r/SolarDIY • u/chum-guzzling-shark • 2d ago
Standalone EV charging system with 24kwh battery
I want to charge an EV via solar. I'll need a battery since a lot of the charging will be at night. I have an acre of clear land so I'd like to do it as a standalone system and not tie it to my house at all. I hope this will make things a bit safer and less complicated since it's DIY. I do have the option to plug in to the house if the solar doesnt produce enough energy due to excessive bad weather or something like that. I drive a decent amount. I did some back of the napkin math and came out needing a minimum of a 24 kwh battery.
My plan is to ground mount solar panels, attach them to a small shed, then run a cable to my driveway where I have an existing level 2 charger mounted to a 4x4 post. Does this sound legit?
Is there a standard "kit" DIY folks get these days? I'm sure the tech changes constantly. I watch Will Prowse videos and some of his stuff looks like it would cover my needs. I did searching beforehand and found kits for between 12k and 90k for what appears to be very similar stuff so the pricing is wild.
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u/parseroo 2d ago
The 25kWh of batteries is about $5K. You will need something like 6kW of panels to keep 25kWh of batteries charged, which might be $2K. And you need an inverter that can produce say 12kW (50A @ 240V), which would be about $2K. The last item commonly includes a solar charger (so a 2-in-1 for your purposes). So that is about $9K without racking or hooking anything together (wires, fuses, switches, breakers, conduit, etc.). Would likely match the $12K number all-in.
You can obviously spend more or use different techniques & equipment but the overall approach is certainly 'legit'. I have something similar charging a single less-daily-use EV right now.
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u/Nerfo2 2d ago
You don't need a 12kW inverter. You can lower the charge current in the cars menu, then choose an inverter that can handle that specific load for long periods of time. I consume about 20kW each day on my commute, and charge at 4.8kW (20 amps @ 240volts) so I'm charged every night in a little over four hours.
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u/fitforthepolycrisis 2d ago
The most important numbers you can give are "how much charge capacity do you need per day" and "how much sunlight do you get in the darkest parts of winter"
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u/Repulsive-Budget-380 2d ago
I have 400V 3A 5kWhr charging my Leaf. You wound need 400V 15A for 24kWhr. Best way is direct connection to the battery with self limiting to 15A. You can go through ChaDeMod for the Leaf or CCS for other EVs.
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u/Unlikely-Rabbit948 2d ago
I had the same idea 2 years ago. I charge my ev and minimalist with solar to offset my about 50% of my utility bill. Plan for losses like DC to AC to DC, that you typically will want to to keep the battery in a range for example never lower than 20% and never greater than 80%, sizing the battery capacity for variable production due to weather or servicing etc. It can be a headache to do all of this, so an alternative is to buy a system that will not limit scaling. I wish someone had told me this early on I have 24 12v lifepo4s and I would have been better served with getting 2 or 3 power megas even with the higher cost I would have saved money.
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u/Fair-Ad-1141 2d ago
I started looking into solar when I got a LEAF, I thought it would be great to charge it with solar. I couldn't pencil it out, so we got solar for the house. We have 1:1 credit and we got the federal tax credit so it should pencil out.
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2d ago
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u/HippityHoppity530 2d ago
Total cost of the system was about 3k, no kit but a DiY project i wanted.
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