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Discussion Starter · #1 ·
We're experiencing -20°C ish weather currently in Ukraine and I neither have a garage nor battery heaters yet, so you can imagine I'm locked on a very low charging power (3 to 5 kW normally, 2013 Zoe with a ZE40 battery upgrade). At such power when charging off three phase stations, the per-phase current is very low and in such conditions, both the efficiency and the power factor suffer, but I never realized just how much the latter does. Seems the answer is "you get as much reactive power as you get active". On top of that, the station does actually bill it (it's a per-station thing, talked to the owners of few local networks). But even if you aren't billed, that's still not very good for the grid and someone upstream of you is paying premium, or your company maybe if you charge at work.
So I did an experiment and it really seems to work: when you force Zoe to do one phase, at low charging power you effectively bump the current for the same power and thus force the charger into a more effective region where no reactive currents appear, or at least very little do. Here's some proof gathered on the same station. The bottom graphs correspond to normal 3 phase charging, the top one was collected with a type1-to-type2 adapter effectively cutting 2 phases out. Sure it's a Ukrainian thing to have J1772 connectors all over the place, but it might just be helpful for someone when deciding between a 3phase and 1phase home charger while living in a very cold place.
PS: The "active power" is a reading straight from the car. It does seem right for 1 phase scenario but is very suspicious for 3 phase, I mean it's nearly 100% all the time so I don't think the red line has too much truth to it. The black one however was cross-validated with what the station sees as consumption (dashed black line).

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The adapter in question (50€):
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PS: reposting from my own posting in RZOC just in case :)
 

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Co-author of CanZE. Q210 nov 2013
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As far as I know the car does fairly decent "current following", modulating the chopper in phase with the AC voltage. However, there is ALWAYS the 6A reactive power of the filter capacitor bank (100uF), which of course should be vector-added to the real power to get the total. IOW, it's not so much a matter of "when it is really cold, real is the same as reactive", more like "real current on a very cold battery cannot go above the equivalent of about 6A grid side". And that low power setting is really to protect the battery.

Bottom line: charge immediately after driving when it's cold ;-)
 

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Discussion Starter · #3 · (Edited)
That's odd, I mean are you sure it's always flowing? Based on the graphs here, single phase stays in an okay-ish power factor region for much longer. Which I assume is because said reactive currents happen per-phase, so you get 3 times as much of it when on 3 phases. And this would also explain why I'm getting this big of a difference when charging at the same DC power limit between 2 setups. However, since they go over 95% active power, surely it would mean the reactive current is getting reduced when the power goes up? I mean, imagine you plug into 16A socket and draw full amps, but 6A is reactive, you would never go above 2.3 kW DC in such a setup will you? Nevermind that works out to 15A.

UPD: self-corrected, I forgot that pf isn't % of active power

Bottom line: charge immediately after driving when it's cold ;-)
When you start out with -20 and there's no heater, you can hardly go over 5 kW even if you drive full to empty, sadly.
 

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Discussion Starter · #4 · (Edited)
Right, I followed up with the idea of "6A applies to each of the phases at all times" and modeled the % of active power in terms that the German article uses, seems both repeating what they had experimentally (I mean not quite, but the shape is same overall)
and more or less explain why I get more reactive power at low active power for 3 phases vs 1 phase, thanks @yoh-there
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