Transcript Slide 1

What does this picture
have to do with……
Battery Charger Sizing?
Half Full?
Neither,
Wrong Size Glass!
Half Empty?
Would you charge this
battery…
Wrong Size!
…using this charger?
Battery charging is definitely a
matter of size.
Battery charging is definitely a
matter of size.
Properly sized chargers
will result in;
•Properly charged batteries.
•Properly maintained loads.
•More efficient operation than if
the charger is oversized.
•Lower cost at inception.
•Lower cost over the life of the
system.
Standards that describe
battery charger sizing;
•IEEE Std 446-1987, also
known as the “Orange Book”
•IEEE Std 946-2004
Constant Potential Charging
One of the oldest methods
of battery charging – first
used for aircraft…….
Constant Potential Charging
Provides a means to keep the battery
charged without overcharging by
maintaining a constant voltage while limiting
charger output current.
….Today constant potential
charging is used for just
about everything………..
Utility
Stationary
Communications
Oil & Gas
Petro Chemical
Chemical
Transportation
Constant Potential Charging
Important terms………..
Basics we must all understand about battery charging.
Float Charge – maintains the battery
voltage and prevents self discharge from
occurring.
Important terms………..
Basics we must all understand about battery charging.
Float Charge – Float charge voltage
ranges are determined by the battery
manufacturer.
Important terms………..
Basics we must all understand about battery charging.
Equalize Charge – used to
cause a battery’s cells to
become more equivalent
in their voltages.
Equalize charge voltages
are also determined by
the battery
manufacturer.
Important terms………..
Basics we must all understand about battery charging.
Constant Loads –
defined as those loads
which remain steady
and present.
Important terms………..
Basics we must all understand about battery charging.
Transient Loads –
defined as those loads
which are fleeting.
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
AH removed – AH removed from the battery as part of the load profile.
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
AH removed – AH removed from the battery as part of the load profile.
R = Recharge Factor
•Wet Vented Lead Acid – 1.1, 1.15
•Valve Regulated Lead Acid – 1.15
•Wet vented Nickel Cadmium – 1.3, 1.35, 1.4
•Valve Regulated Nickel Cadmium – 1.4
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
T = Recharge time desired, usually a number between 8
hours and 24 hours, typically 8 to 12 hours.
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
L = Constant Loads, not transient loads as those are
handled by the battery.
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Amperes Charger – the output current determined to be
adequate for the application.
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
(150AH x 1.15)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
(150AH x 1.15)
---------------------------------- + L (constant loads) = Amperes Charger
8 Hours
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
(150AH x 1.15)
---------------------------------- + 25 Amps = Amperes Charger
8 Hours
The Formula
(AH removed x R)
---------------------------------- + L (constant loads) = Amperes Charger
T (desired recharge time)
Let’s give it a try………………………………………………..
Assume 200AH wet vented lead acid battery with 150AH
removed recharge in 8 hours and a constant load of
25Amps
(150AH x 1.15)
---------------------------------- + 25 Amps = 46.563A use  50Amps
8 Hours
Other Considerations…..
Temperature
Other Considerations…..
Temperature
Other Considerations…..
Altitude
Other Considerations…..
Temperature and Altitude are interrelated.
•As altitude increases the ambient temperature
usually decreases.
•Also as altitude increases the molecules available
to heat sink decrease.
•As ambient temperature increases, the charger’s
ability to operate at full rating will therefore
decrease.
Other Considerations…..
Temperature and Altitude are interrelated.
•Check the manufacture's suggestions. Usually
they have a chart that shows the relationship
between altitude and temperature.
•Note the relationships between temperature and
altitude it may be acceptable to operate without
de-rating by just adjusting the useful ambient
temperature allowance.
Other Considerations…..
Design Margin –
Big enough to do
the job?
Other Considerations…..
Design Margin –
Big enough to do
the job?
•It is important to have
enough capacity without
over sizing.
•Also, use current limit
values as long as you
can get full capacity
from the charger.
Other Considerations…..
Anticipated Growth –
Did I plan for the future?
Other Considerations…..
•Should I use a larger charger now or plan for redundancy later?
•Perhaps a complete parallel system would make sense?
•Is growth budgeted or assumed?
Other Considerations…..
•Was the battery sized for future growth such that the charger
calculation already takes this growth into account?
•Finally, just adding capacity is not good “insurance” if you really do
not need it! Good engineering is the best insurance.
In conclusion…..
•If I plan my application carefully and realistically my
charger, battery, and all associated equipment will be
properly sized.
•Insist on getting the facts before sizing the application.
•Separate your transient loads from your constant loads –
the charger does not accommodate the transient loads.
•Use the formula! Don’t assume or use a “standard rule of
thumb”, use engineering practices.
•Doing a thorough job of application engineering will result in
a properly sized application that will work correctly and as
efficiently as possible.
•This means…………….
In conclusion…..
Correct size glass!