Solar panel voltage

Submitted: Friday, Apr 02, 2004 at 21:31
ThreadID: 11777 Views:1966 Replies:3 FollowUps:2
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I was given a small ish solar panel for my birthday and I'm wondering about the output voltage, the panel gives out around the 21 to 24 volt mark in bright sunlight, the instructions say to just "plug it in" or "connect to the battery terminals", having a Nissan patrol 3.0 litre turbo with all the electronic gizmos and a computer controlled everything is it safe to just "plug it in"? Or do I get some sort of voltage controller. I can just imagine the conversation with the warranty dood when I rock up with a fried computer, any advice greatly recieved.
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Reply By: Eric Experience. - Friday, Apr 02, 2004 at 22:50

Friday, Apr 02, 2004 at 22:50
Martyn.
The amount of current [amps] that your smallish panel can produce is negligable, it will not be able to over charge the battery so just plug it in and relax. You could use it as an excuse to by a multy meter to monitor the current. Eric.
AnswerID: 53006

Reply By: Glenno - Saturday, Apr 03, 2004 at 11:05

Saturday, Apr 03, 2004 at 11:05
Martyn,

Put a small load on the Panel and then measure the voltage. They tend to give off a false reading with no load applied.

If its a small panel then there is probably minimal risk of overcharging the battery, provided you dont leave it on for weeks on end without using the batter!

Cheers,

Glenn.

AnswerID: 53046

Reply By: phil - Saturday, Apr 03, 2004 at 17:14

Saturday, Apr 03, 2004 at 17:14
Depends what you mean by "smallish". A 6 watt panel will not ever give over 0.5 amp, generally much less, and this is quite safe to apply to the battery without any regulation.
Solar panels produce quite high voltages in bright light but when connected to a battery they are essentially at a constant voltage and deliver a current depending on the light intensity. An average of only about 0.2 amp over 24 hours is about right to keep a battery in full charge. The battery voltage will probably be mush less than when the alternator is charging.
Phil
AnswerID: 53080

Follow Up By: Martyn (WA) - Saturday, Apr 03, 2004 at 21:58

Saturday, Apr 03, 2004 at 21:58
Phil,
It's rated at 350 milliamps, 5 watts at 24 volts, well that's what's on the back anyway. I tried the panel out today and it wouldn't light up a normal 5 W light globe is that normal? Not sure how to check the panel actually works, I get a voltage reading no problem.
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Follow Up By: phil - Tuesday, Apr 06, 2004 at 11:39

Tuesday, Apr 06, 2004 at 11:39
Matryn,
Connect the panel to a 12v battery and use an ammeter to measure the actual charging current. Most multimeters will have a current range which is sufficient to handle the small current from this panel. It will be less than 350 ma since this is the short circuit current when in illumination of 1000 watts/sq metre. Your sunlight will probably be less than this.
Not sure why it did not light up the 5W bulb. It should show some glow.
Phil
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