Odd Thing Today

[securespark]

Where the "fuel gauge" read 91% at the start of the day. The car did a short journey of 3.5 miles and it still read 91%. Then we did the first 5.5 miles of a journey on a high speed A road and Mway.
It was only then (after 9 miles) that the level dropped to 90%.

Normally, it drops more regularly and evenly.

 

[siteguru]

Was some/much of that journey downhill?

 

[fnegroni]

Where the "fuel gauge" read 91% at the start of the day. The car did a short journey of 3.5 miles and it still read 91%. Then we did the first 5.5 miles of a journey on a high speed A road and Mway.
It was only then (after 9 miles) that the level dropped to 90%.

Normally, it drops more regularly and evenly.

Have you slow charged the battery to 100% at all in recent past? The battery management system needs that from time to time to give an accurate read out even on NMC batteries.

 

[Martinonline]

On my weekly shopping trip to a downhill supermarket I gain battery power and range. I think using the battery warms it and this allows a range increase.

 

[securespark]

Thanks, people.

They are trips we do a lot. The shorter one involves some downhill on the way there, but then (in this case) we took the same route on the way back, thus going uphill on the way back. The longer trip is reasonably flat, apart from an on slip and an off slip.

I last charged to 100% around 4 weeks ago.

 

[siteguru]

Was that on an AC charge point and did you leave it until the car said it had finished charging?

 

[securespark]

I used our Ohme Home Pro charger at home. I left it charging overnight and when I woke up it was on 100.

 

[fnegroni]

I used our Ohme Home Pro charger at home. I left it charging overnight and when I woke up it was on 100.

Was it on 100 and it had finished charging or still charging but at a lower rate?

I must admit with my SE’s LFP battery which is allegedly less precise than NMC batteries, the percentage indicator has been so precise I don’t even read the miles left guessometer nor the consumption indicators anymore. I just go by battery percentage
for example I know that my trip from the kids’ home to my place in London is 25% battery. A bit more when it’s cold, a little less if I take it easy on the motorway part.
Infact I have started claiming back expenses not by watts used but by percentage used.

 

[Rolfe]

I find the same thing. I think if the battery is allowed to go to 100% and balance every time you charge, rather than being run up and down in the middle, it's very accurate.

Of course if you're on a long trip you have to run it up and down in the middle, but again I haven't had trouble, perhaps because I was able to get on a type 2 charger at my destination and go to 100% and balance there. At any rate, when I was on my way home I was playing it quite tight on the last leg after three goes on ultra-rapid chargers, and it was spot on.

 

[fnegroni]

Just like with tyres, I’m pretty overzealous to follow the charge schedule to 100% at least once a week, and I nearly exclusively slow charge (and by slow charge I mean 2kW or 3kW mostly) even when partially charging and discharging throughout the week.
I also did a couple of slow charging sessions from 7% or less to 100%
Car was delivered with 7 miles on the clock in August, and an 75% charge, and I slow charged it and balanced it at 100% on the very first charge.

 

[Rolfe]

I did the same, although at first I didn't know what the extra half-hour tacked on the end was and stopped it at least once.

I was charging on a 50 Kw rapid five minutes walk away over the summer for speed and convenience, but since the weather has made that five-minute walk much less pleasant I've just been using the granny charger. I think in future I'll keep the rapid charger for when I'm really in a hurry to put range on the car, which frankly is not often.

 

[securespark]

Was it on 100 and it had finished charging or still charging but at a lower rate?

I'm sorry, I can't remember.

 

[GaryMG4]

I had a similar oddity at the weekend. I had it on charge soaking up some sunshine and it stopped at 80% although it was still taking 1.9kW whenI finished the charge. A 33 mile round trip to the theatre that (cold) evening resulted a drop to 73% after just a few miles but by the time I got home it was only down to 62% which was probably about right given the temperature. My last 100% balance charge was at the end of September so I guess it might be time for another.

 

[Jto]

Where the "fuel gauge" read 91% at the start of the day. The car did a short journey of 3.5 miles and it still read 91%. Then we did the first 5.5 miles of a journey on a high speed A road and Mway.
It was only then (after 9 miles) that the level dropped to 90%.

Normally, it drops more regularly and evenly.

Hello
you need to think more about your 12v battery more than the driving battery. Sounds like you do a lot of very short runs and this means your 12v may not say fully charged and now the cold weather is coming this could effect the 12v battery. Read the manual on this, also consult with you dealer about doing a trickle 12v battery charge every few weeks. You would have seen lots of posts on here about not been able to start the car because the 12v battery is drained.

 

[Rolfe]

Doesn't sound like a 12v issue to me. Either not being balanced often enough, or an unusual route with uneven power consumption.

 

[fnegroni]

Doesn't sound like a 12v issue to me. Either not being balanced often enough, or an unusual route with uneven power consumption.

I think @Jto was just pointing out, as a side note, that the 12v battery might be depleted by the short journeys. Not that the two are necessarily related. But there might be a connection too if you ask me.

 

[Jto]

Doesn't sound like a 12v issue to me. Either not being balanced often enough, or an unusual route with uneven power consumption.

Nothing ii wrong with it as if not balanced often enough you would get a message on the screen. only charge 4 weeks ago which tells me low mileage done so 12v battery is at risk. When you charge on 7kw the car battery management will do one if needed and the only way you know it’s done one is it take a bit longer.

 

[Ian Key]

As far as I know the MG4 doesn't show a message on the screen if the battery needs balancing but I'm happy to be corrected.
The main battery will charge the 12v battery when needed. I do a lot of short journeys and a couple of months ago I hadn't used my car for two days and saw on the iSmart app the 12v battery reading 14.5v.
Those who have had a flat 12v battery have either had a loose battery terminal and or needed a software update.

 

[GaryMG4]

Page 188 of the manual has "Please slow charge the vehicle" shown on Instrument pack if equalisation charge not carried out for some time. Not seen it myself, in 6 months/4500 miles and only 2 balance charges done so far.

 

[Jto]

Here are some screenshots from the MG user manual
1 the 12v battery will be charged from the HV but there are some exceptions which over ride this. Page 23

2 read page 291

3 page 176 second paragraph

I have not seen any report back that on lose terminals or software updates but not rule them out.