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Solar cell roofs for EV cars.

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BrianHG:
Seriously, will this even make a realistic dent in drive distance of a full size EV?

Maybe an extra few Km a day if you park outside in an unshaded area (ie away from buildings which create a moving shadow during the day.) on a 0 cloud day in the summer.

station240:
Really only of use for keeping the 12V battery charged. Vampire Drain is a big issue with EVs, as there is no way to switch everything off, electronics to maintain the battery and other systems does add up.
The usual setup is to have the HV battery supply power and charge via a DC-DC converter, which then slowly drains the big battery.

1-2kW of solar cells won't do anything useful to charge the main battery, especially in hot climates where parking in the sun means wasting power to cool the now hot car/battery. 

rrinker:
 But then, where is the best place to park an EV? In the shade created by the roof over the whole parking area to hold the solar panels that run the chargers.....

sokoloff:
Being generous, let's assume that the solar panels could be about 1 square meter which could generously generate 250W for 8 hours. That's 2 kWh per day or about a 1/2 mile / 1 kilometer of driving, assuming no further losses in the charging circuits.

It's much more gimmick, "statement", or decoration than practical improvement to the car. You would still be better off economically parking your car in the garage for the day.

tszaboo:

--- Quote from: station240 on February 14, 2018, 10:04:42 am ---Really only of use for keeping the 12V battery charged. Vampire Drain is a big issue with EVs, as there is no way to switch everything off, electronics to maintain the battery and other systems does add up.
The usual setup is to have the HV battery supply power and charge via a DC-DC converter, which then slowly drains the big battery.

1-2kW of solar cells won't do anything useful to charge the main battery, especially in hot climates where parking in the sun means wasting power to cool the now hot car/battery.

--- End quote ---
In my 3rd gen Prius, the DC-DC only works when the car is running. If you leave the light on, the 12V might discharge completely, while the traction battery is still fully charged. That is personal experience  :-[.

It also has a solar panel (sol premium package). I wouldnt have payed more for this, but I bought used, and it comes with the sunroof, which is nice.
So the solar panel in that one does not charge the battery, because they had EMI problems with the radio.  It runs the AC unit's fan, and that is very very useful. On a hot, very sunny Belgian day (haha, good joke) it just lowers the temperature inside the car.
I guess people dont realize, that plug-in and electric cars could have their AC or heater operational, when the battery is charged, so even in a cold winter, you can sit into a warm car in the morning.

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