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Discussion Starter · #1 ·
I don't want to start loads of hares running, and I appreciate this topic has been discussed, but I've read various threads on the subject of BMS updates (flawed and successful) and my head is spinning.

My car was in for its first service today (February 24th), and my dealer told me that it had had the "BMS Update", and that action was now required from me. I should let it discharge to about half then apply a balancing charge using the granny charger not a 7kW AC charger. Rinse and repeat three or four times and all would be well.

All that is visible to me is that the GOM has lost a substantial number of miles since the car went in this morning. More than will have been driven. It's showing 150 or so miles at 7 bars on the meter.

Foolishly, I hadn't read up on the issue on this site beforehand so wasn't primed to ask sensible questions. So, could someone who understands the situation please put an old man out of his misery?

Is there any way to tell whether I have the "good" BMS update from 15th January? And, if so, is the granny charging advice right? And, finally, is there anyway to tell when all is well? (Voltage of ~450V, is that right?)

Sorry to raise the issue again - I just want to be sure I've understood what has been a tortuous. if not actually tortured, discussion!

Thanks.
 

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The most 'troublesome' BMS was the one rolled in vehicles between late October 2020 and mid January 2021. If your BMS was not updated in that period then it is unlikely your car will be much out of balance or need much in the way of remedial action.

To understand the health of your car, allow a full charge and balance to complete using something other than a rapid. It doesn't much matter if you use a granny, 3kW or 7kW charger. The MG badge pulses when charging, is on constantly while balancing then goes off when complete.

Turn on your freshly balanced car, make sure HVAC, heated seats etc. are turned off, and view the number of volts and amps. If all is well you shouldn't be drawing many amps and voltage should be around 449v. Anything much less and your range will be compromised - you will need to use some of the battery, recharge and rebalance. The further you are from 449v, the longer it will take to return your battery to full health.
 

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Discussion Starter · #3 ·
Thanks. I should be OK. The only time the car has been updated was for teh Comfiort upgrade in about July. Nothing in the Autumn.

Anyway, the car is on charge now, so I'll check the voltage when it finshes.
 

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Rather than start a new thread I thought I'd put this on here as it's close to the thread's title.

I've had my first service yesterday. I had it taken away and delivered after service, so haven't been to the dealer's. As far as I can tell, no updates have been applied.

There's a couple of worrying pieces of data on the post service report. In the battery check bit it reports the SOC% as 98%. However the GOM was showing 75 miles leaving and (what I would expect) 69 miles on return. Even taking into account that the GOM doesn't show the full non BMS range (about 211 miles) something is wildly out. Even worse is the SOH% which is showing 80% on a one year old car. Can the OVMS make mistakes or does it seem that the technician has made these figures up?

Even weirder, after a complete charge last night. The GOM is showing 196 miles range! :eek: THe voltage is 453, so somewhere about normal. I imagine that the 12v has been unplugged during the service.

Has anyone else notice this sort of thing after their service. I will be contacting the dealer's Monday morning.
 

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Discussion Starter · #5 ·
Rather than start a new thread I thought I'd put this on here as it's close to the thread's title.

I've had my first service yesterday. I had it taken away and delivered after service, so haven't been to the dealer's. As far as I can tell, no updates have been applied.

There's a couple of worrying pieces of data on the post service report. In the battery check bit it reports the SOC% as 98%. However the GOM was showing 75 miles leaving and (what I would expect) 69 miles on return. Even taking into account that the GOM doesn't show the full non BMS range (about 211 miles) something is wildly out. Even worse is the SOH% which is showing 80% on a one year old car. Can the OVMS make mistakes or does it seem that the technician has made these figures up?

Even weirder, after a complete charge last night. The GOM is showing 196 miles range! :eek: THe voltage is 453, so somewhere about normal. I imagine that the 12v has been unplugged during the service.

Has anyone else notice this sort of thing after their service. I will be contacting the dealer's Monday morning.
My numbers didn't look like that. SOH% was 100%, SOC%was 90.4% from memory, pretty consistent with 7 bars on the gauge. GOM mileage had dropped, but not dramatically.

I granny charged it yesterday and after equalisation finished the battery was at 448V. OAT was 2C however. GOM was showing 180+.Lower than we would normally see but not wildly so, especially given the temperature.
 

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Quite happy with how the car has turned out. It feels a bit punchier with the acceleration and is definitely quieter.

The 196 on the GOM didn't last very long. Had to go to B&Q for a masonry drill, about 3 miles. By the time I had got there it had dropped to a more normal 169 miles. M/kWh was 3.1.

I'm going to have a word with the service manager on Monday about the SOC/SOH anomalies. It's a shame we can't look these things up for ourselves.
 
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Quite happy with how the car has turned out. It feels a bit punchier with the acceleration and is definitely quieter.

The 196 on the GOM didn't last very long. Had to go to B&Q for a masonry drill, about 3 miles. By the time I had got there it had dropped to a more normal 169 miles. M/kWh was 3.1.

I'm going to have a word with the service manager on Monday about the SOC/SOH anomalies. It's a shame we can't look these things up for ourselves.
What does OVMS say? Is it what's showing low SOH? Maybe worth flagging up your issues on the discourse group, or the FB group (watch out though some of the 5 owners seem to have right a right grudge on ZS owners).
 

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Rather than start a new thread I thought I'd put this on here as it's close to the thread's title.

I've had my first service yesterday. I had it taken away and delivered after service, so haven't been to the dealer's. As far as I can tell, no updates have been applied.

