900-0127-01-00 Rev B 7
70°F 80°F 90°F 100°F 110°F 120°F 130°F
21°C 27°C 32°C 38°C 43°C 49°C 54°C
Temperature
90
80
70
60
50
40
30
Storing EnergyCell GH Batteries
The EnergyCell GH must be kept in storage no longer than the shelf life indicated in Figure 3 for a particular
temperature. At the end of this time it must be given a freshening charge. (That is, a battery stored at 40°C
should be stored no longer than six months, while it can be stored up to 48 months at 10°C without a charge.)
Stored batteries should be checked for open-circuit voltage at intervals. Any time the battery voltage is less than
2.10 volts per cell (12.6 volts per battery), it should be given a freshening charge regardless of the storage time.
At 40°C, the EnergyCell GH voltage should be checked every 2 months. At 30°C, the interval is 3 months. At
25° to 20° the interval is 4 months. At temperatures lower than 15°C, the voltage only needs to be checked every
6 months.
Storing EnergyCell RE Batteries
The EnergyCell RE must be given a freshening charge every six months when stored at 77°F (25°C). The charge
should be every three months if stored at temperatures of up to 92°F (33°C). If stored in higher temperatures,
the charge should be every month.
Capacity
Battery capacity is given in ampere-hours (amp-hours). This is a current draw which is multiplied by the duration
of current flow. A draw of Xamperes for Yhours equals an accumulation of XY amp-hours.
Because the battery’s chemical reaction constantly releases energy, it tends to replenish its own charge to a
minor degree. Smaller loads will deplete the batteries less than larger loads because of this constant
replenishment. This means that effectively the battery has more capacity under lighter loads.
For example, if the EnergyCell 170RE is discharged at the 48-hour rate (a load expected to drain 100% of its
capacity in 48 hours), it will be measured to have 163.9 amp-hours. However, at the 4-hour rate, a heavier load,
only 120.6 amp-hours will be measured. For discharge rates and amp-hours of all EnergyCell batteries, see
Table 3 on page 17.
The EnergyCell models are named after their capacity at the 100-hour rate.
State of Charge
The battery state of charge (SOC) can be determined by two methods.
One is to measure its voltage. This is accurate only if the batteries are
left at rest (no charging or loads) for 24 hours at room temperature (77°F
or 25°C). If these conditions are not met, then voltage checks may
not yield usable results. If they are met, then on average, a battery at
12.8 Vdc will be at 100% SOC. 12.2 Vdc represents roughly 50% SOC.
The more accurate method is to use a battery monitor such as the
OutBack FLEXnet DC. Using a sensor known as a shunt, the monitor
observes the current through the battery. It keeps a total of amp-hours
lost or gained by the battery and can give accurate SOC readings.
For optimal battery life, it is recommended not to discharge below 70%
SOC (30% depth of discharge) on a regular basis. The battery should
never be discharged below 50% of its capacity, as this will significantly
shorten its life. If operated in the recommended range, the EnergyCell will typically have a life of hundreds of
cycles. With consistently lighter discharge, the battery may have thousands of cycles. (This can be affected by
temperature. Figure 4shows the effect of ambient temperature on battery life.)
