He Didn't Build That" I Did...(Part 5)

Solar Charge Controller

Solar Charge Controllers

The solar charge controller provides a regulated DC output and stores excess energy in a battery. It also monitors the battery voltage to prevent under/over charging. It may be used to power 12-volt or 24-volt DC equipment with solar panels, as well as in charging cell phones and laptop computers.

Once we have sized our battery bank and solar panel array, determining which charge controller to use is comparatively straightforward. All we have to do is find the current through the controller by using:

  Power = voltage x current; P = V x I

Take the power produced by the solar panels and divide by the voltage of the batteries:

I = P/V = 400 watts/12 volts = 33.33 amps.

Now introduce a safety factor of 25%. Multiply the value we have found by 1.25 to account for variable power outputs: 33.33 x 1.25 = 41.6625 amps

In our example we would need at least a 45 amp. controller. The Flex Max 60 MPPT Charge Controller would fit our specifications, or we can have individual charge controllers for each 100-watt solar panel:

I = P/V = 100 watts /12 volts = 8.33 amps. x 1.25 = 10.41 amps

Therefore we can use one (1) - 60 amp. charge controller, or four (4) - 15 amp. charge controllers.  It’s your call; the choices you make will depend largely on the price of each controller. Usually charge controllers come free with individual solar panels, so check that out first before making any purchases. If you have to buy your own controller, I suggest that you choose one with a USB port(s) and with multiple DC voltage outputs: 3V, 6V, 9V and 12V for charging your cell phones and other electronic gadgets.

Next time, we are going to discuss solar inverters.