use of solar panel at spoiler on roof?

[johnr]

The solar panel spoiler serves a very important purpose: "Hey, look - I've got a solar panel on my car! Too bad your car doesn't, LOL"

If it powered a small fan to keep the interior of the car from getting too hot while parked in the sun, like the solar panel on the Prius, then that would be a very useful and practical feature.

[mitch672]

On my Gen 2 Prius, their was a "resitive" heater than ran of the HV until the engine warmed up, on my Gen 3 Prius, they don't even have the restive heater any longer (engine waste heat only). The Air Conditioer does indeed run off the HV battery on the Prius, which is one of the reasons the engine starts more often (to recharge the HV battery at times)

I would fully expect the Leafs resistive heater, and Air Conditining compresser will run off the HV as well. Pretty much everything else I would expect to run off the 12V system.

[AndyH]

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

Here's a real world example of a small solar panel used to maintain a 12V battery during storage. This is what VW dealers use for cars sitting on the lot.
http://cgi.ebay.com/ebaymotors/VW-Solar ... 500wt_1122

Max: 18.8V
Max: 170mA
Max: 3.2W

Andy

[garygid]

This 12v charger would need a cig. lighter or "power" port that is "always on".

Do modern cars have this?
I thought most were "switched" now.

What do the LEAF "ports" do?

[AndyH]

Dunno Gary. I've never seen one that' switched. I only presented the VW panel because it's roughly the size of the Leaf panel. Not a lot of power.

[MikeBoxwell]

The panel is so small on the LEAF that it would maintain the 12v battery, but probably would not even charge it up. Assuming it is a 100Ah 12v battery pack and the car was parked up and not used, you could expect the pack to lose around 5-10% of its charge every month - so lets say that equates to around 90 watts.

A 6 watt panel (assuming that is what it is), flat on the roof of the car, would provide around 36 watt-hours of energy per day if the car was parked in sunlight, assuming it is a Californian summer, or around 4 watt-hours of energy per day if the car was parked in sunlight, assuming it is a British winter.

So in a Californian summer, it would take around one month to recharge your 12v battery pack from flat (assuming an 80% depth of discharge), whilst in the depths of winter in the United Kingdom, the solar panel would only just maintain the existing charge in the battery.

What you can do with 36 watt-hours per day of energy in a car (Californian summer)
There is some guesswork going on here, but this is what you can do with the 36 watt-hours of energy you can generate in a Californian summer with the built in panel:

Constantly run two small extractor fans inside the car to extract the heat from the cabin when the car is left unattended
Recharge a mobile phone, an iPod and a hand-held sat nav system all at the same time
Run the in-car sat nav system for 1½ hours
Switch on the headlights for around 15 minutes
Listen to the radio for around 45 minutes, or play a CD for around 25-30 minutes
Run the heating on max for around 50 seconds
Run the air conditioning on max for around 25 seconds

What you can do with 4 watt-hours per day of energy in a car (English winter)
Just about charge up a mobile phone if you leave it plugged in all day and don't use it
Half-charge a hand-held sat nav system (again, if you leave it plugged in all day and don't use it)
Run the heating on max for around 5.5 seconds


A few years back, my cigarette lighter packed up in my car. Because I relied on the cigarette lighter socket to power my hand-held sat nav system and I was in a hurry, I quickly rigged up a 12 watt solar panel I had lying around with a car cigarette lighter adaptor that I also had lying around, and put it on the rear parcel shelf. It worked a treat for keeping my mobile phone and sat nav running.

[planet4ever]

Since the OP asked about charging the "main batteries", you should have added one other item to your excellent list:

California summer: Drive the car 25 yards or so.
English winter: Drive the car 2 or 3 meters.

[MikeBoxwell]

Since the OP asked about charging the "main batteries", you should have added one other item to your excellent list:

California summer: Drive the car 25 yards or so.
English winter: Drive the car 2 or 3 meters.

OK. I've worked it out - 665 feet and 3 inches for a Californian summer, 73 feet and 10 inches for an English winter (assuming 5 miles per kWh and 30% system losses).

[garygid]

In older cars the cig. lighter was always ON, connected through a fuse to the battery.

In newer cars, the cig. lighter (and / or "power port") are not powered when the car is turned off, so it would seem that they go through a relay in addition to the fuse.

For example, a "handheld" GPS, plugged into one of these "switched" 12v "power ports", will ... lose external power when the car is switched off.

Since they are not "connected" to the battery when the car is OFF, they will not work for maintaining the 12v battery charge level.

Also, in the EV, do not expect a heavy 100-amp 12v battery. More likely it will be a much lighter, smaller battery, something like 20 to 30 amp-hours (240 to 360 Wh).

Typically, immediately after driving the car, this EV 12v battery will be "full", but have a very small "load", to keep the RFID-detection electronics alive, if nothing else.

[Nubo]

... 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.

I would suspect that the battery management system would leave some amount of "headroom" on the service battery. For example, say they set a target where the system attempts to keep the service battery at 70% charged at all times. This would provide a "reservoir" to let you get some benefit from the panel. Whatever extra you manage to feed to the service battery equates to a period of driving where the traction pack is not called upon to "feed" the service battery.

That said, yes it's a small amount. Over the course of a year it probably wouldn't amount to a day's driving. Over the life of the car it might just pay for itself. But it should start good conversations.