solar panel dissapointment

[gabi]

so.... i bought a pair of solar panels 5 watts each to install in my car,back window
the problem is that i have tinted windows 75%, and i knew i wont get the rated power,but i'm berely getting about 1 watt from each panel....and thats at high noon ,perpendicular exposure to the sun
thats at load,when they are hooked to the battery
at no load i get a little better, about 2.25 watts out of each

I,m thinking is better off to mount them somewhere around the house and charge some lithium battery that i can transfer to the car when full.
I was thinking to get something like the power tools batteries,at about 5 amps, that should work.

Has anybody tried something like this before?
what would be the best battery to try?
any ideas apreciated

[Ryland]

Are they weather tight? if they are then either mount them on the hood or roof, mounting them behind even non tinted glass will reduce their output.

[gabi]

yes they are weather tight, is just I dont want to mount them permanently on the outside of the car. I can put them in and out as the situation allows.
i was just hoping for a permanent mounting inside of the car

[groar]

If their width isn't very important, then you may put them over the dash board under the front windshield. Preferably on the passenger side to avoid reflection in front of the driver.

If you put them against the windshield, in case of emergency stop they shouldn't move, or if they move they shouldn't be as dangerous as they would be under the back window.

Anyway, photovoltaic doesn't generate a lot. Here where I live (New-York's latitude) in summer you can have only 7x peak power, ie 7x5x2=70Wh which is 5.8Ah of a 12V battery, ie a tenth of a standard battery (and I didn't included losses such as voltage mismatch, cable lengths...).

Also be careful that if your battery is charged then your solar panels will push up the battery voltage over the limit (14.6V) and deteriorate it, you will then have to manage the water level of your battery. A small 1A charge controller should protect your battery, noticeably when you don't use your car during several consecutive days.

Have fun,

Denis.

[gabi]

thank you,
the front window does give me a little more power...1.7 watts compare to 1, but still...
i do have a charger rated 7 amps,so i should be ok
also i live in Atlanta,so i should do a little better than NY

I recently ordered all LED lights for my car,so the idea was they will run of solar energy.Its certainly doable,

[Ryland]

what is the output if they are not behind the extra layer of safety glass?
for the 10 watts total you could get out of the PV panels in full sun that is not going to be enough to worry about over charging your battery, it will help keep it topped off and should then help it last a year or two longer but that is about it.

[groar]

My experience : a 13W solar panel (amorphous silicon) and my old car battery put in the trunk and used only to feed the gps, the phone charger and other misc 12V such as an USB fan.
After a few weeks I could measure 15+V while solar charging

I moved the battery from the car and looked at the water level : too low. I filled-up the battery and put it on a 220V charger. Sadly the voltage went over 14.6V in a couple minutes and the charger put the voltage on maintenance (13.6V). I let it all night long and the day after I put the battery back into the car's trunk.

After a week, the panel was always overcharging the battery and the water level was again too low. After refill, I tried to "exercise" the battery so I depleted it (an old unused 220V 40W lamp through a 12/220V converter) and charged it 3 times. Each charge was followed by a night long maintenance. charge and use phases were separated by 2 hours of rest. Each time the charge and use periods were longer.
Put back the battery in the trunk and monitored the voltage while panel charge. It was OK during a few days, but after a week it was over 15V

Then I had to use a battery for a geek project at home. It was involving higher currents (up to 8A) and the battery was used and charges through a charge controller. The battery worked very well during the 3 weeks tests.

As it was then mid-September I decided to not put back the battery and the 13W solar panel as their weight were certainly canceling the saving on alternator.

Denis.

[Arragonis]

Can you remove some tint from where the panels are mounted ?

75% is quite high and would be illegal here on front windows, including side ones. The Police have a policy of prosecuting people or offering to fix it at the roadside. The drivers of such vehicles often look puzzled at the policeman but given the alternative of 3 points and a fine they agree - and then the policeman just peels the tinting film off the windows. He/she doesn't do it neat but they do remove it.

So if you don't care too much you could slice it and then peel off enough for the panel to be mounted.

[gabi]

Originally Posted by Arragonis

Can you remove some tint from where the panels are mounted ?

75% is quite high and would be illegal here on front windows, including side ones. The Police have a policy of prosecuting people or offering to fix it at the roadside. The drivers of such vehicles often look puzzled at the policeman but given the alternative of 3 points and a fine they agree - and then the policeman just peels the tinting film off the windows. He/she doesn't do it neat but they do remove it.

So if you don't care too much you could slice it and then peel off enough for the panel to be mounted.

thats funny

this is actualy a police car, a former sheriff crown vic interceptor

the percentage is how much it lets in,so the actual blockage is 25 %, so i'm legal

[Arragonis]

Originally Posted by gabi

thats funny

this is actualy a police car, a former sheriff crown vic interceptor

the percentage is how much it lets in,so the actual blockage is 25 %, so i'm legal