Battery Care.
Storage and temperature limits
Shelf life and top charging
Charging recommendations

Battery Care and Maintenance.

The capacity of a SLA battery is the amount of electrical energy which can be obtained from a fully charged cell.  The capacity is expressed in ampere hours.  The capacity is dependent upon the discharge current, the temperature during the discharge, the final cut-off voltage and the batteries general history (storage temperature, charge, maintenance, etc.).

Storage and Temperature Effects.

Whenever possible, store batteries in a clean, cool and dry place so that it is not effected by sources of radiant heat such as sunshine, heating units, radiators or steam pipes.  The recommended storage temperature and humidity levels are as follows:
Storage Temperature between 32 and 104 degrees Fahrenheit (0 to 40C).
Storage Humidity should be as low as possible.
Battery storage should be avoided where temperatures can exceed 104F.

The temperature limits for SLA batteries in operation are as follows:
Charging:      5F to 122F (-15C to 50C).
Discharging: -4F to 140F (-20 to 60C).

The ideal operating temperature for SLA batteries is approximately 68F to 77F (20C to 25C).  Operation at temperatures below -4F could result in physical damage.  When operating and charging at temperatures above 140F results in accelerated drying of the electrolyte.  Thermal runaway and severe swelling may occur.  
Remember that extreme temperatures shorten battery life. 

Shelf Life and Top Charging.

Due to the chemical components of SLA batteries, a reaction takes place in storage called Self Discharge, which is a slow drain of a batteries capacity and is sometimes referred to as Shelf Life.  At room temperatures, the self discharge rate is about 3% of rated capacity per month.  This low self discharge rate and the batteries excellent charging characteristics permit storage for up to one year without loss of efficiency or performance.

SLA batteries require a Top Charge with a given time frame while being stored.  The Top Charge replenishes the capacity that was lost to the battery while in storage.  After long term storage, all batteries deliver less than the rated capacity.  Full capacity will be obtained through several discharge/charge cycles.  For longest life, batteries should be fully charged before going into storage.  Brief periods of high temperatures (a few days) will have no effect on storage times.  However, periods of one month or more at temperatures higher than 78F will require an increase in the frequency of Top Charging.
recommended Top Charging Intervals:

Storage Temperatures

Shelf Life

32 F or Lower

12 months

32 F to 78 F

6 months

78 F to 104 F

3 months

Top Charging Recommendations For SLA Batteries.

It is important to charge SLA batteries with a well matched charger.  Because the capacity or life of batteries is influenced by ambient temperatures, charging voltage and other parameters, it is important to use a charger matched to the battery and its application. 

Charging Recommendations.

It is recommended that the charge voltage be adjusted to compensate for the battery temperature.  This may be done by detecting the ambient temperature near the battery instead of the actual battery.
The reasons for temperature compensation of the charging voltage are:
To prevent thermal runaway of the batteries when they are used in high temperature conditions.
Sufficient charging when the batteries are used in low temperature conditions.

Temperature compensation of the charging voltage can prolong the trickle or float life or batteries as follows:
Approximately 5% compared with no compensation at 86F (30C).
Approximately 10% compared with no compensation at 95F (35C).
Approximately 15% compared with no compensation at 104F (40C).

When the batteries are used in low temperature conditions, temperature compensation of the charging voltage does not affect the trickle or float life of batteries.  The benefit then of temperature compensation is to keep the trickle or float charging current almost the same as it would be at 77F (25C), even though the temperature around the batteries varies.
In summary, batteries should be charged at:
An ambient temperature within the range of 32F to 104F (0C to 40C).
The most effective charging range is 41F to 95F (5C to 35C).
Charging temperatures below 32F (0C) or over 104F (40C) is not recommended, as the batteries might be deformed by heat or not charged enough.


Union Battery Corporation