For decades I have had this problem that I need to have some kind of current indicator when charging my batteries from small solar panels. Measuring the current just once does not work, because seawater makes all conctacts so unrealiable. Traditional solution has been a blinking LED protected with a Zener, but the damn thing wastes 4 Volts of valuable Voltage.
Design below wastes only 0.7 Volts and blinks always when anykind of
current is going in the right direction. In fact, because this also
replaces the reverse-current protecting diode, this wastes no voltage
at all. ("Any Diode" means of course any diode with 0.7V drop and suitable
current rating :-)
This is the optimal place for the charging indicator, so you can keep the panel outside the tent and watch the blinking light and battery inside. Components are immersed in hot clue.
Timo Noko 2008
Disclaimer: I there is anything you do not understand on this page, please do not ask anybody or do experiments, just forget this. Do not make backcountry trips where your survival depends on DIY devices, whose functions you do not understand.
Disclaimer #2: There are dangers in charging batteries, causing property damage and injuries. If you do not throroughly understand these issues, please do not follow any advice on this page, except this one.
W: "Batteries come in many sizes and shapes, it is darn difficult to connect any wires to those. Especially difficult ones are in cameras and cellphones."
A: Bale Wire Rules.
