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in full sunlight, it measured (via multi meter): * 23v * 66 milli amps (=1.5W)
noticed that if the blue light is flashing it's getting some kind of charge (at least enough to light the blue LED). in minimal light situations (ie. shade), sometimes the blue light will go on, but as soon as i put a load (ie. multi meter) on it , it goes off... (eg. 5v, 0.25 milli amps)
according to many articles i've read (while i was trying to hunt down and debug a parasitic drain), 50 milli amps in most cars is "typical acceptable parasitic drain" when the car is off (ie. to keep memory settings of the computer, etc... alive)... so this is perfect for offsetting "acceptable parasitic drain", especially if you're letting the car sit for a while.
also researched "will 23v overcharge my battery"... while the instructions say you should get a controller, my understanding is that the electrical system of the car will only pull what's needed (eg. 13-14v), even if the panel is a constant 23v (at full sun)... also 66milli amps is very small.
that said, i bought a controller, not because i thought connecting the panel (23v at full sun) directly to a battery will kill the battery,
but because the controller will convert 23v @ 66ma to 14v @ ~100ma (ie. it's more efficient), if the battery needs it.
having dealt with alot of dead batteries, i can't help but think that some of the negative reviews ("didn't charge my battery") here are done by folks that are expecting too much from this panel. it will not recondition a dead battery. by itself, even in full sun, it will take a very long time to charge a drained battery (think faucet drip to fill a 5 gallon bucket)
other considerations: * are you plugging it into a cigarette lighter that's always on? (originally i didn't :P) * if you say it's "not working" are you actually measuring with a multimeter? (if so, kudos! and *then* return it :P) * can i leave it plugged it when i start/run the car? (i think instructions say not to, but i haven't seen anything negative (both with/without controller attached).. presuming there's a diode or similar built in to prevent back flow of electricity. * does not look waterproof.. (which is fine since it'll be on the inside of my jeep)