Single phase charging

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doggy
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Real Name: David Kerr
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Single phase charging

Post by doggy » Tue, 30 Apr 2019, 14:19

Three phase charging of Zoe at 22kW is pretty good. Typically, as long as the SOC is 80% or below, I get 20.7kW into the battery at the DC level. So, 94% or better.

Here are some single phase figures I have just measured on my Zoe at 75% SOC:

Pilot=32A. Actual=32A. Power at meter box=7.6kW. Power at EVSE input=7.35kW. Power to 12V battery=100W. Power to HVbat=6.5kW (377V 17.3A). Efficiency=90%
Pilot=20A. Actual=20A. Power at meter box=4.89kW. Power at EVSE input=4.75kW. Power to 12V battery=60W. Power to HVbat=4.05kW (374.5v 10.8a). Efficiency=86%
Pilot=10A. Actual=9A. Power at meter box=2.12kW. Power at EVSE input=2.04kW. Power to 12V battery=50W. Power to HVbat=1.61kW (375V 4.3A). Efficiency=81%
Pilot=6A. Actual=6A. Power at meter box=1.11W. Power at EVSE input=1.06kW. Power to 12V battery=50W. Power to HVbat=0.56kW (375V 1.5A). Efficiency=55%

Several points:
a. I have corrected for power to the 12V battery. This could be significant at low charging currents if accessories have been in use.
b. If the aircon has to run to cool the battery, you have zero left at 6A as it will use between 500 and 1000W.
c. Powers are measured with a 1% accuracy power meter, so reactance and power factor are taken care of. Power factor is somewhat below 1 between 6 and 10amps
d. If we turn the above figures upside down and calculate how much power we actually need to add 32kW from 0% to 80% SOC we get the following:

32A three phase. 34kWhrs. Wastage=2kWhrs
32A single phase. 35.7kWhrs. Wastage= 3.7kWhrs
20A single phase. 37.2kWhrs. Wastage= 5.2kWhrs.
10A single phase. 39.5kWhrs. Wastage= 7.5kWhrs.
6A single phase. 58.2kWhrs. Wastage = 26.2kWhrs

I did these measurements to see if it was worth my while storing excess solar into a 12kW lithium battery at times when there was not enough excess solar for efficient Zoe charging and then dumping it into Zoe at a constant 20A through a 5kW inverter. This would also allow timeshifting as Zoe is often out when the sun is at its best. It all depends upon the round-trip efficiency of excess-solar->battery->inverter->Zoe and at the moment it looks possibly not worthwhile. Though it would improve the feel-good situation further.....still thinking about it....

Cheers,
Dave

antiscab
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Re: Single phase charging

Post by antiscab » Wed, 01 May 2019, 08:01

There is value in having home storage beyond charging the zoe more efficiently. Do you have time of use power? Not using power in peak periods there's likely to be some savings.

Are you export limited to 5kw? I'd be super tempted to put up more Solar, so there's more time where the surplus is above 6A, and simultaneously set the Zappi to minimum 10A charge and Max import 4A
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells

doggy
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Re: Single phase charging

Post by doggy » Wed, 01 May 2019, 09:22

Hi Matt, I am in a very treed area. So the solar varies a lot with shade hitting panels. That is why I have an Enphase system (which is working well). I already have 5kWhr of Calbs (24V) which I use to flatten out the day and it runs all computers, modems, servers, CCTV etc in the house pretty much 24/7 (we are a very compute-intensive house!) Yes, I can and do set the OpenEVSE to min 10A. I have no limit on the export other than 20c/kWHr for the first 170kWHr/month thence 10c. But I am about to change to someone else with a flat 12.5c/kWhr.
I probably will proceed with the 5kW inverter- I just need to get the right one. I have previously designed and built a 2.8kW unit but would rather not expend the time and energy this time.
Cheers,
Dave

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LouB
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Re: Single phase charging

Post by LouB » Wed, 01 May 2019, 13:02

Hi Dave
As Matt says, it all seems to depend on how much power you have available. At our place, we seem to be blessed with more solar than we actually need. Even after charging a house battery, more than than 1/3 is going back into the grid. It accrues credits that we will probably never get back. This good performance from solar is not due to clever design but totally to happy accident. The part of the roof with the PV panels faces North, the roof slope is greater than 20°, and there is never any shading. It means that we have been able to adopt a fairly lazy attitude to charging Zoe and/or conserving power.

I also agree with Matt that more solar, and possibly more storage is the way to go. Also, if the trees are yours, it is not environmentally irresponsible to prune them a little to reduce shading.

doggy
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Re: Single phase charging

Post by doggy » Wed, 01 May 2019, 13:25

Hi Lou,
Thanks. 60-70 metre Pittwater gums are not easy or cheap to prune!

Hm, I do not think I would like solar credits. We get 20c/kWhr atraight off the power bill.

I am stuck with shade and suboptimal direction (azimuth 70deg, tilt 23deg ). It only became practical & moderately cost effective to install solar last year and then only because of one inverter per panel. Even though a 4.3kW system, solar provided 80% of all power used plus fully charged Zoe (except for 2 interstate trips) over an 8 month period. Most of my electronics run off 24V or 12V and my 5kW 24V battery has proved very effective. We have also exported 600kWHrs since January 1 this year. I have also done a huge amount over the past 5yrs to cut home power usage. I even built my own solar HWS (using 36 evac tubes). Hot water costs me less than $10 per annum. Offpeak boost has been 2.2kW in the past 8 months and that system had paid for itself three years ago.

Anyway, the real purpose of this thread was to give Zoe owners a good feel for the Chameleon charger efficiency. Overall, given it has to cover from 6A 240V to 32A three phase, it does a pretty good job (methinks).

Cheers,
Dave

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