Mismatch with %age and efficiency on MG5 Long range EV

We’re really enjoying our new MG. 890 miles now from new as a pre-reg with 6 miles on the clock.

I’d be really grateful for any thoughts please. . .

I did a balance charge after 712 miles on our granny charger overnight yesterday and travelled 89 miles straight after this morning using 39% (61% remaining) at an efficiency of 4.2 MpKW. While at Granny’s we used the granny charger again charging to 81% a then travelled back using 37% (44%) at an efficiency of 3.7 MpKW.

I may be a novice EV driver, but something doesn’t quite make sense. how could we use less battery power, but also be less efficient? Given that I equalised the battery cells and the temperate difference was only 2 degrees outside (warmer this evening), I can’t understand why we’d have a mismatch.

Hi P Walker I’m in about the same boat as you MG5 facelifted Trophy model now about 900 miles on the clock.
Now before I go any further you do not sat if you car is Trophy or SE (which reminds me I need to update my avatar picture ) but there is a difference in range said to be down to the bigger wheels on the Trophy.

So you figures 4.2 and 3.7 mpkh look pretty good to me I’m struggling to get anything like that more like 3.3 tonight I am doing my first full charge and am going to let it balance as well I need it full tomorrow for a 200 mile trip to Berkshire in the morning now that will be mainly Motorway so it will be interesting.
Before this car I had the earlier MG5 with the 50 kw battery now that when fully charge would around 200 miles after a fully charge and balancing and on a motorway drive the same as I’m doing tomorrow would do about 4.2mpkw but I don’t think this new car will it weighs more as a heavy battery and bigger wheels so I’m expecting high 3s for motorway work I will update when I get back next week
Les

There seems to be about a million different things that affect range and efficiency, just something you get used to over time. Ambient temperature is a big one which you mentioned, what you're carrying, hills, weather, I could go on.

I remember my first long-ish journey to North Wales, I left with 80% battery and arrived with 50%. Great I thought, no need to charge up, expected to arrive home with 20% - using 30% each way. But the return journey used nearer to 40%, I still made it home but was surprised at where the extra 10% went! Then it occurred to me the outward journey was largely downhill, so there was a fair bit of regenerative braking, whereas the return was largely uphill meaning I had to use more power just to get up them. It was a bit scary but also fascinating. And I won't make that mistake again!

Les burrows said:

Hi P Walker I’m in about the same boat as you MG5 facelifted Trophy model now about 900 miles on the clock.
Now before I go any further you do not sat if you car is Trophy or SE (which reminds me I need to update my avatar picture ) but there is a difference in range said to be down to the bigger wheels on the Trophy.

So you figures 4.2 and 3.7 mpkh look pretty good to me I’m struggling to get anything like that more like 3.3 tonight I am doing my first full charge and am going to let it balance as well I need it full tomorrow for a 200 mile trip to Berkshire in the morning now that will be mainly Motorway so it will be interesting.
Before this car I had the earlier MG5 with the 50 kw battery now that when fully charge would around 200 miles after a fully charge and balancing and on a motorway drive the same as I’m doing tomorrow would do about 4.2mpkw but I don’t think this new car will it weighs more as a heavy battery and bigger wheels so I’m expecting high 3s for motorway work I will update when I get back next week
Les

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Thanks Les. we’re driving an old shape Mg5 115kW Excite EV 61 kWh 2022, which was pre registered. I guess the efficiency might be down to driving 55mph on the motorway!

What mpg did you get today and how low did you let the battery get before a charge?

rjb1970 said:

There seems to be about a million different things that affect range and efficiency, just something you get used to over time. Ambient temperature is a big one which you mentioned, what you're carrying, hills, weather, I could go on.

I remember my first long-ish journey to North Wales, I left with 80% battery and arrived with 50%. Great I thought, no need to charge up, expected to arrive home with 20% - using 30% each way. But the return journey used nearer to 40%, I still made it home but was surprised at where the extra 10% went! Then it occurred to me the outward journey was largely downhill, so there was a fair bit of regenerative braking, whereas the return was largely uphill meaning I had to use more power just to get up them. It was a bit scary but also fascinating. And I won't make that mistake again!

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Good point, thanks. The wipers were on intermittently on the way down. I guess having n ev I’ll get used to learning just how much energy different device use! the Thing that is confusing is that if the battery is at a higher percentage on the return journey, I’d expect the efficiency to be higher too. Maybe it’s lo for something to do with charging, balancing and incorrect measurement of the battery packs capacity.

