Hydrogen detection system of battery charging stations

All batteries which construction is based on galvanic lead cells filled with sulfuric acid solution, release hydrogen during charging which, without adequate ventilation and detection, poses considerable risk. Batteries of such construction are widely used e.g. in forklift trucks, passenger cars and trucks. Hydrogen is a gas with extremely high flammability and it forms an explosive mixture with air. More information on the properties of hydrogen can be found in the hydrogen calculator tab.

During technological processes in which hydrogen may appear its detection is very important. The aim of detection is to detect rapidly the increasing amounts of hydrogen due to e.g. inadequate ventilation or leaks. Detection of hydrogen is possible thanks to the installation of its detection, which we use in our projects of battery charging rooms. System installation, periodic inspection, replacement parts must be carried out by trained operators only, with a suitable manufacturer certificate. We periodically review the hydrogen detection systems of charging traction batteries posts.

The hydrogen detection system that we use for the battery charging rooms, is built on GAZEX company components. This system consists of the MD control panel cooperating with the DEX- type gas sensor and the SL visual/audible system. The heart of the system is the DEX hydrogen detection sensor equipped with a semiconductor gas sensor. The sensor works by measuring the voltage at a four-branches resistor measuring bridge, where one line of the bridge is a gas sensor. This sensor is made of a tube which is made of tin dioxide that is threaded on a heating cable. After powering the sensor it takes about 1 minute to heat this sensor - during that time a heating wire heats up to about 350°C.

How does the detection of hydrogen system work?

When the hydrogen detection sensor is located in the clean air then the sensor resistance does not change and the bridge is in equilibrium - the voltage between the branches of the bridge is 0V. When the sensor finds the atmosphere containing gas then the gas molecules drift into the sensor and change its resistance and the bridge is in a state of imbalance. Depending on the size of the gas concentration the voltage measured between the branches of the bridge changes.

Since the connection between hydrogen concentration and the voltage is highly non-linear, hydrogen detection sensor calibrates two alarm levels. It is assumed that for battery charging stations the concentration of 20% LEL (Lower Explosive Limit) is the threshold for ALARM 1 and 40% LEL as the threshold for ALARM2. If the sensor in the hydrogen detection system generates an alarm signal, the MD control panel will register it and wait approximately 20 seconds to eliminate, the so-called, false alarms. After this time, the MD control panel activates the SL optical signaling (for ALARM 1) and opto-acoustic (for ALARM2) and stimulates the ALARM 1 and ALARM 2 relays, which cause unconditional activation of ventilation and / or disconnecting the power supply rectifiers.