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Old 07-19-2011
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New 10W Solar Panel. Question Regarding Wiring (with pictures)

I just bought a 10W solar panel to keep my lightly used battery fully charged. The panel came with a cheap looking charge controller and instructions on installation. They say the leads from the solar panel go to the charge controller, two other leads go from the charge controller to the battery, and in addition, two more leads are supposed to go from the charge controller to the loads, see first picture.

I was wondering why the charge controller can't go between the solar panel and the battery (as in the second picture), and the load go from the battery as it already is?

I'm confused because the leads coming off my battery are fairly large relative to the tiny wires that are supposed to leave the charge controller to the load.

Finally...one of the reasons I got such a small panel was because I thought at that size a charge controller was unnecessary. Do you think its safe for my battery (elecsol 100 carbon fibre) to utilize the solar panel without a charge controller at all?
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Old 07-19-2011
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in the absence of a schematic for the charge controller and a theory of operation for it...I would hook it up per the directions provided. Not sure why it is set up that way, except to have a load on the controller so that it "sees" discharge and allows the panel to charge the battery.

I sure would not risk what appears to be a high dollar AGM battery to "test" a $25 panel,

YMMV
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Old 07-19-2011
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I just bought a 10w SP myself. It is wired directly to the battery without regulators of any kind.

I just fitted a 5A diode (a bit overkill, I know) in series, to avoid battery discharging at night...

Without wanting to take too long writing about what others have allready writen I'd just say that, except if yours is a rather small battery, you won't need a regulator at all for a 10W panel...

For further info check this out

Best wishes!

PEdro
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Old 07-19-2011
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Thanks for the responses.

kd3pc, I see what you mean about allowing the charge controller to sense the need for charging via solar panel by carrying the load, but the receptors on the charge controller for the load wires are tiny, like 14/16 gauge...maybe smaller. That doesn't seem right to have the entire load of the boat, albeit small, to come off the charge controller with such small wires. The wires coming off my battery carrying the load now are large (car battery wire size). Plus that would mean rewiring the entire system. Something doesn't seem right, here's a link to the exact panel I purchased. Amazon.com: Instapark® 10W Mono-crystalline Solar Panel with 12V Solar Charge Controller: Patio, Lawn & Garden

Pedro, I'm tempted to do the same setup, but I don't want to loose efficiency by using a diode that is more than necessary for my system. Is there a way of calculating a proper size diode based on your systems needs?
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Old 07-19-2011
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I would wire it as in your second diagram. The controller should sense the battery being low and the battery will only accept what it needs anyway.

I agree the loads should be from the battery with larger gauge leads and not direct from the controller. Also as posted, a controller is not really necessary with a panel that will never put out as much as 1 amp.
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Old 07-19-2011
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Quote:
Originally Posted by liveincolor View Post
Thanks for the responses.
Pedro, I'm tempted to do the same setup, but I don't want to loose efficiency by using a diode that is more than necessary for my system. Is there a way of calculating a proper size diode based on your systems needs?
Indeed there is. One should use a diode 25% above the expected current flowing throught the circuit... That's the "general" 1/4 rule of thumb...

Oversizing a diode won't do any harm to the circuit though... A normal "rectifier" diode (which is what we're talking about here) represents a voltage drop of arround 0.7V, regardless of the ampere rating. I'd say without too great an error that a 1A standard 1N4007 will drop the voltage as much as a bigger 5A diode, like the one I've used (because those were the only ones available at my "bits" box).

Cheers!
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Furthermore I'd like to point out that there's little chance your regulator is prepared for marine duty, so I'd rule out the idea of using it... It's to great a danger to have landlubber electrical equipment aboard and unattended as a solar panel normally is...

In my case I just replaced all the crap wire that came with the panel for proper grade UV resistant wire and connected it to the battery placing, as said, a diode in between...

Best wishes!

Pedro
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Old 07-19-2011
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I wired my 40W panel like your second diagram. The load terminals are only if you want to connect a load directly to the panel and they should not be connected internally in the controller to the battery.
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Old 07-19-2011
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Quote:
Originally Posted by liveincolor View Post
Thanks for the responses.

kd3pc, I see what you mean about allowing the charge controller to sense the need for charging via solar panel by carrying the load, but the receptors on the charge controller for the load wires are tiny, like 14/16 gauge...maybe smaller. [/url]
yes the "receptors" or sense wires are smaller gauge, they are only measuring some small amount of current to "sense" what to do.

Again, at the risk of damage to the AGM battery - I would wire it as directed, or return it and get a more "marine" friendly system from a reputable vendor like HamiltonFerris or Defender...

If not that, trash the controller and do as Pedro indicated, install the diode which for the current capacity of the panel will work nicely and is not subject to failure as readily as the controller included with your panel.

YMMV
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Old 07-19-2011
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I betting that if you check the manual the "load" taps are limited to a very low current. Check that and let us know. It is probably not applicable to your installation; use plan B. There are some application (highway signs and ATNs, for example) where is is just a bit more efficient to use some power directly, and the load is by definition, limited to about the panel output. This is VERY common and does not hint that it is not marine friendly.

Remember to place a small fuse between the batteries and the charger. Very important.

Does the charger have an AGM setting? If not, it is unsuitable for your batteries.
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