The ideal design would be to take the solar panel DC output and use it to charge the electric vehicle's DC battery directly. But there are several reasons why today's electric vehicles cannot do this.

Strictly speaking, the charger is actually in the electric car. The plug, cord, and box that attaches to the wall is called the Electric Vehicle Service Equipment (EVSE) or "Charging Station." The EVSE supplies an AC voltage (not DC) to the car's charging socket. It contains complex circuitry to regulate the charging process.

The EVSE may be just a small portable unit, with a cord with the J1772 plug for the car on one end and a standard plug for an AC outlet on the other end (either a 110V or 220V outlet or both).

There are great differences between the voltages and currents of solar panels and electric cars.

A usable solar panel outputs 15V to 17V at about 8 amps (120 Watts). A typical plug-in EV expects input from 110V at 10-12 amps (Level 1 charging), 240V at 30 amps (Level 2), up to 500V at 30 amps (Level 3 or DC Fast Charge).

So we must have a DC/AC inverter to convert the solar panel's low-voltage DC to higher voltage AC.

We also need batteries to store the daytime solar energy for use at anytime to charge the car. So we will use the solar panels to charge the batteries, then connect the batteries with the inverter to drive the EVSE.

A 2ft. by 5ft. solar panel outputs 15V to 17V at about 8 amps (120 Watts) and costs about $500..

We are considering 12V, deep-cycle, gel cell (sealed, maintenance free) batteries

A 100AH (amp-hours) battery costs about $225. A 32AH battery costs about $75.

Gel cell batteries from China are half the price, with minimum orders of 20 pcs.

The gel cells are much more expensive than lead-acid (standard car) batteries, but they are designed for the repeated deep discharging needed for the EV.

A 12V to 110V inverter is probably the most common one available, widely used to convert the car battery from 12v to 120V.

The inverter from the batteries can feed a standard duplex receptacle (NEMA 5-15).

Each solar panel produces 120W (15 volts x 8 amps). When converted to 120V, we get less than one amp! (120 volts x 1 amp = 120Watts). To have as much amperage as a typical 15A, 120V circuit, we would need 15 solar panels. At $500/panel, this would cost $7500. Fifteen gel cell batteries would add another $2000 or so. Maybe a solar powered EV charger is impractical with today's technology.

Solar panels only make sense if the generated power is used immediately and continuously - fed back into the electrical grid to spin the meter backwards! Storing energy in batteries, which can take only so much and then the solar energy is lost, is impractical.

The EVSE comes with a J1772 plug to connect to the EV.

For level 1 charging, we can just use the typical 110/120V cable that comes with the electric car (e.g., the Nissan LEAF).

If we use three 12V 100AH batteries ($225 ea.), we could generate about 15A for 20 hours at 12V. But this is only 1.5A at 120V! This is about one-tenth of the 3.5 kWH total needed to charge the LEAF completely in 15 hours or so.

For level 2 charging, we have a Schneider Electric EV charger that expects 220V at 30 amps input.

Again, with three 12V 100AH batteries ($225 ea.), we could generate about 30A for 10 hours at 240V. We could also buy an AeroVironment portable TurboCord for $650, which does both 120 and 240V charging and plugs into standard electric outlets.

We are considering a Nissan LEAF. It has a 24 kWH battery.

The standard LEAF comes with a 3.3 kW charger. A 6.6 kW charger is also available.

It will be better to install solar panels on the roof of 77 Huron where the solar electricity will get fed back into the grid.

We could still put a small array of solar on the garage roof, as long as we can feed it back into the grid from there. No batteries needed, just the inverter.

What goes on top of the garage is a standard solar panel array attached to the electrical grid. Being off the grid, as I originally imagined, makes no sense. Generated solar energy would be wasted whenever the batteries are full.

If we used just three panels as above, they would generate about 3 kWH each day. We average only 15 miles of driving per day or about 5 kWH. So we should install 5 or 6 panels to claim that my car is running entirely off solar power from the panels on the garage.