Using Solar Power to Charge Batteries
If you’ve ever seen a solar yard light, you’ll know that it’s easy to charge batteries using solar power. Let me edit that: it’s easy to charge some batteries. It’s easy to charge the cheaper end of the battery spectrum. I’m talking the NiMh and NiCad batteries, found in the usual sizes and costing somewhat more.
All you need to charge one of these batteries is to connect it to an electrical source—the only caveat being you should protect the battery from the circuit reversing polarity, which can damage your batteries. To do this, you add a diode (such as 1N4001 diode, Adafruit P/N 755) between the positive lead of the solar cell and the positive lead on the battery pack, as seen in Figure 4.19.
FIGURE 4.19 Protect your solar cell from energy flowing back into the battery pack.
If you want to use one of those more compact LiPoly batteries in your project, an example is Adafruit’s Lithium Ion Polymer battery (P/N 1578) that delivers 3.7v at 500mAh, and they have a number of variants if that’s not the configuration you want.
Adafruit also sells a solar charger (P/N 390) that goes with the battery, as well as solar panels (such as P/N 417) guaranteed to work with it. You can see this arrangement in Figure 4.20. The advantage with going with a preconfigured setup like Adafruit’s is that you know it works, with no experimentation or ordering new parts when one configuration doesn’t work.
FIGURE 4.20 A LiPoly battery getting charged with a solar panel.