 This
page displays a list of frequently asked questions about EFOY fuel cells,
arranged according to subject. Just click on a question for an automatic
link to the answer.
What is charge equalization?
How is charge equalization accomplished?
How frequently should a battery be equalized?
What will PowerCheq™ do?
How is PowerCheq™ equalization different from string
equalization?
How often does the PowerCheq™ equalize?
How many PowerCheq™ modules are needed for a given
battery system?
How does PowerCheq™ equalize series batteries?
Will PowerCheq™ provide uni-directional or bi- directional
equalization?
How about the efficiency of PowerCheq™?
What is the Amp rating of PowerCheq™?
What is the Amp-Hour rating of a battery that can utilize
PowerCheq™?
Will PowerCheq™ work with any battery voltage?
Does PowerCheq™ require any external control?
How PowerCheq™ is different from dissipative equalization
techniques?
How is PowerCheq™ different from centralized equalization
techniques?
How is PowerCheq™ different from the flying capacitor
approach?
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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. |
