The alarm output for CellLog

One of the Cell Logger’s functions is the alarm output. The Alarm output can be triggered according to several settings of the CellLog. It uses the open collector design - this kind of output can be found on many integrated circuits or electronic modules.

How to connect a DC relay to this alarm output: The output forms either an open circuit or a connection to ground. This gives you the advantage of switching loads up to 50V and 500mA. In other words it can be possible to control 12/24V relay easily. In most cases the power to trigger such a relay will be provided from a separate power supply (e.g. isolated DC-DC). In case you connect the relay to the battery directly, please note that ground pin of the ALARM is not isolated! It is connected to the GND of the battery pack.

See an example connection of 24V relay to 8 cell LiFePO4battery pack. This way you can turn off your charger or disconnect the main contactor in case alarm is triggered. Do not forget to connect the protective diode parallel to the relay-coil otherwise you will most probably break the output!