Is there a way to read battery state in kWh?

[fourevah]

I don't know if anyone else has faced this, but I consistently see a 10% discrepancy in the charging rates and wonder if I can get to the bottom of this.

I charge at work using Amp/Fuuse chargers, which consistently report 7kW charging rates.
When I check the MG iSmart app about charging rate, it always consistently reports 6.2kW charging rate.

This is a ~10% discrepancy between the two rates. I can understand that there would be some cable losses, but 10%???
Since the battery reports in %age, (yes, I know I can multiply by 64kWh to get exact values), but I wonder if there is anyway to resolve the discrepancy with raw kWh values?

Thanks

 

[haloweenhamster]

Not just cable, AC to DC converter

 

[kenneth104]

Yeap

The car AC to DC it's about 90% efficiency

 

[Coulomb]

Not just cable, AC to DC converter

But the AC to DC converter (the on-board charger) is in the car.

The car AC to DC it's about 90% efficiency

A little over 90% I believe. The rest is from heater or A/C use, and 12 V loads via the DC-DC converter, and its losses.

 

[kenneth104]

Temperature here is very suitable for battery charging, the power required for battery temperature regulation is likely to be 0

As for the consumption of 12V, it can be ignored

 

[tsedge]

It is normal expected losses. Can be even higher if you have a really long charging cable.

 

[Everest]

If you want to get more accurate readings you could purchase a CANBus interface that will plug into the OBD port. Then using an app like Car Scanner to display the raw data on your phone.

Take a look at Bjorn Nyland's EV reviews - he uses it all the time to get the raw data from the car's BMS. Often the SOC is also 'manipulated' for the driver's display vs. the actual SOC from the battery's BMS.

e.g.

 

[Everest]

A little over 90% I believe. The rest is from heater or A/C use, and 12 V loads via the DC-DC converter, and its losses.

+ FWIW... I was researching into V2L losses a while ago and read the Ioniq5 has a quiescent use of around 200W when the car is discharging in addition to the losses within the inverter. I'd hazard a guess that a) there would be a similar quiescent usage of the car's electronics when charging as well and b) the MG4 would have roughly similar quiescent usage.

 

[siteguru]

Indeed. And that's why a granny charge unit is inherently less efficient than a 7kW charge point, which is less than an 11kW charge point, etc. Standing usage (losses) are a greater proportion of the charge rate where the lower is that rate.

 

[Kithmo]

10% losses sounds about right based on what my Pod Point reports as kWh used and how much went into the car.

 

[Surfdog]

EV charging is like filling an ICE car up with 50 litres of fuel but only 45 litres reaches the tank with 5 litres leaking out the hose and going down the drain. You've paid for that 5 litres but are never going to see the benefit from it.

 

[ReintjeWA]

EV charging is like filling an ICE car up with 50 litres of fuel but only 45 litres reaches the tank with 5 litres leaking out the hose and going down the drain. You've paid for that 5 litres but are never going to see the benefit from it.

Yeah but if petrol was as cheap as electricity most people probably wouldn’t care about that either

 

[wattmatters]

EV charging is like

It's more of an issue with AC charging than EV charging per se.

 

[haloweenhamster]

It's more of an issue with AC charging than EV charging per se.

???
EV (Electric Vehicle) charging can be AC or DC, AC doesn't stop it from charging your car

 

[HazardLights]

???
EV (Electric Vehicle) charging can be AC or DC, AC doesn't stop it from charging your car

I think he means because of AC conversion losses.

 

[Coulomb]

Probably also the fact that most of the conversion losses when DC charging are on the supplier side: you pay for the power that gets to your charge port. Of course, the supplier will pass the cost of those losses on to the consumer, in the form of higher per kWh rates, so really that point is somewhat irrelevant. The supplier will have AC to DC conversion losses. Perhaps these will be slightly smaller because higher power converters are nearly always more efficient, but there are also site cable losses, connector losses, lighting for safety, etc.

But also the other losses will he quite small compared to a typical DC charge power level.

 

[wattmatters]

???
EV (Electric Vehicle) charging can be AC or DC, AC doesn't stop it from charging your car

DC charging does not require use of the car's onboard AC to DC converter (that's already been taken care of by the DC charge station) plus the amount of sundry energy consumption (e.g. to power the car's systems and charge the auxiliary 12 V battery) are relatively trivial when charging a car at circa 100 kW compared with circa 7 kW.

IOW with DC charging a greater proportion of the energy passing through the charge port ends up in the drive battery.

 

[grange]

If you want to get more accurate readings you could purchase a CANBus interface that will plug into the OBD port. Then using an app like Car Scanner to display the raw data on your phone.

Take a look at Bjorn Nyland's EV reviews - he uses it all the time to get the raw data from the car's BMS. Often the SOC is also 'manipulated' for the driver's display vs. the actual SOC from the battery's BMS.

e.g.

I have an OBD2 reader, that connects to Car Scanner.
The app gives 3 different percentages for SOC, but doesn’t give a value in kWh left in battery.
I have emailed the owner of the car scanner app, but after two weeks so far, no reply from them.

 

[nanomad]

There's no such reading of kWh in the official diagnostic tool as well. You have raw battery SoC% and its displayed SoC%

 

[wattmatters]

kWh remaining is reported by the SAIC API. It's an entity in the Home Assistant integration.