User`s manual

UPS25 26 RTD Embedded Technologies, Inc
Discharging can also be initiated by setting the discharge bit #1 in the control
register to a high, and bringing this bit to low again. Care must be taken not to
overheat your system since the discharged battery power is converted to heat
directly into the metal heat sink. Only discharge when the ambient temperature is
low enough, or when adequate cooling is present. In any case Ni-MH batteries do
not require as critically periodical discharging as Ni-Cd batteries do. This
procedure is recommended to do only every now and then to make sure that
battery performance in maintained. For Ni-Cd systems it is recommended to
periodically perform the discharge-before-charge to maintain good battery
performance and reduce memory effect of the Ni-Cd battery pack. Discharging
may be required if the back up is used very infrequently and for a very short
period of time.
The discharge resistor is pictured below as R15 and either attaches to the heat
stand-alone heat sink or frame (in an IDAN).
By default the discharge resistor is not populated. A suggested resistor is the Ohmite TCH35P7R50JE. This resistor is
a 7.5 Ohm 35Watt power resistor. Please contact RTD if you require a discharge resistor. As an example, if one has a 1000 mAhr 9.6V
battery they want to discharge and it is fully charged with no R15 present, there still exists R1 in parallel with R15. R1 is a 1 Watt 1K
resistor. R1 will dissipate 0.092 Watts. The battery should discharge in about 4.3 days. If R15 is installed as a 7.5 Ohm resistor, 12.38
Watts will be dissipated. The battery will be fully discharged in about 47 minutes. Keep in mind that adding 12 Watts to the existing
heat of your system should be considered. Choose a discharge resistor value that you can remove the heat from.
Charger mode configuration- solder blobs B2 and B3
The solder blobs shown in Figure 4-3 below let you configure the operation of the
battery charger unit and the charge algorithm. These blobs connect to GND while
the top two connections are closed and to VCC while the bottom two are closed.