Using solar panel to charge 12 volt game feeder

[Josef]

I have numerous game feeders which use 12 volt dry
cell batteries. Presently I have to check the batteries
ever couple of weeks and change them out charging
the one I removed.
I would like to go to solar power but when I google it
I can't find much information that helps me. I would
like to know the pitfalls if someone could help me.
I've read about diodes and controllers etc.
I can find panels for $20.00 with free delivery on Amazon
but really don't know what I need to be on the outlook for.

 

[sagor]

There are several factors, like what is the battery capacity, and the load (how many A or mA does the load use).
Many of the low power panels are between 2.5W to 10W, and are just about self regulating when it comes to charging a standard 12V battery.
Other factor is battery capacity vs the charging current. A small panel will supply anywhere from 150mA to almost 1A of charge current while the sun shines. Take the hours of sunlight times the panel charging current, and that gives the Amperehours (Ah) of energy produced. Assume 10 hours of full daylight, you would get between 1.5Ah to 10Ah into a battery. Now, the battery has to take this, so if you have a 5Ah battery, you would be overcharging with 10Ah, but be fine with 1.5Ah.
Then the load. If your load uses 100mA 24/7, then you would use up 2.4Ah of energy every day. Your battery has to handle that load, for a few days at least, without sunlight (cloudy days). Try to match up the solar panel in this example to provide at least 2.4Ah per day, preferably a bit more (like 5Ah on a good day).

Some of this is just plain experimentation, load vs battery vs solar panel. One tries to match all 3 items as close to the same as possible. For example, a huge 12V deep cycle battery would be too big for a small solar charger to keep up with the "self discharge" of the battery itself. Keep the battery size reasonable. Lots of factors to consider.

In your case, it sounds like the load is very small, as are the batteries. I would think a 5W to 10W panel would be more than enough. Not sure what cells you have (must be 12V), as that is a factor as well. If your batteries are very small, then a 2.5W solar charger may do.

 

[Tooljunkie]

If anything it will extend your change out time. Double the time before recharging for example.

 

[Josef]

I certainly want to thank you both for the useful help especially
Sagor for the in depth useful information. I believe I have a handle on it now.

 

[CaveCreekRay]

Is this a great community or what?