Discharge Voltage Cutoff; Charger Optimization/Diagnosis - US BATTERY US1800 XC2 User Manual

6
PERFORMANCE
OPTIMIZATION

6.3 DISCHARGE VOLTAGE CUTOFF

To determine the necessary voltage cutoff at a specified discharge rate and time, use
the following graph:
DIAGRAM 15
LEAD ACID BATTERY DISCHARGE CUTOFF VOLTAGE VS
DISCHARGE TIME THEORETICAL AND STANDARD 1.75 VPC
Theoretical and Standard 1.75 vpc
2.00
1.90
1.80
1.70
0.50
1.60
0.30
1.50
0.25
0.20
1.40
0.15
1.30
1.20
0.12 hr
1.10
1.00
0.1
Discharge times between the 2 hour and 20 hour should use the 1.75vpc cutoff volt-
age. Discharge times less than 2 hours should use the specified voltage cutoff. The
voltage cutoffs were determined at the standard temperature; 80ºF. Temperature com-
pensation must be applied for battery temperatures significantly deviating from the
standard temperature.

6.4 CHARGER OPTIMIZATION/DIAGNOSIS

Undercharging is one of the most common reasons for reduced operating time and
overall poor performance of golf cars and other types of electric vehicles that use deep
cycle flooded lead-acid batteries. While many golf car operators blame the batteries,
32
20 hr
10
5
3
2
1 1.75 1.75 1.75 1.75 1.75
Theoretical Cutoff Voltage at 80ºF
Cutoff with Standard 1.75 vpc
1 10 20
Discharge Time (hours)
the problem can also result from a poorly performing charging system. Keep in mind
that battery chargers are subjected to temperature extremes and corrosive environ-
ments that can affect their performance over time. So before you replace another set of
batteries, try these diagnostic procedures to ensure your charger and charging meth-
ods are working properly:
1. Connect the charger and make sure it is on and charging. Test the voltage at the
battery pack positive and negative terminals. On-charge voltage will normally
continue to increase until the charger terminates the charge automatically. It is
important to determine the maximum on-charge voltage and charge current (on
the charge meter if available) observed near the end of the charge cycle just
before the charge terminates.
2. Once the charger has completed a charge cycle and has automatically turned
off, unplug the power to the charger. Wait one to two minutes and reconnect it.
The charger should resume charging normally. Note the charge current and the
time at the beginning of charge. This is usually described as an 'equalization
charge' and should continue for at least 30 minutes before checking the
charger's performance. With many chargers, this step can also be performed
by unplugging the DC power cord from the charger to the battery pack. If this
method is used, confirm that the charger restarts and continues to charge for at
least 30 minutes.
3. It's at this point that you can begin to check the charger's performance. Check t
he on-charge voltage at the battery pack's positive and negative terminals. The
voltage will normally continue to increase to the range of 2.50-2.60 volts per cell,
until the charge terminates automatically. See "Table 1" to determine the
minimum and maximum on-charge voltages for the battery pack based on
nominal pack voltage. If the voltage does not increase or initially increases and
then decreases, record the following information.
a) The maximum and final on-charge voltages.
b) Charge current (if available).
c) The charging time from the start until it terminates automatically.
4. The next step is to check the on-charge voltage of each battery and compare
it to Table II to determine the acceptable Charge Voltage Variation for each
battery's nominal voltage. If the voltage varies beyond the values stated in
Table II (either variation from pack average or variation from highest to lowest),
replace the lowest voltage battery and repeat the diagnostic test. Test the failed
battery separately to determine mode of failure.
User Manual 33