I am thinking of building a small solar battery charger for future QRP portable operations where power supply conditions do not exist. I got this two 6V/2W solar panels many months ago from ebay, but only these days I got the chance to test them properly.
Througout ebay there are a lot of models with various voltages and currents. After a long scout I took these two panels for testing. It is probably the best price per watt I could find at that time.
The main goal is to charge the batteries for my FT-817ND. Instead of the stock battery pack, 9.6V @ 1400mAh, I have also 8 x AA Sanyo 2700mAh rechargeble batteries. So two solar panels of 6V each putted in series will handle the 9.6V of each pack.
This is the setup I used for testing. Beetwen the batteries and the panels I mounted a schottky diode for reverse current protection from the batteries (with this diode I have a voltage drop of about 0.3V – it is a 5819 type, supplied by the chinesse ebay seller in the solar panels packing). A voltmeter and ammeter was monitoring the circuit. Note that no limiting resistor is used, the panels are going directly to the batteries only via diode.
The maximum current I got was 200mA, with bright sun from 1 to 2 PM that day. The voltage was around 10.9V at the battery pack, aprox. 1.36V/cell, and 11.2V at the panels. These values were constant during one hour.
With no load, the panels in series deliver about 13 to 14V.
So with this setup, at 200mA, I think I will be able full charge the 1400mAh in about 10hours, at C/10, and for the 2700mAh pack the time will go double, aprox. 20hours. But the sun will not always bright for this long in a ordinary day, so I will probably go for an extra pair of panels to add to the setup. I am thinking also to charge the cellphones with those. With proper connectors and voltage protection will be a nice tool also for camping.
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