Sens F3 SERIES Manual

F3 SERIES
CASE SIZE 3A
FILTERED BATTERY CHARGER
OPERATION & MAINTENANCE
MANUAL
SENS part no.: 101146
Document revision: 1.7
DCN number 103681
Date 8/16/01
1840 Industrial Circle
Longmont, CO 80501
Fax: [phone]
Tel: [phone]

F3 Series Charger Manual
2
Installation or Service problems? Call SENS at [phone]
between 8:00 am and 5:00 pm Mountain time Monday through Friday

F3 Series Charger Manual
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IMPORTANT SAFETY INSTRUCTIONS
SAVE THESE INSTRUCTIONS
This manual co
ntains important safety and operating instructions for Stored Energy Systems (SENS) model
F3.
Before using the battery charger, read all instructions and cautionary markings on the battery charger,
battery and equipment connected to the battery system.
WARNING:
Please read these
safety warnings
and heed them.
Failure to do so
could result in
either severe
personal injury or
equipment
damage.
This equipment uses and generates potentially lethal voltages. The equipment should only be installed
and maintained by trained persons. Do not attempt to install or operate this equipment unless you are
certain you are adequately trained.
To reduce the risk of injury, charge only properly sized lead-acid or nickel cadmium batteries. Other types
of batteries orunder-sized batteries may burst causing personal injury and damage.
• Do not install or operate charger if it has been dropped or otherwise damaged. Return it to the factory for
repair.
• Install the charger in accordance with all local codes.
• Do not expose charger to rain or snow.
• Do not disassemble charger; return to factory when service or repair is required. Incorrect assembly may
result in a risk of electric shock or fire.
• To reduce risk of electric shock, de-energize and disconnect the AC input and the battery from the charger
before attempting maintenance or cleaning.
• Use of an accessory not recommended or sold by SENS may result in a risk of fire, electric shock or
personal injury.
• During normal operation, batteries may produce explosive hydrogen gas. Never smoke, use an open
flame, or create sparks near the battery or charger.
• Remove jewelry, watches, rings, etc. before installing battery or charger.
Maintenance
Instructions User maintenance is limited to charger adjustment. All on-site servicing should be performed by qualified service personnel. If qualified personnel are not available, return the charger to the factory for repair, or
contact the factory to arrange for field service.
When returning a unit to the factory for repair, ship it in the original factory packaging if possible. If the
original carton is not available, pack in a carton with at least 2 inches of approved packaging material on all
sides of the charger to help prevent shipping damage.
1
Overview
This manual covers installation, operation and troubleshooting of SENS model F3 filtered battery charger.
1.1 READ THIS FIRST
Please follow the installation and use instructions. They are vital to the satisfactory operation of the

F3 Series Charger Manual
4
charger. If youhave any doubts about adjusting, maintaining or servicing the equipment, contact SENS
service department.
Changing factory-set potentiometers voids the warranty. Contact the factory if you believe that the
settings on your charger are incorrect.Before determining that the charger is not working correctly, check
the following:
1. Are three phases of AC power available to the charger?
2. Are any circuit breakers tripped or fuses blown?
3. Is the charger connected to a battery of the correct voltage?
4. Was the charger damaged in transit or installation?
5. The charger may have shut down to excessive output voltage. To ensure that the high volt shutdown
has been reset, turn off both the AC input breaker and DC output breaker for five minutes. This is more
than sufficient time for the DC voltage to decay and reset the shutdown.
6. If the battery is being over-or undercharged, check whether the output voltage settings have been
tampered with. The pots should be covered with either white adhesive paper dots or a hard colored
varnish. Under no circumstances change the adjustment of control board pots other than R33 and
R34.
1.1 Description and Application
The F3 is a fully automatic battery charger and DC current source offering the following features:
• Constant voltage output
• Electronic current limiting
• Filtered output (on battery rated in AH four times amp rating of charger): 12, 24, 48V: 30 mV rms; 120V: 150
mV rms; 240V: 300 mV rms
• Temperature compensation to maximize battery performance and life
• Circuit breakers for AC input and DC output
The chargers are designed to supply equipment requiring a low ripple DC source and to automatically
recharge and maintain a parallel connected lead-acid or nickel-cadmium battery. All units can operate the
load without battery connected, but the output ripple will increase.
1.2 Upon Delivery
Inspect the charger for damage caused during transit, and report damage to the carrier immediately. Then
contact SENS to determine how best to repair/replace the damaged unit.
2
Installation
2.1 Mechanical Installation
Caution: Heed the following warning to prevent damaging the lower cover of the charger!
FIGURE 2.1
Lifting Instructions

