Do your solar batteries get hot during the charging process?
While it is normal for batteries being charged or discharged to become warm, you may have genuine concerns about how hot they should get without danger of damage or explosion especially if you are pumping or drawing high currents from them.
In this article, I go share my findings on why solar batteries get hot in the first place, how hot you should let them get to and what you can do to prevent them from overheating.
Why Do Solar Batteries Get Hot?
There are several reasons why solar batteries become hot in the first place.
It is normal for solar batteries to generate heat when charging and discharging them
During the charging and discharging process, the conversion of energy from electrical to chemical and vice versa is not 100% efficient.
Some of the energy is wasted as heat which explains why the battery temperature builds up.
When small currents are pumped or drawn from the batteries, they may feel cool or warm to the touch.
The battery temperature can build up to higher levels when this current increases especially if proper management of battery temperature is not done.
When the charge controller is not able to adjust the charging rate according to battery temperature
The charge controller should adjust the battery voltage or current during the charging process.
If it has no means of accurately monitoring the battery temperature, then it is cannot adjust it during the charging process to prevent the batteries from becoming hot.
This can happen when the charge controller does not have a temperature probe connected, if it is not properly installed, or if it is faulty.
Thermal runaway
The battery temperature can buildup to excessive levels during the charging process when the battery voltage drops as its temperature increases and the charge controller are not able to reach the correct battery charge state and temperature and continue to increase the charging current or voltage
Tight spacing between batteries restricting airflow
If the solar batteries are closely stacked next to each other with no spaces in between then there will not be proper airflow and cooling of the battery bank which can result in the high-temperature build-up of the batteries.
Battery bank installed in a room with poor ventilation
If the solar battery bank is installed in a room with poor ventilation such as a closed room and is subjected to high charging currents then the batteries will not cool properly because of poor airflow and the temperatures can build up to excessive levels quickly.
Shorting cell in the battery results in high current draws from the battery and high temperature buildup.
How Hot Should Solar Batteries Get?
The recommended maximum temperature for solar batteries during discharge is about 140°F (60°C) and 122°F (50°C) when charging.
If the battery is subjected to higher temperatures during charging or discharging then it increases its chances of failure.
Can You Make an Overheated Solar Battery Work Again | What to Do?
If a solar battery gets too hot, you may be able to recover it sometimes. It helps to quickly disconnect it from the charger, allow it to cool, and then charge it slowly.
Note that there is no guarantee that it will work again. It is better to prevent overheating in the first place.
Is 40°C too Hot for a Solar Battery?
This really depends on the recommended operating temperature range for your type of battery.
Always check your battery manual first.
That said, the maximum operating temperature range for several battery types is about 140°F (60°C) and 122°F (50°C) when charging.
How to Keep Solar Batteries Cool (3 Tips provided)
Here are 3 tips to help you prevent your solar batteries from overheating.
#1. Connect a temperature probe to your battery bank
If the battery charger or solar charge controller has a temperature sensor, install it on the battery bank. Check the manual for guidelines on how to properly install it.
The temperature probe monitors the battery temperature during charging and adjusts the charging current to prevent overheating of the battery.
This can lead to boiling of the battery, bulging, and potentially an explosion.
Note: Temperature sensors tend to be specific to the charger or charge controller.
#2. Install the battery bank in a well-ventilated area. This improves the airflow over the batteries and helps minimize overheating of the battery bank.
#3. Provide for spacing between the batteries in the bank – do not stack them against each other. This slows down the airflow over the battery surfaces and stops them from cooling properly.
Related questions:
Can Solar Batteries Catch Fire or Explode?
Yes, solar batteries can explode and catch fire if they overheat and the excessive heat and gases given off are not managed properly.
All that is needed is a spark to ignite the gases for the explosion. This is why proper ventilation is important.
Final Thoughts
There recommended operating temperature for solar batteries depends on the battery manufacturer – check the manual for your battery type.
Several batteries types have a recommended temperature of about 140°F (60°C) and 122°F (50°C) when charging.
The main causes of overheating in batteries are high charging and discharging current from the battery and poor ventilation and spacing of the batteries in the battery bank.
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