Specific problems for battery equalization in continuous hard cyclic applications
In hard cyclic applications, like in diesel-battery hybrid systems supplying telecom base stations, cell unbalancing is quite intense and active battery equalization is necessary.
The competitive voltage based equalization systems, available in the market, cannot be used here, because the instant cell voltage is not at all a reliable indication for the state of charge and may lead to results to the wrong direction. The internal resistance, which is continuously varying during the cycle stages, in combination with the large reversing currents, flowing continuously through the cells and with the shallow DOD, hide almost completely any unbalance signs. Things are even worse for LiFePO4 batteries due to their flat voltage characteristics.
The ampere-hour (charge) integrating systems, also cannot be used due to the varying charge efficiency of the individual cells.
That’s why there are no competitive products proposed for such applications.
Our Active Battery Management systems, (installed to) for cycling systems, detect the SOC and the overall condition of the cells, by long-term analysis of the variation of their parameters, using specially developed sophisticated algorithms and not from their instantaneous values.
The conclusions (results) of the analysis are used to control battery charging and to schedule (plan) the necessary charge exchange among the cells to modify their SOC relation, in order to apply our Dynamic Battery Management Concept which preserves battery health, maintains cell equalization within the desired margin and the charging efficiency within the cost-effective area (see next sections).