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post #1 of 15 Old 08-01-2013 Thread Starter
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Stupid solar question

I'm new to all this. My solar panel is vastly inadequate for my needs. Does not ever get the batteries up to a full charge. I don't have an inboard.

I ordered this panel:
RENOGY 100 Watt 100w Monocrystalline Photovoltaic PV Solar Panel Module 12V Battery Charging
http://amzn.com/B009Z6CW7O

This is the controller I have:
Sunforce 7 Amp Charge Controller
http://amzn.com/B0006JO0XI

I know it's crappy. Ill replace it at the end of the season. But as far as I can tell that panel should work with that controller, yes?

Thanks!
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post #2 of 15 Old 08-01-2013
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Re: Stupid solar question

I have a large 85 watt solar panel I was told that i should use a 15 or 20 amp controller.

The cheapest i found was 15.00 GB Pounds from eBay...

Fitted into a lift up hatch It does keep both 120 amp batteries fully charged...With no Problems.

See Here PAGE 12

By the way there is Nothing stupid about asking questions.
After all how would we know the answers..

Last edited by macwester26; 08-01-2013 at 04:11 PM.
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post #3 of 15 Old 08-01-2013 Thread Starter
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Re: Stupid solar question

I guess my question is am I likely to damage the panels controller or battery this summer until I get a better controller?
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post #4 of 15 Old 08-01-2013
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Re: Stupid solar question

Quote:
Originally Posted by sully75 View Post
I guess my question is am I likely to damage the panels controller or battery this summer until I get a better controller?
I've heard of cheap controllers "sticking" and frying batteries. But I don't know how common that is, or if pricey controllers are any less prone to such malfunctions.



From the link in your post:
Quote:
Handles up to 7 amps of array current and up to 105 watts of solar power
I would be particularly leery of hooking up a cheap controller to a panel that is within 5% of its rated capacity.

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Last edited by SlowButSteady; 08-01-2013 at 05:48 PM.
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post #5 of 15 Old 08-01-2013 Thread Starter
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Re: Stupid solar question

Yeah I was wondering if they were making those numbers to fit a 100 watt panel. Problem is that I'm on the boat, the panel is coming tomorrow and I don't have a place to get another controller unless there's somewhere in RI to buy one. I don't have an address here.
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post #6 of 15 Old 08-02-2013
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Re: Stupid solar question

Quote:
Originally Posted by macwester26 View Post
I have a large 85 watt solar panel I was told that i should use a 15 or 20 amp controller.

The cheapest i found was 15.00 GB Pounds from eBay...

Fitted into a lift up hatch It does keep both 120 amp batteries fully charged...With no Problems.

See Here PAGE 12

By the way there is Nothing stupid about asking questions.
After all how would we know the answers..
As a simple concept, watts = amps x volts. So at 13 volts x 20 amps, the 20 amp controller is capable of managing a 260 watt array. Even at 15 amps it adds up to 195 watts. You have 85 watts. Mmmmmm.

I have two 140 watt panels that are managed by a 20 amp controller and the reason the setup continues to work is that the panels never deliver 100%. YMMV


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post #7 of 15 Old 08-02-2013
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Re: Stupid solar question

7 amps is fine.
When you get the money buy a MPPT controller, the output will amaze you.
You really do get what you pay for, provided you shop for quality.

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post #8 of 15 Old 08-02-2013
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Re: Stupid solar question

If you're under charging your batteries they will be damaged I'm just not sure of the timeline. I couldn't find any specs on the maximum input voltage to your charge controller but assuming the 18.9V of the solar array isn't to high you shouldn't damage anything else.

Any chance you can dock the boat and use an ac powered charger to top off your batteries as often as possible?
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post #9 of 15 Old 08-02-2013
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Re: Stupid solar question

The cheap charge controller is just a regulator. What it will do is lop off any extra voltage coming from the panels, which might put out 22 volts unregulated at their max. So the charge controller is making sure the panels don't cook the battery, but it is set to 14.2 volts, and that might still cook a battery in extended use. If the battery is never getting fully charged, no problem, 14.2 should be fine for bulk charging wet lead cells.

the charger also apparently has a cut-off, so that it will prevent the battery from pushing back into the solar panel in low light conditions, which saves you from needing a diode to do that.

Instead of lopping off excess voltage, an MPPT controller convertes it to lower voltage at higher amerage, so you may see 10-20% more charging power from the panel but you've got to balance that against the higher cost for an MPPT controller.

On the amp ratings, you're OK where you are. Odds are that if the battery is never getting fully charged, you're just not getting enough power from that one panel and lop-off controller.

If you have conventional lighting on board, replacing it with LED lighting can sometimes do more for your charging needs than spending the same amount of money on anything else.
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post #10 of 15 Old 08-18-2013
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Re: Stupid solar question

So if you add panels, do you use a cut off switch while sitting at a docks and the boat is hooked to shore power and battery chargers? Looking to add some to mine and just in the planning and learning stages of what I need and how to tie it all together
Thanks

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