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post #1 of 11 Old 08-02-2014 Thread Starter
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30 Watt Solar Panel Output

I have a 30 watt solar panel which is twenty years old, I suspect it is somewhat degraded in terms of output. What should be the expected output in volts in full sunlight in the Northern Hemisphere?

It also seems to lose charging power between the panel and the battery. Is this normal? If so, what percentage loss is acceptable?

Thanks.

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post #2 of 11 Old 08-02-2014
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Re: 30 Watt Solar Panel Output

It is most likely to be a 12 volt nominal panel with a max voltage of about 19 volts.

How do you know it is losing charging power (current) between the panel and the battery?

What type of controller are you using? You do need a controller to avoid frying the battery. A fully charged battery needs very little current to keep it charged. After it is fully charged if there is not a controller the voltage will rise and the battery will be destroyed eventually. This link is very informative:
Do I Need A Solar Charge Controller ?? Photo Gallery by Compass Marine How To at pbase.com


Best arrangement is to place the controller close to the battery. This reduces any voltage drop after the controller to almost zero.

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post #3 of 11 Old 08-02-2014
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Re: 30 Watt Solar Panel Output

I have a 1.8 watt solar panel to hook up to a 125 ah house battery I use about one ah each day on lighting and charging my cell phone would it be prudent to put in a controller or a waste of funds until I purchase a larger panel

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post #4 of 11 Old 08-03-2014
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Re: 30 Watt Solar Panel Output

I wouldn't bother with a panel that small.

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Re: 30 Watt Solar Panel Output

Thanks for all the replies.

Quote:
Originally Posted by mitiempo View Post

How do you know it is losing charging power (current) between the panel and the battery?

What type of controller are you using?
I recently bought a new Group 24, 650A, 12 volt marine deep discharge battery. I also bought a Genasun GV-4 controller. The only electrical draw on the battery is an ST1000 autopilot at max 1.5AH and a handheld GPS. I also installed a voltmeter. I use a flexible 20 year old solar panel which can be connected/disconnected about 12' before the battery.

After a bit of use on the above, I noticed the battery charge was dropping. I disconnected the panel before the battery and checked the output voltage. I then reconnected the panel to the wiring to the battery and checked the voltage at the end of that. The reading from the panel was 6.2 and at the end of the complete wiring it was 5.1 indicating a possible loss of power in that additional wiring. This was in about half sunlight.

I suspect that, after twenty years, the solar panel has degraded.
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Re: 30 Watt Solar Panel Output

Quote:
Originally Posted by mitiempo View Post
I wouldn't bother with a panel that small.
It was free and multi meter says it works

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Re: 30 Watt Solar Panel Output

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It was free and multi meter says it works
What I meant was I wouldn't bother with a controller with a panel that small. The downside is that a panel that small is close to useless.

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Re: 30 Watt Solar Panel Output

Quote:
Originally Posted by petertribo View Post
Thanks for all the replies.



I recently bought a new Group 24, 650A, 12 volt marine deep discharge battery. I also bought a Genasun GV-4 controller. The only electrical draw on the battery is an ST1000 autopilot at max 1.5AH and a handheld GPS. I also installed a voltmeter. I use a flexible 20 year old solar panel which can be connected/disconnected about 12' before the battery.

After a bit of use on the above, I noticed the battery charge was dropping. I disconnected the panel before the battery and checked the output voltage. I then reconnected the panel to the wiring to the battery and checked the voltage at the end of that. The reading from the panel was 6.2 and at the end of the complete wiring it was 5.1 indicating a possible loss of power in that additional wiring. This was in about half sunlight.

I suspect that, after twenty years, the solar panel has degraded.
The Genasun is a good choice. As far as the panel output it is hard to say without measuring voltage in full sunlight but you could be right, it may have degraded over the years. Check the wiring connections for corrosion.

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post #9 of 11 Old 08-03-2014
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Re: 30 Watt Solar Panel Output

Quote:
Originally Posted by mitiempo View Post
What I meant was I wouldn't bother with a controller with a panel that small. The downside is that a panel that small is close to useless.
Don't take me at face value I'm a retired USN hull tech I have a ferry demented since of humor and I understood what you were saying and yes almost useless but over the ,east month I have seen no appreciable loss in the sundown charge in the battery but also just charging my old kyoceria non smart phone so not much draw anyway

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post #10 of 11 Old 08-03-2014
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Re: 30 Watt Solar Panel Output

Quote:
Originally Posted by petertribo View Post
Thanks for all the replies.



I recently bought a new Group 24, 650A, 12 volt marine deep discharge battery. I also bought a Genasun GV-4 controller. The only electrical draw on the battery is an ST1000 autopilot at max 1.5AH and a handheld GPS. I also installed a voltmeter. I use a flexible 20 year old solar panel which can be connected/disconnected about 12' before the battery.

After a bit of use on the above, I noticed the battery charge was dropping. I disconnected the panel before the battery and checked the output voltage. I then reconnected the panel to the wiring to the battery and checked the voltage at the end of that. The reading from the panel was 6.2 and at the end of the complete wiring it was 5.1 indicating a possible loss of power in that additional wiring. This was in about half sunlight.

I suspect that, after twenty years, the solar panel has degraded.
diode voltage drop might account for that
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