Abstract: When in long term storage, battery degradation is avoided by performing battery charge cycles at a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum, rather than discharging the battery to its minimum storage capacity and then charging to its maximum storage capacity. Further, based on physical and practical limitations, such battery charge cycles can instead be performed within a range or delta Depth of Discharge (“DOD”) and corresponding battery voltage levels rather than at a single voltage level, while still avoiding battery degradation.

Abstract: When in long term storage, battery degradation is avoided by performing battery charge cycles at a voltage level where a change in the battery's voltage divided by a change in the battery's storage capacity is at a minimum, rather than discharging the battery to its minimum storage capacity and then charging to its maximum storage capacity. Further, based on physical and practical limitations, such battery charge cycles can instead be performed within a range or delta Depth of Discharge (“DOD”) and corresponding battery voltage levels rather than at a single voltage level, while still avoiding battery degradation.

Abstract: Improved battery charge state determination. The estimated charge state of a battery comprising a plurality of series connected cells is updated using Coulomb counting during battery operation, for example, while operating an electric vehicle motor. The estimated charge state may be coupled to a fuel gauge. When the battery is in a no load state, a no load voltage measurement is made. During testing, a set of relationships between battery no load voltages and associated known good charge states have been determined. The measured no load voltage is compared to the set of no load voltages associated with known good charge states. A known good charge state associated with the measured no load voltage is used to update the estimated charge state, thereby providing a more accurate indication of the actual battery charge state, thus providing a more robust and accurate fuel gauge.

Abstract: An energy storage system having one or more battery packs and a system controller for controlling the battery packs. Each battery pack has rechargeable storage cells and a battery pack controller in communication with the system controller. Through the operation of the system controller, battery packs with different initial charge states can be operated in parallel during a charge process and a discharge process. Discharging multiple battery packs in parallel offers not only a higher capacity and a longer run time than is available from a single battery pack, but also offers higher peak currents than available from a single battery pack, which are important in motor control applications. A battery pack design including a battery pack connector with both power and control contacts supporting user replacement of the battery packs.

Abstract: Improved protection for a rechargeable battery from damage by being discharged below a cut-off voltage is provided. The measured voltage of a battery under load is lower than the measured voltage of the battery under no load. As the cut-off voltage for the battery is specified as a no load voltage, comparing the measured voltage of the battery under load to the cut-off voltage would result in stopping use of the battery with useable charge remaining. Through testing, a set of relationships for estimating the no load voltage of a battery under load has been determined. Using this set of relationships with battery measurements, an estimated no load voltage for the battery is determined. This estimated no load voltage is compared to the cut-off voltage. This allows for full use of the battery while stopping use of the battery when its voltage reaches the cut-off, thereby preventing damage.