RECHARGEABLE BATTERY SHELF LIFE

Nickel Cadmium ( NiCd )Battery Storage

 Batteries and Fuel Cells 

The sealed nickel-cadmium cell can be stored in the charged or discharged state without damage. It can be restored for service by recharging (one or two charge/discharge cycles). [Ed. note: or three charge/discharge cycles].
 
Store NiCad batteries in a dry location with low humidity, no corrosive gasses, and at temperature range of -20°C to +45°C. Storing batteries where humidity is extremely high, or where temperatures fall below -20°C or above +45°C

Because long term storage can accelerate battery self-discharge, and lead to the deactivation of reactants, locations where the temperature ranges between +10°C and +30°C are suitable for long term storage.
1% to 2% self-discharge per day at room temperature should fully recover after a few charge cycles, practical shelf life approx 5 years.

When storing batteries for more than one year, charge at least once a year to prevent leakage and deterioration of performance due to self-discharging.
When using a rapid voltage detection charger carry out charge and discharge at least once every 6 months.
 

Nickel Hydride ( NiMH ) Battery Storage

Generally speaking, a loss of voltage and capacity of batteries due to self-discharge during storage is unavoidable. The factors inducing this self-discharge of Nickel-Metal Hydride batteries is listed below:
·             The inside of the cell is a hydrogen atmosphere at low pressure, which gradually reduces the active materials at the positive electrode, resulting in a drop of cell capacity. Accompanied by this, the negative electrode which is thermodynamically unstable in its charged state gradually gives off hydrogen gas, thus reducing cell capacity.
·             The active materials at the positive electrode in its charged state self-decompose, causing the cell capacity to decrease.
·             Impurities within the cell, especially nitric ions, are reduced at the negative electrode and diffuse to the positive electrode where they are oxidized. This results in a lowered cell capacity.
The factors (2) and (3) also apply to Nickel-Cadmium Batteries. As discussed above, the self-discharge of Nickel-Metal-Hydride Batteries during battery storage causes a loss in stored energy. However, once recharged, this lost portion of the capacity will be almost completely restored. The self-discharge characteristics of Nickel Metal Hydride batteries is affected by storage temperature. . . If the battery is stored at high temperatures, the self-discharge will be accelerated. Also, the longer the storage period, the more the cell capacity decreases. As mentioned above, since the capacity of Nickel Metal Hydride batteries lost by self-discharge can be restored by recharging, there are virtually no noticeable adverse effects of battery storage. However, prolonged storage at high temperatures may deteriorate or deform the gasket or the separator, and should be avoided. Either fully charged or discharged, Nickel Metal Hydride ( NiMH ) batteries may be stored indefinitely. . . In either cased (charged or discharged) the capacity is recovered within two or three charge / discharge cycles. 

Shelf Life of Nickel Hydride Batteries.

Due to the fact that long-term storage can accelerate battery self-discharge and lead to the deactivation of reactants, locations where the temperature ranges between +10°C and +30°C are suitable for long-term storage.

When charging for the first time after long-term storage, deactivation of reactants may lead to increased battery voltage and decreased battery capacity.
To restore batteries to original performance repeat several cycles of charging and discharging.
When storing batteries for more than 1 year, be sure to charge at least once a year to prevent leakage and deterioration in performance due to self-discharging.

You should store NiMH batteries in a dry location with low humidity, no corrosive gases, and at a temperature range of -20°C to +45°C. Storing batteries in a location where humidity is extremely high or where temperatures fall below - 20°C or rise above +45°C can lead to the rusting of metallic parts and battery leakage due to expansion or contraction in parts composed of organic materials.