Monitoring of lead acid batteries Continuous measurement of the acid concentration

Conference: Intelec '05 - Telecommunications Conference - 27th International Telecommunication Energy Conference
09/18/2005 - 09/22/2005 at Berlin, Germany

Proceedings: Intelec '05 - Telecommunications Conference

Pages: 6Language: englishTyp: PDF

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Mörbel, Martina; Kohnke, Hans-Joachim; Helmke, Joachim (Gaskatel GmbH, Kassel, Germany)

A new sensor will be presented, detecting concentration and temperature inside of lead acid batteries. Inserted into battery-management-systems like for example badicheq, the unit is able to indicate the state of charge under almost any circumstances. It is important to know the state of charge of a lead acid battery and it is easy to detect by measuring the acid level and the acid density. While charging and discharging the battery these parameters change very fast and an automatic control is required. So far there is no commercial unit available. We like to present a zero serie unit of such a control, called DensoFlex. The sensor material is a 100 mm long ion exchange material, which changes its length depending on the water concentration. In order to compensate temperature effects, we have placed a miniaturised temperature sensor close to the sensor. Therefore we are able to measure concentration and temperature at the same time in the liquid electrolyte. Depending on the battery type this is possible in-between the plates, at the edge of the plates or above the plates. DensoFlex has been inserted in stationary batteries with liquid electrolyte - like for example Ogi Block - with the following results: - DensoFlex detects the self discharging rate; - Maximal charging and discharging currents are detectable; - Overcharging is preventable; - Together with a level control deep depletion is preventable. As the fluid level has a high effect on the concentration, DensoFlex has to be connected with a level control. In this case the battery is in perfect control under open circuit conditions and discharge mode. To control the battery while charging one has also to consider the cell voltage.