How efficient is your charger?

[Waterstoney]

I wouldn't worry too much about power consumed by the wallbox. 10W of power usage there is negligible next to the approx. 400W power used by the car.

If I could charge at 7kW instead of 3.6kW, I absolutely would. However, I'm not willing to spend several thousand € to get my house wiring up to that, because that would take forever to recoup.

Wallbox is connected 24hr a day, 7 days a week.
Car is only "on" for consuming power when charging or standing by.

It would take forever to recoup for installing a wallbox. I like the size of ICCB. I only have a short wall on porch for wallbox installation on side of letterbox. Large box or cable would be hazardous environment to postman.

 

[Waterstoney]

I have some conclusion on charging efficiency and cost in preference order.

MG 3 pin ICCB charging at home:
90% efficiency (iSmart/energy monitor)
2kW charging speed (iSmart reading)
34p/kWh with EON.
No dedicated circuit at my house yet:
Charging circuit safety needs to be checked on voltage drop, temperature rise, connections on sockets in cuicuit.

Podpoint at Tesco
89% efficiency
5.82kW iSmart (6.51kW podpoint)
44p/kWh (or 49p)
£5 minimum top up with pod point app

char.gy on street
91% efficiency
4.94kW iSmart(5.43kW char. gy)
65p/kWh (29p 24:00-7:00)
No topup - pay at end Plug

ESB CCS at London underground station
90% DC charging
48kW (53kW)
74p/kWh
£20 minimum topup with EV plug app

As aserraric said, AC/DC conversion is with car on-board charger. There is no real difference with AC chargers.

 

[Bodgerx]

I have some conclusion on charging efficiency and cost in preference order.

MG 3 pin ICCB charging at home:
90% efficiency (iSmart/energy monitor)
2kW charging speed (iSmart reading)
34p/kWh with EON.
No dedicated circuit at my house yet:
Charging circuit safety needs to be checked on voltage drop, temperature rise, connections on sockets in cuicuit.

Podpoint at Tesco
89% efficiency
5.82kW iSmart (6.51kW podpoint)
44p/kWh (or 49p)
£5 minimum top up with pod point app

char.gy on street
91% efficiency
4.94kW iSmart(5.43kW char. gy)
65p/kWh (29p 24:00-7:00)
No topup - pay at end Plug

ESB CCS at London underground station
90% DC charging
48kW (53kW)
74p/kWh
£20 minimum topup with EV plug app

As aserraric said, AC/DC conversion is with car on-board charger. There is no real difference with AC chargers.

Do you have a smart meter?

 

[Waterstoney]

Do you have a smart meter?

I have a smart metre with Eon. It is for whole house.
I use TP Link energy monitor for measurement and timer.

 

[Bodgerx]

I have a smart metre with Eon. It is for whole house.
I use TP Link energy monitor for measurement and timer.

Just an observation that you are leaving money on the table if you have a smart meter for cheaper overnight charging.

A good use case for having a 7kw dedicated charger over anything lower powered is that you are able to get a decent amount of over night charge in that cheaper bandwidth overnight (for the ZS SR that's have the battery charged overnight on a cheap rate).

 

[Waterstoney]

I am a low milage driver. I used 400.4kWh driving 1392miles (a third on motorway) in 4 months of EV ownership. Efficiency is about 3.5 mls/kWh. ZS reported 3.8 mls/kWh. That is about correct with charging loss on AC/DC converter and my 10m long extention leads.

If all EV charging is from my house, it would cost £136 with my current flat rate of 34p/kWh. My electricity bill would be £300. Total cost would be £436.

If I use Eon cheap rate at night tariff, day rate would be increased from 34p to 40p .Night rate would be 15p. EV charging would cost £59 and house cost would be £334. Well, surprisingly I would save £43 if I only charge EV at night rate. Thanks Bodgerx.

 

[GaryMG4]

I must admit I didn't consider or was even aware of charging losses when I started. It's not really an issue at present as I mostly use 3pin charger during the day when my solar panels are producing in excess of the 2.2kw used by the charger to add 1.9kw to the car. But I did start to wonder when I tried a Tesla Supercharger yesterday. The Tesla app showed 134kwh being drawn from the charger, the car showed 126 going into the battery, so around 94% efficient at those speeds. Although Im sure how happy I would have been splashing my boots with a couple of litres of petrol each time I filled my MX5

 

[johnb80]

I am a low milage driver. I used 400.4kWh driving 1392miles (a third on motorway) in 4 months of EV ownership. Efficiency is about 3.5 mls/kWh. ZS reported 3.8 mls/kWh. That is about correct with charging loss on AC/DC converter and my 10m long extention leads.

If all EV charging is from my house, it would cost £136 with my current flat rate of 34p/kWh. My electricity bill would be £300. Total cost would be £436.

If I use Eon cheap rate at night tariff, day rate would be increased from 34p to 40p .Night rate would be 15p. EV charging would cost £59 and house cost would be £334. Well, surprisingly I would save £43 if I only charge EV at night rate. Thanks Bodgerx.

If you went to Octopus Intelligent your peak rate would be less than 30p and the night rate for 6 hours 7.5p. You would have to get an Ohme charger though to reap the rewards.

 

[Eclectic]

If you went to Octopus Intelligent your peak rate would be less than 30p and the night rate for 6 hours 7.5p. You would have to get an Ohme charger though to reap the rewards.

It's having to change my dumb chargemaster unit to get IO that totally makes it unfeasible for me. £1000 - £1200 for the Ohme charger will take an awful lot of kWh to recoup at the cheaper rates

 

[johnb80]

It's having to change my dumb chargemaster unit to get IO that totally makes it unfeasible for me. £1000 - £1200 for the Ohme charger will take an awful lot of kWh to recoup at the cheaper rates

If you shop around, circa £550 for the wallbox and a sparky shouldn't charge much more than £150 for an install, a bit less than your £100+ suggestion.

 

[Bodgerx]

I am a low milage driver. I used 400.4kWh driving 1392miles (a third on motorway) in 4 months of EV ownership. Efficiency is about 3.5 mls/kWh. ZS reported 3.8 mls/kWh. That is about correct with charging loss on AC/DC converter and my 10m long extention leads.

If all EV charging is from my house, it would cost £136 with my current flat rate of 34p/kWh. My electricity bill would be £300. Total cost would be £436.

If I use Eon cheap rate at night tariff, day rate would be increased from 34p to 40p .Night rate would be 15p. EV charging would cost £59 and house cost would be £334. Well, surprisingly I would save £43 if I only charge EV at night rate. Thanks Bodgerx.

Understood

It's having to change my dumb chargemaster unit to get IO that totally makes it unfeasible for me. £1000 - £1200 for the Ohme charger will take an awful lot of kWh to recoup at the cheaper rates

You wouldn't need to for Octopus Go tariff. Currently 9p off peak and no requirement for a special car or charger.

 

[Waterstoney]

I understood how Intelligent Octopus can save money. Peak power usage cost three time more to the energy supplier. Peak usage is normally generated by oil burning gas turbine generator, like the one at Dartford in London. Instead of using expensive power supplier, Octopus controls power consuming by EV charging to smooth power supplying and consuming. Solar power from homes is "junk" to energy companies because of poor quality.

I could recoup £900 Ohme ePod installation from Octopus EV charge in over three years if I can meet requirement with Intelligent Octopus:

• use Ohme app for charging EV
• have only one charging schedule ideally from "4am to 11am" according Octopus.
• cheap rate is between 11:30pm to 5:30 am. I have a doubt with the two different time period.
• become Octopus customer installing SMET2 smart meter.

I like Ohme ePod as it is small, tidy (without tethered cable), consuming less than 3w power.

Thanks Johnb80 for your suggestion.

If you went to Octopus Intelligent your peak rate would be less than 30p and the night rate for 6 hours 7.5p. You would have to get an Ohme charger though to reap the rewards.

 

[aserraric]

I have to revise my earlier statement. Yesterday, I had the opportunity to use a 7 kW wallbox, and I noticed that the losses are actually higher when charging at 6.6kW (~600W losses) compared to charging at 3.6kW (~400W losses). So while charging at 6.6kW is faster, it is only very slightly more efficient.
(Which, incidentally, makes me feel better about only being able to use 3.6kW at home, it is not as wasteful as I thought.)

 

[Waterstoney]

I have to revise my earlier statement. Yesterday, I had the opportunity to use a 7 kW wallbox, and I noticed that the losses are actually higher when charging at 6.6kW (~600W losses) compared to charging at 3.6kW (~400W losses). So while charging at 6.6kW is faster, it is only very slightly more efficient.
(Which, incidentally, makes me feel better about only being able to use 3.6kW at home, it is not as wasteful as I thought.)

You were right that AC/DC convertion is carried out by on-boarding charger on car. So AC charging efficiency is dominent by rectifying loss whatever it is 3 pin ICCB charger, wallbox EVSE charger or public fast charger. It is about 89% to 92% efficiency.

3 pin ICCB charger may have lower efficiency at start when battery is cold. It's efficiency increases in 10 minutes. Long thin 13A extention leads and long house circuit may add 2% to 5% energy loss.

Expensive DC charging equipment can reach 92% efficiency easily using CCS charging connector (base on my test and limited feed backs).

 

[Waterstoney]

After 17 years with EON, I decided move to Octopus for their 7.5p Intelligent Octopus rate. Thank johnb80 for his recommendation.

Now I am on one month waiting list for Ohme Epod charger installation. Octopus told me that my EON smart meter is compatible but I have not got my reading from Octopus app yet two weeks into new supplier.

My reason for installing a dedicated circuit is on safety and efficiency apart from energy cost. Efficiency can be calculated:
13A extention cable is normally 1.3mm2, which is with 15 ohme/km. 10m extention is 0.3 ohme for return circuit. The total reisitence is 1 ohme include plugs, house ring circuit. With 10A 3pin ICCB charger, 100W or 4% of energy is lost. For averaging 12k miles per year driving, with 3mls/kWh efficiency, 4000kw(=12k/3) is required. 2kWh can be topped up per hout. 2000hours(=4000/2) is required for charging. 200kWh (=100W x 2000h) is lost on extention charging. That is about £70 a year losting on extention socket circuit for EV charging.
On other hand, 4mm2 cable is with 5ohme/km resistence. A dedicated thick cable is only with a fraction of energy lost even with 3 pin ICCB charger.

 

[Waterstoney]

My Ohme ePod charger was installed yesterday. 5m long 6m㎡ cable were used. Charging efficiency is 90.8% . It is almost the same efficiency as 3 pin charger if energy loss on 10m long 13A 1.3m㎡ extention leads is ignored.

The temperature on new isolator switch box next to electricity meter rised 8.4°C while charging. Untethered outdoor box temperature rised 5°C. It is less than half of temperature rising for 3 pin charger with extention.