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Storage recommendation for various battery types in the manufacturer's words.
It makes a lot of sense to read what the battery manufacturers say about long term battery storage.
Alkaline Batteries
A refrigerator, with a temperature range from 0°C to 10°C [32°F to 50°F], is a good place for storing batteries, especially primary batteries. The refrigerator may, of course, also be used to store secondary batteries, but since they are rechargeable, their loss of capacity during storage may be better compensated by recharging, particularly as they can take up substantial space in the refrigerator (e.g. automotive batteries).
Another tip: During the summer months, the glove compartment of an automobile is a quite unsuitable place to keep a flashlight. If the sun shines down on the car, temperatures may rise up to and even exceed 60°C. Consequence No. 1: The internal resistance of the batteries increases and the batteries dry out. Consequence No. 2 : When it is needed the flashlight may provide only a dim flicker. The same applies to a battery-operated emergency light in the car's trunk. This too should be checked regularly to ensure that it is functioning properly, and if necessary, the batteries should be replaced in good time.
Sealed Lead Acid Battery Storage
Batteries should not be stored in a discharged state or at elevated temperatures. If a battery has been discharged for some time or the load was left on indefinitely, it may not readily take a charge. To overcome this, leave the charger connected and the battery should eventually begin to accept charge. Although lead acid batteries have a low self-discharge rate which permits storage of a fully charged battery for up to a year, it is recommended that a battery be charged 6-9 months after receipt to account for storage from the date of manufacture to the date of purchase. Otherwise, permanent loss of capacity might occur as a result of sulfation. To prolong shelf life without charging, store batteries at 10 degrees Celsius or less.
Periods of inactivity can be extremely harmful to lead acid batteries. When placing a battery into storage, follow the recommendations below to insure that the battery remains healthy and ready for use.
NOTE: Storing, charging or operating batteries on concrete is perfectly OK. The most important things to avoid:
- Freezing. Avoid locations where freezing temperature is expected. Keeping battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to battery's plates and container. [Freezing can happen between -19 F (40% charge) and -98 F (fully charged)]
- Heat. Avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 80° F accelerate the battery's self-discharge characteristics.
- Step by step storage procedure: 1. Completely charge the battery before storing. 2. Store the battery in a cool, dry location, protected from the elements. 3. During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less. Completely charge the battery before re-activating.
Cyclon Batteries
When a Cyclon battery is kept in storage, i.e. on open circuit, the ambient temperature should be controlled to prolong storage time and maintain maximum capacity over time. To get the best storage results, batteries should be charged at room temperature or below, and charged prior to being put back in service.
The OCV (open circuit voltage) of each battery must be monitored on an individual basis. If the OCV measures 1.93 Vpc, it has zero effective capacity and should be boost charged immediately. Even if the OCV reads higher than 2.00 Vpc at the end of 12 month's storage, the battery should be recharged before use. Thus, to maintain maximum reliability, batteries should be boost charged once every 12 months, or when the OCV reads 2.00 Vpc, whichever occurs earlier.
If the OCV is allowed to drop between 1.93 and 1.80 Vpc, some permanent damage may occur to the battery. However, if it drops to less than 1.80 Vpc, the battery will most likely be unchargable by conventional methods. Therefore, under no circumstances must the OCV be allowed to drop below 1.80 Vpc.
Just as high temperature accelerates the aging of a battery, so does it accelerate the self-discharge rate. Thus, when the storage temperature exceeds 25°C, one must monitor the open circuit voltage more frequently.
NiMH (Nickel Metal Hydride) Battery Storage
Ni-MH batteries can give years of safe and reliable service if they are used in accordance with recommended procedures and are not abused. Batteries should be kept clean and dry both during use and storage. They can be stored for many months in a charged or discharged state without any detrimental effects as long as they are not exposed to extreme temperatures for any long period of time. After periods during which the battery has not been used, the battery should be charged before being placed in service. Extended overcharging or overheating of the battery should always be avoided
Under the recommended storage conditions (-20 C to +35 C) NiMH batteries can be stored indefinitely in either a charged or uncharged state. Recovery may take several cycles. If a battery is stored for a prolonged time connected to a load, electrolyte fluid will leak, the battery will begin to deteriorate, and capacity will be impaired after storage. During long time storage battery deactivation may tend to occur, and for this reason charging may stop early during recharging after storage. This problem can be solved by charging and discharging the battery several times.
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.
When storing batteries for more than one year, charge at least once a year to prevent leakage and deterioration of performancedue to self-discharging.
Panasonic Lithium Ion Battery Storage
The batteries should be stored at room temperature, charged to about 30 to 50% of capacity. We recommend that the batteries be charged about once per year to prevent overdischarge.
Budget Batteries Note: Test data confirms that storage of lithium-ion batteries is best if the cell is partially discharged. In one test by Cadex Electronics ( http://www.buchmann.ca ) after 1 year storage at 25°C the non-recoverable capacity remaining is 96% when stored at 40% initial charge level, but only 80% if stored with 100% initial charge level. This effect is reduced at lower temperature and is a non-issue at 0°C. At higher temperatures the effect is much worse. Cadex's recommendations are to store below 15° C at 40% of full charge (2.5 volts per cell).
