15
HOW TO SET
There are four different ways the
Link 20
can approximate time of operation
remaining. You may select present consumption level, a four-minute rolling average, a
16-minute, or a 32-minute rolling average. Which method is best for you depends on
your installation. Most installations will find the four-minute average appropriate.
1.
Press
SET
for five seconds.
SEL
will appear in the numeric display.
2.
Press
SEL
four times.
The light will come on and
001
will
appear in the
Link 20
numeric display.
3.
Press and hold
SET
.
The numeric display will move up in
1
unit
steps with choices of:
Instant:
Display:
000
4-Minute Avg:
Display:
00I
16-Minute Avg:
Display:
002
32-Minute Avg:
Display:
003
4.
After 10 seconds, the displayed
setting is stored in memory and
normal operation resumes.
INTRODUCTION TO RATE COMPENSATION
AND THE PEUKERT EXPONENT
Your
Link 20
shows true amp hours consumed in the numeric amp-hour display.
However, the light bar above it shows how much of the
available
battery capacity has
been consumed. You may experience times when the light bar shows more than 60% of
capacity consumed, yet according to the numeric display less than half of the battery
capacity has been consumed. How can this be?
In 1897 a scientist named Peukert demonstrated that as you discharge a battery
more quickly, its
effective size temporarily decreases
. A battery is considered fully dis-
charged when it is no longer able to maintain 10.5 volts under load. As you'll see in the
following table showing the effect on a typical liquid cell battery, the faster the discharge
rate, the smaller its effective capacity:
Hours to Discharge
Capacity as percent of 20-hr rating
20
100%
10
84%
5
67%
2
56%
1
47%
In other words, a 100 amp-hour battery discharged completely in one hour will only supply
47 useful amp hours.
