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Discussion Starter #1
Hi y'all,

I'm interested to know what's going on with my Zoe/Homecharge unit. My car was plugged in to charge last night and was unplugged this morning before going out. No pre-heating.

The Polar/Homecharge Dashboard shows the 'Duration' of charge (basically when the plug was fitted/disconnected) as 10h24m. End battery charge was, obviously 100%. I think I recall seeing 11% as the charge started.

What I find odd is that it reports the kWh used as 44.6. Is this correct, and if so, why? This is more than the battery capacity by some margin, so was the battery being kept warm leading to extra power used?

I assume this is normal?
 

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What I find odd is that it reports the kWh used as 44.6. Is this correct, and if so, why? This is more than the battery capacity by some margin, so was the battery being kept warm leading to extra power used?
That sounds about right. The Zoe on board charger isn't that efficient, especially at low powers. I noticed that it's fairly toasty under the bonnet after its been charging.

So you're losing around 10% during charging?
 

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Discussion Starter #3
@cah197 Thanks for the reply.

Hmmn... glad I'm on the Octupus EV tariff and that's only a few pence! Ordinarily I'd be unplugging a great deal earlier, but I don't reckon there would be much power pulled after reaching 100%. This is a 7 kWh unit BTW.
 

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˙ǝןƃƃnɹʇs ןןıɥuʍop ɐ sı ǝɟı˥
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Hi, Steve.

This is perfectly normal. Battery charging is never 100% efficient, typically 80 to 90%. That is, although the battery has 40 kWh capacity, it will take 44 to 48 kWh to fully charge it from zero.
If yours started at 11% capacity then it needed 35.6kWh to reach 40kWh. It used 9kW more, just over 25% and therefore 75% efficiency.
However, you’ll find Z0E will start charging more than once during cold nights because the fully charged battery will loose 2 to 3% over time and so it calls for a top up charge to return to 100%. That may explain the extra juice used and therefore the apparently lower than expected efficiency.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #5
@Philip Pronto Thank you. So a combination of charging (in)efficiency, long-time connected, and on a coldish night! Maybe I should make sure I unplug earlier in the morning after a charge, too!

Thanks for explaining, guys.
 

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I think the Zoe is a little different in the way it measures battery capacity. It can charge to 100%, then as it cools the SOC reduces due to cooling of the battery.

I'm sure someone has a better explanation, but the SOC can change magically overnight. :)
 

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had an R240, got an R90, might get a ZE50
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I have a Polar charger and I know the data it gives is quite unreliable.
I’d check your consumption via the meter, and estimate any other loads you may have.
The Zoe should charge reasonably efficiently at 7kW, as this is the design load for single phase, 22kW uses 3 phase.
Lithium ion batteries are reasonably efficient, wouldn’t expect to lose 25%.

Having said that a cold lithium battery will have a higher internal resistance, so there will be some heating loss.
That’s why I tend to charge as late as possible so the battery is warmer when I use it.
 

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Just for comparative data points for reference, in my experience;
Fluence required 24kWh to recharge nominal 22kWh
Ampera required 11.8~12kWh to recharge nominal 10.4~10.8kWh
Soul requires 35kWh to recharge nominal 30kWh.
 

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I have a Polar charger and I know the data it gives is quite unreliable.
I'd second this; comparing the power reported by our charge point and the difference in SOC before and after shows they don't really have much in common. It can report a lot of electricity consumed for a top up charge but not much used for a nearly complete recharge. I haven't bothered to look at it for ages because of how next to useless the figures are.

I've intended to add a specific meter or energy monitor for the charger, but haven't got around to it yet...
 

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The zoes charger isn't designed for charging...
Its designed for moving the car.

That's the coolest thing about the zoe.
So losses are to be expected
 
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