Solar trickle chargers - Fuel Economy, Hypermiling, EcoModding News and Forum

JJW · 06-09-2008, 04:12 PM

Has anyone tried running a solar panel to supplement the vehicle charging system, and were there any gains worth the trouble? It seems any load removed from the engine would be a good thing, but I'm thinking the 4 watts (optimistic) that most car trickle charge panels put out might be a drop in the ocean. I was thinking specifically of the VW panels that can be had for free if you know where to look..

MetroMPG · 06-09-2008, 05:02 PM

On a car which isn't driven regularly, a solar panel save more fuel than on a daily driver.

An infrequently used battery will self-discharge over time (approx 1% per day is a figure I've seen thrown around), and has to be recharged via the alternator each time it's started up. So a panel that can keep that battery topped up will help a little bit.

But on a daily driver, you're right in thinking the small panels will amount to a drop in the ocean.

getnpsi · 06-09-2008, 06:09 PM

I would use them around the house to power small fans to circulate air. I was skimming thru threads in the around the house section and was pickin up a lot of ideas. If i stop modding the car and mod the house i would probably save more in the long run.

vtec-e · 06-09-2008, 10:13 PM

I have a little 1.5 amp solar charger mounted in my rear window and i have to say i think it has made a small (positive) difference in my mpg. I reckon around 1 or 2 mpg but its hard to tell. I cant use a scanguage so i am flying blind there. The car starts much quicker though. It was never slow to start but now it fires instantly. I got it cheap so it's doing no harm anyway.

ollie

Jason · 06-09-2008, 10:35 PM

Quote:

Originally Posted by JJW

I was thinking specifically of the VW panels that can be had for free if you know where to look..

What are these VW panels you are talking about?

Quote:

Originally Posted by vtec-e

I have a little 1.5 amp solar charger mounted in my rear window

How do you have this wired in the vehicle?

Thanks...

JJW · 06-10-2008, 08:29 AM

Well, the VW panels are getting harder to find. VW ships their cars to dealers with a solar panel plugged into the lighter socket or OBD-II port. The idea is that the panel keeps the battery from going flat which causes problems with some of the electrical systems in the car. The dealer is supposed to remove the panels and send them back to VW for reuse, but some dealers were a bit lax and would have piles of the panels collecting dust. About two years ago, if you went to any VW dealer and asked nicely they would hand you as many as you could carry. Now VW seems to have caught on, and the dealers are sending them back to VW for the most part. I haven't scored a free one in awhile. They are about the size of a sheet of paper, and put out about 3 watts @ 12V. They were suction cupped to the windshield.

MetroMPG · 06-10-2008, 09:28 AM

I got one about a year ago. I dropped into a dealership, found a parts guy and essentially said, "I heard this rumour..." and repeated JJW's story. The guy confirmed, said "hold on" and went and got me one.

I imagine if you knew someone at a dealership you could have had a steady supply. (The number of them that were on eBay at one point suggests that some people were in just that situation...)

vtec-e · 06-11-2008, 03:02 PM

Hi jason, i put the panel in the top left side of the rear window and ran the lead under the interior panels toward the front of the car. They just pushed in real easy. Then i just let it hang out under the dash and over to the power point that used to be a cigarette lighter. Then i rewired the lighter plug to be always on. I just ran a wire through the bulkhead to the battery and fused it. Works a treat. The hardest part was rewiring the plug to be always on.

ollie

JohnnyGrey · 06-11-2008, 03:14 PM

I have one permanently installed in the rear deck of my sister's car. She only drives it when she's back from college, every 2-3 weeks, and the battery tends to go flat after a while. This keeps it topped off. However, I do not believe that these are helpful in a FE context. The watt or two they may relieve the alternator from, they nullify by their own weight.

Ryland · 06-11-2008, 03:34 PM

If the vehicle sits for a week or more at a time without being used then it will for sure help make it start easier and once it starts the engine will have less of a load on it because the battery is nearly full (aside from the amount the starter used), lead acid batteries also last longer if they spend more of their life charged, so the biggest change you might see is that your battery life could go from lasting 3-5 years to lasting 10-15.