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NoCO2 02-09-2008 03:36 PM

Removing components off engine belt.
I had an idea earlier today and I just want to see your opinions on the feasibility of this mod and what kind of advantages I might see from it.

I am thinking of buying a solar panel and mounting it on either the roof or trunk of my car to replace my alternator as the source of power to recharge the battery. My main question is, what kind of improvements in engine efficiency would I see from removing that off the belt, but keeping the A/C and Heat (I can't do that much surgery). The other question is, how effective do you think it would be at charging the battery and how long do you think the battery would last if a solar panel was connected. That last question actually builds on this one though, how strong of a solar panel would I need to get? Just a 12V one or is there a certain Amperage I should look for?

I am just trying to get an idea here of how doable this is, nothing really set in stone or committed to it yet. Any advice/help/information that you guys can give me would be very helpful.


SVOboy 02-09-2008 05:09 PM

I would poke around and find darin's thread about alternator removal since he deals with most of the issues. You should get a deep cycle battery because solar won't likely be an end all replacement, but it will work to trickle charge a bit.

Have you thought about removing the power steering (if you have it)? I don't have that or a/c and I'm happy.

NoCO2 02-09-2008 08:19 PM

I would love to, but I'm not that mechanically inclined. I thought the Alternator would be pretty simple though since that is just taking something sitting right on top of everything, out, and then running a shorter belt and hooking the leads to the solar panel to the battery (or batteries to get more millage from it) and then running the leads from where the alternator was connected to the stuff in the car, to the battery so everything still has power. On paper that doesn't sound too hard, but knowing my luck it would end up being hard.

How hard is it to disconnect the power steering? I can live without that, the A/C I can't really live without though because I use it to defrost my windows, but I never run it otherwise.

rbhollabaugh 02-09-2008 08:22 PM

The solar panel won't replace the alternator. Period.

Frank Lee 02-09-2008 08:25 PM

Defrost works fine w/o a/c in my area.

trebuchet03 02-09-2008 08:47 PM


Originally Posted by rbhollabaugh (Post 9026)
The solar panel won't replace the alternator. Period.

The all or nothing attitude results in the latter ;) Semicolon.

Coyote X 02-09-2008 08:58 PM

If you can get a lot of panels on the car it is possible depending on how you drive the car. If you swap to LED lights and drive mostly in the daytime with lots of time for the battery to recharge it might work.

The idea that I might do on my xfi project is do the large solar panels but leave the alternator on the car and just turn it off with a switch. That way if you need to drive at night or longer distances you can turn the alternator on and keep driving. When it is off it will be a tiny load on the engine only.

The way I thought about doing it was using a lexan sheet and lay over the trunk lid and heat it to form the proper shape. Then cut away the trunk except for the outer edge and replace it with the lexan. Then just put the panels under it to protect them from damage. Might take the entire trunk lid and maybe the hood to get enough panels to break even with a minimal load with the engine running.

jjackstone 02-09-2008 11:14 PM

Hate to say it guys but the solar panels just won't help very much. You might try Peltier devices if you have a whole lot of money to burn. Here's a link to one experiment.

There are other experiments out there. I think the technology is probably still cost prohibitive though.

SVOboy 02-09-2008 11:16 PM

There's a guy out there with a solar powered scooter that charges while sitting around, so if he can do it I'm sure a low-load car with decent sun exposure and lotsa panels may be fine, :)

MetroMPG 02-10-2008 09:19 AM

Coyote is on the mark by saying: "it depends".

To the replies stating "categorically, NO!": I have driven my car a fair bit on a solar PV charged 12v system. Not with car-mounted panels, but by depleting the battery for local driving, then recharging via PV when parked (including aiming the car at the sun so I could leave prop a panel up in the windshield).

You can get away with smaller PV area, as Coyote says, if you drive infrequently and have lots of time between battery depletion for recharging (my situation).

If you're trying to size your array to generate the necessary amount of power to run the car without depleting the battery, then it becomes much more challenging.

An 80 watt 20v consumer grade panel is about 8 square feet. You'd need two of those at a minimum just to support the electrical demands of the engine - ECU, fuel pump, injectors, occasional brake & signal lights (no other electrical accessories on, including lights, wipers, radio etc.). And they'd need to be perfectly aligned to the sun to generate their peak power. Change any of those factors, and you need even more panels.

Check this thread for more info


NoCO2 02-10-2008 01:05 PM

Ok, so I'm going to say that the solar idea is out. I over-estimated how much power a solar panel can produce and underestimated how much power the car actually uses. I was thinking that this 6'x3' cell I found a Fry's would cover it, but if it won't then that is the largest I can fit on the roof of my car, period. But now I'm thinking of removing the power steering which will remove some load, but the question is, will I see a noticeable improvement, enough to make it worth my time and effort to bother removing it? I have tried driving the car just rolling with no engine and it's pretty easy to turn without power steering so that would be really the only thing I can sacrifice off the engine at that point.

And to what Frank Lee said about the defrost working without A/C. There are some days that the only way I can get the windows to become un-fogged is to run the A/C. It usually happens when it's raining and cold outside so opening the windows to compensate for the temperature difference just isn't feasible so the A/C is my only option.

jjackstone 02-11-2008 03:00 PM

On the third hand, what if you made an aerodynamic trailer to attach to the back of your car that happened to be completely covered in solar panels? That, added to what you mounted directly to the vehicle might make a difference. Would have to know how long a trailer you felt comfortable with to do some basic calculations.

AndrewJ 02-11-2008 03:47 PM

Yeah, but the trailer would defeat the original reason for unbelting the alternator anyway.

Hauling a trailer will kill more MPG than unbelting the alternator will gain.

IMO, the best way to go would be two high AH 6v batts with a charger. Plus keep the alternator belt and a wrench in the trunk for those longer trips.

hondaworkshop 02-11-2008 04:04 PM

You could go as far as adding regenerative brakes or even wattage-generating suspension if you had lots of engineering and fabbing resources at your disposal, but an easier route might be to find an oversized pulley for your alt, so it takes less parasitic effort from the engine, and can still produce just enough charge to keep LED lights on and the battery trickling.

PaleMelanesian 02-11-2008 04:44 PM

I find that my engine is off enough of the time, I barely get enough charge. I get 14.x volts when the engine is running, but that's 1/2 or less of the driving time. This time of year, with headlights a necessary evil, I'm happy to keep it charged enough to crank the starter. No way I can/will change the pulley on my alternator.

It's close, though. LED's would probably tip the balance just enough.

MetroMPG 02-11-2008 04:52 PM

PaleMelanesian: it's for that reason (higher electrical loads in winter) that I don't mess around with alternator optional running at this time of year. Also, the cold temps degrade battery performance. So on top of the added draw, you also have lower capacity. Bad combination.

Hondaworkshop: I understand that if you underdrive an alternator, the voltage regulator will simply compensate for the reduced output by increasing the field current.
So it's a wash in the end. The only (small) benefit from underdriving then is limited to belt losses & less aero drag from the pulley fan.

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