Signs that a Solar Charge Controller is Bad | What to Look out for

Solar charge controllers can work reliably for many years but do fail too. The extent and type of failure can vary, in some cases, it can be catastrophic and quite obvious such as when the charge controller is burnt-out.

In other cases, it can be less obvious, with the charge controller seemingly working well yet not charging the battery optimally or at all.

So, how can you tell when the charge controller is bad or damaged? For example, when the controller has only 2 LEDs – a solar panel and a battery charge indicator.

How do you test a charge controller?

This post lists ways you can test and confirm if the charge controller is working well, the possible ways and symptoms it can fail and how you may be able to fix it.

What Checks you Can Do

If you suspect that the charge controller is faulty, double-check the following to rule out any other challenges that can affect the charge controller performance.

#1. Double check the wire connections between the solar panel and the battery. They should be firm and properly connected.

#2. Additionally, confirm that the charge controller is set to charge the battery type installed. Wrong settings for the battery type affect which voltages the battery should be charged to and can give the impression that the charge controller is not working well.

The battery can overcharge or undercharge depending on the settings selected. Refer to your owner manual for guidance on how to check and confirm if the battery type selected in the charge controller matches your battery type.

Signs that a Solar Charge Controller Works

Assuming that the solar panel and battery are properly connected to the charge controller then the charge controller is probably working if:

  • it has LEDs, the solar panel and battery voltage LED indicators light up. Consult the owner manual to check that their lighting sequence does not reflect an error condition with the controller.
  • the controller has an LCD display, it should be on with no error condition unless the error is confirmed in the corresponding component, the battery, or the solar panel.
  • the voltages at which the charge controller displays the bulk, absorption, or float voltages (by way of LEDs or display) correspond to the battery voltages measured with a digital voltmeter.

Signs a Solar Charge Controller is not Working

Your charge controller is probably not working if you notice and confirm the following:

#1. The solar charge controller receives power from the solar panels but does not charge the battery. You can use a digital voltmeter to measure the voltage from the solar panels and the connections terminal at the solar charge controller.

Is the battery charging? To check whether the battery is charging, if your charge controller has a charge status monitor, you can check if the readout for energy (watt hours) or Ah increases over time.

Alternatively, you can measure the battery voltage at intervals of say 1 hour. Assuming the wire connections are connected properly and the battery is in good condition, there should be an increase in the battery voltage.

#2. The Solar charge controller does not seem to be regulating voltage output to the battery. If the voltage at the battery terminals of the charge controller is as high as that from the solar panels then the charge controller is probably faulty.

A charge controller in good working condition should be able to regulate the output voltage of a 12V solar panel (as high as 18V) to the maximum recommended voltage of 14.5V for AGM batteries to avoid overcharging.

How Long a Solar Charge Controller Lasts?

This really depends. On one end of the spectrum, there are solar charge controllers that have been in service for 10+ years and still going strong while there are others that last for a few months or less. There are several factors that contribute to the longevity of the charge controller, in no particular order:

  • quality of build and manufacture,
  • connecting and the disconnecting charge controller as recommended by the manufacturer
  • properly sizing your charge controller to avoid overload
  • installing the charge controller in the recommended environment away from water or high temperatures

What Causes Damage to a Solar charge controller

#1. Connecting or disconnecting solar charge controller in the wrong order

To avoid damage to the charge controller, when installing a charge controller, always connect the battery first before installing the solar panel.

Similarly, when removing and disconnecting a charge controller, always disconnect the solar panel first before the charge controller.

It helps to install a double pole single throw switch that can handle your solar panel current between the solar panels and the charge controller to conveniently and safely isolate solar panel power from the charge controller.

#2. Sometimes the charge controller can fail of its own accord. Sometimes a charge controller can fail on its own even when you’ve followed the correct sizing and installation instructions. You can check here for information on how a charge controller can fail.

Closing Thoughts

Your solar system charge controller is likely bad if the display does not work, is not charging the battery or the battery voltage is as high as the solar panel voltage to mention a few of the possible systems.

Note: This assumes that the solar panel, battery, and the associated wiring are properly connected

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