BMS Update?

[ging353]

Is it necessary to get the January BMS Update if my car did not get the bad one last year?
My dealer Eric Stead said that it was only needed if the car had the bad one to put it right
and that MG would tell them what updates the car was in need of. The car in question is
a ZS EV and was bought in March 2020. It has had the Comfort 2 update , the HV fuse change
and the replacement wiring loom in the door.

 

[Cocijo]

initially it was suggested all cars would be updated and move to the latest BMS 450v update.
The original BMS pack has around 455v when fully charged (this is one of the ways to check that your pack is not out of balance) . The updated version about 450v.
The idea (as well as to cure those cars with a faulty BMS) is to reduce stress on the battery pack by reducing the top end voltage and at the same time lowering the bottom end voltage to maintain range.
Cars with a faulty BMS are given the latest 450v BMS. Cars without the faulty BMS and running 455v don’t seem to be being updated as a matter of course, although I did understand that this would happen for additional protection to the battery pack. My car runs 450v BMS and I’ve not been asked to have it updated. I will ask the question at next service but I have no range or BMS issues with my version.

 

[ging353]

initially it was suggested all cars would be updated and move to the latest BMS 450v update.
The original BMS pack has around 455v when fully charged (this is one of the ways to check that your pack is not out of balance) . The updated version about 450v.
The idea (as well as to cure those cars with a faulty BMS) is to reduce stress on the battery pack by reducing the top end voltage and at the same time lowering the bottom end voltage to maintain range.
Cars with a faulty BMS are given the latest 450v BMS. Cars without the faulty BMS and running 455v don’t seem to be being updated as a matter of course, although I did understand that this would happen for additional protection to the battery pack. My car runs 450v BMS and I’ve not been asked to have it updated. I will ask the question at next service but I have no range or BMS issues with my version.

 

[ging353]

Thanks for your reply Cocijo. I don't seem to have range problems. My voltage after a full charge is usually 455v. But on it's latest charge from 50% full it charged from 00.30 to 11.32am. Presumably a lot of this was battery balancing. I just wondered if not having the latest update was doing the batteries any harm.
Many thanks.

 

[Cocijo]

No problem. I should have said my car is running the 455v not 450v as in my post. There is much discussion about best practice for battery packs but the general consensus is not to leave them for long periods fully charged or very low if you can avoid doing this.

 

[FCat53]

Not needed to get the latest conservative BMS, the original BMS settings should be fine. My 4 year old Leaf , even without battery cooling has less than 4% degradation, so no real issue.

 

[ging353]

Not needed to get the latest conservative BMS, the original BMS settings should be fine. My 4 year old Leaf , even without battery cooling has less than 4% degradation, so no real issue.

Thanks for that.

 

[Kithmo]

Is it necessary to get the January BMS Update if my car did not get the bad one last year?
My dealer Eric Stead said that it was only needed if the car had the bad one to put it right
and that MG would tell them what updates the car was in need of. The car in question is
a ZS EV and was bought in March 2020. It has had the Comfort 2 update , the HV fuse change
and the replacement wiring loom in the door.

Mine's going in for its first service next month at Eric Steads, I also have the old 455v BMS and I'm glad they're not updating. I was going to ask them not to when I took it in, now I don't need to.
If it ain't broke, don't fix it I say.
FWIW. mine shows 456.25v, SOC 97% and 100% SOH, when fully charged, on the app.

 

[notdodgy]

The advantages of the newer BMS are better rapid charging and regen being available when fully charged.
The usable range of the battery is around 90% of the *theoretical physical capacity.

The new BMS means it still has the same usable capacity but when fully charged there is space for a bit more. So even when fully charged regenerative braking works.

At rapid chargers it now charges at a good rate up to 90% charge, so you can get a few more miles out of a rapid charge.

*batteries are not an exact science as we have observed - things like temperature affects them significantly.

 

[Paulie68]

Not needed to get the latest conservative BMS, the original BMS settings should be fine. My 4 year old Leaf , even without battery cooling has less than 4% degradation, so no real issue.

Sorry, but you can't compare to the Leaf, which actually stops charging at a lower 4.1V per cell anyway.

