We at Saint Isidore Acres have long been proponents of micro solar installations. You may have seen some of the work we have done with the installations on our cabins and pump houses, as well as the solar trailers we have worked on.
This is slight break with the “traditional” setup that we have been using — which generally involves a 24V or 12V array, a MPPT Charge Controller, and a 12V battery bank.
Here we are looking for a “set it and forget it” outdoor, weather-worthy AA battery charging device. Ideally we could load this with double-A batteries (the more the better) set it outside, and then collect it in a few days or a week. Obviously this means that it at least needs to have a blocking diode so that it does not drain over night. The current pattern for charging these AA’s on our farm is an always-on 16-bank charger. It’s nice to have, but running anything 24/7 on solar + battery systems just doesn’t make sense.
With that prelude, here are the most likely candidates available at the moment:
This is the first thing we found ($36 on eBay). It has the limitation of neededing to charge 4 batteries at once, but it has several other nice features as it appears to be waterproof/weatherproof and has a blocking diode. However, I have bought items with this general appearance (unbranded) several times and been disappointed with the quality in the past, so I am wary about what its actual performance will turn out to be.
This PowerFilm product for $72 looks like a good option. It appears to be fairly weatherproof (and a simple frame of clear glass over the top may help that) but it has the downside of being twice as expensive as the eBay option above and only charges 2 AA batteries at a time. Again, the application for this is to be able to set and forget, and come back in a relatively long amount of time later to fully charged/maintained batteries. However, my confidence in this product to perform as advertised is fairly high.
This Anker 21W device for $50 may be a good middle point. With 490 reviews converging on a 5-star rating, it is certainly the most popular and most rated item in its class on Amazon. However, it does not charge traditional AA batteries directly…. So it would have to be used in tandem with another type of AA, like these:
So…. no conclusions as of yet. But it is interesting to see what the options are. Another alternative would be to use the traditional 16-bank charger running off of 12V, but to utilize some type of “auto-off” or timer to limit energy use over multiple days. The trick would be to still keep the batteries maintained and in a constant-ready state.