How to store lead acid batteries

All lead acid batteries discharge when in storage – a process known as ‘calendar fade’ – so the right environment and active maintenance are essential to ensure the batteries maintain their ability to achieve fill capacity.

This is true of both flooded lead acid and sealed lead acid batteries.


  • The ideal storage temperature is 50°F (10°C).

In general terms the higher the temperature, the more chemical activity there is and the faster a sealed lead acid battery will discharge when in storage.

Tests, for example, by Power-Sonic on their 6 volt 4.5 amp hour SLA battery found it would need recharging within two months when stored at 104°F (40°C) compared to 18 months when stored at 41°F (5°C).

SLA shelf life at different temperatures
The PS-640 shelf life at different storage temperatures

When it comes to the cold electrolyte in a fully charged battery can withstand temperatures down to -33°F (-36°C) before freezing. When fully discharged the electrolyte is basically water so it will freeze at  32°F (0°C).


  • The ideal storage humidity is 50%

Some sealed lead acid batteries have terminals which will start to rust in very humid conditions. Surface rust can quickly be cleaned away with sandpaper or baking soda mixed with water but if there is serious corrosion this will create an uneven surface on the terminal which could cause connection issues when attempting to use the battery.

If you are in an area with high humidity and the terminals are from a metal that will rust then smear them with grease to provide a water proof layer.


Sealed lead acid batteries need to be kept above 70% State of Charge (SoC). If you are storing your batteries at the ideal temperature and humidity levels then a general rule of thumb would be to recharge the batteries every six months.  However if you are not sure then you can check the voltage as follows:

  • If the battery has been stored in the cold bring it to room temperature (this can take several hours for the battery to warm right through).
  • Check the manufacturers data sheet to determine how many cells are in the battery
  • Use a voltmeter to check that the cells has at least 2.07 volts.

So, for example, a 6 volt battery with 3 cells should have a voltage of 6.21 volts when it is 70% charged.

Shelf Life

Assuming a sealed lead battery is stored at the ideal temperature and regularly recharged when required, its life can be  3- 4 years in storage.

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