There's a couple of worrying pieces of data on the post service report. In the battery check bit it reports the SOC% as 98%. However the GOM was showing 75 miles leaving and (what I would expect) 69 miles on return. Even taking into account that the GOM doesn't show the full non BMS range (about 211 miles) something is wildly out. Even worse is the SOH% which is showing 80% on a one year old car. Can the OVMS make mistakes or does it seem that the technician has made these figures up?

Even weirder, after a complete charge last night. The GOM is showing 196 miles range! :eek: THe voltage is 453, so somewhere about normal. I imagine that the 12v has been unplugged during the service.

Has anyone else notice this sort of thing after their service. I will be contacting the dealer's Monday morning.
Your car hasn't been updated, it should now show 449v/450v when fully charged. I wouldn't trust what the tech has written down either, if they couldn't be bothered to update the software as required by MG, they're either lazy or incompetent.
 

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What does OVMS say? Is it what's showing low SOH? Maybe worth flagging up your issues on the discourse group, or the FB group (watch out though some of the 5 owners seem to have right a right grudge on ZS owners).
Sadly, I don't have an OVMS reader. The figures come from the post service report (the tick sheet). It's all about how stringent the technician was in his attitude to the job?
 

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Have I missed some drama?
I got fed up of some of the 5 drivers. Keep going on about how the 5 is superior to the ZS. Nope... its just different, has different strength and different weaknesses. Taking a break from the group until at least my service, see if anything has changed with my car by then. Currently its running great, did 48miles over the weekend on 24.6% which I was happy with. Still cold at night too, gritters were out when I was out at shops last night.

Sadly, I don't have an OVMS reader. The figures come from the post service report (the tick sheet). It's all about how stringent the technician was in his attitude to the job?
I said this with CanZE, it's definitely worth investing in a tool that lets you monitor SOH yourself. Ok so CanZE only cost you a £30 dongle and OVMS costs you £199 and they currently do similar things, but there is the possibility that OVMS will become more on the ZS.
 
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I got fed up of some of the 5 drivers. Keep going on about how the 5 is superior to the ZS. Nope... its just different, has different strength and different weaknesses. Taking a break from the group until at least my service, see if anything has changed with my car by then. Currently its running great, did 48miles over the weekend on 24.6% which I was happy with. Still cold at night too, gritters were out when I was out at shops last night.
Charged to 100% last night - drove 110miles with 20% left (last 30 miles was caning it to get the battery down!) and have plugged it into my friendly neighbourhood 22kW unit to see how many kWh it eats to get to 100% again.

Certainly much perkier at low SoC than before the 15.1.21 BMS re-update (85-100% power even below 25% SoC), and seems to have peaked at 449V @ 100%

Will report back tonight with the final capacity results - historically was getting ~45.5kWh from the same charger 0-100% pro rata before the November BMS fiasco (so ~40.5 into the battery).
 

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Spoke with technician today. He said the anomalies may be down to the battery not being full and needing balancing. Don't believe that one bit, but, and because all seems to be working okay, it may show him that some of his clients are taking note of what he's doing may improve his diligence in future servicing and I'll not be taking it further.
 

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I'm finding that mine has peaked at 449v for a full balanced charge too. Regeneration soon into a journey can see this rise to 452v demonstrating some headroom and that regen is possible even when charged to 100% though.
Yup - regen was pretty weak this am at 100% though it was 4°C.

I have seen 400V and 105A regen slowing from 80mph so ~42kW seems max. regen power.
 

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I got fed up of some of the 5 drivers. Keep going on about how the 5 is superior to the ZS. Nope... its just different, has different strength and different weaknesses. Taking a break from the group until at least my service, see if anything has changed with my car by then. Currently its running great, did 48miles over the weekend on 24.6% which I was happy with. Still cold at night too, gritters were out when I was out at shops last night.



I said this with CanZE, it's definitely worth investing in a tool that lets you monitor SOH yourself. Ok so CanZE only cost you a £30 dongle and OVMS costs you £199 and they currently do similar things, but there is the possibility that OVMS will become more on the ZS.
The good thing about OVMS is that it can be transferred to different cars. It is not MG specific. There are other coders working on different cars as they are released.

So instead of buying one for a Leaf, another for Zoe etc, you just have the one universal box.
 
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Will report back tonight with the final capacity results - historically was getting ~45.5kWh from the same charger 0-100% pro rata before the November BMS fiasco (so ~40.5 into the battery).
First charge on this post since updated BMS: 33.47kWh in 5.0 hours (6.69kW avg) from 20->99% SoC (448V) = 42.4kWh equivalent 0-100% charge

Perhaps still some balancing to do* and may have gone from 20.5% to 98.5% (=42.9kWh), but seems to still be a couple of kWh down from before.

(* or perhaps some fubared cells after being over discharged? :devilish:)
 

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First charge on this post since updated BMS: 33.47kWh in 5.0 hours (6.69kW avg) from 20->99% SoC (448V) = 42.4kWh equivalent 0-100% charge

Perhaps still some balancing to do* and may have gone from 20.5% to 98.5% (=42.9kWh), but seems to still be a couple of kWh down from before.

(* or perhaps some fubared cells after being over discharged? :devilish:)
You need to allow about 10% for charging losses, so the car got around 38.16kWh, if that was indeed the 0% to 100% figure, it seems too low.
 

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You need to allow about 10% for charging losses, so the car got around 38.16kWh, if that was indeed the 0% to 100% figure, it seems too low.
I know - I've been saying it has ~40.5kWh usable since the start - even the fanboy club seem to accept this now rather than trotting out "44.5kWh usable"
 
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