BMS updates and warranty

[Chrisb]

Does anybody know whether it's compulsory to have the BMS updates to keep the warranty valid?

My car had the August updates when I got it, and I'm happy with the car, it can charge up to 455v, I only ever charge it up to 100% every couple of months, most of the time I only charge to 80% to try and help preserve the battery life. I would rather do this, than have a slightly reduced range enforced on me by MG to try and help them preserve battery life (if that's their plan, just guessing), but at the same time wouldn't want to invalidate my warranty by not having the BMS updates.

 

[Cocijo]

Your thoughts about battery preservation did also cross my mind. I don’t think that the issue with the bms update is MG trying to preserve battery life. As you mention, these type of batteries do not like to be at either end of the charge scale for too long (fully charged or fully discharged). They prefer to operate in the middle range If possible. That said if you have a relatively small battery you may need to fully charge it each day to meet your needs - and they do contain safeguards (what we see is fully charged is actually less than the battery can actually take.) Although letting it sit at very full or very empty for long periods is not good for the battery. Other makers have built in the functionality to set the charge %. This is fine if you have for example a 75kw battery (Tesla Model 3 for example) and hardly ever need the c300 mile range that it gives you - so you can charge to say 65% for everyday trips and 100% for longer jaunts. From what I’ve read annoying as it is, the MG bms issue is a software bug and not an attempt to throttle the batteries.

 

[Chrisb]

I do hope that your right and it's just me being cynical, it'll be interesting to see what voltage the car chargers to after the next update.

I tried to do a bit of research as to what type of cells were used in our cars, and did come across ev cells sold by catl, took a photo of the label on the battery of our car, with nominal voltages, amps etc, and to cut a long story short, the cells for sale fit in perfectly maths wise with the specs on our car, and it would seem that at 455v the cells are actually nearly at 100%, and according to my calculations from the catl cells online there would be approx 15% of the battery which we can't use at the bottom, so my thinking goes that i would be happy if they wanted to take some voltage off the top, so long as it was replaced with some available from the bottom that would be fine, I'd still have the same usable capacity. But whether they do that is another story, try might want to gradually reduce our range to preserve battery life and ultimately to want us to buy a new car after 7 years, I hope I'm wrong, I'm probably being unfair, but it does seem strange that they could get updates so wrong, reducing people's usable range, from what was perfectly fine before these updates, but will see what the new update brings.

 

[Cocijo]

some goods points. The MG warranty covers degradation below 70% for 80k miles or 7 Years I believe. How they interpret/measure and support this is a different matter. Assuming that you got to 70% you’d be at 114 miles range based on the published 163 miles - your real world would be well below 100 miles. If the starting mileage was around 100 (which some people are reporting after the bms update you’d be right down to below 70 miles. My experience is smaller batteries do degrade quicker than larger ones - mostly because they get worked harder.

 

[Kithmo]

some goods points. The MG warranty covers degradation below 70% for 80k miles or 7 Years I believe. How they interpret/measure and support this is a different matter. Assuming that you got to 70% you’d be at 114 miles range based on the published 163 miles - your real world would be well below 100 miles. If the starting mileage was around 100 (which some people are reporting after the bms update you’d be right down to below 70 miles. My experience is smaller batteries do degrade quicker than larger ones - mostly because they get worked harder.

Wouldn't battery degradation show on the HV battery meter ?

 

[Cocijo]

I’m sure that you would see a drop in the batteries ability to hold a full charge plus a change in voltage - but by how much and how MG measure this I don’t know.

 

[Mark Holmes]

I’m sure that you would see a drop in the batteries ability to hold a full charge plus a change in voltage - but by how much and how MG measure this I don’t know.

Mike Proctor noted about a 1% drop in capacity after 1 years (approximately 12000 miles) on his car and so that looks good, but as he says he very rarely rapid charges if I recall correctly....and so that looks promising for us if we look after our batteries. Noted comments about 455 volts on a full charge mine is now showing 454 on a full charge at present with just under 14,000 miles completed, I don’t know; I presume they are related I.e. volts to capacity.?.

 

[Cocijo]

It’s very easy to get infatuated with battery stats. It’s good to just drive and enjoy the car. Top it up when you need to and take advantage of the low running costs. This battery degradation theme runs through all ev forums and makes. It’s good to have this forum to know that you can ask for expert advice if you need it. It sounds like your battery is as good as new! And Mikes too.

 

[Mark Holmes]

It’s very easy to get infatuated with battery stats. It’s good to just drive and enjoy the car. Top it up when you need to and take advantage of the low running costs. This battery degradation theme runs through all ev forums and makes. It’s good to have this forum to know that you can ask for expert advice if you need it. It sounds like your battery is as good as new! And Mikes too.

I’m hoping that it’s down to very little rapid charging, besides that the car needs to last the test of time as I cannot afford new cars every couple of years..

 

[Cocijo]

I’m sure it will and it has a 7 Year warranty

 

[Zoomy]

Chrisb - your BMS will have a fault in it that will be observed as having overly long (half a day) doing a balance. I have the same level as you. Miles has said MG are releasing a fix this week. They took at stab at fixing it in August, then again November (applied with battery heating) but still wrong, hence all the recent posts about range and charging