Solar Charge Controller not Charging Battery Troubleshooting

Expert step-by-step DIY directions for troubleshooting and fixing a Solar Charge Controller not Charging battery problem properly.

Solar Charge Controller not Charging Battery?

If your battery connected with the solar system but doesn’t charge properly, the problem is likely to be a battery problem, a wrong system connection, or a problem with the solar charge controller settings. (Note: The Panels, charge controller, and battery must be configured correctly.)

To diagnose the problem, do the following:

  1. Measure the whole system from the battery, the solar charge controller to the solar panels with a multimeter, First, Disconnect the solar panel connection and measure the voltage, As long as there is sunlight, there will be solar output. If there is no voltage detected, a problem of solar panels or rectifier diodes may exist. It is also necessary to measure the voltage of the battery. The actual voltage of the battery is lower than 20% of the nominal voltage. The charging controller does not work because of the battery low voltage and outputs protection. then need to charge the battery with extra charger.
  2. Measure the Solar Charge controller Terminal Output Voltage, check whether the output voltage is in the right range or not if the output range is not as the rated value, the solar controller may have a problem, replace a new controller to try.
  3. Measure the Battery Voltage, make sure the battery voltage is not too high nor too low.

Solar Charge Controller not Charging Battery Factors Checklist

Broadly, there are 4 factors you’d need to consider.

  • solar charge controller factors
  • solar panel factors
  • battery factors
  • weather factors

Let’s understand each of the scenarios one by one.

Solar Panel Charge Controller Factors

Solar Panel Charge Controller Enters Charging Protection Mode to stop the charging

1. Direct charge protection point voltage: Direct charge is also called rapid charge. It’s a fast charge process. Generally, the battery is charged with high current and relatively high voltage when the battery voltage is low. However, there is a control point, also called a protection point. The point is the value in the above table.

When the battery terminal voltage is higher than these protection values during charging, the direct charge should be stopped. The direct charge protection point voltage is also the “overcharge protection point” voltage. When charging, the battery terminal voltage cannot be higher than this protection point, otherwise, it will cause overcharge and damage to the battery. ‍

2. Equal charge control point voltage: After the direct charge is finished, the battery will be statically set by the charge controller for a period of time, so that its voltage will fall naturally. When it falls to the “recovery voltage” value, it will enter the equal charge state. Why design an equal charge? That because after the fast charge, there may be some batteries that are “backward” (the terminal voltage is relatively low) to the battery bank. In order to pull these individual molecules back and make all the battery terminal voltages have equal consistency, it is necessary to match the high voltage with a moderate current to recharge the battery for a short while, so it called equalization charging also called a balanced charging.

The charging time should not be too long, usually from a few minutes to ten minutes. The longtime setting is not good. For a small system with a two-cell battery, it doesn’t make much sense to use the equal charge. Therefore, the street light controller generally does not have an equal charge, only two stages.

3. Floating charge control point voltage: Generally, after the equal charge is completed, it’s terminal voltage naturally falls. When it falls to the “maintenance voltage” point, it enters the floating charge state, when the battery voltage is low, it will be charged a little. and the battery will continue to rise. High, this design is very good for the battery, because the internal temperature of the battery has a great influence on the charge and discharge.

In fact, the PWM method is mainly designed to stabilize the battery terminal voltage, and the battery charging current is reduced by adjusting the pulse width. This is a very scientific charging management system. Specifically, at the end of charging, when the remaining capacity (SOC) of the battery is >80%, it is necessary to reduce the charging current to prevent excessive outgassing (oxygen, hydrogen, and acid gas) due to overcharging.

4. Over-discharge protection voltage: It is easy to understand. Battery discharge cannot be lower than the rated value. the battery manufacturers also have their own protection parameters (enterprise or line standard),for safety reasons, the 12V battery over-discharge protection point voltage is artificially added plus 0.3v as the zero-drift correction of the temperature compensation or control circuit, so that the over-discharge protection point voltage of the 12V battery is: 11.10v, then The over-discharge protection point voltage of the 24V system is 22.20V. At present, many manufacturers of charge and discharge controllers use the 22.2v (24v system) standard.

Both PWM Solar Controller and MPPT Solar Charge Controller has the above Feature of Protection. The MPPT controller is recommended when you have a longterm demand of solar power.

Solar Panels Factors

1. Solar Panel do not output Power, Confirm that the solar panel connection is correct, and make sure the positive and negative poles did not reverse connect.

2. Check the Solar Panel to make sure the panels did not block by shadows nor cover by stains to ensure the solar collection.

3. Check whether the specifications of the solar panel is correct. whether the open circuit voltage meets the requirements of the controller.

4. Check the power of the solar panel exceed the rated value of the solar controller or not. if The power is too high, which may cause the solar controller to burn out.

5. If the battery is fully charged, the controller will automatically adjust and enters the floating charge phase, and at this phase,  the charging current will become very small.

Battery Factors

Battery Fully Charged but Run out Soon.

1. Check Whether the battery capacity design is reasonable or not, if the capacity is too small, then the running time will be short.

2. The battery is aging, the service life of the battery is generally 2-3 years, the capacity of the battery is greatly attenuated, after this period, the battery needs to be replaced regularly.

3. Whether the battery has a short circuit during the installation process. Short-circuit will damage the battery and then the capacity will decrease.

4. The load power exceeds the design power.

Battery Low Voltage Protection

When the battery is run out of power and idle for a long time, it’s hard to charge the battery by the solar system directly, Now you need to check the voltage of each battery, find the lowest voltage battery out and fill it with a large current charger.

Faulty Battery

If a battery in the battery pack is damaged, the entire battery will not be successfully charged. Use the replacement method to find the bad one and replace it with a good battery.

Weather Factors

Weather factors, if there is no sunshine for a long time, it will result in less solar collection, and the output voltage may too small to charge the battery.

Solar Charge Controller not Charging Battery Treatment:

1. There is an open circuit or certain device damage, the treatment method: replace or repair the device
2. The sun is not strong enough, the treatment method: move to a place where it is easier to collect sunlight.
3. Voltage mismatch, processing method: increase the booster, add several photovoltaic panels in series


Will a solar panel charge a dead battery?

A: No, the Solar Charge controller will automatically detect the battery voltage and if the battery dead, the charging process wont working, we recommend use a Individual Battery Charge to Fix and Restore the Dead Battery before reconnect it to solar system.

How to Read Solar Charge Controller Error Code?

A: Solar Charge Controller Error Code indicate whether a specific Problem the Charge Controller Detected, Following the User Manual to resolve the problem.


Solar Charge Controller not Charging Battery is a very common problem that many people will encounter and it is easy to solve. Just follow the above instructions step by step to troubleshoot and then replace it to restore the vitality of the solar system. or connect a zhcsolar expert for help, go to the contact us

Where to Buy the Best Quality MPPT Solar Charge Controller?

ZHCSolar Offers the Best Quality and Reliable MPPT Solar Charge Controller, Get Free Shipping Now.

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