Solar panels test for portable battery charger

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.

Solar panels

6V 2W Solar Panels

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.

Solar panels charging the 9.6V pack

Solar panels charging the 9.6V QRP pack

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.

See also related articles:

PIC Frequency Counter

Simple RF Generator

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