25/01/21: Just had latest BMS software. Observations...

[Mark Holmes]

Here are my thoughts and I must add I’m far from an expert on battery capacity and voltages.
455v in 44.5kw/hr battery produces 97.8amps
If the current remains the same but voltage drops to 450v then capacity falls to 44kw/hr losing 0.5kw/hr on capacity or say 1.5miles. MG are also able to tweak the usable capacity so that it remains roughly the same. I’m not sure if monitoring small voltage changes provides any real value - if there is a 5v difference on some cars the real-world impact would be negligible if any.

Again like you I’m no expert on this, but these voltage differences must make minor range differences.

 

[Cocijo]

I agree - I think that they’re quite minor and can be negated by adjusting the useable party of the pack. I.e. more low end capacity. The net result is the same.

 

[BobsEV]

Had the revised BMS done today as part of service (never had the previous dodgy BMS updates). Charged to 100% and was getting 439v ish. But range was 159 miles (normal mode) which for winter (and max 163 miles) seems about right. It reminds me of pre comfort 2 ranges which was much more accurate on the GOM than after, eg after comfort 2 GOM was showing anything up to 190miles which is not really possible on the MG ZS EV. Therefore I'm not going to worry too much about the voltage as that doesn't seem useful. Seems like the new levels are about right but will continue to monitor how range drops on drives and whether it seems disproportionate. Also equalisation took 6 hours which is about right according to the manual (up to 9 hours if car hasn't been used for a while or not equalised for a while). After equalisation finished the voltage was 450, range the same as before.

Finally car now charges without locking too (didn't have this before).

 

[Lovemyev]

Firstly, can I thank you personally for your comments regarding this subject.
I think we are now on a very similar thinking pattern here folks.
Quickly becoming tired & frustrated at chasing that strange and mythical 455 battery voltage unicorn.
Under these very trying times ( C19 restrictions ) I seriously would not be charging my car to the maximum 100% and then leaving the car to balance for hours and hours on end, just to make the weekly short trip to the local supermarket - why ?.
Then leaving the battery feeling like the trouser's of somebody who has just eaten the largest Sunday diner of his life, and bursting at the seams !!. LOL.
If you are a "Key" worker and are using your car for long journeys on a day to day basis, then you will get the chance to try out this theory.
But for many people that are unable to use their cars as they would really like, this charging / balancing and then consuming the range under lock down is going to take forever ( if ever ) to achieve.
It's just not practical for a lot of people right now !.
It could end up being a LOT of effort to gain very little, if not nothing at all.
We have to leave this project to the high mileage key works to conduct now folks and rely on their future findings in a positive or negative manner.
My "Puny" 30 miles a week is never going to prove / disprove anything here sorry folks.
Surly if MG had reviewed the results after applying the latest BMS update and the max voltage was seen around 448 - 450 volts, then this should have been reported back to the owners at the time of the update ?.

 

[Jeps]

I am starting to think if it is a blessing or a curse that there ended up to be a read out for voltage on the MG!
Before the latest update I never looked at the Voltage figures. And as lovemyev says, I am also not gonna charge that often, so I will take it easy and look at it occasionally.

 

[JodyS21]

Here are my thoughts and I must add I’m far from an expert on battery capacity and voltages.
455v in 44.5kw/hr battery produces 97.8amps
If the current remains the same but voltage drops to 450v then capacity falls to 44kw/hr losing 0.5kw/hr on capacity or say 1.5miles. MG are also able to tweak the usable capacity so that it remains roughly the same. I’m not sure if monitoring small voltage changes provides any real value - if there is a 5v difference on some cars the real-world impact would be negligible if any.

I don't think the amps calculation is relevant for figuring out the battery capacity.
We know (well think!) the car has a 44.5KW/H battery capacity.

Bosch power tool example. 18V battery, but they advertise e.g. 3AmpHour battery, so you'd have to use the formula to calculate the batteries actual power capacity - 54Watt/Hour battery.

It can draw whatever (in reason) it wants in amps depending on you right foot. If we knew what voltage the motor was, based on the real-time amps reading, you could calculate what the real-time consumption was in KW, that'd be interesting...

