so are there any problems with poor efficiency at slow charge rates?

Yes. R isn't too bad but Q Zoe is especially poor on a granny lead.

 

Granny as your "standard" charger is, in general, not a very good idea. Not only is the efficiency indeed lower than higher "full type 2" hookups, the latter are also a lot safer:
- the car instructs the chargepoint to disconnect the mains when the battery is full;
- the entire installation is "fixed", almost always with it's own MCB and RCD, and no other contacts between the fuse box and the chargepoint.

 

If you're charging for free with the granny lead, why not!? I often do that with my Leaf's granny.

 

I only have 8 pv panels. 4 East-facing and 4 West, so I only get a proportion of my charge from them, but there is a feel-good factor, a bit like collecting firewood for a stove.

 

Indeed. I've got 8 facing east and 8 facing west so get power from them presently from quite an early hour to gone 9 pm. Around mid-day both sides working well so have power to spare while charging (depending on the weather.) The best days seem to be when there is cumulus cloud which reflects the light to the panels not facing the sun.

 

Wow, I had not appreciated that Zoe charging at 10amps was only 50-70% efficient. Why is that? I would have imagined it was more efficient due to less need for the battery thermal management system to operate. I can see I have a bit to learn. I have only had Zoe for 10 weeks.
Next time I charge I will need to read my electricity meter before and after.
BTW I am really enjoying driving the Zoe

 

Why is that? I would have imagined it was more efficient due to less need for the battery thermal management system to operate.

The charger is tuned for peak efficiency at full power. For an R Zoe that is 22kW on 3-phase and 7kW on single phase.

The exact number depends on the design, but it looks something like the blue line in the graph with peak efficiency at 7kW.

 

My Granny at 10A is less efficient than via my16A polar at around 63% vs 75% respectively
The loss is mostly through the AC to DC inverter plus some to ancillaries because when charging energy is still being used by other systems and these have a pro-rata higher overhead at a low charge current.

I

 

50% is really not realistic, but other than that, @andrew*debbie narative is spot on. And yes, the entire premise depends a lot on the micro/macro-energy mix, and if you're looking from an overall or "for me" point of view.

As for the ancillaries, if we assume for the moment the system is not cooling the batteries, for the ZOE that draws in the order of 2 amps on the 12 volt bus. All computer stuff. That 25 watt give or take would be only 1%-ish.

Now if the active battery cooling kicks in using the AC system, it can easily draw 1 kW, though I must admit I have never heard it "take off". The "rumble" fans on the batteries for just venting and the big boy under the bonnet for cooling the electronics through the coolant circuit regularly do though in summer.

Can't talk for other EV's.

 

Yes, the car has to power the inverter whatever amps the car is charging at. The present Leaf granny draws 2.25 kW but the car is only charging at 2 kW. (The early larger Nissan granny's drew 2.4 kW to achieve the same thing.) Then from a 3.3 kW point the Leaf only charges at 3 kW. To be honest, the difference is negligible.

Something else to consider is that the battery charges better when it is warmer. That is usually during the daytime.

 

Yes, the car has to power the inverter whatever amps the car is charging at. The present Leaf granny draws 2.25 kW but the car is only charging at 2 kW. (The early larger Nissan granny's drew 2.4 kW to achieve the same thing.) Then from a 3.3 kW point the Leaf only charges at 3 kW. To be honest, the difference is negligible.

Yes for a 3kW LEAF. R Zoe charges at 7kW per phase max. Q Zoe is most efficent at 14kW per phase.

As mentioned before, the Ancillary power is negiliable. The real loss is in the charger.

As you drop down from the max, the car looses more power in the actual charger circuit. Dropping a 3kW LEAF to 10Amps isn't the same as throttling a 63Amp. Q zoe down to 10 amps.

 

Ah, it seems I should charge my Zoe using the Chargemaster 7kW EVSE except on very sunny days, maybe. The reason I bought the granny cable was so that I could charge after a long journey at my destination, where no other option was available. The idea of maximising use of power from my solar panels was secondary.
Very helpful comments from all; I continue to learn.

