Why your Solar Charge Controller may not be Turning on (+ Suggested Fixes)

Picture this – you’ve just purchased your solar system – solar panels, battery, charge controller, and inverter followed the wiring instructions and you’re ready to start your off-grid solar system but unfortunately, the charge controller fails to power up!

You may have a solar system already with a charge controller that just fails to start one day. Why does your solar charge controller fail to come on and how can you fix it?

This post lists the common reasons why your charge controller may not power on and what you may be able to do to fix it.

Why your Solar Charge Controller may Not Turn On?

There are several reasons why your charge controller may not turn on:

#1. Confirm that the charge controller wiring is properly connected to the battery. If the charge controller wiring to the battery is improper, the charge controller will usually not turn on.

To check this, do the following:

  • Confirm that the positive and negative terminals on the battery are wired to the terminals marked battery positive and negative respectively on the charge controller. Interchanging the wire connections or reverse polarity will stop the charge controller from working.
  • Also double-check that the terminals from the battery are not wired to the load output terminals instead of the battery terminals on the charge controller as this can also stop the charge controller from working.
  • Check that the wires from the battery connect with the metallic terminals on the charge controller. There are instances where the insulation from one or both of the wires is not stripped properly and continues to restrict the flow of current to the charge controller.

Measure that voltage at the charge controller battery terminals and compare it with the battery voltage. It should read the same if the charge controller is properly connected to the battery. This way you’re sure that the battery is properly connected to the charge controller.

#2. Is the battery voltage at least 10-11V? The charge controller needs to be at least 10-11V to power on. If the battery voltage is too low then the charge controller will not power up.

Measure the voltage the charge controller is receiving from the battery by placing the multimeter probes across the terminals marked batt + and battery negative on the charge controller.

You may have to connect a fully charged battery to rule out that the charge controller is not working because of low battery voltage.

#3. Check that the solar charge controller is not damaged. A damaged charge controller may also not turn on. The charge controller can suffer mechanical damage, or be damaged when exposed to water, extreme heat, or electrical damage.

Inspect the controller for any signs of physical damage, burn marks, or burnt smell as this can point to a damaged controller.

A charge controller may suffer electrical damage if the output terminals are accidentally short-circuited or if it is connected to a solar panel array with a power output that exceeds what it can handle. If damaged, you’ll likely need to get a replacement controller.

Closing Thoughts

Your charge controller may not power up if: it is not properly connected to the battery, the battery voltage is below a certain voltage threshold usually 10-11V, or if the charge controller has suffered mechanical or electrical damage.

If the charge controller has suffered physical or electrical damage then you’ll usually need to replace it with another one.

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