Batteries as we probably all know, output their highest voltage when are fully charged and then the voltage goes down as their charge lowers - shows up very well with the old ni-cad/ni-mh batteries. Lithium batteries tend to keep outputting their nominal voltage for most of their capacity and then only when they get to a low capacity does the voltage output drop.

If the total cells voltage output at "full" charge, was 455 previously, then now being at 450 must mean the batteries have not been charged as much as they were previously.
But we will never know how many KW the battery really is charged to. Is the so called specified 44.5KW/H battery when it's charged to the point of outputting 455volts, or were we putting more power into the battery previously and it was say storing 45KW/H before, and now with them stopping the charge at 450volts output is that actually storing 44.5KW/H in the battery.

I guess, if we knew what cell the battery pack was made from, and we had detailed information from the cell manufacturer of the voltage vs what power stored (I think they produce a graph for this usually), then we could work out the actual capacity, knowing how many cells are in the battery pack - assuming all the cells were balanced. But realistically, multiplying all this up, the chances of getting an accurate result at the end of it, I'm not sure we'd be able to accurately know what the capacity was at 450 vs 455volts.

Well that was a lot of waffling on and, I'm not expert, I have just read a lot about batteries over the years!!!!!!!!!

 

[Lovemyev]

I don't think the amps calculation is relevant for figuring out the battery capacity.
We know (well think!) the car has a 44.5KW/H battery capacity.

Bosch power tool example. 18V battery, but they advertise e.g. 3AmpHour battery, so you'd have to use the formula to calculate the batteries actual power capacity - 54Watt/Hour battery.

It can draw whatever (in reason) it wants in amps depending on you right foot. If we knew what voltage the motor was, based on the real-time amps reading, you could calculate what the real-time consumption was in KW, that'd be interesting...

Batteries as we probably all know, output their highest voltage when are fully charged and then the voltage goes down as their charge lowers - shows up very well with the old ni-cad/ni-mh batteries. Lithium batteries tend to keep outputting their nominal voltage for most of their capacity and then only when they get to a low capacity does the voltage output drop.

If the total cells voltage output at "full" charge, was 455 previously, then now being at 450 must mean the batteries have not been charged as much as they were previously.
But we will never know how many KW the battery really is charged to. Is the so called specified 44.5KW/H battery when it's charged to the point of outputting 455volts, or were we putting more power into the battery previously and it was say storing 45KW/H before, and now with them stopping the charge at 450volts output is that actually storing 44.5KW/H in the battery.

I guess, if we knew what cell the battery pack was made from, and we had detailed information from the cell manufacturer of the voltage vs what power stored (I think they produce a graph for this usually), then we could work out the actual capacity, knowing how many cells are in the battery pack - assuming all the cells were balanced. But realistically, multiplying all this up, the chances of getting an accurate result at the end of it, I'm not sure we'd be able to accurately know what the capacity was at 450 vs 455volts.

Well that was a lot of waffling on and, I'm not expert, I have just read a lot about batteries over the years!!!!!!!!!

Not that it tell's us much, but i think the net capacity is nearer 42.3 kw ????.

 

[Mike]

I am reliably informed that prior to the January ‘21 BMS update, there was a 6% buffer at the bottom and a 3% buffer at the top that was unusable out of the 44.5kWh. That means we actually have around 40.5kWh useable.

Now with the reduced voltage by 5V, that some of you are saying is the new normal, they may have shifted the buffers slightly.

The guys working on OVMS will be able to tell.

 

[Chrisb]

I am reliably informed that prior to the January ‘21 BMS update, there was a 6% buffer at the bottom and a 3% buffer at the top that was unusable out of the 44.5kWh. That means we actually have around 40.5kWh useable.

Now with the reduced voltage by 5V, that some of you are saying is the new normal, they may have shifted the buffers slightly.

The guys working on OVMS will be able to tell.

Thanks Mike, I have run mine down from full to empty and calculated mine to hold approx 42kw, the battery does have a nomical capacity of approx 44kw according to the sticker on the battery, but fully charged it will be slightly more than 44kw, which might explain the 42 KW capacity I got out of mine (455v BMS) .

