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Charging EV with Solar...

  • 13-10-2021 11:02pm
    Registered Users Posts: 4,978 ✭✭✭

    Just a thought that popped into my head...

    Is it possible to set up a system that generates power from the sun, store it in a battery and have that battery set up to a charger for an EV?

    Apologies of this is a stupid question


  • Registered Users Posts: 2,224 ✭✭✭bullit_dodger

    Not stupid - and yes it would work, but it's not a "good" solution. The problem with doing that is that you lose 10-15% putting energy into the battery in the house, and then create wear and tear on the house battery as you charge the EV.

    Ideally what you would want to do is charge the EV directly with the electricity generated from the panels straight into the EV. The obvious drawback is that you have to have the car there at the house during the day, unless it's high summer...... in which case you might get some charge into it before you leave for work and again when you come home from work (depending on your panel orientation)

  • Moderators, Sports Moderators Posts: 17,888 Mod ✭✭✭✭slave1

    Battery losses in/out is closer to 20% so as pointed out it’s more efficient to charge direct from solar, on a good full sun day I can get 20kWh into my EV if home and sitting on driveway

  • Registered Users Posts: 2,224 ✭✭✭bullit_dodger

    Actually that's also a good point slave that we should mention. House batteries are (usually) in the region of ~ 5Kwhr. Car battery capacity are in about the 50-60Kwhr.....depends on the car of course. But ballpark it, if you used a fully charged house battery to charge your car, it will charge probably just move the needle on the dial of a car 10% or abouts.

    Of course you could build yourself some kick ass house storage unit of 20+Kwhr, and that would work to give you ~35%, but your building ever elaborate solutions rather than just charging the car off the solar panels directly. Sure, with WFH ending many cars will be not at the house during the day, but there is Sat/Sunday?

    Again, not a stupid question. On the surface it would seem like a good thing to do - but the reality is that there's good engineering reasons why not to.

  • Registered Users Posts: 9,955 ✭✭✭the_amazing_raisin

    As others have mentioned, the best approach is to charge the car directly using solar rather than try to store it in a house battery

    There's chargers available now that will do this, they all work in a similar way. They use a current sensor around either the mains feed to your house or the feed from your solar inverter (or both) to sense when your house is generating more electricity than it's demanding

    What often happens is that you'll start exporting power to the grid, and the current reading on the grid sensor will go negative because it's flowing out of your house

    The EV charger will then see this and start charging the EV at the same rate so as to put that exported energy to use

    Of course, the EV needs to be connected and have space for more charge for this to work, however it seems to work well for a lot of people

    It's also worth noting that EVs require a minimum of 1.4kW to begin charging. So if you have a small array then it's likely you'll be exporting more than using to charge the EV

  • Registered Users Posts: 1,925 ✭✭✭jkforde

    my experience is that the Zappi and its different modes works flawlessly with my Nissan Leaf (2012), the Zappi has some known issues with other makes so should be easy to find out from MyEnergi. the Zappi talks to the grid sensor and in Eco+ mode only uses surplus solar energy once it reaches a stable min. 1.4kW. in Eco mode it'll maintain a minimum 1.4kW charge with or without solar surplus. brilliant system.

    🌦️ 6.7kwp, 45°, SSW, mid-Galway 🌦️

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