When 7kwh is 4kwh issue

[bear1]

Just drove the 17 miles home from work in my SE SR. Battery dropped 4% in the first three miles and by the end had gone from 28% to 11%. My maths suggests that's something like 7kwh.
The energy usage screen says 1kwh had been used for heating and 3 for driving. It's also reporting 3.4 miles per kWh.
Had similar battery depletion on Tuesday (50% more than normal) but normal in Wednesday.

Is this the BMS being unable to accurately guage the battery because of its chemistry. I've had the car a month and not done a balancing charge (my charging circumstances make this difficult)?

 

[Stageshoot]

Twice now I have had our Trophy refuse to charge on our home charger till its been reset with a 12v battery disconnect

Both times after long runs from 100% down to single figures,

After its reset its started to charge at 7kw but the % has stayed them same for nearly an hour before going up.

I really am starting to think the BMS is losing track of the battery capacity and its causing issues like the losing 5% in a couple of miles when you set off

MG say no issues reported or updates available. But keeping a close eye on mine as we run it full to nearly empty on a regular basis

 

[the briggie]

What models are you driving to differentiate battery type SR or LR

 

[bear1]

What models are you driving to differentiate battery type SR or LR

As mentioned (but easily missed) SR. As I understand it, this battery chemistry doesn't allow exact measurement of charge levels.

 

[the briggie]

Sorry never paid attention. SR lfp batteries are not so good with BMS measurements as the voltage levels stay more linear during usage and a regular 100% charge is required to help with that known feature (at minimum weekly). It may well be that, that causes the strange readings you are getting?

The Trophy (L-ion) should be displaying % charge increase more regularly (my current EV shows it % by % as it is charging) I would have thought? Does it show more quickly going from above say 15 - 20% that it does from above 5% to 15 % added charge as a matter of interest.


I wonder if any other owners are experiencing this?

 

[siteguru]

Charged my SE SR twice since getting it, no issues either time. (2nd time I left it overnight so it did a full charge and the option to do a BMS balance if it wanted to - no idea if it did, or how I would even be able to tell).

 

[bear1]

Sorry never paid attention. SR lfp batteries are not so good with BMS measurements as the voltage levels stay more linear during usage and a regular 100% charge is required to help with that known feature (at minimum weekly). It may well be that, that causes the strange readings you are getting?

The Trophy (L-ion) should be displaying % charge increase more regularly (my current EV shows it % by % as it is charging) I would have thought? Does it show more quickly going from above say 15 - 20% that it does from above 5% to 15 % added charge as a matter of interest.


I wonder if any other owners are experiencing this?

I think this is likely the issue, because I'm using somebody else's charger, and to stay within Octopus discount hours, I've been bouncing better 20% and 90%. I assume that a 100% charge should restore the accuracy?

 

[the briggie]

I think this is likely the issue, because I'm using somebody else's charger, and to stay within Octopus discount hours, I've been bouncing better 20% and 90%. I assume that a 100% charge should restore the accuracy?

it should help but until you try it?

 

[BugEyed]

My first SR was never charged to 100% from new (including in the PDI) for over three weeks and for over 1,500 miles (long story) but never displayed that characteristic. Apparently you should get a message suggesting that you need to do a balancing charge but I never saw it.
When I finally managed to get it to take a full 100% charge and balancing charge nothing changed.
But I'd still suggest that you give it a go. Is there not a public charger that you could leave it on overnight?