Specific EV Charger - why bother?

nicwood

Hi,

Not sure if this is too techie for here but it's worth a shot...
I get a company car and have just had a new Mercedes Hybrid delivered. I also get the benefit of free personal fuel which works out to cost about £100 a month in personal tax. As such it would technically cost me more to charge the car at home rather than just use the free fuel but as I have a 5kw PV system with a 7kw battery on the house I was interested in getting a smart charger for the car that could just charge it using any excess energy as a way of being a bit more environmentally friendly. I've been looking at the Zappi charger and have had quotes at just under £1k (including the current grant) to have the charger fitted.
What I can't quite work out in my head is whether I'd just be better off just using a solar immersion diverter (I currently have a Solic 200 fitted) with a plug socket fitted that I can plug the car into using the 13a charging cable... I'm unlikely to generate in excess of 2kw most of the time so I think that cable/setup would be sufficient to charge the car using any excess energy. The only thing it would lack is the ability to press a button and 'fast charge' at 7kw+ but I'm not really looking to do that.
Sorry it's a bit of a ramble but I'd be interested in any thoughts!

Thanks,
Nic

NigeWick

I've got a Mk1 Zappi and it can be set use a less than 2kW to charge the car. I think the actual number is 1.4KW.

Petriix

You can't just vary the input current on a standard socket and expect anything plugged into it to work. That only works for dumb resistive loads (like an immersion heater or maybe a bar fire etc.).

You are not going to recoup the £1000 cost of the Zappi installation so you'd be better off just using the 13amp 'granny' charger when it's sunny enough for you to feel like it's worth it.

nicwood

Isn't the point of the Zappi (and other smart chargers) that it does vary the input current based on the excess energy that's available?
From my limited understanding, most given batteries can be charged at different rates using depending on the supply from the charger i.e. the same mobile phone can be charged via a fast charger or via a laptop USB socket at different rates... 
What I'm really looking at is whether the Zappi does much more than something like a solar immersion diverter other than it's ability to run at higher loads. Both of them will look at how much excess energy is being fed back to the grid and feed as close to that amount as they can to whatever is plugged into them. It seems that the only issue would be that the immersion diverter would be limited to a couple of KW whereas the Zappi could obviously run at 7kw+. 

Dave_Fowler

nicwood said:

Isn't the point of the Zappi (and other smart chargers) that it does vary the input current based on the excess energy that's available?
From my limited understanding, most given batteries can be charged at different rates using depending on the supply from the charger i.e. the same mobile phone can be charged via a fast charger or via a laptop USB socket at different rates... 
What I'm really looking at is whether the Zappi does much more than something like a solar immersion diverter other than it's ability to run at higher loads. Both of them will look at how much excess energy is being fed back to the grid and feed as close to that amount as they can to whatever is plugged into them. It seems that the only issue would be that the immersion diverter would be limited to a couple of KW whereas the Zappi could obviously run at 7kw+. 

The Zappi charger can indeed change the output to match the excess solar power.  However it does it in a completely different way from a solar immersion diverter.  The immersion diverter reduces the power by rapidly swiching the 3kW power to the immersion on and off to provide an average power to match the solar excess, the car charging system would have kittens if you tried to reduce the power in this manner.

The specification of the car charging system allows for a fully variable rate and this is done by a control signal between the car and the charger.  The electicity is supplied constantly and it is the car charger that is told to vary the rate by the Zappi.

In other words, the immersion heater control is done by the Immersun (or whatever make is used), but the car charging control is done at the car charger under instructions from the Zappi.

Dave F

nicwood

Ah ok, cheers Dave. That's the kind of information I was after as I wasn't sure which element actually controlled it with regards to the car charging.