Recent BMS update

[Mike]

@JodyS21 you paid for a 44.5kWh battery pack and that is what you have got. That is what it says on the battery! Look on the left hand side underneath near the front!

Oh, and MG never stated it was useable either!

 

[Lovemyev]

Gross and net ratings of the HV battery packs are two completely different animals.

 

[Chrisb]

I agree with you both that mg never advertised it as the useable capacity, but also see Jodys21 point, I must admit when I bought my mg I thought the same, that it had 44.5 KW capacity to use, what's the point of advertising a car with certain size battery if you can't use that capacity, to me it's like advertising an ICE car with a 50 litre tank, but then finding out it can only hold 30 litres when you fill it up for safety. Do other manufacturers do this? Does the Nissan leaf have a 40kw battery but only 35kw usable capacity? I have no idea, and think information like this should be in the advertising information somewhere, I believe some countries maybe Japan, stipulate the manufacturer have to advertise the usable capacity, I believe our government should bring in similar legislation, otherwise this may catch people out who aren't aware of this.

 

[JodyS21]

I cannot find anywhere on the MG website that it says the 44.5kWh battery is gross or net / or that only X amount is usable.
I have found elsewhere on a few review sites that they think it has 42.5kWh usable, but that is unofficial.

By MG just stating that it has a 44.5kWh battery, that implies that you have use of 44.5kWh. It may as well say it has a 50kWh battery if it's meaningless as a useful figure.

Looking into the WLTP test; they fully charge the car, run/test it for say 1/2hour, take the mileage, then fully charge it again noting how many kW are used (including charging losses). This give the miles per kW figure, which that they multiply by the battery capacity. I'd like to see if they've used 44.5 or 42.5 etc as the figure to multiply it by. I cannot find this info anywhere on internet.

I'm trying to find the photo someone posted of the plate on the actual HV fitted battery, I seem to recall it actually said it was less than 44.5, my memory says 44.0 but I could be wrong.

I wish I seemed to have 42.5kWh of usable battery.

 

[Chrisb]

I do seem to have approx 42.5 Kw usable capacity, but my car chargers to 455v, and I drove until my car reached 450v, I did 6 miles at 3 miles per kw, so the 5 volts at the top works out about 2kw of energy, which could mean you infact do have 40.5 KW usable capacity, if you've had the latest update (450v) and MG haven't allowed anymore capacity to be used at the bottom end. I can't comment on this though because no one has given information about what voltage readings they're getting at the bottom end.

 

[JodyS21]

I do seem to have approx 42.5 Kw usable capacity, but my car chargers to 455v, and I drove until my car reached 450v, I did 6 miles at 3 miles per kw, so the 5 volts at the top works out about 2kw of energy, which could mean you infact do have 40.5 KW usable capacity, if you've had the latest update (450v) and MG haven't allowed anymore capacity to be used at the bottom end. I can't comment on this though because no one has given information about what voltage readings they're getting at the bottom end.

Thanks, that is very useful and interesting data.

 

[Chrisb]

Bear in mind aswell, that MG aren't actually doing anything wrong by reducing the voltage and range by approx 5% because the warranty on the car covers for a loss of 30% over 7 years.

 

[Mike]

It is quite common with EV’s to quote gross.
For example every single Nissan to date has been gross. The 24, 30 & 40. None of them were useable figures.

Tesla have stopped quoting battery size. What really matters is range. How far will it go. Preferably in winter in freezing & wet conditions at night.

 

[Mike]

Bear in mind aswell, that MG aren't actually doing anything wrong by reducing the voltage and range by approx 5% because the warranty on the car covers for a loss of 30% over 7 years.

They aren’t reducing the range we have been told. Just reduced the top end voltage and the bottom end to keep useable battery capacity the same and hence the range the same.

 

[Davemac278]

I have the latest update and can now charge whilst unlocked. Voltage has dropped from 455v to 449v but my range hasn't changed.

 

[SCB86]

I saw that on Facebook.

