We advise anyone who is building a solar powered application to test power flow going into your battery system or device. You will get to see whether it is working (LED indicators aren’t always reliable) and you can capture data that will let you make more informed estimates about performance.
We’re currently testing a number of camera chargers to make sure they work with our new solar chargers (they’ll have 2 2.0 Watt, 6 Volt panels that can switch between series and parallel, 6 and 12V). To recreate the setup, you’ll need:

– a solar panel
– 2 multimeters ($15)
– a breadboard ($5)
– connecting cables, I use the ones from Adafruit, and solder them to gator clips (to connect to the multi meter probes) and output wires from the solar panels.
Then its simply a matter of connecting everything up properly. As a reminder, connect the Voltage readings in parallel to your target device or battery. Connect the Amp readings in series with the current flow.
Here’s the first reading on a hot, but cloudy day on a DUMBO rooftop. You’ll see we’re getting 9.82V from our 10V panels and 11.3 mA. That is only .1 Watts. Part of it seems to be the clouds, but the Amps are jumping all over the place so we think there is a charge controller that doesn’t perform well at low current (The charger in the left corner performed better at low light).
The sun appeared (still a bit hazy) and current jumps to 147.8 mA, or 1.45 Watts flowing through the battery. Both chargers performed well in full sunlight. The Canon NB2L battery is 5.3 Watt hours and we know there is some loss factor (lets assume 20%), so we can estimate that it would take about 4.4 hours to charge this battery in this level of sunlight (5.3/1.45 * 1.2). We’ll check in throughout the charge cycle to make sure the current and Voltage remain stable.
Here’s a picture of the modified breadboard wires from Adafruit.

One Response

  1. Gary Clarke

    Hi thanks for this. I’m trying to measure power going into one device using two multimeters, one for volts and the other for amps.

    I was told to measure volts in series and amps in parallel.

    I can do the two individually but not at the same time, since when i put my amp meter across the output it shorts the volt meter out.

    How can i do this properly, is there a special circuit on the breadboard ?

    Thank you.

    Reply

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