 

[jamesie]

Bjorn Nyland estimated that his Thai ZS EV had a usable 42.5kWh but that the pack had a likely 48kWh. I can't remember how he calculated those numbers (and can't find the video) but he is usually fairly accurate.

 

[rbpasapera]

Bjorn Nyland estimated that his Thai ZS EV had a usable 42.5kWh but that the pack had a likely 48kWh. I can't remember how he calculated those numbers (and can't find the video) but he is usually fairly accurate.

He calculated the usable capacity after a range test in Norway using this formula:

KWh = (Km driven * consumption Wh/Km) / (%SOC used/100)

KWh (UK) = (miles driven / consumption mi/KWh) / (%SOC used/100)

 

[notdodgy]

That's the main cause of confusion, Technician at the dealer don't seems to know or want to commit to a voltage figure that can be used as a benchmark. 449V is what I have got after BMS update for a new car with 200 miles driven.

Similar to my experience - just a few more miles than you.
Now doing my third charge after the update - expecting to see the balance time come down.

 

[Smendon]

Not sure if this is a silly question or not, but by discharging the battery a little and then doing a charge to equalise, will that damage the battery in the long term?

 

[Chrispydoc]

I looked at my voltage today.

My software has not been updated for many months. And it won't be!!

 

[Lovemyev]

I looked at my voltage today.

View attachment 1330

My software has not been updated for many months. And it won't be!!

In Eco mode I assume here ?.

 

[JodyS21]

I would be very disappointed if it was discovered that the battery pack could hold 44.5KWh and the MG software restricted you not got being able to use that amount of capacity.
If it's advertised at 44.5KWh, then that's what we owners should be able to use, otherwise I'd say this is mis-selling.
I'd have thought to be honest they'd have a battery pack that could hold more than the advertised figure but then in the software restricted it to the useable figure. I've read about other manufacturers that do this.
There's another thread on the battery details.

 

[MAS]

I looked at my voltage today.

View attachment 1330

My software has not been updated for many months. And it won't be!!

Hi Chrispydoc, is this with HVAC off? If it is, it seems that my 449V (updated BMS) has beaten your 456V by 2 miles.

 

[Jeps]

I would be very disappointed if it was discovered that the battery pack could hold 44.5KWh and the MG software restricted you not got being able to use that amount of capacity.
If it's advertised at 44.5KWh, then that's what we owners should be able to use, otherwise I'd say this is mis-selling.
I'd have thought to be honest they'd have a battery pack that could hold more than the advertised figure but then in the software restricted it to the useable figure. I've read about other manufacturers that do this.
There's another thread on the battery details.

The electric car manufacturers are deciding them self on how they list their car batteries, they either use gross or netto capacity, nothing unusual in that.

 

[Cocijo]

The electric car manufacturers are deciding them self on how they list their car batteries, they either use gross or netto capacity, nothing unusual in that.

Tesla have moved away from even quoting battery size if they can. They focus on range. I think that’s the way it will go.

 

[colsky]

Hello all, first post from a happy ZS EV owner!

I've just booked my car in for its first annual service (and comfort software update). I mentioned the BMS software when I booked it in, and he saw on his system that there was an updated software release for that a couple of days ago. Am I right in thinking that this software should now be ok and bug free?

Incidentally, and sorry, nothing to do with this thread(!) does anyone watch the comedy programme called Back on Channel 4 starring David Mitchell? Mitchell and his girlfriend/ex wife drive a Pimlico Blue MGZSEV Exclusive, the same as my car. I watched episode 6 yesterday, and it seemed to me that MG must have paid a product placement fee! They were in the car a number of times in the first half of this episode, and there were quite a few gratuitous shots of the car, from the front, rear, and above, even when it wasn't relevant to the scene! It was almost like watching an advert. There was something very odd though - at one point they got in the car, and there was superimposed the sound of a petrol car starting up before they drove off. I guess them starting the car was part of the scene, and just pushing a starter button in silence wouldn't have been as dramatic!!

Back: Back - On Demand

Comedy starring David Mitchell and Robert Webb

www.channel4.com