Samlex America BBM-1225 User Manual
Battery
Back-up
Owner's
Manual
Please read this
manual before
operating your
VOJU
Model:
BBM-1225
INDEX
Safety instructions ...........................................................2
Description ......................................................................2
Principle of operation ............................................. 3,4,5,6
Installation ....................................................................7,8
Specifications ..................................................................9
Warranty information ....................................................10
SAFETY INSTRUCTIONS
Precautions when working with batteries.
- Batteries contain very corrosive diluted sulphuric acid as electrolyte. Precautions
should be taken to prevent contact with skin, eyes or clothing
- Batteries generate hydrogen and oxygen during charging resulting in evolution of
explosive gas mixture. Care should be taken to ventilate the battery area and follow the
battery manufacturer’s recommendations.
- Never smoke or allow a spark or flame near the batteries.
- Use caution to reduce the risk of dropping a metal tool on the battery. It could spark or
short circuit the battery or other electrical parts and could cause an explosion.
- Remove metal items like rings, bracelets and watches when working with batteries. The
batteries can produce a short circuit current high enough to weld a ring or the like to
metal and thus cause a severe burn.
- If you need to remove a battery, always remove the ground terminal from the battery
first. Make sure that all the accessories are off so that you do not cause a spark
DESCRIPTION
This unit is used to allow any 12 VDC / 24 VDC power supply to function as a DC Uninterrupted Power Source (UPS). This unit is a passive device and acts only as an
interface between the power supply, the battery and the DC load. As long as the power
supply is operating normally, it will supply the load as well as float charge the battery. In
case the output of the power supply fails, the battery will start feeding the load immediately thus ensuring un-interrupted DC power to the load. The battery will start discharging. Once the output of the power supply is resumed, the power supply will take over the
load and will also re-charge the battery at its float voltage.
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PRINCIPLE OF OPERATION
Please refer to the schematic diagram at Fig. 1
The power supply is connected to the positive and negative input terminals. The
battery is connected (through a fast acting fuse of the appropriate current
capacity) to the battery terminals and the load is connected to the load terminals.
The voltage from the power supply is fed through the isolating Schottky diode
D1 to the load and to the battery through the charging current limiting resistors
R1 and R2. Diode D1 provides isolation between the power supply and the
battery to prevent the battery from feeding back into the power supply circuit.
D1 has a forward voltage drop of 0.4 (at < 1 A) to 0.5 V (at > 10 A). Hence, the
voltage available to the load and to the battery for float charging will be 0.4 to
0.5 V lower than the output voltage of the power supply. In a battery backup
application, the battery will normally remain in a fully charged, standby
condition most of the time. It will discharge to the load only when the power
supply fails. Under this standby application, the battery should be charged
at the recommended float voltage. Assuming the standby float char ging
voltages of 12 V / 24 V sealed lead acid (SLA) batteries to be 13.5 V to 13.8 V
and 27 V to 27.6 V ( at 60ºF to 77ºF) respectively, the output voltage of the
power supply should be adjusted as follows:
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