Power-Sonic Sealed Lead Acid Batteries - Technical Manual - Manual (Page 20)

Charging
Charging in Parallel
Power-Sonic batteries may be used in parallel with one or more batteries of equal voltage.
When connected in parallel, the current from a charger will tend to divide almost equally between the batteries. No
special matching of batteries is required. If the batteries of unequal capacity are connected in parallel, the current will
tend to divide between the batteries in the ratio of capacities (actually, internal resistances).
When charging batteries in parallel, where different ratios of charge are to be expected, it is best to make provisions to
assure that the currents will not vary too much between batteries.
Temperature Compensation
Power-Sonic batteries perform well both at low and high temperatures. At low temperatures, however, charge efficiency is
reduced; at temperatures above 45°C (113°F), charge efficiency increases so rapidly that there is a danger of thermal
runaway if temperature compensation is not precise.
The effect of temperature on charge voltage is less critical in float applications than in cyclic use, where relatively high
charge currents are applied for the purpose of short recharge times.
Temperature effects should definitely be considered when designing or selecting a charging system. Temperature
compensation is desirable in the charging circuit, especially when operating outside the range of 5°C to 35°C
(41°F to 95°F). The temperature coefficient is -2mV/cell/ºC below 20°C (68°F) in float use and -6mV/cell/ ºC below
20°C in cyclic use. For higher temperatures the charge voltage should be correspondingly decreased.
Top Charging
All battery lose capacity through self-discharge, it is recommended that a “top up charge” be applied to any battery that
has been stored for a long period of time, prior to putting the battery into service.
To successfully top charge a battery stored for more than 12 months, the open circuit voltage must be higher than 2.0
volts per cell, in this case, always confirm open circuit voltage prior to attempting top up charging.
Ambient Charge Voltage Per Cell
Temperature Cyclic Use (V) Float Use (V)
-40°C (-40°F) 2.85 – 2.95 2.38 – 2.43
-20°C (-4°F) 2.67 – 2.77 2.34 – 2.39
-10°C (14°F) 2.61 – 2.71 2.32 – 2.37
0°C (32°F) 2.55 – 2.65 2.30 – 2.35
10°C (50°F) 2.49 – 2.59 2.28 – 2.33
20°C (68°F) 2.43 – 2.53 2.26 – 2.31
25°C (77°F) 2.40 – 2.50 2.25 – 2.30
30°C (86°F) 2.37 – 2.47 2.24 – 2.29
40°C (104°F) 2.31 – 2.41 2.22 – 2.27
50°C (122°F) 2.25 – 2.35 2.20 – 2.25
Table : Recommended charge voltages for different temperatures.