mkove electronics

Maintaining Lead Acid Battery Systems


The following information is general but applies to all batteries. For specific details refer to the battery manufacturers recommendations.

General Use


In the simplest terms lead acid batteries should be kept full.[1]


After they have been discharged they should be recharged. When they are not in use they should either be left in a full state for up to six months or they should be maintained by a floating charge.


When cycled they should not in general be discharged more than 50 percent in order to achieve maximum utilization from the batteries. Occasional discharges to around 20 percent are not especially harmful. Discharges to flat (approximately 10.8 Volts for smaller loads, lower voltages for high loads) should be avoided. Discharges beyond flat (where lights start to dim) are very harmful to the battery.


Even more critical is that when discharged the battery should not be left in a discharged state. The longer it is left and the lower the discharge state the more harm that is done to the battery. Batteries should be operated in a cyclic manner where the end of the cycle includes returning the battery to a full state.


How to Kill a Battery


Discharge a battery to flat and then leave it. The plates will sulphate and then crystallise. Left for any period of time the battery will become unrecoverable.[2]


Leave a battery connected to a charger which maintains a voltage higher than 13.8 volts. This will continually overcharge the battery and eventually corrode through the positive plate.


Regularly discharge the battery below 50 percent.


Leave a fully charged battery in storage in hot conditions for six months. The battery will self discharge and form large crystals on the plates leading to permanent loss of capacity. In cold conditions the storage time can be extended up to twelve months.


Leave a partially charged battery in storage for any significant period of time. Self discharge and the lower initial state of charge will quickly result in permanent loss of capacity.



How to Store a Battery


Batteries can be stored by leaving them in a fully charged state for up to six months at a time. In general they should be checked and recharged at least every few months.


They can be also permanently stored by holding them at a floating voltage but it is common for batteries to be overcharged or undercharged if the floating voltage is not selected carefully. Float voltages vary by battery type with 13.4V for flooded and 13.6V for AGM (VRLA) being a reasonable starting point. The float voltage should be varied for temperatures much outside of 25ÂșC. For specifics refer to the battery manufacturers specifications.



self discharge

Source PowerSonic PDC-121100 datasheet


[1] Battery University Do's and Dont's

[2] Living on 12 Volts with Ample Power. David Smead and Ruth Ishihara.