Mathematical charging anomaly ?

[OriginalBigAl]

Charged the car to 80% and ran it down to 30 % , did 174 km with the usage monitor hovering around 16.6 kWh/100km. All pretty much normal. Charged last night expecting to put in around 30kWh .... this morning the value was 21 kWh input, with the car again at 80% .???? The timer said 2hrs 15 mins at 10kW so that checks out, the expected range for 80% is 320 km and 100% 415 km . I certainly don't think I've been getting 8 km a kWh which is suggested by a 21 kWh used, mystery?

 

[Black estate]

Charged the car to 80% and ran it down to 30 % , did 174 kms with the usage monitor hovering around 16.6 kw/ 100kms . All pretty much normal. Charged last night expecting to put in around 30kw .... this morning the value was 21 kw imputed , with the car again at 80% .???? The timer said 2hrs 15 mins at 10kwh so that checks out, the expected range for 80% is 320 km and 100% 415 km . I certainly don't think I've been getting 8 kms a kw which is suggested by a 21 kw used, mystery?

What's the weather been like over there as 8 km = 5 miles which is quite doable in warm weather.
I've been getting near 5 miles per kWh in my S5.

 

[MickeySw]

Charged the car to 80% and ran it down to 30 % , did 174 kms with the usage monitor hovering around 16.6 kw/ 100kms . All pretty much normal. Charged last night expecting to put in around 30kw .... this morning the value was 21 kw imputed , with the car again at 80% .???? The timer said 2hrs 15 mins at 10kwh so that checks out, the expected range for 80% is 320 km and 100% 415 km . I certainly don't think I've been getting 8 kms a kw which is suggested by a 21 kw used, mystery?

Assuming you have a 61 kWh battery then you ‘used’ about half the capacity for your trip and therefore I would also expect 30 kWh + to get back to 80%??

I therefore think that the current SoC displayed isn’t accurate but this should sort itself out during the next journey. A HW reset (12V disconnect) should have the same effect?

 

[fnegroni]

Charged the car to 80% and ran it down to 30 % , did 174 kms with the usage monitor hovering around 16.6 kw/ 100kms . All pretty much normal. Charged last night expecting to put in around 30kw .... this morning the value was 21 kw imputed , with the car again at 80% .???? The timer said 2hrs 15 mins at 10kwh so that checks out, the expected range for 80% is 320 km and 100% 415 km . I certainly don't think I've been getting 8 kms a kw which is suggested by a 21 kw used, mystery?

maybe the battery wasn't really down to 30% or perhaps it's not at 80%. You might need to do a balance charge to 100% or possibly even a full discharge to <10% and back up to 100%.
you most likely did use the 30 kWh claimed by the trip meter but the SoC % is lying to you

 

[EvTek23]

As the battery started off at 80%, then this is only 52kWh of the 64kWh capacity. Using the car to 30% and then recharging it back to 80% would mean you'd only need to charge 50% of 52kWh which is around 26kWh. So taking into consideration all the other factors about the real SOC, GOM etc it doesn't seem wildly out , as the charger will report actual recharge power.

 

[fnegroni]

As the battery started off at 80%, then this is only 52kWh of the 64kWh capacity. Using the car to 30% and then recharging it back to 80% would mean you'd only need to charge 50% of 52kWh which is around 26kWh. So taking into consideration all the other factors about the real SOC, GOM etc it doesn't seem wildly out , as the charger will report actual recharge power.

it's not wildly out but i'd still do a bms learning and balance charge from <10% to 100% and equalisation just to be sure

 

[MickeySw]

you'd only need to charge 50% of 52kWh which is around 26kWh

SoC is always based on total battery capacity:
80% -> 51kWh
30% -> 19kWh

 

[OriginalBigAl]

What's the weather been like over there as 8 km = 5 miles which is quite doable in warm weather.
I've been getting near 5 miles per kWh in my S5.

Its averaged out at around 12c for the latest charge, I don't hang around and there are lots of hills. My normal usage for mid-summer is around 6.5 -7 km per kw, 28 - 32 c .

maybe the battery wasn't really down to 30% or perhaps it's not at 80%. You might need to do a balance charge to 100% or possibly even a full discharge to <10% and back up to 100%.
you most likely did use the 30 kWh claimed by the trip meter but the SoC % is lying to you

It had a balance charge a couple of weeks back and as a rule within a small percentage all the figures normally are as expected. As to the SOC then next week will either confirm or dispel that therory.

As the battery started off at 80%, then this is only 52kWh of the 64kWh capacity. Using the car to 30% and then recharging it back to 80% would mean you'd only need to charge 50% of 52kWh which is around 26kWh. So taking into consideration all the other factors about the real SOC, GOM etc it doesn't seem wildly out , as the charger will report actual recharge power.

I hear what you are saying but it has never reported it like that in the previous 2 ans a half years. As Mickey EV as said its always a percentage of the total capacity.

 

[Montego]

I tried doing the maths once. Early in my EV adventure. I couldn't get the sums to work either. Gave up and just started charging when needed, either based on residual battery or how much is needed for next journey. Much the way I used to work with a petrol car.
I kept a very close eye on my previous, petrol, car as it was used for work, but at the end of the day used to just charge for the miles driven, to may variables to make sense of it!

 

[OriginalBigAl]

I tried doing the maths once. Early in my EV adventure. I couldn't get the sums to work either. Gave up and just started charging when needed, either based on residual battery or how much is needed for next journey. Much the way I used to work with a petrol car.
I kept a very close eye on my previous, petrol, car as it was used for work, but at the end of the day used to just charge for the miles driven, to may variables to make sense of it!

I think I have got the maths pretty much sorted including adjustments for all the variables . For the past 8 months all has tallied up as expected both with my expectations and the figures as reported on the screens and different pages concerning usage. I am not obsessive about it , its just interesting trying to work out how MG have calculated their algorithms and then putting the theories into practice, so when a obvious anomaly which is 30% out of kilter and not immediately soluble comes along and punctures the apparent normality of expectation my interest is again peaked. All might be revealed during the next week if the efficiency drops like a brick suggesting a SOC reporting glitch.

 

[MickeySw]

its just interesting trying to work out how MG have calculated their algorithms and then putting the theories into practice, so when a obvious anomaly which is 30% out of kilter and not immediately soluble comes along and punctures the apparent normality of expectation my interest is again peaked.

Sometimes it doesn’t make sense, I.e just home from a quick spin into town, started @ 90% SoC, returned with 83%, did 42km, hope nobody suggests I can drive 600km on one charge?