So interesting journey today in my facelift MG5 Trophy started out fully charge at 100% Gom showing 256 miles at switch on comfort mode level 2 regen
So switch to Eco mode level 1 on the regen gave an extra 11 miles of range now at 267

So set off motorway all the way more or less set the Cruise Control to 63 MPH which we kept as much as possible, several sections limited to 50mph on the M6 southbound,
So after 188 miles we get to beaconsfield services on the M40 I still had around 30 miles to my destination but I had planed to stop here anyhow to try a Rapid charge on an
IONITY 350 Kw charger to see if the car would charge at the rated Charing speed which I’m please to report it did.

So as you can see from the picture above no where near the predicted Gom figures just of 256-267 miles I have now drove 188 miles and I have 25 left on that Gom that’s holding 63 mph with no heating or aircon apart from a couple of short bursts to clear the screens 2/3 times 14-15 degrees and moderate cross winds.

So I plug into the 350kw charger and it starts off at 83 kw I’m at 12% it then increased to a max of 88 kw At around 17% and then went down to 71 at 25% which is where I unplug as I now had enough to complete my journey and there was others queuing for chargers these next pictures are not the best because of the bright sunlight sorry pictures got a bit mix up but you can see Im sure
Les

Paul Walker said:

We’re really enjoying our new MG. 890 miles now from new as a pre-reg with 6 miles on the clock.

I’d be really grateful for any thoughts please. . .

I did a balance charge after 712 miles on our granny charger overnight yesterday and travelled 89 miles straight after this morning using 39% (61% remaining) at an efficiency of 4.2 MpKW. While at Granny’s we used the granny charger again charging to 81% a then travelled back using 37% (44%) at an efficiency of 3.7 MpKW.

I may be a novice EV driver, but something doesn’t quite make sense. how could we use less battery power, but also be less efficient? Given that I equalised the battery cells and the temperate difference was only 2 degrees outside (warmer this evening), I can’t understand why we’d have a mismatch.

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You are right. A higher MpKwh should use a smaller battery percentage for the same journey length - the reverse of what you are seeing. I have a LR ZS EV rather than the MG5 but on the ZS, I have noticed that the % gauge is not completely linear. My guess is that had you started both journeys at the same percentage (whether that be 100%, 81% or something else), the numbers would have worked out as expected. It is probably the non-linear percentage gauge that is causing the problem hence you need to use it at the same operating point for a true comparison.

rpannell said:

You are right. A higher MpKwh should use a smaller battery percentage for the same journey length - the reverse of what you are seeing. I have a LR ZS EV rather than the MG5 but on the ZS, I have noticed that the % gauge is not completely linear. My guess is that had you started both journeys at the same percentage (whether that be 100%, 81% or something else), the numbers would have worked out as expected. It is probably the non-linear percentage gauge that is causing the problem hence you need to use it at the same operating point for a true comparison.

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Surely you can't get much more linear than a percentage.

It think it is not sensible to make direct comparions of outward and return journeys because there are so many factors that affect performance. However, that doesn't stop me having fun trying to compare them. For instance a return journey to my daughter (approx 100 miles each way) gave 3.9 mpkwh out and 4.4 mpkwh back. Same weather and temperatures, and the only (significant?) difference is that the outward journey was "uphill" and the return "downhill" (there being a diffence of several hundred feet in elevation between our 2 homes.)
I have just visited Devon and charged at Exeter Services in both directions. These journeys (about 125 miles each way home to Exeter)) gave figures of 4.3 mpkwh out and 4.0 mpkwh back. Although different, I can't see any obvious explanation for this difference. Other longer journeys show similar differences, and I don't think it is sensible to look for explanations as I think the figures are close enough!
What I have noticed, however, is that battery consumption seems to be better for higher states of charge, for instance I seem to cover more miles per % of battery when it is in the 50 to 100% range, than once it drops below 50%. In particular, once it drops to about 35% the miles eat up the battery more quickly. Whether this is actually so or my imagination I am not sure - time for some experimentation I think over the next few weeks. If it is so, then the moral of the story seems to be to recharge the battery once it gets to about 40 to 50%. (My return from Devon took it down to 10% as I didn't want too much charge left as I can charge at home more cheaply than on the road!)
PS I drive the original, ie non-facelift, SR Excite, and love the car. My only gripe (and this is not serious) is the relatively slow charging rate on public chargers compared to other cars, but I can live with that as my forays to the "north island" are relatively infrequent.
Happy motoring to one and all.

Gomev said:

Surely you can't get much more linear than a percentage.

