Make a Solar AA Battery Charger by TL497 (review)
This is a project to use a solar panel to charge a small battery, such as a NiMH battery in the 3V to 9V range, with mAH measuring between 1,000 to 2,000 mAH. It's just great to see that they have also included the PCB layout for you on this design. Something I don't see very often.
The TL497 integrated circuit is a fixed-on-time variable-frequency switching-voltage-regulator control circuit. It features frequency control and current limit sensing, among other things.
|Make a Solar AA Battery Charger by TL497 from Electronic Projects Circuits|
First things first, I have to point out that I am not using their circuit as designed.
The circuit calls for a 5V 100 mA solar panel, and I only have a 6V, 1 watt solar panel available. Secondly, I am trying to use it to charge 4 AA NiMH batteries, rated 2500 mAH, which is also not to specifications. Third, it calls for a 40 uH inductor. I don't happen to have a collection of inductors, but I do have a few toroids available.
Be aware that I am not using this circuit as designed, so your results may be different.
Even with my changes, it looks to be working for me. However, I hope to be performing more testing on this unit.
The circuit seems to work well for me using AA batteries when I cover the toroid about 4 times, or for about 90 turns of 22 guage wire.
I don't have a micro Henry meter, so I cannot specify what I have in those units at the moment.
I am testing in ambient light, such as what you might get in the shade, or when indoors.
At the moment, this one appears to perform better than the Solar Charger Circuit Project, and also appears to out-performs the 3 Volt to 9 Volt Converter (with either a 4.5V solar panel or a 6V 1 watt solar panel (that I have posted elsewhere). That is, sometimes it appears to perform better than the 3 Volt to 9 Volt Converter, sometimes not.
I will be doing more measurements, and trying to figure out the best way to test even though I don't have everything to specifications.
Solar Charger Circuit Project (my review)
3V to 9V Conerter (my review)
Currently testing for parallel charging, which is typically harder to do than charging in series.
You may get better results from charging in series.
I will also be looking at variations, such as number of turns on the toroid, etc.
Update Sep 7, 2015:
I have yet another AA charging circuit posted here: