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Old 01-07-2009, 06:28   #1
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Basic Solar Hookup - Help!

Got a decent deal on a small Solar system to assist in keeping my batteries up and wantedd some advice. I currenlty have a group 29 deep cycle and a starting battery - 12 volt system. The system I got is a charge controller and a 20 watt solar panel (1.15 amps) . Am I correct that I hook the solar to the controller and the charger controller to the battery (deep cycle)? Positive to Positive, neg to neg? - The controller say it prevents drain and overchargeing...which I guess is what charge controllers do...correct? Anything else I should know? - Oh.....what gauge cables or wiring should I use?


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Old 01-07-2009, 07:20   #2
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correct on the hookup of the wires. the controller will prevent drain and overcharging. i used 10 gauge for my setup; 10 gauge should work for you unless you have unusually long runs. you might want to consider a circuit breaker or fuse.
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Old 01-07-2009, 08:06   #3
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You should have a fuse less and 9 inches or so from the battery going to the controller, and then one between the controller and the panel.
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Old 01-07-2009, 10:41   #4
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so I should add a 2 fuses on the hot (red) lines? How do I gauge the fuse size? based on the panel amp capcity? I know it's a 20 watt with operating around 1.12 amps.
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Old 01-07-2009, 11:14   #5
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so I should add a 2 fuses on the hot (red) lines? How do I gauge the fuse size? based on the panel amp capcity? I know it's a 20 watt with operating around 1.12 amps.
If you're never going to upgrade to a high output solar system 10 guage wire is a big waste of money.

Referring to the following post:

http://www.cruisersforum.com/gallery...=500&userid=79

From the chart and doing the calculation for a 20 foot run 16 guage would be quite adequate. If you have to go a bit further 14 would handle it fine.
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Old 02-07-2009, 12:00   #6
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If you're never going to upgrade to a high output solar system 10 guage wire is a big waste of money.

Referring to the following post:

http://www.cruisersforum.com/gallery...=500&userid=79

From the chart and doing the calculation for a 20 foot run 16 guage would be quite adequate. If you have to go a bit further 14 would handle it fine.
Oddly enough, I agree.
While #16AWG may be electrically adequate (ampacity & voltage drop) when new; I'd also prefer #14 for mechanical (strength) reasons, and allowing for more leeway for inevitable electrical degradation.
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Old 06-07-2009, 11:06   #7
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So should I add a fuse? Maybe between panel and controller on the hot line? How should I choose the fuse size? Is it a certain size per watt or amp?

Also, with reference to amps and batteries and power consumption. My group 29 has like 125 or so AH. My understanding is that you simply add the amp draw up for all your stuff and that gives you the amps per hour you use. So if you have a stereo and a VHF radio that each draw 5 amps....that will be 10 amps an hour....so I could run them both for about 12 hours before my battery drained correct? The solar panel return amps to the batteries......extending my time. AM I on base here?
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Old 06-07-2009, 13:34   #8
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So should I add a fuse? Maybe between panel and controller on the hot line? How should I choose the fuse size? Is it a certain size per watt or amp?

Its the Amps that are important for a fuse. A 2A fuse is correct for your 20w solar panel mounted close to the battery preferably fuse both + and -.

Also, with reference to amps and batteries and power consumption. My group 29 has like 125 or so AH. My understanding is that you simply add the amp draw up for all your stuff and that gives you the amps per hour you use. So if you have a stereo and a VHF radio that each draw 5 amps....that will be 10 amps an hour....so I could run them both for about 12 hours before my battery drained correct?

In theory to drain the battery completely yes, but the battery is not likely to be 100% charged and for various reasons it will not meet these theoretical claims. Its real capacity is probably 100AHRs, but for reasonable battery life it is better to restrict the discharge to 50%. So you have about 50AHrs to play with.
The good news is the power consumption of the VHF in recieve is only likely to about 1A and most "car "sterios are about 1 to 1.5A

The solar panel return amps to the batteries......extending my time. AM I on base here?

Yes . Depending on the time of year location etc the output will vary enourmously, but about 5Ahrs a day would be an average
Cheers John
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Old 06-07-2009, 15:41   #9
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So should I add a fuse? Maybe between panel and controller on the hot line? How should I choose the fuse size? Is it a certain size per watt or amp?
A fuse protects downstream gear - primarily wire.
ie: #14 wire should be fused at 15A maximum.
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Old 06-07-2009, 16:38   #10
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20 watt solar panel (1.15 amps) .


Isn't the reality on a 20 watt panel that there is NO chance of overcharging a battery unless the boat is left unattended for months in the tropics?

Instead of wasting money on a regulator or fuses, wouldn’t it just be better to put in a diode to prevent night time discharge? Don’t most solar panels have that diode anyway?

So in a practice sense isnt it just better to put in the solar panel and stuff the rest of the expense?


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Old 06-07-2009, 17:00   #11
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Corkscrew;

Typically you only want to discharge your battery by half its available amps. So, with your 125 amp hour battery, you'd be better off with a 10 amp load for 6 hours. So your math is correct. If you start draining a Lead Acid battery by more than half you significantly shorten the life of the battery.

Mark is also correct, with that small a panel and that large a battery, you could do without the charge controller. But, it sounds like your controller has facilities for keeping the batteries from discharging to the panels at night (blocking diodes). So, since you already have it, I'd use it.

Keith
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Old 06-07-2009, 17:07   #12
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if you're anything like the rest of us...

...two weeks after you get that 20-watt panel fired up you'll decide that you need AT LEAST another hundred watts.

So go with the 10-gauge wire now so you don't have to upgrade the system when you add the next panel.
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Old 07-07-2009, 07:06   #13
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Well, the panel I have coming in is a simple 20 Watt (1.14 amps). I did get a controller...just to be safe and have a diode for reverse charging. Most of the time they won't even be in use as I'll be hooked to shore power, but the system is just going to be for overnights and long days out....to help keep the battery relativly up. If I like the panel I will add 1-2 more. If I add the second one I'll be at 40 watts (2.25 amps approx) - that should be fine for my needs. The only things I really have running all the time are (stereo, GPS/Depth/Alarm and VHF) - at night maybe a few lights, a fan.....etc. Now someone told me that stereos and VHF run like 5-10 amps each...is that true?
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Old 07-07-2009, 08:15   #14
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The only things I really have running all the time are (stereo, GPS/Depth/Alarm and VHF) - at night maybe a few lights, a fan.....etc. Now someone told me that stereos and VHF run like 5-10 amps each...is that true?

It is better to measure the consumption yourself as equipment does vary, but I think your energy budget would look something like this

stereo, GPS/Depth/Alarm and VHF about 2.5 A assuming they are on for 16hrs thats about 40AHrs (2.5 x 16)
3 lights and a fan say 4A over 5Hr gives 20Ahrs

Therfore 60Ahrs used. 5Ahrs from the solar pannel gives 55Ahrs taken from the battery. (assuming no input from engine charging)
Conclusion just OK for 24 hours away from shore power.
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Old 07-07-2009, 08:18   #15
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And with a little trickle solar of maybe 2-3 amps...I should be very fine for 1-2 days....i expect.
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