use of solar panel at spoiler on roof?

[bradford]

how useful is the solar panel's charging? does it's 'trickle' help the main batteries, or is it somehow a boost for the accessories (like wipers, radio, heater...)?

thanks, Tom

[garygid]

Apparently charges only the 12v battery, not the main (traction) battery.

[palmermd]

Apparently charges only the 12v battery, not the main (traction) battery.

But that keeps you from using the main traction battery to charge the 12v battery when you are going down the road with the radio on and the turn blinkers and brake lights "blaring".

[garygid]

If the panel even supplies 1 amp (12 watts) to the 12v system, and accessories take 10 to 100 amps, it does not help all that much while driving.

Likewise, parking at night (or in a garage) will not really help much either.

So, long outdoor parking would seem to be the "only" benefit?

Note: If one arrives at work with a fully-charged 12v battery (which would be the usual case), parking in the sun for 8 hours will be of little (or no) benefit.

[palmermd]

If the panel even supplies 1 amp (12 watts) to the 12v system, and accessories take 10 to 100 amps, it does not help all that much while driving.

What in the world do you have on your car that takes 100 amps? Lights (headlights, tailights, blinkers) are LED, and the radio/navigation system should be low power. Climate control will be run from the main pack. Where is all the other power going? Granted the panel may only put out 15-20 watts, but that is a large percentage of the power required. I suspect about 25-50%.

[garygid]

The seat, steering wheel, and cabin heating perhaps?

[MikeBoxwell]

It's a really tiny panel. And it is amorphous, which means it is pretty inefficient (but cheap). At a guess, the solar panel can generate a peak of around 5-6 watts, which would work to trickle charge your mobile phone or sat nav system, but probably no more than that.

Back in the early 1990s, Audi put a similarly sized solar panel onto the roof of the Audi A8. They used it to power some tiny fans to extract hot air from the car in the summer. The idea was that when you got back into the car on a really hot day, it wouldn't feel like a cook-house. Apparently it worked pretty well for that. I wouldn't know, the United Kingdom never has a summer.

Actually, I lie, the United Kingdom did have a summer last year. I missed it as I was combing my hair at the time and the year before I was brushing my teeth.

[Bicster]

The seat, steering wheel, and cabin heating perhaps?

Those things will surely use the traction battery. They will be more efficient at higher voltages. Not to mention, they can be powered via the charge port.

[EVDRIVER]

The seat, steering wheel, and cabin heating perhaps?

Gary, I must give you an F grade since you are an engineer. The consumption is never going to get even remotely that high on the 12V system. The heat will run off the pack and be the biggest load and pull about 16-20A, the power steering should be electric and on the 12V side pulling only a few amps from the pack side via the DC/DC and the seat will be about 5 amps max on the pack side, for power seats unless heated which would be silly. On my EV with every accessory on and the heater and including EPS I could not pull 12A off the pack side of a 240 pack, let alone a 300V plus pack. Even normal headlights would pull less than 1A off the pack. The way to load the 12V system is with aftermarket stereo amps.

The solar cell is almost pointless except for long term parking as it will trickle the 12V battery which controls the contactors for the main pack. If the 12V battery dies and you pack is charged you could be out of luck as the DC/DC is usually off when the key is off and the 12V is requires to activate the contactor to the DC/DC. If you leave a LED marker light on while parking for safety the solar panel would easily cover that.

[garygid]

Indeed.
It depends upon which things are run off the 12v system.

The seat heaters and steering wheel heater will surely be 12v for safety.

The cabin heating and the air-conditioning are big unknowns (at least to me).

The 10 to 100 amp (12v system) range was intended to cover ... a wide range of "LED-lights" configurations.

The Prius headlights are not LED, and the DC-to-DC there is good for about 150 amps (12v), I believe.