Why can I recharge lead acid batteries with solar but not lithium ion? Answered
I just got a 5 watt solar panel and started experimenting with it today. I want to use it to charge a single 10 watt hour/2.5 amp hour 18650 lithium ion cell. The solar panels have an open voltage of 22 volts. I connected the solar panel to an anyvolt3 (boost/buck power regulator), set the anyvolt3 to put out 4.2 volts, then connected the anyvolt to the lithium cell with a blocking diode. I accounted for the voltage drop of the blocking diode and the panels charged the lithium cell at .1 watts. Pathetic.
Then I tried charging a 20 amp hour Werker sealed lead acid 12 volt battery. I set the anyvolt to 14.4 volts. The panels charged the lead acid battery at 4.5 watts. Thats pretty good.
Now why can I charge the lead acid but not the lithium. The lithium is what I really want to charge because i want to use the solar panel to charge lithium cells when I go on long bike tours. I don't want to take any heavy lead acid batteries on my bike trip.