MG5 Disappearing charge

[5teep]

One year down the line and the mystery disappearing charge cropped up again, although I think I have worked out why.

The other day I completed a single 180 mile journey in miserable weather against a stong headwind and finished the journey with only a scary 7% charge left. It was late so I didn't get around to charging until the following morning by which time the charge had dropped to 2% and no miles on the GOM!

I then slow charged on a granny lead to 80% before heading out. Now I noticed the opposite effect. I travelled more than 10 miles before the battery dropped to 79%.

So, clearly the battery warms with use and extends the range - an effect probably only noticable in the winter.

The upshot of this is, don't assume you have enough charge to get to a public charger if you run very low and then leave the car in the cold!

Were you driving in ECO mode on the way home? because when you start the car it defaults to normal mode with less range showing.

/edit scratch that, I misread your post. If the actual charge is dropping it will not be your settings.
It's possible your car needed a balance charge, I often see the range stick for a time after mine balances.

 

[crispyjay]

One year down the line and the mystery disappearing charge cropped up again, although I think I have worked out why.

The other day I completed a single 180 mile journey in miserable weather against a stong headwind and finished the journey with only a scary 7% charge left. It was late so I didn't get around to charging until the following morning by which time the charge had dropped to 2% and no miles on the GOM!

I then slow charged on a granny lead to 80% before heading out. Now I noticed the opposite effect. I travelled more than 10 miles before the battery dropped to 79%.

So, clearly the battery warms with use and extends the range - an effect probably only noticable in the winter.

The upshot of this is, don't assume you have enough charge to get to a public charger if you run very low and then leave the car in the cold!

I’ve had this in my FL5. Drove 10 miles at 93% after 7kW charge before % started to drop.

 

[WigglePig]

Battery % is calculated using the voltage, which itself varies with temperature. It’s quite likely that the cooling battery will show lowering terminal voltage, hence calculated %.

Either that or it wandered off somewhere for a while.

 

[Coulomb]

While I agree the GOM will be affected by temp but the % of charge should stay fairly static.

I think that the GOM responds to battery voltage, and that is reduced in the cold. If that's right, then it's not surprising.

 

[dragon2611]

Anecdotally there seems to be suggestions that some cars are more likely to go into turtle mode at a higher SOC in very cold weather to protect the battery.

Therefore, I'd suggest trying to avoid going into low SOC during winter months as you might end up with a nasty surprise.

I've been told off by the car for "Aggressive Driving" when trying to pull out of a junction onto a hill at 7% SOC but it didn't power limit me.

 

[shpub]

First thing is that the SOC is not very accurate and is dependent on lots of things including temperature. It is very hard to measure as the battery discharge curve is almost flat. Coulomb counting is about the only real way but that is also quite complex. Same affect that you see on power tools. Battery drills that are full of energy during the day can be very sluggish in the morning if left in the cold overnight. Warming them up will recover the "lost" energy. In reality the charge is not lost as such, but the ability to extract it is affected (Peukert's Law if you want to look it up). It can be worse with the lower state of the batteries. So leaving a nearly flat battery to cool overnight will reduce the reported SOC. Letting the car warm up would restore the SOC. The problem is in the winter it is hard to do so recharging is done which warms the battery as well as increase its SOC.