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WHEN INSTALLING
DO NOT LIFT UNIT
FROM MIDDLE OF
LOWER COVER - THE
COVER WILL BEND.
USE A SPREADER
PLATE EQUIVALENT TO
1" THICK PLYWOOD
ACROSS THE BOTTOM
OF THE UNIT WHEN
LIFTING
The charger can be
mounted either on a wall or in a standard 23” relay rack. Locate the charger in a dry place as close to the
battery and load as possible to minimize voltage drop.
WARNING: These chargers are not approved for operation in mines or other places with explosive
atmospheres
Wall Mounting
Mount the system to a robust wall using 1/4” bolts with flat washers behind the mounting holes if
necessary to level the charger on an uneven wall. The charger should be located as close to the battery
and load as possible to reduce voltage drop in the charging leads. Refer to the mechanical drawings at the
end of this document for case dimensions and mounting dimensions.
Relay Rack Mounting
The charger is shipped on its back with the mounting flanges in the wall-mount position. Place the charger
in a vertical position, then unbolt and reverse the mounting flanges. CAUTION: When changing the
angles from wall mount (the standard shipping configuration) to rack mount, you MUST either stand the
charger up vertically, or otherwise remove the charger’s weight from the rack angles when removing the
rack angle bolts. If you do not, the bolts in heavy chargers may strip on their way out.
Protect the charger from construction grit, metal chips, paint or other debris. Clean away debris after
installation and before turning on the charger.
2.2 Electrical -Power Wiring
WARNING: Heat sinks and many other metallic components inside the charger are LIVE with either line or
output voltage. These voltages can be lethal. Do not touch any exposed metal surfaces inside the
enclosure while the charger is operating.
Remove the two 1/4-turn fasteners securing the charger's top front panel and open the front panel. Make
AC and DC connections direct to the AC and DC circuit breakers in accordance with diagram 2.2 below.
Caution: Small sense leads are connected to the output side of the DC breaker. These must remain
connected to the output side of the breaker after installation of the DC cabling, or the charger will not
function properly.
FIGURE 2.2
Power Connections

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DC OUTPUT
-+
AC INPUT
ØA ØB ØC
Connection should be made by a qualified installer in accordance with national and local electrical codes.
The installer should determine the gauge of wire to be used based on the length of cable run and the
ampere requirements of the charger. Size the DC cabling to keep voltage drop in the charging leads as low
as possible.
Refer to TABLE 2.2 for the charger’s AC requirement of your charger. The input voltage and frequency are
marked on the charger’s front panel. Maximum current consumption will be approximately 75% to 80% of
the breaker’s rating. Typical efficiency is 85% for 24 volt units, 88% for 48 volt units and 91%+ for 120 and
240 volt units. Power factor is approximately 0.8 at rated input voltage.
WARNING: The battery charger must be connected to a grounded permanent wiring system. A ground
stud or terminal is provided for this purpose
TABLE 2.2
AC Input Circuit Breaker Ratings
Charger output Rated Charger AC Circuit Breaker (/Phase)
208V 240V 380V 400V 415V 480V
VAVAVAamps amps amps amps amps amps
24 100 48 50 20 15 15 15 15 15
24 150 48 75 25 20 15 15 15 15
24 200 48 100 30 25 20 15 15 15
48 150 35 40 25 25 25 20
48 200 60 50 35 30 30 25
120 25 20 20 15 15 15 15
120 35 25 25 15 15 15 15
120 50 35 30 20 20 20 15
120 75 55 45 30 30 25 25
120 100 75 65 40 40 35 30
Caution: Do NOT connect the battery backwards; charger damage may result
The voltmeter will show battery voltage as soon as the DC connection is completed. Check the voltmeter
as soon as the DC connection has been made. If the meter reads zero or is deflecting below zero, reverse
the polarity of the battery connections.
2.3 Alarm Connections

