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Discussion Starter · #1 ·
I have an e-Niro and I've done 458 miles since getting the car, with the car reporting an average efficiency of 3.6 mi/kWh. That means it's used about 127 kWh. However, my Rolec 7.4kW A/C charge point says I've used 163 kWh, meaning 28% of the electricity being used is lost. Does this sound right? I was expecting the loss rate to be more like 10%, maybe 15% in the winter. Could the Rolec app just be reporting incorrect numbers? I know the total will include a bit of usage during installation and testing but surely that wouldn't add up to much.

I wish I'd paid more attention before my most recent charge because I can't remember what the battery remaining was. I think it was 28%, meaning the 64 kWh battery needed 46 kWh to fully charge. The app reports 55 kWh was used, meaning a loss of 19.4%. I may be wrong about that 28% though, that might've been after the first 30 minute charge segment.
 

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I'd say the Rolec figure is the correct one if you want a real world end-end figure.

From the charge point to the battery you will lose about 7-10%. There will also be some losses getting the energy back out of the battery.

As for the additional discrepency it might be down to how the car calculates the mi/kWh figure. For instance, does that include heating and regen.

Ultimately, dont worry about it.... its cheap driving either way and you cant do anything about the losses... they are what they are.
 

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As above, I suspect that the consumption ignores heating and cooling usage, and roundtrip from mains to battery and back to the motor losses are 10-15% so it's believable.
 

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Ioniq 38kwh 2020
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That seems a bit off too much to me. I only charge on the granny but I estimate a full charge takes around 44kwh on a 38kwh battery so around 15% (estimated in that when I've checked with a watt meter a charge from say 25%-100% I've seen that a 75% charge ie28.5kwh has used 33 kwh.
Are you including the very first charge? I assume your car didn't arrive fully charged, so you had to charge it? And there is currently miles in the battery that haven't been driven yet - unless your battery is currently at 0%
 

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Ioniq 38kwh 2020
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As above, I suspect that the consumption ignores heating and cooling usage, and roundtrip from mains to battery and back to the motor losses are 10-15% so it's believable.
Certainly in the Ioniq, it includes heating/cooling as you can see the miles/kWh figure going down when you are sitting stationery with the heating on. And driving with the heating on will just give a lower figure. It should be a fairly simple calculation of just total kwh used since last reset, divided by miles driven since last reset

Losses from battery to motor should all be part of the miles/kwh figure though.
 

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Discussion Starter · #8 · (Edited)
Losses from battery to motor should all be part of the miles/kwh figure though.
Yes I believe this to be the case.

That seems a bit off too much to me. I only charge on the granny but I estimate a full charge takes around 44kwh on a 38kwh battery so around 15% (estimated in that when I've checked with a watt meter a charge from say 25%-100% I've seen that a 75% charge ie28.5kwh has used 33 kwh.
Are you including the very first charge? I assume your car didn't arrive fully charged, so you had to charge it? And there is currently miles in the battery that haven't been driven yet - unless your battery is currently at 0%
The mileage in the battery isn't considered because I'm going by "used kWh", which is calculated using the car's mileage figure and mi/kWh figure.

However, your comment about the first charge is the key here. I charged it briefly to 78% before our first trip and judging by the driver display delivery photos it was delivered to me with ~67% battery (186 miles GOM):

137830


Side note but why on Earth is the battery meter split into 18 segments? No-one wants to say "oh yeah I have 14 18ths left", why not make it 20 segments? Sigh.


Anyway, let's assume it was on 67% to start with. The car has still driven 458 miles and therefore used 127 kWh since I got it. However, the car now has around 21 kWh more energy than it started with, so although it's used 127 kWh, it has taken an extra 21 kWh from the charge point to get to 100% battery. That equates to 148 kWh total and thus 10% loss, which is much more sensible. Thank you for pointing out the flaw in my calculations! :)
 
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