Solar panel to offset alternator load

[Cobb]

Maybe you should do a bit more planning before pulling the trigger? When I use to precharge my hybrid battery I also put the starter battery on charge. Someone referred to it as a mini phev mod. I did it to top off the starter battery to get max mpg.

My current setup was used with parts from around the house. The batteries were from an electric wheelchair I currently do not use, the charger was for my father to use since its soo light weight. The inverter was to use during power failures, but we got a generator now. The mean well power supply was to repair a mini fridge. Then I hacked up an extension cord from the dollar store for wire and used the cord from a bad power strip to plug it into the inverter. The only thing I purchased was the light switch for 70 cents and the zip ties. Hell, the lumber was in my yard and the fan was from an old pc I put a better one in.

Ive made a tank of gas last 2 weeks now.

I think PHack has a small solar panel on his hood. Not sure if it helps to top off the starter battery or if it serves another purpose. I got a few myself 5,10, 12 and a 15 watt panel. I had considered wiring 2 panels of the same size in series to ensure I have enough voltage in indirect sun light to be useful.

[oil pan 4]

Originally Posted by oldtamiyaphile

When I turn the headlights (in round figures let's call that 100W, it has LED's where possible) on in my Jeep at idle, my LPH jumps up by 0.3. Since my average speed is 50km/h that's 0.6l per 100km. That's nearly 1MPG.

In a city driven car like my T5 with an AVG speed of 27km/h, that would be ~1.6MPG per 100W.

That's why I said "not alternator watts".
100 alternator watts could be as much as 200 to 300 or more accessory watts since the alternator is so inefficient.

[oil pan 4]

Originally Posted by silvermazda

oilpan4, do you think it will work in reverse? Would loading 100W burn as much gas as removing it?

Not really since electrical load is pretty light. That figure was for accessory load removal, such as power steering delete, vacuum pump delete, belt driven water pump delete.

One of these days when working on air compressors I need to quantify how much power it takes just to turn a belt on and idler pulley. I have read that it can be up to 1hp but I really doubt that.

[silvermazda]

Originally Posted by oil pan 4

That's why I said "not alternator watts".

So I calculated your .1MPG/100W of alt load and I got .3mpg then your 2x from the type of car and I got .6mpg. That's too low for a 200 buck investment.

And to Cobb, that's why I was going to buy the 100W instead of accumulate cheap panels.

ANd to the peltier guys, I was going the cheap route and buying the TEC's on amazon for $12/4 units 40x40mm or $25/10units. Yes they will make less. Like closer to 2-4W, but its less of an investment.

Testing:
I'll run 30 miles and fill up a tank to see how much my cabin fan on High (~12amps or 144W) eats in extra gas.

[oil pan 4]

Originally Posted by silvermazda

So I calculated your .1MPG/100W of alt load and I got .3mpg then your 2x from the type of car and I got .6mpg. That's too low for a 200 buck investment.

Did you use realistic numbers to represent accessory load or did you use way over optimistic numbers that ecomodder supplies with the calculator?
Because if you use the way over optimistic numbers, that is what I would expect you to get.

[silvermazda]

I used the units you stated in page 2.

[HaroldFerrier]

Originally Posted by silvermazda

I was interesting in solar panels some time ago, but the 1-5Watt ones never peaked my interest as 5w divided by 12V equals about 1/2 an amp and they were costly 20-50 dollars a panel. No point.

I recently found about peltier coolers, but those dont generate much. I though about hooking up 10 to the top of the radiator, enough heat (~180*F), though I am not sure if it will work with out a heat sink on the other side, will it?

Recently I found a flexible 100W solar panel on amazon for $200 bucks, almost twice the cost of the conventional flat ones. I need it flexible to place it on the trunk of the car, plus its only a few MM thick. Bonus! and not aero penalties. 100W is about 8amps. I am unsure how many my car eats, but I estimate a good 10. And I've been reading the constant drain/no alternator thread, so I am guessing this will be a 10% improvement/ 3mpg increase. What do you guys think?

Okay calculated that if mpg goes from 30 to 33. It would take 16.6K miles to pay back the 200 bucks. Or 3 yrs. (by the way, wasn't there a calc around here that would calculate when a mod would break even?)

Sounds very effective.. Well I will try out the method and hope for some fine results..

[serialk11r]

Originally Posted by silvermazda

ANd to the peltier guys, I was going the cheap route and buying the TEC's on amazon for $12/4 units 40x40mm or $25/10units. Yes they will make less. Like closer to 2-4W, but its less of an investment.

If you can, try sticking these on the muffler. Mufflers aren't as hot as the rest of the exhaust system components and don't conduct as much heat so I would think they'd land the TEC in about the right operating temp. Much better source of heat than the sun. Extruded aluminum heatsinks are super cheap, just chop them up and stick them on the TECs.

[Ecky]

I have a much smaller panel installed in my Insight, and I feel it's next to useless. Behind very slightly tinted glass it's almost never putting out enough voltage to charge the battery, and it's not waterproof. If I put one on the outside it would ruin the excellent aerodynamics and probably hurt more than it helps. I'm planning to install a small battery maintainer which I'll run in the evenings off grid power, to help with short trips, and a solar panel wouldn't help with night drives anyway, which most of my longer trips involve. It doesn't begin to charge the battery until it drops below ~12.5v, which means there's probably a very large amount of unused capacity.

In my case, grid charging the 12v and, when it's time for a replacement, a larger battery, would probably net the most improvement.