Charging with Intelligent Octopus Go - 5% Short

Chris H

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I use intelligent Octopus Go for my charging, with a Zappi charger.
The way it works is that you tell Octopus what charger you have and what car you have when setting it up.
To charge, you can plug in any time of day and you say you want it to add X% charge by a certain time, and Octopus schedule the charging and whatever time of day they schedule the charging to take place (usually overnight, but not always) they charge 7p/kWh. All great.
I had an MG ZS SR and the charging was spot-on every time. If the battery had 40% left I could set Octopus to add, say, 50% by 8:30 am and I'd get in the car in the morning and it would be at exactly 90% charge. Great.
I now have an MGS5 LR and reconfigured IOG for the new car and it charges every time, but is always around 5% short. So if it's at 40% I might set IOG to add 50% and when it has finished it will be 85%, not 90%. If I set it to add 20% it will add about 15% etc. All a bit strange because the configuration looks right, it's set up for a 64Kwh battery.
It's not a big problem, I can always add an extra 5% to the amount to add but I'm interested to find out anyone else had this, or if anyone can speculate as to what might cause it.
 
So yesterday the car was at 49%, so I set it to add 45% to be ready by 08:30.
While it was still charging I checked the charging rates. Zappi was saying the power was 7.2kW, yet the MG was saying 6.6kW (see screenshots). When it had finished Zappi says it had added 31.05kWh (which is 50% of the 62kWh usable capacity), yet the MG says it is now at 90%, ie it has added 41%, which is around 25.5kWh.
What is going on? Where has that extra 5.5kWh gone (31-25.5), which I'm being charged for? I'm only getting 82% of he energy I'm charged for into the car.
(I'm not setting any battery heating or pre-warming the car.)
 

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What is going on? Where has that extra 5.5kWh gone (31-25.5), which I'm being charged for? I'm only getting 82% of he energy I'm charged for into the car.
Inevitable losses. Most will be lost in the conversion from AC to DC within the charger. Some will be used to heat the batteries to a suitable temperature during charging. Some will be lost powering the vehicle's electronics. Some, hopefully a smaller amount, will be lost as heat in the cables between the Zappi and the EV.
 
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