Power-Sonic Sealed Lead Acid Batteries - Technical Manual - Manual (Page 23)

POWER-SONIC Rechargeable Batteries
Important Do’s and Don’ts
Charging
• 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.
• Continuous over-or undercharging is the single worst enemy of a lead-acid battery. Caution should be exercised to
ensure that the charger is disconnected after cycle charging, or that the float voltage is set correctly.
• Although Power-Sonic batteries have a low self-discharge rate which permits storage of a fully charged battery for
up to a year, it is important that a battery be charged within 6 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°C (50°F) or less.
• Although it is possible to charge Power-Sonic batteries rapidly, i.e. in 6-7 hrs. it is not normally recommended.
Unlimited current charging can cause increased off-gassing and premature drying. It can also produce internal
heating and hot spots resulting in shortened service life. Too high a charge current will cause a battery to get
progressively hotter. This can lead to “thermal runaway” and can destroy a battery in as little as a few hours.
• Caution: Never charge or discharge a battery in an airtight 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. Generally,
ventilation inherent in most enclosures is sufficient to avoid problems.
• When charging batteries in series (positive terminal of one battery is connected to the negative terminal of
another) the interconnecting cables must all be of equal length and resistance to insure equalization of the load.
All batteries in the string will receive the same amount of charge current, though individual battery voltages may
vary.
• When charging batteries in parallel (positive terminals are connected to the positive terminal and negative
terminals to the negative), all batteries in the string will receive the same charge voltage, but the charge current
each battery receives will vary until equalization is reached.
• High voltage strings of batteries in series should be limited to twenty 6 volt or ten 12 volt batteries when a single
constant voltage charger is connected across the entire string. Differences in capacity can cause some batteries
to overcharge while others remain undercharged thus causing premature aging of batteries. It is, therefore, not
advisable to mix batteries of different capacities, make, or age in a series string.
• To minimize the effects of cell or battery differences, charge the string in 24 volt battery groups through a constant
current source with zener diode regulation across individual batteries or battery groups.
• Recharge time depends on the depth of the preceding discharge and the output current of the charger. To
determine the approximate recharge time of a fully discharged battery, divide the battery’s capacity (amp. hrs) by
the rated output of the charger current (amps) and multiply the resulting number of hours by a factor of 1.75 to
compensate for the declining output current during charge. If the amount of amp. hrs. discharged from the battery
is known, use it instead of the battery’s capacity to make the calculation.