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Discussion Starter #1
I have a Leaf Tekna 30kWH with a 6.6kW on-board charger and a 5kW home solar panel installation.

There is now smart technology which can be connected to the Solar Inverter which can harvest just the power which would have been exported to the grid from the solar panels, when available, and push this to a household 13A socket (to be used to heat water via an immersion heater, for example, or charge a battery for storage) on the basis that this energy is effectively "free" (as the rebate payments for solar energy are based upon the power generated, not the power exported to the grid).

If I were to connect the Leaf to such a socket, the power would fluctuate depending on the household demand and solar power output so whilst the voltage would remain constant at 240V, the power available might sometimes be 5kW or Zero (when there is no sun) or somewhere in between.

My question is whether the car's charging system would be able to handle this power fluctuation or whether it would treat a lack of power as a disconnection and then not resume charging when power once again became available.

Also, would the fluctuations in power being supplied to the car damage the charging system or batteries?

Any advice or opinions would be greatly appreciated!
 

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Have you seen the Zappi charger? Sounds like its exactly what you need.
 

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If I were to connect the Leaf to such a socket, the power would fluctuate depending on the household demand and solar power output so whilst the voltage would remain constant at 240V, the power available might sometimes be 5kW or Zero (when there is no sun) or somewhere in between.

My question is whether the car's charging system would be able to handle this power fluctuation or whether it would treat a lack of power as a disconnection and then not resume charging when power once again became available.

Also, would the fluctuations in power being supplied to the car damage the charging system or batteries?
The way the "solar diverters" for immersion heaters work is usually by varying the supply voltage to the immersion element, which is fine for a resistive load. But it would play merry hell with an EV charger.

It's not obvious to me how the output voltage could be kept at 240V and yet restrict the available power without using "time slicing" (PWM) - effectively switching the supply on and off rapidly based on the load, to get the power output to the desired point. Something like the Zappi can communicate with the car's charger to tell it (with its switched mode power supply) to restrict how much power it pulls to the desired level, if necessary several times per second - but I can't see how that would work with a plain 3 pin socket as the output. I'd be a little wary...
 

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I understand the wish to maximise your solar but I just use the granny charger from an outdoor socket. The cost will be negligible to make up any shortfall over and above your PV generation.
 

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Discussion Starter #9
Dan, that's exactly the issue. My new Leaf came with free installation of a 3kw pod point (which I upgraded to a 7kw pod because the car has a 6.6kw charger). So if I get a Zappi, I will have to pay £495 for it with no government grant, which probably makes it uneconomic. If I'd known about the Zappi before I bought the car, I would have got that instead of the pod point!
 

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Dan, that's exactly the issue. My new Leaf came with free installation of a 3kw pod point (which I upgraded to a 7kw pod because the car has a 6.6kw charger). So if I get a Zappi, I will have to pay £495 for it with no government grant, which probably makes it uneconomic. If I'd known about the Zappi before I bought the car, I would have got that instead of the pod point!
Yes £495+fitting would take a while to recoup over just plugging in on a reasonably sunny day.

If you have a hot water tank with immersion heater then a solar diverter (e.g. an immersun (now called eddi)) is a good way of using spare juice.

Economy7 is also worth considering if you haven't already got it.
 

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Solar can make a contribution, but it is hard to justify it financially compared to using E7 overnight. It is even harder to justify paying money for any device that enables it, especially as the returns will be low as the charging current is generally low. It also has the fundamental problem that the sun shines during the day when you want to use the car. You also need to ask yourself if you are prepared not to charge the car on the basis that you might get sun tomorrow - I'd rather have it at 100% on the drive. Add to that for half the year, you can forget it completely.

E7 and solar PV go together really well. Charge the car overnight on E7 (and move washing machines, dishwashers etc too), and use the solar PV to heat water using a diverter and heat a cheap radiator if it has a second channel.
 

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Discussion Starter #12
Thanks, Guys! All very valid points. We don't have E7 but I think that's the way to go for normal charging at night. And maybe just the odd daytime top up on a sunny day using my pod and hoping to get some energy from the PV.
 

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We don't have E7 but I think that's the way to go for normal charging at night. And maybe just the odd daytime top up on a sunny day using my pod and hoping to get some energy from the PV.
Exactly what I do. If you can sneak a PV charge then do, otherwise, use the PV to offset the higher unit charge for peak time units on E7.
 

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With the pod point chargers you can downgrade them using the switches inside. For instance if you are hitting 5kW of solar or thereabouts on a sunny day then if you were say charging at 3.6kW or 3.1kW you would be charging using a higher percentage of solar than if you took the full 6.6kW. You could also have a battery storage unit that could take the excess power (say 1kW whilst on charge in full sun or more if not at home) and provide you with a longer charge period as you go into the evening or overnight.
 

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With the pod point chargers you can downgrade them using the switches inside. For instance if you are hitting 5kW of solar or thereabouts on a sunny day then if you were say charging at 3.6kW or 3.1kW you would be charging using a higher percentage of solar than if you took the full 6.6kW. You could also have a battery storage unit that could take the excess power (say 1kW whilst on charge in full sun or more if not at home) and provide you with a longer charge period as you go into the evening or overnight.
Presume you can't upgrade a 3.6kW PodPoint charger?!

You can also obviously use the brick charger - e.g. I'm getting about 2.2kW from the solar as we speak so could almost top up for free as that draws about 2.4kW.
 

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Discussion Starter #17
Not sure if you can upgrade a pod point charger. When I ordered mine, there was an option to choose either 3.6kw or 7kw. I'm assuming that the cable and circuit breaker will be different for the higher power so you would have to swap all the components.

I could use the 13A charger to limit the charge rate but that sort of defeats the purpose of having a tethered pod point plus it will take 10 hours to charge my 30kwh Leaf.

It would be clever if the car had a built-in option to set the maximum charging rate so you could select 3kw or 6kw on the dashboard.
 

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It would be clever if the car had a built-in option to set the maximum charging rate so you could select 3kw or 6kw on the dashboard.
Not sure why they have not already done this on the Leaf, you could also have a bluetooth dongle (for people with solar PV) that attaches to the mains supply to the house that you could program different actions from within the car when charging (working in much the same way as a zappi unit), it'd only cost a few quid for a current sensor and bluetooth coms unit and something I would definitely buy.
 

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Have a look at OpenEVSE and openenergymonitor. OEM sell the openEVSE charger in the UK. They can do what you need. As to any damage to batteries, regen braking doesn't seem to harm them, and that can be very "spiky" charging!
 
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