Power-Sonic Sealed Lead Acid Batteries - Technical Manual - Manual (Page 18)

Overcharging
As a result of too high a charge voltage excessive current will flow into the battery, after reaching full charge, causing
decomposition of water in the electrolyte and premature aging.
At high rates of overcharge a battery will progressively heat up. As it gets hotter, it will accept more current, heating up
even further. This is called thermal runaway and it can destroy a battery in as little as a few hours.
Undercharging
If too low a charge voltage is applied, the current flow will essentially stop before the battery is fully charged. This allows
some of the lead sulfate to remain on the electrodes, which will eventually reduce capacity.
Batteries which are stored in a discharged state, or left on the shelf for too long, may initially appear to be “open
circuited” or will accept far less current than normal. This is caused by a phenomenon called “sulfation”. When this
occurs, leave the charger connected to the battery. Usually, the battery will start to accept increasing amounts of current
until a normal current level is reached. If there is no response, even to charge voltages above recommended levels, the
battery may have been in a discharged state for too long to recover.
If in any doubt, or if concepts of proper use and care are unclear, please ensure that you contact Power-Sonic’s technical
department.
Charging for Cycle Operation
Cyclic applications generally require that recharging be done in a relatively short time. The initial charge current, however,
must not exceed 0.30 x C amps. Just as battery voltage drops during discharge, it slowly rises during charge. Full charge
is determined by voltage and inflowing current. When, at a charge voltage of 2.45 ± 0.05 volts/cell, the current accepted
by the battery drops to less than 0.01 x C amps (1% of rated capacity), the battery is fully charged and the charger should
be disconnected or switched to a float voltage of 2.25 to 2.30 volts/cell. The voltage should not be allowed to rise above
2.45 ± 0.05 volts/cell.
Charging for Standby Operation
Standby applications generally do not require that the battery be charged as fast or as frequently as in cycle operation.
However, the battery must be kept constantly charged to replace the energy that is expended due to internal loss and
deterioration of the battery itself. Although these losses are very low in Power-Sonic batteries, they must be replaced at
the rate the battery self discharges; at the same time the battery must not be given more than these losses or it will be
overcharged. To accomplish this, a constant voltage method of charging called “float charging” is used.
The recommended constant float voltage is 2.25 - 2.30 volts per cell. Maintaining this float voltage will allow the battery
to define its own current level and remain fully charged without having to disconnect the charger from the battery. The
trickle current for a fully charged battery floating at the recommended charge voltage will typically hover around the
O.OO1C rate (1OmA for a 10AH battery, for example.)
The float charger is basically a constant voltage power supply. As in cycle chargers, care must be exercised not to exceed
the initial charge current of 0.30 x C amperes.
Charging
Caution! Never charge or discharge a battery in a hermetically sealed enclosure. Batteries generate a mixture of
gases internally. Given the right set of circumstances, such as extreme overcharging or shorting of the battery,
these gases might vent into the enclosure and create the potential for an explosion when ignited by a spark.