Solar Charge Controller Not Charging the Battery? What to Do

A solar off-grid system can for the most part require minimal maintenance. Unfortunately, you cannot rule out the occasional challenge.

One such challenge you may face with both a newly installed or existing system is when the solar charge controller stops charging.

What shows that it’s not working and what can you do to get it charging again?

In this post, you’ll find tips to get the solar charge controller working again, and reasons why it may stop charging so that you can avoid the issues in the first place.

Tips to Get the Solar Charge Controller Charging Again

If the solar charge controller stops charging in an existing installation check:

  • the solar panel and battery cables are intact and still firmly connected to the charge controller terminals and
  • the solar panel is clean and not shaded too.

Reset the Charge Controller

If the charge controller is still not charging, reset it. Depending on the charge controller (consult the owner manual), this can involve the following steps:

  • disconnect the solar panel,
  • then the battery and
  • then reconnecting the battery and lastly
  • reconnect the solar panel.

This can reset the charge controller and clear a firmware lockup that’s stopping the charge controller from working.

Why your Charge Controller may not be Charging (5 Reasons)

If you find that the solar charge controller is not charging the battery, it may be because:

1. The solar panel is shaded or damaged. When this happens, the output voltage can drop significantly to a point where it’s no longer high enough to charge the battery.

Measure the voltage at the charge controller solar panel output terminals. For a 12V solar panel, the voltage at the solar panel terminals measured with a digital multimeter should be in the 18-20V range depending on the solar panel output voltage specification.

Should the voltage be lower,

  • inspect the panel it’s clean and that it is in direct sunlight (no shadows)
  • Confirm that the cable connections between the solar panel and the charge controller are firmly connected at the terminals.

2. The battery voltage may be low. A charge controller will stop working if the battery voltage drops to about 11.5V (estimate).

This is because the charge controller relies on the battery power to work!

Is the battery below 11.5 volts? Then this is definitely a factor that can stop the charge controller from working.

Charge it first, reconnect and check if the charge controller works when the solar panel is connected.

Replace the battery if it’s aged and cannot hold charge or it is damaged.

3. The Charge controller may be faulty. Charge controllers can fail too. The charge controller can fail because:

  • the solar panel output voltage exceeds what it can handle,
  • it overheats because there isn’t enough airflow or
  • there’s a short-circuit at the controller connecting terminals for the solar panel and battery
  • the cables are wrongly connected (interchanged or reversed), or
  • the solar panel cables are connected first before the battery is connected. Always connect the battery first then the solar panel.

If the solar charge controller is damaged, replace it with another.

What Shows that Charge Controller is not Charging

The charge controller is probably not working if:

1. The LED status indicators are blank, and the LCD display shows an error status such as:

  • the charge controller is not charging,
  • there’s no solar panel voltage detected and yet the solar panel, cable connections, and battery are in good working connection and are properly connected.

2. The battery voltage does not change (increase at all) with the solar panels and batteries properly connected.

You may also be interested in this post: Why the solar panel may not be charging the battery

Closing Thoughts

Solar charge controllers can fail too. When they fail, the battery will not be charged.

Possible causes of a charge controller not working include solar panel output voltage exceeding what it can handle, short-circuits of the solar panel, and battery cable terminals at the charge controller among others.

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