Testing Alarm Charging Voltages

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Alarm batteries generally last around 4-5 years. They should be kept on charge all the time and tested at least annually. If your system is showing a low battery, follow this guide to test the charging components and voltages on your board before you purchase a new battery.

You will need a volt meter with AC and DC scales.

Set your meter to DC VOLTS. If you need to select a range, set it to approx 20V (available ranges may be different on different meters).

Place the test leads on the battery. Make sure you do this with the panel POWERED UP and PLUGGED IN as normal.

If your battery is charging normally, the meter should read approx 13.5 - 13.8 Volts. Anything below this means your panel is not charging the battery correctly, or the battery is old and loading down the power supply.

Remove the leads from the battery and place the test leads on the fly leads as shown.

If the voltage stays at or comes back to approx 13.5 - 13.8 Volts, then the charger on your system is OK, and you do need a new battery.

If the voltage drops down to Milli-Volts or very low volts, as shown below - it means the charging circuit on your panel is faulty or your plug pack might be faulty. It's not a battery fault. Lets test the AC plug pack voltages now.

Make sure you change the scale on your meter to AC VOLTS. If you need to select a range on your meter, set it to approx 30 volts.

Once you have changed your meter to the AC scale, place the test leads on the AC input terminals.

The correct voltage here should be approx 18-21 Volts AC. If there is no voltage here - then you need a new plug pack, or check that the power is turned on to the alarm plug pack where it is plugged into the 240V power point.

All images and text copyright Bosch Security Systems and Cheap Alarm Parts. Do not copy text or images.