At the old BMS setting, the MG battery cells are charging to 4.22V, chemistry variances aside, this is unhealthy for any Lithium, the new BMS tops out at 4.16V. Much safer for longevity.

My advice is get the latest update. MG dealers have all been told by MG to upgrade to the latest 449V BMS during annual service anyway. If your dealer doesn't they are ignoring MG UK advice.

 

[Kithmo]

I see what you're saying guys but TBH the advantages of having the new BMS update don't really apply to me anyway.
1. I don't use rapids, I've used one once in 11 months.
2. Longevity of the battery is of no real concern to me because I'll probably trade the car in for the 73kWh version when it comes out next year or the year after and I still have the same 7 year warranty on the battery even if I don't trade in. Maybe me not using rapids and only charging up to 100% once every 4-6 weeks might compensate for the unhealthy 4.2v cell charge.
3. Regen starts working normally on mine after travelling 3 miles anyway so that's no big problem.
I guess if I was keeping the car for longer I would probably be looking into getting the new BMS, just for battery longevity, but in my present circumstances, I won't for now.

 

[ging353]

I've emailed MG to see what they have to say. I get that many conflicting messages that it would be interesting to know once and for all.

 

[jamesie]

I've emailed MG to see what they have to say. I get that many conflicting messages that it would be interesting to know once and for all.

Would be very interested in the reply you get. I'm on the original BMS which appears to be fine but don't want to cause any "damage" by not moving to the latest revision. Problem is, I don't trust the MG dealership to do the job!

 

[FCat53]

Sorry, but you can't compare to the Leaf, which actually stops charging at a lower 4.1V per cell anyway.

At the old BMS setting, the MG battery cells are charging to 4.22V, chemistry variances aside, this is unhealthy for any Lithium, the new BMS tops out at 4.16V. Much safer for longevity.

My advice is get the latest update. MG dealers have all been told by MG to upgrade to the latest 449V BMS during annual service anyway. If your dealer doesn't they are ignoring MG UK advice.

The top cell voltage for lithium cells depends on the detail chemistry of the cell, without that knowledge any pronouncement on cells being damaged by a particular voltage is not possible.
I am a retired vehicle engineer with a history in battery electric vehicles and I could not say that 4.22 volts is damaging without detailed chemical analysis of the cells. I can say that actively cooled cells have greater longevity than passively cooled ones.

 

[Lovemyev]

I see what you're saying guys but TBH the advantages of having the new BMS update don't really apply to me anyway.
1. I don't use rapids, I've used one once in 11 months.
2. Longevity of the battery is of no real concern to me because I'll probably trade the car in for the 73kWh version when it comes out next year or the year after and I still have the same 7 year warranty on the battery even if I don't trade in. Maybe me not using rapids and only charging up to 100% once every 4-6 weeks might compensate for the unhealthy 4.2v cell charge.
3. Regen starts working normally on mine after travelling 3 miles anyway so that's no big problem.
I guess if I was keeping the car for longer I would probably be looking into getting the new BMS, just for battery longevity, but in my present circumstances, I won't for now.

What's the old saying ?.
"If it's not broke, don't try to fix it".
Something along them lines !.

 

[Paulie68]

What's the old saying ?.
"If it's not broke, don't try to fix it".
Something along them lines !.

But it is broke! SAIC MG haven't lowered the upper voltage just for fun, they've realised if they leave it as is they're going to be seeing claims for battery degradation before 7 years is up.

 

[jamesie]

But it is broke! SAIC MG haven't lowered the upper voltage just for fun, they've realised if they leave it as is they're going to be seeing claims for battery degradation before 7 years is up.

Why haven't they recalled all the cars for an update?

 

[Paulie68]

Why haven't they recalled all the cars for an update?

Because the idea was to quietly update them all as part of the annual service I think, but the shambolic dealer network are balsing it all up, as usual!

 

[jamesie]

Well it's a poor effort if that's so. What about those that don't get their cars serviced by a main dealer?

I don't trust that they are making a change that is better than the original, tbh!!

 

[Paulie68]

Well it's a poor effort if that's so. What about those that don't get their cars serviced by a main dealer?

I don't trust that they are making a change that is better than the original, tbh!!

It is indeed a poor show. It's a fact though, that lowering cell voltage to 4.16V will increase battery life.