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F3 chargers are supplied with one of three following alarms configurations:
TABLE 2.3
Charger Part Number Suffix and Alarms Configuration
Second digit of part number suffix (e.g. "F5E2")
Alarms “0” Alarms “5” Alarms “6” < Alarm system code
Indications
none Float or boost modeFloat or boost mode LED
none AC fail AC fail LED & Form C contact
none Charger fail Charger fail LED & Form C contact
none Low battery voltage Low battery voltage LED & Form C contact
none High battery voltage High battery voltage LED & Form C contact
none none Ground fault + LED
none none Ground fault -LED
none none Ground fault + or -Form C contact
none Summary of above Summary of above Form C contact
Connect to the charger’s Form C contacts according to Figure 2.3
1. Make connections to the system's Form C alarm contacts as shown.
2. Run alarm wiring out of the charger separately from the AC supply wiring
3. Use 16 to 22-gauge wire.
4. NOTE: Do not exceed the relay maximum current rating of 0.5A @ 117 VAC or 1A @ 24 VDC.
The remote alarm connection board is located on the circuit breaker pan, adjacent to the control board. See Figure 2.3

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FIGURE 2.3
Remote Contact Terminal Block
FAIL OK COM
GROUND
FAULT
AC
FAIL
CHARGE
FAIL
LOW DC
VOLTS
HIGH DC
VOLTS
LOW DC
DISC.
OPTIONSUMMARY
FAIL
OK COM
FAIL OK COM FAIL
OK
COM FAIL OK COM
FAIL OK
COM FAIL OK COM FAIL OK COM
2.4 Temperature Compensation
F3 chargers include battery temperature compensation (TC). TC is required by all batteries for maximum
performance and life. The TC feature automatically reduces the charger’s output voltage at high
temperatures and vice-versa.
The F3 has provision for either local or remote sensing of temperature. Local sensing is done by
components located on the charger’s control board, which is exposed to the ambient air. At installations
where the battery is located in a different room, or is otherwise subject to ambient temperatures different
from the charger it is necessary to sense temperature at the battery. The SENS remote sensor is optional.
The control board automatically selects the remote sensor over the local sensor. If the remote sensor is
damaged or disconnected temperature sensing automatically reverts to local.
The two leads of the RTS are connected to a port on the control board as follows: Connect the yellow lead
of the sensor to J6 “K” and the violet lead to J6 “A”. If the sensor is connected properly D12 will not
illuminate when the charger is in operation. If D12 stays lit, check that RTS leads are not reversed, and
check that the RTS is not damaged.
NOTE: D12 on the control board will remain lit whenever the remote temperature sensor is either not used,
or if the remote sensor is disabled. This is normal when RTS is not used.
3
Operation
3.1 Start-up
Start with both input and output breakers OFF.
First, check that the connected battery voltage is correct (e.g. 120 volts for a 120 volt charger). It is OK if
the battery voltage is different from the nominal value by a few percent. If the battery voltage is more than
10% different from the rated voltage of the charger, recheck your connections BEFORE turning on either
breaker.
First close the AC input breaker. Check that the charger voltage comes up to approximately 15% above
nominal. (Some voltage overshoot on initial startup is normal).
Next close the DC output breaker. The charger will immediately begin to supply current if required by the
battery orload.
In chargers with alarms code “5” or “6”, the front panel AC FAIL and CHARGE FAIL lights will extinguish,
and should be replaced by the green AC ON light.
The charger will automatically supply power to the load and maintain the battery withoutfurther attention.
If the charger does not start as described, or appears to have failed, check the following:
• Verify that AC mains power is available
• Verify that no external circuit breakers are tripped

