UPSs are designed to save your devices from the effects of sudden fluctuation or outages in the power supply. The UPS itself is dependent on batteries that store charge for the rainy days. These are rechargeable batteries and can serve you good for several years even with continual usage. However, these batteries will age out and lose their capacity over time. You must always store an extra battery to make sure you have an immediate backup when required.
Storing batteries, however, is not just-wrap-and-put-it-in-the-store job. Whether it is a lithium ion battery for your laptop or a lead acid battery for a UPS, you must store it properly in order to ensure that its capacity and quality remains intact.
It is true that batteries will lose their capacity over time. Prevention is not quite possible, but proper storage ensures that the loss is minimum. When storing the batteries, several important factors must be kept in mind. Let’s take a look!
Temperature plays an important role in battery storage. The ideal temperature recommended for most batteries is 59 F. However, most of them are also able to bear the extreme temperature as low as -40 F and as high as 122 F. In order to store the batteries for long time and retrieve them with a high capacity, it is best to store them at the recommended temperature in a cool and dry place. However, storing them in a freezer is not a good idea!
There is a limit to the storage period for every battery. You can’t expect to store them for several decades. However, alkaline and primary lithium batteries can be stored for around one decade. Even after ten years, the loss of capacity is only minimal. Nickel-cadmium batteries can also be stored for three to five years. While Nickel based batteries also suffer a capacity loss, it can be greatly reversed with priming. As for lead-acid batteries, the suitable storage period is not longer than two years.
State of Charge
When it comes to storing batteries, state of charge is a factor that shouldn’t be overlooked. The state of charge SOC defines the optimal charge level at which the batteries should be stored. Depending on the chemical composition of the battery, SOC also varies from battery to battery. Typical lead acid batteries must be stored at full charge while the recommended SOC for a lithium or nickel based battery is 40%. And now we leave with a graphical representation of recoverable capacity of various batteries when stored at different temperature and SOC over one year.