You know the crazy cheap <$5 solar drive way lights? Well the last time mine failed (even after diy repairs) I just bought two new ones. Sure enough years later I started to notice that they were not behaving similarly. Since the battery is the likely suspect I replaced the batteries but still experienced noticeable differences. I probably should have ignored it but decided to take matters into my own hands and started modifying. Since I had two lamps operating inconsistently is decided to sacrifice one for betterment of all.
My first experiment was to put two solar cells in parallel and that was a loser... So next night I tried the two cells in series and that helped. In the meantime I bought more new ones (for only $3 ea). The franken-lamp with two solar cells and 600mAH battery was spanked by a new stock lamp with 300mH battery. Not surprisingly the two solar cell lamp turns on about 15 minutes later at dusk from the 2x higher light energy capture.
My next experiment was to borrow an inductor from the parts lamp and connect it in parallel. Based on my guess about how those work that should increase the switcher current. It was pretty bright but for an even shorter time. The next obvious experiment was putting the two inductors in series, that should cut the current in half... Unexpectedly that worked like a charm. LED was similar brightness and burned hours longer into the night.
The stock lamp appears pretty well engineered but modern white LEDs may have increased in efficiency since that design was first buttoned up (I see no difference in brightness between 2x and .5x current). Since I don't need driveway lamps after 1AM I don't think I will modify any more.
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If you look closely at the picture you can see a slight tint color difference between the two solar cells making me think different solar cell batches used by vendor in original manufacturing. This could explain the differences I saw, or not.
JR
My first experiment was to put two solar cells in parallel and that was a loser... So next night I tried the two cells in series and that helped. In the meantime I bought more new ones (for only $3 ea). The franken-lamp with two solar cells and 600mAH battery was spanked by a new stock lamp with 300mH battery. Not surprisingly the two solar cell lamp turns on about 15 minutes later at dusk from the 2x higher light energy capture.
My next experiment was to borrow an inductor from the parts lamp and connect it in parallel. Based on my guess about how those work that should increase the switcher current. It was pretty bright but for an even shorter time. The next obvious experiment was putting the two inductors in series, that should cut the current in half... Unexpectedly that worked like a charm. LED was similar brightness and burned hours longer into the night.
The stock lamp appears pretty well engineered but modern white LEDs may have increased in efficiency since that design was first buttoned up (I see no difference in brightness between 2x and .5x current). Since I don't need driveway lamps after 1AM I don't think I will modify any more.
===
If you look closely at the picture you can see a slight tint color difference between the two solar cells making me think different solar cell batches used by vendor in original manufacturing. This could explain the differences I saw, or not.
JR
