I used a public street charger with my EV today...

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Did my first public charge with my Dacia today, to use up some of my Mobilize credit.

I found a Wenea 7.4kW on street charger. I put in 9.83 kWh, which cost an incredible £5.87!!! (Compared with £2.07 at home)

Worse, it added exactly 30% charge on the guessometer, which assuming a 24.3kWh battery, is only 7.3kWh, so the charging efficiency at 7.4kW is 74%. (It was still charging at 7.4 kW when I got back to it)

I haven't bothered working out efficiency at home as I just charge it and it goes on the electric bill, but I'm less than impressed, I'd expected nearer 90% with LFP chemistry.

I didn't think to pull the bonnet and see what is getting hot. (2kW is going somewhere if my figures are correct, certainly the cable was warm, but not 2kW hot...)

Overall it was dead easy, just plug the cable in both ends, then tap the card on the RFID symbol to start the charge, then tap the card again to stop it and release the plug at the charger, I still had to release the plug at the car by unlocking.

(Luckily I'm retired now, so I have nothing better to do with my time than drive miles to a charger and go for an 80 minute walk to save £2!)

I can see why EVs are never going to catch on in the UK, if you don't have zero effort access to a cheap charger.

WellKnownSid

Funny you mention things getting hot - I remember our first jaunt from Scotland to London - baking hot day - stopped at a motorway services and picked up some screenwash.

Opened the bonnet prepared for the huge rush hot air from the toasty engine inside after several hours of motorway - nothing! Quite an anticlimax.

Keep_pedalling

The type of battery you have does not really impact the charging losses which will mainly be down to the efficiency of the AC-DC converter. Are you sure you were charging at 7.4kW from what I have read the Spring’s can only AC charge at 6.6KW and that is using a three phase charger it is 3.2kW in single phase.

WellKnownSid

https://forums.moneysavingexpert.com/discussion/comment/81988321#Comment_81988321

It has a single phase 29A rated OBC.

A 7kW home EVSE will give around 6.6kW

An 11kW public EVSE will give around 3.7kW

A 22kW public EVSE will give around 6.6kW

A DC charger will give up to 40kW

ididgetwhereiamtoday

you don’t know the meaning of the word ‘hot’ until you’ve been on a long road trip in a first gen Leaf!

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It was showing the full 7.4kW on the charger screen.

being a nasty, cynical, suspicious person, and having spent years in measurement & control, I wonder if the pwm waveform from the onboard charger confuses the metering and it actually over reads.

I haven't done the measurement at home, where I have a proper analogue motor driven meter, I'd have to switch everything in the house off for the duration and compare the reading on the charger with the electric meter and then with the guessometer on the car.

There is also the possibility that the guessometer SOC is way off, but 25% seems a lot.

Next time I will have to see what is getting hot, if the figures are correct there is 2kW being dissipated as heat, after an hour something should be pretty hot ;) The cable was warm, but not 2kW warm!

QrizB

There is also the possibility that the guessometer SOC is way off, but 25% seems a lot.

That's almost a certainty.

Next time I will have to see what is getting hot, if the figures are correct there is 2kW being dissipated as heat, after an hour something should be pretty hot ;)

Were you sitting in the car during the charge, with the heater running?

I found a Wenea 7.4kW on street charger. I put in 9.83 kWh, which cost an incredible £5.87!!!

60p/kWh is towards the cheaper end of public charging, in my experience. A similar price per mile to an ICE car.

noitsnotme

it’s a Dacia, it’s probably got a leak in the elektrikidy tank 😄

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I got the calculator to the Dacia published figures.

Using their published charge times for an 80% charge (20-100%) the charge efficiency at 2.3kW is 83%, at 7.4kW it drops to 78% (the 40kW DC charge time for a 60% charge gives 75%- it does bypass the OBC though)

There is also a chance that the charge reduces a bit as it gets to the high 90%s rather than staying at full current until it switches off.

So if the published charge efficiency is only 78% and I made two guessometer SOC readings the 74% I got is well within spec. 😪

Admittedly there are only 2 AC figures, but the efficiency drops as the current increases, someone said the Zoe is inefficient because it uses the motor as the inductor, maybe the Spring does too, and these are hysteresis losses in the laminated iron core, which will increase with current.

So I'd expect the motor to be rather hot after an hour's charging- I'll have a good look at where the water pipes go, either the motor will be hot or the radiator will.

It has a single phase 29A rated OBC.

I and another owner have noticed that the Spring draws consistently 1A less than our "chargers" request- We set 10A we measure 9A, we set 16A we measure 15A, (We could have the same "charger" innards though) if it is actually maxed out at 29A (6.67 kW) but I'm being billed at 7.4 kW that would account for a lot 😉

QrizB

if it is actually maxed out at 29A (6.67 kW) but I'm being billed at 7.4 kW that would account for a lot

The public charger will measure the power being supplied. You will be billed for the kWh delivered. Any discrepancy between kWh delivered and hWh added to your battery will be down to parasitic loads (all cars have them, usually a few hundred watts even without the cabin heater running) and losses.

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https://forums.moneysavingexpert.com/discussion/comment/81988436#Comment_81988436

I didn't have anything on, I went for a walk for 80 minutes. I suppose it will charge the 12V too, but I wouldn't expect it to account for that much loss.

Yes, I know 60p is cheap (although Lidl offer 42p I believe and 61p for DC charging) but not compared to home charging. (Plus, I only actually save 21p a kWh whatever the price, I got some time limited charging credit when I bought the car so it is a case of "use it or lose it" - "free" motoring, just if I got a paper round during the time I have to waste charging to get it I'd still be well in profit after paying my home electricity bill and income tax 😁)

I've read all the negative comments about EVs and charging, but it isn't until you go through it that you realise what an expensive inconvenient chore it actually is, I can see why someone would get rid of an EV after a few months if they didn't have zero effort access to cheap charging.