Granny lead charging speed

[halogen]

Hello. Just took delivery of my new mg4ev magnify here in Indonesia. It's a weird combination of 51kwh battery with trophy spec ...
Anyways. Was charging the first time. I'm curious why am I getting 1.3kwh instead of 2kwh. While my amp meter was showing 8.7amp drawn... should it be close to 2kwh?
Thank u for the forum.

 

[siteguru]

What is your standard voltage? 230V?

8.7 x 230 = 2kW as you say. However the charge unit is not 100% efficient ... more like 80% at best. (Losses in the granny charge unit plus losses in the onboard charger). That should still be nearer 1.6kW though.

 

[halogen]

What is your standard voltage? 230V?

8.7 x 230 = 2kW as you say. However the charge unit is not 100% efficient ... more like 80% at best. (Losses in the granny charge unit plus losses in the onboard charger). That should still be nearer 1.6kW though.

thank u for the reply. the standard voltage in indonesia is 220-230volt. if its showing 1.3kwh. man losses are about 35%.. which is 65% efficiency. is there any way i could minimize the efficiency loss? btw the granny lead is a type B plug. i had to use a 10amp 250v adapter plug . will that be another loss factor?

 

[Buster72]

thank u for the reply. the standard voltage in indonesia is 220-230volt. if its showing 1.3kwh. man losses are about 35%.. which is 65% efficiency. is there any way i could minimize the efficiency loss? btw the granny lead is a type B plug. i had to use a 10amp 250v adapter plug . will that be another loss factor?

In the UK, I typically get between 1.8 and 1.9 kWh charging with the MG granny charger.

 

[JoeBlow]

Also get out of the car and lock it/turn it off.

You will see the number go up in the app.

As far as I can work out, the number shown on the screen is after “losses”. So with the car on and air conditioning running it will be less.

 

[halogen]

Also get out of the car and lock it/turn it off.

You will see the number go up in the app.

As far as I can work out, the number shown on the screen is after “losses”. So with the car on and air conditioning running it will be less.

i dont have the app. i cant bind the car , dealer said something about software upgrade . bummer.

 

[wattmatters]

is there any way i could minimize the efficiency loss?

A higher power charger will reduce relative losses. The small brick charger is probably the least efficient charge method.

You would require an electrical circuit capable of delivering up to the car's on-board AC charger limit, which is probably ~ 6.6 kW. With a 220-230 V AC supply, that's 29-30 A plus losses, so it's a minimum of a 32 A circuit, normally such chargers use a 40 A breaker.

I see my car's on board system reports 1.5 kW while my home monitoring shows the circuit drawing 1.7 kW.

My charge station is being installed soon and it will have the ability to vary the charge rate so I'll have more data on charge efficiency at high power levels which I intend to share.

 

[halogen]

A higher power charger will reduce relative losses. The small brick charger is probably the least efficient charge method.

You would require an electrical circuit capable of delivering up to the car's on-board AC charger limit, which is probably ~ 6.6 kW. With a 220-230 V AC supply, that's 29-30 A plus losses, so it's a minimum of a 32 A circuit, normally such chargers use a 40 A breaker.

I see my car's on board system reports 1.5 kW while my home monitoring shows the circuit drawing 1.7 kW.

My charge station is being installed soon and it will have the ability to vary the charge rate so I'll have more data on charge efficiency at high power levels which I intend to share.

i was looking at those variable amps wall chargers too... do share with pics when u have them.

im curious if u choose 32amps and does it shows 7.3kwh... or less...

 

[siteguru]

It'll show the charge into the car (max. 6.6kW) divided by the efficiency. e.g. if 90% efficient then the wall box will be using approx. 7.3kW. if 95% efficient then it'll be 6.95kW.

 

[wattmatters]

The efficiency measure is reliant on the accuracy of how the power (or energy) data is measured/reported. For the car's battery charging we don't have much choice in that, it's whatever the car reports.

For the AC input then it's a matter of how good that data is. I'm confident of my data being pretty accurate as I have a well calibrated IoTaWatt with dedicated VT and a CT just for the EV circuit.

i was looking at those variable amps wall chargers too... do share with pics when u have them.

Will do. Mine will use OCPP and I intend to hookup with the Charge HQ service so it can take full advantage of our solar PV system.

But for testing I can also choose a charge current level (between designated minimum and maximum values). On a suitable day I intend to capture some data at each charge level and plot the AC input power vs battery charge rate. That will show up any variation in efficiency with power.

 

[fnegroni]

If the A/c is on, you will see charging between 0.4 and 1.2 kW

 

[Rolfe]

Mine generally charges at 1.87 Kw. For information, I charged it from 9% to 100% on the granny charger at the beginning of this week and it took almost exactly 26 hours including the half-hour balance time at the end.

 

[fnegroni]

Hello. Just took delivery of my new mg4ev magnify here in Indonesia. It's a weird combination of 51kwh battery with trophy spec ...
Anyways. Was charging the first time. I'm curious why am I getting 1.3kwh instead of 2kwh. While my amp meter was showing 8.7amp drawn... should it be close to 2kwh?
Thank u for the forum.

Did you by any chance enable the charging current limit?

 

[halogen]

Did you by any chance enable the charging current limit?

hi. yes i set it up to maximum. should i choose 10amp instead?

 

[wattmatters]

hi. yes i set it up to maximum. should i choose 10amp instead?

Only if it had been set at the lower 6 A level. Leaving it on the max setting means it will adapt to whatever the connected EVSE unit can supply.

 

[pollenface]

I bought the 6/8/10/15 adjustable charger off ebay.

At 6a it's 68% efficient

At 15a it's 84% efficient

 

[halogen]

I bought the 6/8/10/15 adjustable charger off ebay.

At 6a it's 68% efficient

At 15a it's 84% efficient

just curious... at 68% efficient... we are still paying 100% of the current drawn even tho the car only receives 68% of the kWh...

 

[halogen]

I bought the 6/8/10/15 adjustable charger off ebay.

At 6a it's 68% efficient

At 15a it's 84% efficient

what brand did u use? how much was it?

 

[siteguru]

just curious... at 68% efficient... we are still paying 100% of the current drawn even tho the car only receives 68% of the kWh...

Correct - that's what efficiency basically is. Charging has fixed (regardless of charge rate) and variable (proportional to charge rate) losses ... the lower the charge rate, the higher the ratio is of fixed to variable losses. That's essentially why low power charging is very inefficient.

 

[pollenface]

what brand did u use? how much was it?

The adjustable charging lead is just a generic one off ebay. The efficiency loss takes place in the car's built-in charger.

Compare the difference of the current draw at the power socket and the rate of the net charge rate being received by the car's battery, then you can calculate the efficiency value