HP 6259B User Manual

feature, a battery may be charged at a constant-current
until the maximum charge voltage is reached, at which
point the supply reverts to constant-voltage operation and
continues to supply a trickle charge current sufficient to
maintain full charge. Thus, the charging operation can be
unattended after properly setting the charging rate and
maximum charge voltage and connecting the battery to the
output terminals of the supply.
-CAUTION-
Any time these supplies are used to charge a
battery, be sure to install a protective diode
CRp in series with the battery as shown in
Figure 3-16 to prevent the battery from dis¬
charging into the supply if the supply is
turned off. Extensive damage to the supply
could result if this diode were omitted.
The use of remote voltage sensing provides no
advantages when performing a constant-current
battery charge as discussed in paragraph 3-89
or a taper charge as discussed in paragraph 3-90.
Because of a serious risk of damage to the
supply, the use of remote voltage sensing
should not be attempted when charging (or
discharging) a battery. Also see the CAUTION
following paragraph 3-32.
NOTE
A large battery, connected as a load, presents
a large capacitance to the output terminals.
This capacitance could cause the supply to
oscillate. If the supply appears unstable, it
may be beneficial to readjust equalization
control R47 located on the main circuit board.
3-89 Constant-Current Charge. To perform a constant-
current battery charge, set the charging rate and full charge
voltage as follows:
a. Turn both the VOLTAGE and CURRENT controls
fully counterclockwise (CCW).
b. Connect a short circuit across the output terminals
and rotate the VOLTAGE control fully clockwise (CW).
c. Adjust the CURRENT control for the desired
charging rate as read on the front panel ammeter.
d. Rotate VOLTAGE control fully CCW and remove
the short circuit.
e. Adjust the VOLTAGE control for an output voltage
0.7 volts greater than the desired full charge voltage. (The
added 0.7 volts compensates for the drop across CRp.) The
supply may then be connected to the battery terminals,
positive to positive and negative to negative as shown in
Figure 3-16 (omit Rj).
3-90 Taper Charge. When charging lead-acid cells, many
manufacturers recommend that the charging current be
reduced as the charge nears completion. This can be
accomplished by inserting a small resistance (Ry) in series
with one of the load leads from the supply to the battery.
(See Figure 3-16.) This resistor alters the normally rectan¬
gular charging plot in such a manner as to provide a taper
charge for the last portion of the charge. The proper value
for this resistor is the difference between the full charge
voltage and the voltage at which the tapering is to start,
divided by the initial charging current. Set the initial
charging rate and full charge voltage as instructed in
paragraph 3-89.
3-91 Battery Discharging
3-92 These power supplies are also useful when batteries
must be discharged at a constant current in order to test
them. Connecting a supply as shown in Figure 3-17 and
following the instructions below makes an unattended
constant-current discharge possible by automatically
shutting off the output of the supply when the battery
voltage reaches zero.
3-93 The supply operates in the constant-current mode,
delivering the current set by the current control. This con¬
stant current flowing through dropping resistor R^ produces
a constant voltage across the resistor. Initially, the battery
voltage is high and the supply's output voltage is low, but
as the battery voltage decreases during discharge, the supply
voltage increases. When the battery voltage reaches zero,
CONSTANT-
>-CURRENT-v
CHARGING
1
E m = BATTERY FULL-CHARGE VOLTAGE
1C 1 CONSTANT CHARGE CURRENT
E t = BATTERY VOLTAGE AT WHICH CHARGE RATE WILL
BEGIN TO TAPER (WITH INSERTION OF R T )
Figure 3-16. Battery Charging
3 13

HP 6259B Specifications

General

Brand	HP
Model	6259B
Category	Power Supply
Language	English