Charge your EV with spare solar power?

Stuart Wright

AVForums Founder
Staff member
An idea I had a while back. A good idea, I think.
Other people will have had the same thought, but nobody, as far as I know, is doing it, yet.
I wonder why not.

 

Stuart Wright

AVForums Founder
Staff member
Surely if your plugged in during the day the car would be using solar power anyway? Not sure about night time other than using a power bank?
Well it depends. With a background usage of about 1kW (running pond pumps, fridge freezers, computers etc.), if we put the (2kW) kettle on, then we'll be using more power than our solar panels will be producing (they are peaking at 3kW while the sun is so high). So at this point, if the car is charging even on a sunny day, we'll be drawing power from the grid and paying for it.
What I'm suggesting is to vary the amount of power going to the car so that only the excess from the solar panels is being used. I.e. when the kettle isn't on. And when, on a cloudy day, the sun makes an appearance. So that instead of the excess power going to the grid, it's charging the car.
This idea wouldn't, of course, work when the solar panels aren't producing any power at all, like at night.
The Tesla Powerwall will be doing a similar thing, I'm sure. Only using excess solar power to charge up.
 

IronGiant

Moderator
You can already buy the kit to dump excess solar power into an immersion heater circuit, so it wouldn't be difficult to send it to a dedicated car charging circuit. It wouldn't take a huge amount of work to integrate it into a Pod Point if the demand was there The only problem as I see it is at what point do you (or a "smart" box) decide there won't be enough solar energy generated on a particular day and switch back to the grid?. I suppose you could plug it in on say a Friday night with an instruction to charge with solar energy only over the weekend and then switch to the grid Sunday night to top it up if the car is needed on Monday.

Edit: just watched the video and I see you have my comments pretty much covered :thumbsup:
 
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neilball

Well-known Member
Or just buy a Zappi charger with appropriate CTs and use their Eco mode.

The main issue with any of this is that most electric cars need a minimum of 6A to charge via AC, so if it’s a low solar day then there may not be enough output to charge your car.
 

IronGiant

Moderator
We have a 2kW or maybe 2.5kW panel and as we have a high background usage, unless we turned everything else off we'd never divert anything to the car with that system. So we do the rather clumsy, if we are exporting anything significant, plug the car in :)
 

radar2018

Standard Member
We do have a Zappy and currently have it set to 50% so if we get 700w it takes half from the PV and half from the grid, if it drops below the Zappy pauses until it reaches 700 again as it charges at the lowest point of 1.4k. The flexibility of the PHEV settings, if we get no sun it will charge from the grid at 3k for whatever time we want to drive.
I think to get the best use from this requires the car to be at home during the day, as last summer we were exporting an average of 15k per day, hence getting the car, so next summer it will be set to 100% and charge only with PV
 

IronGiant

Moderator
This again is a problem we have, as it's a commuter car, so rarely at home during the day other than at weekends. Presumably to get any benefit from Zappy you need to keep the car plugged in most of the time?
 

neilball

Well-known Member
Well unless you invest in fixed battery storage then you cannot use PV to charge at home when you are there...

However, with the current Olev grant it’s not a huge amount extra to get a Zappi over a “basic” home charger and then you have the flexibility to use it as suits you best (even if you only get the benefit of charging via PV at weekends). For example, I have an EV and a PHEV, and am trying to get a second chargepoint installed. As an all electric house with 100A single phase supply the DNO would not normally allow a 2nd 32A charger, but another feature of Zappi is to provide maximum load management. So in this case it can monitor the import power and restrict (or even shut off) the EV charge at from the Zappi is the total power draw is approaching 100A. In reality I will mostly charge overnight so there is no chance I’ll overload the supply, but the DNO requires the system to be foolproof in case a numpty buys my house later and tries to run everything at once.
 

IronGiant

Moderator
However, with the current Olev grant it’s not a huge amount extra to get a Zappi over a “basic” home charger
Obviously I would, if getting a new charger, but as it's no use to me with my weedy panels I woulldn't add one. :)

The power management issue is interesting as we only have a 60A main fuse on the incoming feed.
 

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