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Yesterday, we offered some tips and guidelines for dealing with false collisions and poor intercom speech quality, and today we’ll be focussing on one of the more prevalent fault conditions, namely the battery low condition.

Simply measuring a battery’s voltage under static conditions is generally not sufficient to determine whether the battery is truly flat.  It is more effective, and considerably more accurate, to measure the voltage while the battery is under load, the load in this case being a gate, garage door or boom pole.  This short guide will assist the user in accurately diagnosing a flat gate motor battery.

Required tools

  • AVO meter or volt meter
  • Terminal screwdriver
  • It is useful to have an extra pair of hands standing by to assist with the testing


  • Disconnect the two motor wires from the controller (PC board). The motor wires are generally rather thick and black and blue in colour, though they can be any colour.  The terminals on the controller where the motor wires are connected will be marked ‘MOTOR’ or ‘MTR
  • Switch off the mains supply or unplug the charger from the controller. In CENTURION gate motors, the charger is normally situated directly opposite the battery and may be black or greyish-green in colour.  The reason for eliminating the “charging voltage” is so that the voltage you read from the battery is not biased
  • Engage your gate motor
  • Now connect the motor wires straight onto the battery terminals. It doesn’t really matter which colour wire you connect to which battery terminal, as the polarity of the motor wires simply determine the motor direction.
  • Unless the battery is completely depleted, the gate should start to move the instant you connect touch the motor wires to the terminals. Don’t be startled – this is what it’s meant to do!
  • This is where the extra pair of hands comes in.Ask your assistant to measure the voltage across the battery terminals while the gate is moving, i.e. while you are holding the motor wires to the terminals
  • The battery voltage should at no stage drop below 11V DC under load. If it does, it is safe to say that your battery needs replacement
  • A rule of thumb when dealing with a faulty battery is to also check the charging voltage. To do this, reconnect the charger or switch the mains back on, but now disconnect the battery (thick black and red) wires from the controller.  Measure across the two terminals on the controller where the battery would normally be connected.  For a 12V motor, this voltage should be approximately 14V DC, and approximately 27V DC for a 24V motor.
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