 

[Paulie68]

The reduction in voltage is actually a really good move. Previously the fully charged voltage meant a cell voltage of 4.22v per cell. This is really unhealthy for longevity of this type of lithium cell chemistry. The new figure of 4.16v is much better. I just hope they aren't letting it drop too low to keep the range constant.

 

[guest]

.

 

[Chrisb]

Yeah I did think they may allow more into the bottom voltage, but we will find out if this is the case when people charge from empty to full, because looking at some of the figures on here from people who have had the latest BMS it would now seem people have now got only approx 40kw capacity since the update. If someone who's had the update could say what their voltage is as soon as the battery light comes on and I can do the same, we can then see if this is the case, it's not that I don't believe what Miles is saying, but he did say on a podcast I had seen that he was told the voltage would go back up to 455v when the weather warmed up, which seems not the case now.

 

[Cocijo]

Just a bit curious as to why tweak the maximum voltage down to 450v from 455v to improve longevity of the battery pack? Do MG have doubts whether the usable life of the pack will extend throughout the warranty period? If so what happens to those that are still on the BMS version that charges to 455v max and may never be updated? Are they at risk of being warranty replacements say in years 5 or 6? That is sailing very close in specification terms and I would have thought a 10 year+ life expectancy for something that is warranted for 7 years to be more conservative.

I agree. That was one of the points that I made and asked if MG will be completing the update on all models if it is so important - it seems from posts on here that they are not - if it’s as important to battery pack longevity as is proposed then why not update all cars?

 

[Cocijo]

I have a theory that MG have reduced the voltage on the pack because a number of cars have had the main HV fuse failure.
My local dealer had the fuse fail while carrying out the PDI checks !.
A second car arrived at the dealership on a flat bed with HV fuse failure.
Both cars where shipped out to another dealer about 40 miles away.

You may be right– owners should not have to speculate though! Updates should have clear release notes

 

[Cocijo]

I do seem to have approx 42.5 Kw usable capacity, but my car chargers to 455v, and I drove until my car reached 450v, I did 6 miles at 3 miles per kw, so the 5 volts at the top works out about 2kw of energy, which could mean you infact do have 40.5 KW usable capacity, if you've had the latest update (450v) and MG haven't allowed anymore capacity to be used at the bottom end. I can't comment on this though because no one has given information about what voltage readings they're getting at the bottom end.

Good points. I wonder if reducing the top end voltage also reduces the motor power output? It would wouldn’t it? That would mean the published power has also changed.

 

[Cocijo]

The reduction in voltage is actually a really good move. Previously the fully charged voltage meant a cell voltage of 4.22v per cell. This is really unhealthy for longevity of this type of lithium cell chemistry. The new figure of 4.16v is much better. I just hope they aren't letting it drop too low to keep the range constant.

If that is the case then MG should recall all cars and complete the update shouldn’t they? It seems some have had their cars in service recently and not had the update.

 

[Cocijo]

Realistically most owners - who don’t vacate forums like this one - will only have the limited information that is given them by their MG dealer. They will judge their ownership experience on how the car performs for them, and most I think will be very pleased with it. For this reason I can’t see a change in approach from MG in the short term anyway. I do however think that MG are asking for trouble if they supply for example a HV pack voltage meter - what real purpose does this achieve for the average owner other than to create anxiety over what it should or shouldn’t read? All of this stuff should just happen in the background - owners just want their cars to charge up and work as intended - not have to monitor battery voltages or complete equalisation after equalisation (I’m amazed at how tolerant owners are at diligently completing these tasks.). I’m sure other EV manufacturers tinker with their batteries and BMS systems post production and you never get to hear about it - if you provide customers with information like battery voltages then you must be prepared to meet the challenges that you will face when these change.

 

[Lovemyev]

I agree. That was one of the points that I made and asked if MG will be completing the update on all models if it is so important - it seems from posts on here that they are not - if it’s as important to battery pack longevity as is proposed then why not update all cars?

It would appear that cars leaving the factory or dealers after the PDI are now having the packs set to 450 volts max now according to the latest info from Miles R.