Why Your Solar Battery Bank is Not Holding Charge

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The “battery not charging” indicator is the last thing you want to see on a solar power system. Batteries are the most expensive part of the setup, and realizing it is not charging can be stressful. Fortunately, we can identify the most likely causes and try different ways to fix them.

The most likely reasons a battery doesn’t hold a charge are a defective charge controller, faulty wiring, or the battery is damaged. The battery will not charge if the solar panel, charge controller or battery is not properly configured.

How to Diagnose a Solar Battery Bank Problem

If the battery bank is suddenly unable to hold a charge, perform the following procedures. These steps are necessary to narrow down the possible causes. At the same time you can check the entire system’s health status. If the solar panel is not producing power, the battery will not charge as well.

You will need a multimeter to perform this test. we recommend he AstroAI digital multimeter for its simplicity and versaility.

  • Test the solar panel. Disconnect the solar panel from the system. Use a multimeter to check the panel voltage. There should be a voltage on the solar panels as long as there is sunlight. If there none, the panel is defective and needs to be repaired.
  • Test the battery. Use a multimeter tool here. If the voltage is 0 or under 10.5V, the battery is defective and needs to be replaced.
  • Test the charge controller. All charge controllers have a specific output range. if the multimeter shows the voltage is not close to this value, the controller is damaged.

When you have performed the three tests, you will know which component is at fault. Let us take a look at each one in detail.

Safety Tips First

  • Do not forget to turn the system off before doing any inspection.
  • Also make sure to wear safety glasses and gloves. Remember that solar batteries, especially lead acid, can be dangerous so exercise caution when handling them.
  • Some of the steps below require you to handle wires and cables. If you are not comfortable with these or don’t know how, consult a professional solar installer.

Why is My Charge Controller Not Charging the Battery?

If you suspect the charge controller is preventing the battery from holding a charge, check for the following.

Loose or disconnected wiring. Check the battery solar cable wire if it is still connected to the controller. Give it a gentle tug to see if it is loose. Tighten the connection and turn on the controller. The display should show a voltage reading.

Low battery bank voltage. Some controllers will stop charging if the battery VDC falls below a certain value. Refer to your battery manual for the value. Use a volt meter to check the value, and if it is too low, recharge the battery. That should fix the problem.

Blown fuse. The battery fuse may be defective or blown. Replace it immediately with a new one. If your RV solar panel system uses a side wall port, check for signs of a blown fuse too. While you are it, check the rest of the system too.

Defective charge controller. If the multimeter still shows an incorrect value for the controller, the unit is probably damaged and needs replacement. Try any troubleshooting tips in your charge controller manual, and if they don’t work, a replacement is due.

Charge controller protection mode triggered. The main purpose of a charge controller is to protect the battery . There are built in values in the controller uses during charge, and if the voltage goes above these values, it might stop charging.

The battery terminal voltage cannot be more than the charge controller protection value. This is usually not a problem if the controller is compatible with the battery, so make sure the controller amps can match that of the battery bank.

If you suspect a damaged charge controller, it is better to buy a new one that have it fixed. We suggest getting an MPPT charge controller since they can handle different battery and solar panel voltages. Our favorite is the EPEVER MPPT 40A because it has all the features necessary to run a solar battery. .

Battery Wiring Problems and Solutions

The larger the solar array, the bigger the battery bank. This also means thicker, more numerous wires that are vulnerable to problems.

Loose controller and battery wiring. Check the wire that connects the charge controller and battery. Tighten if necessary and replace if it is frayed or worn out. Use only the manufacturer recommended wire sizes for each component.

Incorrect wiring. If the battery wires are reversed or installed incorrectly, the charge could stop altogether. Correct the wiring and the battery should run again.

Faulty solar panel wiring. The battery, charge controller and solar panels are interconnected. If the solar panel cables are incorrectly installed or damaged, it will reduce energy output and affect battery charge.

Overcharge protection. in rare instances, the controller overcharge mode may get triggered and stop the charge. This will only happen if the panel supplies more current than the battery can handle. As long as the batteries and solar panels match, this will not be a cause for concern.

Battery Charging Problems and Solutions

If the charge controller is working properly, the problem could lie in the battery or batteries. Here are the most common issues and how to resolve them.

Old battery. The older a battery gets, the faster it loses power. The battery will also take longer to charge and have trouble keeping charge. If your solar battery is showing signs of old age, it is time to get a replacement.

Capacity. if the battery capacity is too small, it will not be able to sustain a charge for long. If you are running a solar washing machine or a fridge, these require a lot of batteries. If the bank is too small the internal circuits won’t last and charging becomes a problem.

Damaged battery. The easiest way to check the battery status is a volt meter or multimeter. If the reading is zero, the battery is dead. Check its health status regularly and do not wait for the battery to die out before replacing it.

Left idle for long periods. Batteries left discharged for long periods gradually lose power. This makes it harder to recharge them. Even if it does charge the unit will not be able to hold the current. If recharging the battery does not work, you have to replace it.

Solar Panel Problems and Solutions

Sometimes the problem has nothing to do with the battery or the charge controller, but the soar panel. Remember, everything starts with the solar panels converting the sun’s energy into current, so if there is a problem here, the rest of the system is affected.

Damaged panels. Look for signs of hot spots, cracks, snail tracks etc. These are common solar panel problems that could disrupt or halt energy output. These have to be remedied right away to avoid more problems.

Weather. If is raining, snowy or just overcast, solar panel production will be minimal. So do not expect the battery to charge as fast as it does during the summer.

Shading. is there something blocking your panels? Maybe some foliage or tree branch? Did birds make a nest on one of the cells? Any of these could cause a big issue with solar output. A single blocked cell can significantly reduce solar energy production.

Compare Past Battery Performance

Keeping a record of your solar system’s performance makes it easy to check for potential problems. If the battery was able to last for a specific number of hours running an inverter , but then suddenly drops, you know something is amiss.

If you have not increased the inverter load and the weather is very much the same, the problem is likely due to the charge controller or the battery. But if you did increase the watt load, the battery bank capacity has to be increased as well.

The same goes for the charge controller and solar panel. If your system produces 500W a month and is sufficient, no problem. But if you use more solar accessories and appliances, power consumption might exceed 500W. You will need to upgrade the batteries and controller.


Usually solar batteries run without a hitch, but if there are problems you should always be prepared. Seeing that your battery bank does not hold charge can be alarming, but the possible causes – wiring issues, charge controller or battery defects, etc. – can be remedied and fixed with the right knowledge.