AAA solar batteries acting weird? Answered
I recently got a bunch of solar garden lights intended for a different purpose of course ;)
During the modding stage I made a simple wireless charger for one of the lights an it worked as intended.
However, while testing the light and how long it works I got a bit confused.
The battery states 300mAh (NiCd), which is fine for a single LED solar light and a small cell.
The light uses between 6 and 10mA, depending on the current color.
With my dumb calculations I would say a fully charged battery should last around 30 hours - 24 at least.
But after 8 to 9 hours the light goes off and the battery is down to a low level.
Being dirt cheap I tried the same again with a good 1000mA NiMh battery, which otherwise does a good job in other applications.
The 1000mA battery lasted 3 days, which again is way short of the calculated target.
At this stage I suspect the Joule thief used in the solar light is the culprit as my own circuits don't show this problem...
Would it be worth to get the oscilloscope out to check the actual spikes produced by the circuit?
And how would I go with properly calculating the consumption?
Being a color changing LED (circuit inside the LED) does not make it much easier :(