Hi Tracy,
I would charge the car using AC (either 120V or 240V) for a couple of reasons:
- Most EVs have on-board chargers that designed to perfectly take care of the battery regardless of state of charge (SOC) or battery temperature, a DC-DC system would have to be designed to talk to the vehicle battery manage system (BMS) and regulate the charge.
- Isolated DC-DC converters are about 87% efficient, a little better than the combination of a solar inverter and car battery charger, but not significantly better to warrant all of the work and potential risk to the battery to implement a DC-DC system.
I would definitely charge during sunlight hours if you can to improve solar system efficiency and reduce wear and tear on your home batteries.
Brian
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Brian Jensen
brian@jensenenergyresearch.com------------------------------
Original Message:
Sent: 09-05-2022 09:01 AM
From: Tracy Dahl
Subject: EV's for Off Grid
I'm wondering if anyone is aware of a system for charging an electric vehicle for us off grid folks? Obviously I could just plug it in to a 120V AC outlet when we have adequate sun but that seems like a pretty inefficient and labor intensive way to go about it. I'm thinking of a something more along the lines of our solar deep well pump that directly converts DC to 3-phase AC for the long trip down the well bore. In the case of EV charging it needn't even be inverted to AC, just the correct voltage DC. The current flow would vary based on the resource but the voltage would remain constant, based on the requirement of the EV battery pack. For our use it wouldn't even need to be a large array, as we only drive once or twice a week. I think what I'm really talking about is a robust, programmable DC/DC converter. I don't think there is any technical barrier but the demand may be too low for anyone to develop the product - at the moment. Does anyone know of such a thing?
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Tracy Dahl
Polarsolar@hughes.net
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