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I need to explain my sentence a little better. Let us assume that a battery pack has 60kWh of usable energy, so each 1% of battery is 0.6kWh. At 10%, there should be 6kWh available, at 20%, it should be 12kWh etc. On my LR ZSEV, it does not appear to be totally linear, so going from an indicated 20% - 10% range appears to give less miles than from 90% to 80%. I am sure we have all noticed how if you charge to 80%, the car will remain at 80% for many many miles. The car has to use a number of algorithms to calculate the percentage battery left. Although it does a good job, it is not perfect. It's far more difficult than dipping a petrol tank.

rpannell said:

I need to explain my sentence a little better. Let us assume that a battery pack has 60kWh of usable energy, so each 1% of battery is 0.6kWh. At 10%, there should be 6kWh available, at 20%, it should be 12kWh etc. On my LR ZSEV, it does not appear to be totally linear, so going from an indicated 20% - 10% range appears to give less miles than from 90% to 80%. I am sure we have all noticed how if you charge to 80%, the car will remain at 80% for many many miles. The car has to use a number of algorithms to calculate the percentage battery left. Although it does a good job, it is not perfect. It's far more difficult than dipping a petrol tank.

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I understand now what you are saying, a bit like my old petrol gauge that would go 100 miles hardly dropping then plummet like a stone

When charged to 100% though and balanced on mine it drops pretty quickly for the first few percent then steadies, although that could be because the batteries are still at ambient temperature at first.
Agreed when charging to intermediate levels it does appear to remain at that level for quite a while and even on a couple of occasions it has increased by 1 percent after travelling a short distance. This would indicate to me that as you say it is still calculating the actual percentage complicated possibly by cell imbalance.

We have had a MK1 Excite since mid 2021 and I have come to not take much notice of the GOM or m/kWh, the battery percentage seeming to be pretty accurate. Having said that I did a 4.2 mile return journey last week; downhill gently out and heavily laden return. As I parked up 1% just tripped, a range of 420 miles, that threw me a bit . Absolutely love this car, my favourite all time car and I've driven a lot in the last 50 odd years.

Paul Walker said:

We’re really enjoying our new MG. 890 miles now from new as a pre-reg with 6 miles on the clock.

I’d be really grateful for any thoughts please. . .

I did a balance charge after 712 miles on our granny charger overnight yesterday and travelled 89 miles straight after this morning using 39% (61% remaining) at an efficiency of 4.2 MpKW. While at Granny’s we used the granny charger again charging to 81% a then travelled back using 37% (44%) at an efficiency of 3.7 MpKW.

I may be a novice EV driver, but something doesn’t quite make sense. how could we use less battery power, but also be less efficient? Given that I equalised the battery cells and the temperate difference was only 2 degrees outside (warmer this evening), I can’t understand why we’d have a mismatch.

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I guess you're looking at the wrong figures? 39% of 58 kWh is 22.6 kWh so 89 miles gives an efficiency of 3.9 miles per kWh not 4.2.

Batteries don't discharge linearly. State of charge is inferred from cell voltage. What the software calculates the SoC as may not match reality due to various factors. A round trip will use the batteries on different parts of the discharge curve so quite likely to see differences on the out and return portions.

Paul Walker said:

Thanks Les. we’re driving an old shape Mg5 115kW Excite EV 61 kWh 2022, which was pre registered. I guess the efficiency might be down to driving 55mph on the motorway!

What mpg did you get today and how low did you let the battery get before a charge?

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It varies a lot depending on speed, weather, terrian, temprature.

Ive had as low as 2.6mi/kwh and got 3.8 on a shorter journey earlier today.

Wind speed and direction i'd imagine can make a difference as well.

Did people obsess over their mpg to the same extent as their mpkwh?

Anyway this weekend I've done a 450 mile round trip on mostly motorway at a steady 65 and got about 3.8 over the whole trip, which I was pleased with. Mk I LR.

I charged overnight saturday night and had a short run to do Sunday.

Unplugged the car in the morning and switched on, charge was at 91%.

After a while and a with a stop and start my readout was.....



Yep after 9 miles I had gained 1 percent. I got home shortly afterwards, the next bit was all uphill and arrived with what I supposedly started with.

smokie said:

Did people obsess over their mpg to the same extent as their mpkwh?

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Absolutely!
From the other forum I administer:

Crumbs, what's that for, space rocket engines? Some serious consumption going on there!!!

The other club covers the Ford Focus ST
That particular poll was for the Mk2 version with the 5 cylinder 2.5 litre Volvo engine.