KiwiME
Well-Known Member
Today I charged for 20 hours from 20% SoC to 63% at an average of 1.59 kW, meaning an average of 7 amps at 230VAC.
I was hoping for a slightly higher rate but I discovered that the Ratio Electric EVSE drops down to 6 amps in hot conditions and has to be restarted.
I measured the AC energy using a TP-Link Kasa plug which I believe is very accurate from some comparison tests I've done with another energy measuring adapter. However, the Kasa adapter gets very warm and I think caused the EVSE power plug to trigger an overtemp.
The bottom line is that I needed 31.8 kWh to add 22.1 kWh to the battery, a shocking 69.5% efficiency, much lower than I had thought. With these losses and my overall electricity rate of 33 cents/kWh it would be slightly less expensive and a whole lot faster to simply visit the nearby DC fast charger at 40 cents/kWh.
Combined with the real-life 15.3 kWh/100km I'm measuring, the costing works out like this:
15.3/(0.978 x 0.695) = 22.51 kWh(AC@7A)/100km
In my case $0.33 x 22.51 = $7.43/100km, or for the 290 km trip 2.9 x 7.43 = $21.54
The 0.978 value is the battery cycle efficiency which comes into play between charging and discharging.
To be realistic, gasoline locally is $2.75 / litre for the highest octane. My ICE over the same trip would use 2.9 x 10L/100km x $2.75 = $79.75
So, I'm still 3.7 times better off. However, in just over 2 years EVs have to pay a road user charge which at the current rate of $76/1000 km will add 2.9 x 76/10 = $22.04 to the same trip.
So, at 21.34 + 22.04 = $43.38 it seems I'm still better off cost-wise with an EV.
I was hoping for a slightly higher rate but I discovered that the Ratio Electric EVSE drops down to 6 amps in hot conditions and has to be restarted.
I measured the AC energy using a TP-Link Kasa plug which I believe is very accurate from some comparison tests I've done with another energy measuring adapter. However, the Kasa adapter gets very warm and I think caused the EVSE power plug to trigger an overtemp.
The bottom line is that I needed 31.8 kWh to add 22.1 kWh to the battery, a shocking 69.5% efficiency, much lower than I had thought. With these losses and my overall electricity rate of 33 cents/kWh it would be slightly less expensive and a whole lot faster to simply visit the nearby DC fast charger at 40 cents/kWh.
Combined with the real-life 15.3 kWh/100km I'm measuring, the costing works out like this:
15.3/(0.978 x 0.695) = 22.51 kWh(AC@7A)/100km
In my case $0.33 x 22.51 = $7.43/100km, or for the 290 km trip 2.9 x 7.43 = $21.54
The 0.978 value is the battery cycle efficiency which comes into play between charging and discharging.
To be realistic, gasoline locally is $2.75 / litre for the highest octane. My ICE over the same trip would use 2.9 x 10L/100km x $2.75 = $79.75
So, I'm still 3.7 times better off. However, in just over 2 years EVs have to pay a road user charge which at the current rate of $76/1000 km will add 2.9 x 76/10 = $22.04 to the same trip.
So, at 21.34 + 22.04 = $43.38 it seems I'm still better off cost-wise with an EV.