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Topic: Charge Controller for Solar
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Charge Controller for Solar
on: June 22, 2012, 18:51

This is mostly for those using small-medium sized solar arrays. The larger systems normally have charge control built-in.

For all batteries attached to any solar panel with moderate/significant output. In direct bright sun the solar panel (unloaded) can put out 17 or more volts DC. Many will output 19-20 volts. As a battery becomes charged the current into the battery decreases and the voltage goes up. Beyond about 15 volts (on a 12 volt battery) damage to the battery can occur. Hence the Charge Controller, it's purpose is to regulate the voltage to the battery for optimum charge without danger of over charging it.

For those who prefer to just buy a charge controller there are many choices out there. But those handy with a soldering iron might want to look at http://solorb.com/ They have kits where you can build your own charge controller. I have built a couple, an early version of the SCC3. Before that an SCC2, mine is a 24 volt version.

One advantage to building your own is the information to repair it, should that be needed. Many 'store bought' versions are potted and there is no repair for them.


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Re: Charge Controller for Solar
on: June 22, 2012, 23:10

Etech,


Those are pretty cool. I took a look at the specs, and I think I missed something – how do you specify the max current to the battery? If you had two batteries of the same type, one small, one large, the smaller one is likely to tolerate a smaller maximum current flow without damage as compared to the larger one, and I didn't see how that limit was set.


Bear
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Re: Charge Controller for Solar
on: June 23, 2012, 08:33

Bear,

With this one (and several others, most?) you have no option to set a max current. So if one has a significant panel (say more than 60 watts) you'd need to be careful of hooking up a small amp-hour battery. Of course something like an automotive or marine battery (75 or more amp-hour) you'd not need worry about current.

I have a 'home-brew' charger built many years ago for NICAD/NIMH that will charge at two different rates. Low position is 100 milliamps (100MA) and high is 350 MA. Usually just run from the battery so 12 volts is the source, but it can be hooked on the solar panel side and will charge my small SLA (sealed lead acid) batteries that are small in size/weight like 3-5 AHr type. Most batteries I try to charge at C/10 at a maximum. C/10 meaning 1/10 of the rated capacity, or a 5 AHr battery charged with 1/2 amp current or less. This is conservative but usually gives batteries a longer charge/discharge life. YMMV ~;-)
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