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Q: What is charge equalization?
A: Conventionally, "Charge Equalization" is a technique used to reduce imbalances in series connected battery strings. The goal is to equalize the capacities of individual cells/modules within a given string.
Q: How is charge equalization accomplished?
A: Conventional "Charge Equalization" is accomplished by applying a low chnarging current for an extended period of time at elevated voltages (C/20 for 24 hours, where C is the 5- or 10-hour discharge rate for a given battery).
Q: How frequently should a battery be equalized?
A: Most manufacturers recommend equalization to be performed at some regular periods. In many cyclic applications such as electric vehicles, weekly equalization is recommended. The key to periodic equalization schedules is to prevent cell-to-cell imbalances from progressing to a point where it corrupts the performance of the overall string.
Q: What will PowerCheq™ do?
A: PowerCheq™ is a bi-directional battery charge equalizer that assures all batteries in a series connected string are kept at the same capacity relative to one another.
Q: How is PowerCheq™ equalization different from string equalization?
A: PowerCheq™ monitors for imbalances between individual batteries. When an imbalance occurs, PowerCheq™ immediately corrects the discrepancy by shuffling power from the battery with more energy to the one with less until both are equal.
Q: How often does the PowerCheq™ equalize?
A: The PowerCheq™ operates continually-during charge, discharge and while the battery is sitting idle. This provides the uses with continuous equalization and is the reason behind PowerCheq's ability to extend battery life and capacity.
Q: How many PowerCheq™ modules are needed for a given battery system?
A: PowerCheq™ is connected across each pair of batteries within the string. If there are N batteries in the string, there will be N-1 PowerCheq™ modules. Note that the PowerCheq™ modules are Daisy Chained to provide an equalization path for the whole string.
Q: How does PowerCheq™ equalize series batteries?
A: Since each PowerCheq™ module is connected across a pair of batteries, differences in battery capacities are detected. PowerCheq™ will then shuffle energy from the higher capacity battery to the lower one until both batteries are equalized.
Q: Will PowerCheq™ provide uni-directional or bi-directional equalization?
A: PowerCheq™ is a bi-directional device and thus will equalize battery modules irrespective of the order of the imbalance (i.e. top to bottom or bottom to top).
Q: How about the efficiency of PowerCheq™?
A: PowerCheq™ is a highly efficient charge equalizer. Most of the energy is transferred from the higher capacity battery to the lower one. Typical efficiencies are better than 85%.
Q: What is the Amp rating of PowerCheq™?
A: The Amp rating of presently available PowerCheq™ is 2.0 Amps.
Q: What is the Amp-Hour rating of a battery that can utilize PowerCheq™?
A: Given the fact that equalization is nominally done at a 1%-2% of the Amp-Hour capacity of the given battery, a 2.0Amp PowerCheq™ module can be used to effectively equalize batteries with Amp-Hour capacities in the range of 4-150 Amp-Hours.
Q: Will PowerCheq™ work with any battery voltage?
A: Individual PowerCheq™ modules can currently equalize 6V, and 12V batteries. Although the PowerCheq™ modules can be used to equalize battery systems of any voltage, they are more optimal for battery systems of less than 100V.
Q: Does PowerCheq™ require any external control?
A: PowerCheq™ is a standalone module. It derives its control power from the pair of batteries which it is connected across. Quiescent (idle) current draw is less than 5mA. It does not need any external control as it automatically detects differences in battery capacities, initiates the equalization phase, and finally terminates the equalization phase when the battery modules are equalized.
Q: How PowerCheq™ is different from dissipative equalization techniques?
A: The following table summarizes differences between a dissipative charge equalizer (current shunts) and PowerCheq™.
| Dissipative Equalizers |
• Excess energy is dissipated in a shunt resistor
• Efficiency is zero
• Current limited due to heat generated by dissipated power
• Only works during overcharge periods
• Only acts as a current shunt |
| PowerCheq™ |
• Energy is shuffled from the higher capacity battery module to the lower one
• Efficiency is typically 85%
• High current capability
• Operates during charging, discharging, and idle modes
• A real equalizer, shuffling energy between battery modules |
Q: How is PowerCheq™ different from centralized equalization techniques?
A: Most of the centralized equalization techniques that were developed are optimally designed for long battery strings (20-30 batteries) and may not be easily adaptable to short strings (‹10 batteries). In addition, these systems can not be easily retrofitted into existing systems due to wiring and layout constraints. PowerCheq™, on the other hand, is a modular approach and scales directly with the length of the battery string (need N-1 modules for N batteries). In addition, it can be easily retrofitted into existing systems as each PowerCheq™ module is connected across a pair of batteries.
Q: How is PowerCheq™ different from the flying capacitor approach?
A: The flying capacitor approach can be also classified as a centralized equalization approach and non-modular. This is due to the fact that all of the battery strings are connected to a centralized equalization unit, where the switches as well as the flying capacitor are located. Thus, this approach is not easily scalable to variable battery string lengths. In addition, temperature gradients may exist across the whole string and should be accounted for when energy is transferred from one battery within the string to another. PowerCheq™ is a modular equalizer that is scalable with the length of the string. As discussed in an earlier question, temperature compensation is not of an issue as each PowerCheq™ equalizes a pair of batteries that are in close physical proximity with minimal temperature gradient. Finally, PowerCheq™ implements a patented equalization algorithm to optimize the equalization of batteries. |
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