 

Indeed! I build my own granny charger simply as an "insurance policy". Never had to use it though

 

Granny as your "standard" charger is, in general, not a very good idea. Not only is the efficiency indeed lower than higher "full type 2" hookups, the latter are also a lot safer:
- the car instructs the chargepoint to disconnect the mains when the battery is full;
- the entire installation is "fixed", almost always with it's own MCB and RCD, and no other contacts between the fuse box and the chargepoint.

Hang on, are you saying that the Renault granny lead doesn't have a contactor inside it so the power is connected straight through the cable whether or not the car is charging?

 

ABSOLUTELY NOT! On the contrary. The FlexiCharger, other than regular chargers, has 4 relays so it can cross the leads (as schuko's can be put in either way). What I meant with the second bullet was: no outlets, no plugs, no cable joints, just a direct, usually reasonably beefy wire straight from the fusebox into the fixed chargepoint.

I know what you mean though, the "pseudo" chargers, that have no contactor and just put the "here's the juice" signal on the CP. It is definitely going against the standards (and dangerous too). AFAIK ZOE won't even accept those.

 

Ooh interesting (the self-reversing relays).

Is that facility likely to be built into the uk version as well, even though it will never be needed?

 

I would agree with that (without claiming to KNOW). Also, I would not be surprised if one in, oh say 200 UK outlets had their N and L wires crossed. Any other number is fine too of course. But you really don't want to put L on the car's N pin. So yes, I think the FlexiCharger is ONE device, with just a few different mains plugs available.

Unrelated detail: in some countries the plug has a reed contact to beef it from standard 10A to 13A, see Granny charging (by Renault this time)

 

Doesn't the plug have a thermal sensor in it?

I don't think so, though this could be something that differs per area. As said, some have a reed contact in the plug, so changing the plug might not be totally straight forward.

I have to agree on not using an adapter. That's asking for trouble. If you want a multi-plug charger get something beefy. I know guy who builds these Fivari-charger Website is crappy, but his builds are serious. Can't have it all

 

The Fivari charger is very expensive, especially considering that it's Open EVSE based. Even in it's most basic form, it's nearly 650€.

 

Not that I disagree, but it is well build, three phase 32A. If you need it, you need it. As we both know, a simple single phase 10A lead can be build for just over a 100 euro's, but that's a completely different ball game. If you want to criss cross rural Europe and want to be able to charge at any industrial outlet whatsoever, it's pretty reasonable. Same price as a FlexiCharger really, let alone two, with different plugs.

I think we all agree that using a poundshop adaptor is a really, really bad idea.

Having said that, the need for such things is quickly fading. In my small country alone there are literally tens of thousands of Type 2 chargers. It's really going at an amazing rate.

 

Nothing except sanity.

Using a flimsy travel adaptor with a car charging cable is crazy. They're normally only rated 7.5A, and in reality most of them are cheap Chinese crap and the rating and certification marks are fake.

They sell it, someone will buy it.

2029/WS APSA, Power Entry Connector, Schuko, 16 A, White, Nylon (Polyamide) Body, 250 V | Farnell element14

 

That one is not an adapter. It is supposed to be put on the end of the cable, and apart from it not being very moist resistant, it is not THAT bad actually.

I think @mgboyes was actually referring to scary things like this, which I admit I use, but for nothing heavier than a laptop.

 

Now if the active battery cooling kicks in using the AC system

Slighty drifting away from topic but we've had some pretty hot days the last week and yesterday evening when I hooked up ZOE to the charger the battery temperature was still 30C. The rumble fans and the front fan kicked in and I decided to hook up CanZE.

Front fan 35%
Battery evaporator (Radiator cooling the air entrance of the battery): 8.8 Celsius
Compressor running at a moderate speed, pressuring up to 9.5 bar (when off it drops to under 4 bar static pressure)

I stood by the car for a few minutes as you can see in the very quiet suburban late-evening (don't believe the time scale ) and was impressed by the noise level when on active cooling, especially how the AC can "take off" on a hot day.