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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #1 ·
After my (dumb-but-fun) range test on Saturday I plugged my ID.4 into my Zappi and left it on "Fast" charge all night as I needed another full charge the next day. I'm confident this was as close as I'll ever get to an actual "full charge", since I plugged in at 1% and unplugged just over ten hours later at 100%. When I unplugged I took a pic of the Zappi which showed a total of 80.12 kWh:

149228


I got to wondering - does this mean I had a 3-4% charge efficiency loss (80 kWh put into a 77 kWh-usable battery), or does it mean the usable battery is actually a bit bigger than we are told? Or perhaps both?

Side note: the idea that I was able to drive ALL day (14 hours with the car moving) for a grand total of £8.50 in electricity is pretty amazing to me!
 

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I read that the average efficiency of the AC chargers are around 90%.

with 1% remaining you started with 8kw
you then put 80kw in
that 8+80 = 88kw into 77kw
= 87.5% efficiency by my maths.
 

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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #4 ·
I read that the average efficiency of the AC chargers are around 90%.

with 1% remaining you started with 8kw
you then put 80kw in
that 8+80 = 88kw into 77kw
= 87.5% efficiency by my maths.
1% should be less than 1 kWh in the battery when I started (0.77 kWh if it was exactly 1%). So putting 80.12 kw into a battery where nominally there was space for ~76 kWh = ~95% efficiency, which isn't bad at all if that was indeed what happened here.
 

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I read that the average efficiency of the AC chargers are around 90%.

with 1% remaining you started with 8kw
you then put 80kw in
that 8+80 = 88kw into 77kw
= 87.5% efficiency by my maths.
maybe that should 80 into 77-8=69kw... 86.3% efficiency?

I do believe that even the AC chargers are less efficient in the last 20% than the first 80% of charge.
 

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1% should be less than 1 kWh in the battery when I started (0.77 kWh if it was exactly 1%). So putting 80.12 kw into a battery where nominally there was space for ~76 kWh = ~95% efficiency, which isn't bad at all if that was indeed what happened here.
yeah sorry 1% would be 0.8kw

you are right 80 into 76 is 95%
 

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Kona64
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Trying to get my head around the 10hours bit
to have put more than 72kW in ?
ie 76 kW ?
7.6 per hour speed ?

I suppose 32amp fuse and 240 volts is 7.5 ?
So your street power to your house was a smidge over 240volts most of those 10hours ?

Although isn't the Zappi unit saying I've used 80kW doing what you asked me ?
256volts ?

Am I over thinking this ?!?!
 

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Bit of vampire drain / 12v charging too id imagine.
 

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OBCs are typically around 90% or so efficient at full rated current, but the efficiency drops as the current reduces, so can be much less efficient for the final few percent of a charge. There's also some error on fairly simple measurement system the Zappi uses. Charge point measurements, or those in the car for that matter, aren't anywhere near as accurate as electricity meters, and even an approved electricity meter is allowed to have up to a +2.5%, -3.5% error.

This means that if you had a dedicated electricity meter for charging the car, to the standard required for billing you for energy used, then, for, say, this apparent 80.12 kWh reading, the actual energy delivered could be anything between 77.3158 kWh and 82.123 kWh. You can probably at least double that error band for the measurements displayed by the Zappi.
 

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ID3 1st & e-Golf
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When I asked myenergi how accurate the kWh reading was the technician said he'd be very disappointed if it wasn't within 1%.

When I used to check the readings and compare with my e-Golf obd reader app there was always 9% difference, give or take 0.5%
I haven't found out where to check in the app with my ID3 but 95% sounds very efficient.

The VW cars don't seem to slow down when they get close to 100% charge. I've noticed with my Golf and ID3 that they continue at 7kW right to 100%
 

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1% is cloud cuckoo land for the pretty simple CT method that the Zappi uses. The CT alone has an error of around 3% to 5% over its full range, and that's without taking into account the voltage and phase measurement error within the charge point itself.

Domestic electricity meters don't normally use CT's because of the inherent error that cheap ones have over the full measurement range (and electricity meters are cheap - less than £30 for a non-smart one). All the ones I've seen use a precision shunt for current measurement, to eliminate the inherent errors that CTs always introduce when trying to measure a wide range of current. Even then they have a pretty wide tolerance, between -3.5% and +2.5%.
 

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Usable energy is more likely an estimate. SoC is based on battery voltage.

You drove so efficiently, you got more energy out of the battery than the usable suggests as the current you pulled towards the end was low.
With higher current/power driving style you would have reached 1% with more energy left in the pack.

edit. Fantastic mileage btw!
 

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Leaf 30kWh, HS PHEV
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A long time ago I compared power meter on the charger vs what LeafSpy said it received and the efficiency was 87.5%


Sent from my iPhone using Tapatalk
 

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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #14 ·
Trying to get my head around the 10hours bit
to have put more than 72kW in ?
ie 76 kW ?
7.6 per hour speed ?

I suppose 32amp fuse and 240 volts is 7.5 ?
So your street power to your house was a smidge over 240volts most of those 10hours ?

Although isn't the Zappi unit saying I've used 80kW doing what you asked me ?
256volts ?

Am I over thinking this ?!?!
I had an Ohme for awhile (which shows volts and amps) and I pretty consistently pull 250v from my mains. I know the "240v" standard is more like "230-250v" and I guess I'm just at the higher end of the range. 250v * 32a = 8 kW, so if you are really lucky like me, you can charge at close to 8 kW with a standard 32a supply.
 

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After my (dumb-but-fun) range test on Saturday I plugged my ID.4 into my Zappi and left it on "Fast" charge all night as I needed another full charge the next day. I'm confident this was as close as I'll ever get to an actual "full charge", since I plugged in at 1% and unplugged just over ten hours later at 100%. When I unplugged I took a pic of the Zappi which showed a total of 80.12 kWh:

View attachment 149228

I got to wondering - does this mean I had a 3-4% charge efficiency loss (80 kWh put into a 77 kWh-usable battery), or does it mean the usable battery is actually a bit bigger than we are told? Or perhaps both?

Side note: the idea that I was able to drive ALL day (14 hours with the car moving) for a grand total of £8.50 in electricity is pretty amazing to me!
Get the Octopus Go EV tariff, well worth it for £0.049 KW between 0030 - 0430 each day. Best thing I've ever done. i'll charge my car over a couple of nights to get back to full but cant knock 260-270 miles of charge for only £3.70ish.

(not a sales pitch of any sort, just I've found it useful)

Feel free to help me out also and use the referral link, you don't have to obviously but it would mean we'd both get £50 credit.

www.share.octopus.energy/vivid-eagle-911
 

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'18 Zoe ZE 40 R110 + '21 VW ID.4 1st
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Discussion Starter · #16 ·
Get the Octopus Go EV tariff, well worth it for £0.049 KW between 0030 - 0430 each day. Best thing I've ever done. i'll charge my car over a couple of nights to get back to full but cant knock 260-270 miles of charge for only £3.70ish.

(not a sales pitch of any sort, just I've found it useful)

Feel free to help me out also and use the referral link, you don't have to obviously but it would mean we'd both get £50 credit.

www.share.octopus.energy/vivid-eagle-911
I've been on Octopus Go Since last November. :)
I did a full charge (including the four cheap hours) because I had to drive 200+ miles the next day, so I couldn't afford to spread the charge over 3 days like normal.
 
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