but not seen it mentioned on hear regarding the regen counting.
Sounds like this is going to take a long time to get sorted.
I also noted the dealers NEVER offered to balance the batteries for me the as per the MG paperwork in the posts above. The service staff who I found difficult through the whole process just told me to use the battery up and just keep charging it as normal and it will improve.

 

[Davemac278]

Great info on this thread. I was getting the annoying "slow charge" message and red battery sign to. I also noted I was struggling to get even 85 miles on a full charge in E mode and I was get 4+miles p/Kw some times too. I don't use the heating/Fans but only in extreme situations.
This range was also during the mild weather in spring (before the constant rain!). I only have a granny charger and i've always charged on this but i've just checked my cars volts now and it reads 402V!!!!!!!! and the slow charge message popped up again and i only have 64 mile range!

I've just come back from the MG dealer today as they recalled it for the new BMS update and they said it will take 350 HOURS (yes 350 hours ) of charging to stabilize the batteries. The dealership said driving the car also counts as the re-gen brake also counts but not seen it mentioned on hear regarding the regen counting.
Sounds like this is going to take a long time to get sorted.
I also noted the dealers NEVER offered to balance the batteries for me the as per the MG paperwork in the posts above. The service staff who I found difficult through the whole process just told me to use the battery up and just keep charging it as normal and it will improve.

Who is your MG dealer?

You need to insist that they charge and balance for you as per MG note.

I would contact MG UK if dealer denies or refuses to follow guidance issued to them by MG UK

Insist on a loan car until sorted 4u

 

[Jamlam]

The dealer is eric stead sheffield. Some of the staff at the service and parts desk are so difficult that it gave me a actual headache dealing with them and I deal with obstructive public people every day in my own line of work which does not effect me.
I live about 55 miles from them so they gave me a courtesy car after the staff forgot to book the request in. The car was just for the day -7hrs. It does take my day off work up so I think I will have to see what to do about it and possibly ask MG uk 1st to see what they recommended to so I get some support 1st. Any particular contact details for Mg UK available?

 

[Davemac278]

The dealer is eric stead sheffield. Some of the staff at the service and parts desk are so difficult that it gave me a actual headache dealing with them and I deal with obstructive public people every day in my own line of work which does not effect me.
I live about 55 miles from them so they gave me a courtesy car after the staff forgot to book the request in. The car was just for the day -7hrs. It does take my day off work up so I think I will have to see what to do about it and possibly ask MG uk 1st to see what they recommended to so I get some support 1st. Any particular contact details for Mg UK available?

Hi m8,

The only name I have found was Gary Smart at MG. He was the Customer Service Manager at MG UK that dealers were to contact to get customers a free service following BMS update.

See screenshots for info

 

[Davemac278]

Have you shown the dealer the MG note about them giving Customer option to leave car for them to get car up to a balance charge over all 9 cells as per note?

 

[Davemac278]

I see that Eric Stead has very good feedback from members of this forum. I think it is worth an email to them with attachment note from MG to request formally that they rectify your imbalance and request a courtesy car whilst they sort yours out and get it to 449v fully charged and a balance time of 2 hours. After all they can claim costs back from MG.

See link to reviews here

Post in thread 'Eric Stead Sheffield - MG Dealer Discussion, Opinions & Experiences' Eric Stead Sheffield - MG Dealer Discussion, Opinions & Experiences

 

[Jamlam]

Davemac278 you have been very helpful.
It's certain staff at the service desk at the garage that have let the place down.
I will follow it up! Cheers