Don’t Buy Flat Batteries
Because lead acid batteries normally self-discharge about 3% per month, it is very important to decipher the date of manufacture code stamped on the battery. This is essential for inventory rotation and to avoid stocking old discharged batteries. If you cannot decipher the date code, contact your supplier or battery manufacturer. Be aware that new batteries can take many months to ship from Far Eastern manufacturers, before going through your distributor to you.
Check the Voltage
To avoid potential battery failure problems, it is essential to check the voltage level in new lead acid batteries to ensure that they have been sufficiently charged by the manufacturer before leaving the factory. Any new out-of-the-box battery with less than 6.1V for 6V and 12.2V for 12V must be recharfed overnight and retested before use. Generally, a new battery will have above 6.2V for 6V and 12.4V for 12V batteries.
Constant Charge Voltage
Lead acid batteries require a constant voltage, irrespective of Ah capacity size in order to charge efficiently. The optimum charge voltage required is 2.3VPC (volts per cell) which is 6.9V for a three cell 6V battery and 13.8V for a six cell 12V battery. The voltage tolerance is 2.2VPC min and 2.4 VPC max. The time taken to fully charge is dependent on battery Ah size.
For maximum life and performance, a lead acid battery should be maintained between 20°C - 25°C (68°F - 77°F). At significantly higher or lower temperatures the Ah capacity available could vary by up to 50%. For example, a fully charged 7Ah battery in a hot enclosure above 30°C/86°F could should 9Ah+. The hotter the battery, the higher the capacity - the shorter its life.
To ensure maximum effieciency and to avoid charging problems, where two or more lead acid batteries are connected in parallel or series, make sure that they are the same make, type and Ah szie and after testing have about equal Ah capacity available.
When to Recharge or Replace?
To ensure efficiency, battery manufacturers recommend to recharge or replace the battery when its available Ah capacity falls below 65%. However, if your requirements recommend a higher or lower percentage, then recharge or replace accordingly.