Insular power supply battery manager with balancing and protection unit for Lithium-Ion batteries

Abstract

For insular supply of electricity off-grid, Lithium-Ion Batteries are an optimal choice when disregarding the price due to their high power and high energy capability and low self-discharge rate. However, they require careful balancing and some advanced protection system components that go far beyond standard electronics for lead-acid batteries. Power coming from photovoltaic panels easily can overcharge the battery in summer months. A special high current charge controller was established for input energy turn off once the battery is full. Some safety levels are introduced to reduce risks. In addition to standard full-battery turn off of photovoltaic input a thyristor-short-circuiter is inserted, too. If for any reason voltage at battery exceeds a certain peak voltage the short-circuit-thyristor is fired and this action disconnects the battery from the input by blowing a high current high speed emergency fuse. Lithium Ion batteries easily survive short circuits of limited duration e.g. lasting less than several seconds. A system operation display is integrated. Photovoltaic charging, full battery, balancing of individual cells, over-voltage and under-voltage of the battery are indicated by LEDs. Charge current and battery voltage is displayed by digital voltmeters. A prototype connected to a 12 V / 1600 Ah battery unit is in test application presently.