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GB Industrial
Battery Capacity Ratings and Conversions:
AH (Ampere-Hour) Ratings
6
Hour vs. 20 Hour Ratings: Rating a
battery over a longer time period always means a lower current draw over a
longer period of time. The lower the continuous amperage during discharge,
the more efficient the battery becomes. The opposite is true when the
continuous current draw is increased. ·
Forklift applications usually use the 6hr rating. ·
Off grid power and specialized power applications
usually use the 20hr rating. ·
You cannot directly compare a battery rated at 6hrs
to a battery rated at 20hrs. Always use the same rate when making
comparisons. Conversion: ·
Convert a 6hr rating to 20hr by multiplying: AH @ 6hrs x 1.5764705 = AH @ 20hrs. ·
Use the GB Capacity Calculator to convert 6hr
through 24hr rates: RATE: The AH
rating divided by the number of hours of the rating = continuous amps
(current draw) for that number of hours, to a maximum of 80% depth of
discharge. 80%
Depth of Discharge (DOD): A
Fully Charged battery, discharged to 1.75 volts per cell. ·
Example: A 600AH battery (rated @ 6hrs) will provide
a full 600AH over 6hrs and still have 20% reserve capacity that is
never used. ·
You are not limited to 80% of the 600AH
(480AH) as one might assume. ·
Discharging a battery below 80% will drive the
voltage below 1.70 volts per cell, which will overheat and damage the battery
and any equipment it is powering. ·
Sealed batteries usually have a 50% depth of
discharge, and will be damaged by an 80% discharge. ·
All GB batteries have an 80% depth of discharge, but
can be used in 50% (or less) applications. Rate Comparison
6hr
rate: A fully
charged battery discharged 80% over a six-hour period. Formula: 6 hour AH
rating divided by six hours = continuous amps available over six hours 20hr
rate: A fully
charged battery discharged 80% over a twenty hour period. Formula: 20 hour AH
rating divided by twenty hours = continuous amps available over twenty hours. AH Comparison
EXAMPLE: 6hr vs. 20hr
- Battery Model 6-100-13
600AH
@ 6hrs: 600AH
divided by 6hrs = 100 amps continuous current for 6 hours. The same battery rated at 20 hours
945AH
@ 20 hours: 945AH
divided by 20hrs = 47.25 amps continuous for 20 hours. Definition:
Ampere-hour or AH:
·
A measurement of electrical capacity – the amount of
energy the battery will store. Current multiplied by time in hours equals
ampere-hours. A current of 50 amps for one hour would be 50 AH at the 1hr
rate; a current of 30 amps for 5 hours would be 150 AH at the 5hr rate. ·
AH ratings will vary with temperature, and with the
rate of discharge. For example, a battery rated at 100 AH at the 6-hour rate
would be rated at about 135 AH at the 48-hour rate. Ampere-hours (AH) designate the storage capacity of
deep cycle batteries. SLI batteries are not rated in AH, but in
"CCA", or cold-cranking amps (marine batteries are often rated in
"marine cranking amps"). "6 hour rate" and "20 hour
rate" indicate that the battery is discharged steadily over 6 or 20
hours, and the Amp-hour capacity is measured by amperage over time, until the
cut-off voltage (usually 1.75 volts per cell) is reached.
©
Copyright GB Industrial Battery USA. All rights reserved. Last Updated: Saturday, March 10, 2018 - 10:11
P.M. Eastern Time.
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