Why your solar battery is not fully charging

A man is charging his electric car at a charging station.


Issues with recharging a solar battery can be the result of several problems. Learn the most common causes in this beginner’s guide.

In this article we will cover

Solar batteries are a significant investment for anyone with a solar power system. They’re perfect for ensuring that you always have solar energy available, even at night - but as with all electrical components, they can develop problems that result in poor recharge rates, or even a complete failure to charge.

These problems are typically the result of one or more issues with:

  • The battery
  • The inverter
  • The solar panels

Below, we explore some of the most common problems with battery charging issues and how to spot them.

Does the type of solar battery matter?

There are a number of types of solar battery, usually defined by the chemical materials used to store solar energy. These include:

  • Lead acid
  • Lithium ion (Li-ion)
  • Nickel cadmium
  • Solar flow batteries

Each has different capabilities, costs, and maintenance requirements. Lead acid batteries, for example, are relatively inexpensive, but can experience sulfation - a buildup of sulphate crystals due to the battery being deprived of a full charge - while the more modern and higher quality lithium ion batteries don’t.

This is one of the reasons why ZEN uses and recommends lithium-ion batteries. They simply don’t have the same common issues as other battery chemistries, making them last longer and operate more efficiently.

Problems with the battery

The first offender in the list of charging issues is the battery itself. While most batteries last for years with proper care; poor installation, improper use or an inappropriate environment can cause issues with charging.

  • Battery age. The older a battery gets, the faster it loses power and the longer it will take to charge - it may have trouble keeping charge too. Solar batteries from PylonTech, our preferred provider, have a warranted lifetime of 10 years and a design life of greater than 15 years. If your solar batteries are old, it may be time to look at a replacement.
  • Too little capacity. Smaller battery banks made up of lower-capacity or a small number of batteries when compared to the solar system or house energy usage, won’t be able to sustain a charge for long. If you’re running a washing machine or heat pumps using battery power, these can quickly drain the batteries if not sized correctly. In the same breath, if your household electricity demand increases or is significantly greater than what your solar batteries can provide or your solar energy system can generate, your solar batteries won’t receive enough energy to charge them.
  • Battery damage. Simple wear and tear can result in a solar battery being unable to charge. One of the most common problems with lead acid batteries is ‘sulfation’, which occurs when the solar battery is unable to reach a full charge for a long time. Keep an eye out for a greenish discoloration around your lead acid batteries if you have them - this is a sure sign of sulfation.
  • Rapid/frequent cycling. A “cycle” occurs when a battery fully charges and then fully discharges. If you cycle frequently and/or rapidly, your battery may incur damage. Most solar-powered homes cycle about once per day. ZEN systems use an internal battery management system and high-end solar inverters to safely manage cycling.
  • Overheating. Solar batteries are designed to operate within a specific temperature range. If the environment around them is too hot, they can suffer from ‘thermal runaway’. This happens when the internal heat generated through the battery’s operation can’t dissipate fast enough. This can cause damage to the battery but can also be easily negated with selection of the right solar battery equipment and installation location.
  • Blown fuse. There may be fuses in your solar battery that will trigger if the battery gets too hot or if there is a short circuit. Once blown, the fuses will need to be replaced for the battery to recharge again.

Problems with the charge controller or inverter

Your solar system will come with a charge controller, either separate from or built into the inverter. This helps to keep the solar system in check by regulating the voltage and current flow from the solar panels to the batteries. This prevents issues like overcharging and overheating, making sure your system is durable and safe to use.

Like all electrical equipment, the charge controller can become damaged, and this can result in issues with solar battery charging.

  • Loose wiring. The charge for the battery runs through the charge controller, so loose wiring between them can result in the electricity never reaching its destination. Your charge controller should show a voltage reading if it has a display. 
  • Low battery bank voltage. Some charge controllers stop charging a battery if the voltage falls below a certain value, which will be stated in your manual.
  • Defective charge controller. Sometimes the problem is with the charge controller itself. Poor quality charge controllers or charge controllers not rated for the load on the system can simply break. They can be tested using a multimeter, but it’s best to leave this kind of diagnosis to a professional.

Problems with the solar panels

Solar power starts with the solar panels. If there’s a problem with them, it will affect the entire system - your solar battery charge rate included.

  • Weather issues. Rain, snow or cloud can block the sunlight from hitting your panels and reduce power generation. Low power generation may result in the batteries not being charged as fast or as much as usual.
  • Shade. Overhanging trees or nearby buildings can cast shade on your solar panels, blocking the sunlight and stopping them from charging your batteries. This is why solar panel placement is an integral part of solar installation.
  • Hot spots. After some time in operation, solar panels can develop hot spots. These are small points on your panel that heat up more than the rest, created when parts of shade cover some solar cells. These hot spots can end up actually consuming power rather than making it, and can impact solar panel power output.
  • Cracked panels. Solar panels are tough once installed, but they can be cracked by blunt force trauma. These cracks can cause mechanical failures, so keep an eye out for obvious cracks as well as odd patterns on your panels.

The best way to avoid problems with your batteries is to have a true expert design and install your solar system from the very start. Many of these issues are the result of a poor setup, with lower quality products. 

If you want your solar system to stand the test of time, get in touch with the ZEN Energy team today for peace of mind on the quality of your solar installation and equipment.

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