F3 Series Charger Manual
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• Verify that contractor-installed AC, DC and alarm connections are correct
• Disconnect AC and DC power sources. Open the charger. Verify that no components (e.g. main DC
output fuse, if fitted) or harness connections are blown, loose or damaged
If all of the above appear to be in order, contactSENS at the toll-free service number on the front of this
document for assistance in troubleshooting. 3.2 FLOAT/BOOST MODES
Two modes of voltage control are provided in all F3 chargers as follows:
FLOAT
The float mode is the battery “maintenance” voltage. It is the normally fully charged voltage of the battery.
This is the normal charging position for all batteries, and the recommended charging position at all times for
Valve Regulated Lead Acid (VRLA) batteries.
BOOST
This voltage is slightly higher than the float setting. Boost slightly overcharges the battery in order to
ensure that all the cells of a battery are fully charged to the same voltage. Continued operation in boost is
not recommended because the high charging voltage will cause batteryelectrolyte to boil away quickly.
This is a particular problem with VRLA batteries where there is no way to replenish lost electrolyte.
3.3 FLOAT/BOOST CONTROL
F3 chargers are equipped with one of the four following float/boost voltage control systems depending on
the configuration ordered:
FLOAT/BOOST front panel rotary switch
The charger will operate indefinitely in the mode that is selected. The AUTO position may be shown on the
front panel. If the AUTO position is locked out, the AUTOBOOST feature is not supplied.
AUTO/FLOAT/BOOST front panel rotary switch
When the selector switch is in the FLOAT or BOOST mode the charger will operate indefinitely in the mode
that is selected.
The AUTO mode selects automatic equalization of the battery. The charger determines when the battery is
in need of fast charging, and operates in the fast charge boost mode only until the battery is fully charged.
The charger determines state of charge by the measuring the amount of current drawn from the output
terminals. When the selector switch is in the AUTO position the charger will start in the boost mode and
stay there until current demanded drops below about 50% of the charger’s rated current. When current
demand increases to about 70% of the charger’s rated output the charger will resume operation in the boost
mode.
Please see the Appendix for a diagram of how the Autoboost system works. The AUTO setting eliminates
the need to periodically equalize the cells of a battery as the charger does this automatically. The AUTO
position should not be selected when the continuous load on the charger is greater than about 50% of
the charger’s maximum rated current.
Manually initiated boost timer (either 0-24 hours or 0-72 hours)
When the timer is turned clockwise the charger will be in boost mode, where it will remain until the timer
returns to 0 hours. At the end of the selected time the charger will return to float mode.
Manually initiated boost timer plus AUTO/FLOAT/BOOST rotary switch
Selection of the AUTO position allows the charger to operate in the AUTOBOOST mode (described above)
Selection of the FLOAT mode forces the charger to remain in the float mode unless the boost timer is
activated by turning past zero. If the boost timer is activated, the charger will revert to float mode after the
time selected on the timer expires.
Selection of the BOOST mode forces the charger into boost charge, where it will remain until BOOST is
deselected manually.

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3.4 Alarm Indications
NOTE: Chargers are equipped with a “dead-front” panel. Alarm LEDs are behind the dead front panel and
will be visible when they illuminate due to an alarm condition, or when the TEST button is pressed. See
Figure 3.5 for the location of LED indicators. Chargers with no alarms (alarms code “0”) have no LEDs or
test button.

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FIGURE 3.4
LED Indicators on Charger Front Panel
LOW DC
AC FAIL + GROUND
- GROUND
LAMP TEST
FLOAT
BOOST
AC ON CHGR FAIL
HIGH DC
SHUTDOWN
AC ON
Indicates that AC power is being supplied to the charger.
BOOST
The charger is operating in the BOOST mode.
FLOAT
The charger is operating in the FLOAT mode.
AC FAIL
Indicates that AC power is not available to the charger. Input AC is failed, or AC breaker is tripped.
CHGR FAIL
Indicates that the charger is failing to produce the output current required by the battery and load. When
the battery and load demand no current the failure alarm will not activate.
In the event that the CHARGE FAIL and AC ON lights are illuminated simultaneously, then the charger
has failed. The probable causes of an alarm, in descending order of likelihoodare:
a) A failure of AC power
b) A tripped AC breaker
c) The charger has malfunctioned
LOW DC
Indicates that DC voltage has dropped to approximately 8.5% below nominal battery voltage (e.g. 22 volts
for a 24 volt system). Probable causes:
a) The AC power has failed, and the battery has become discharged
b) The charger has malfunctioned and the battery has become discharged
c) The battery is defective
There is a time delay in the low voltage alarm which prevents the alarm from activating until approximately
30 seconds after the low voltage condition starts.
HIGH DC
Indicates that the charger’s output has exceeded a pre-set threshold level (approximately 20% above
nominal battery voltage -e.g. 29 volts for a 24 volt system). If this alarm stays activated for any period of
time, the charger should be shut down and serviced. The charger may have malfunctioned, or the alarm
card may be misadjusted. The alarm actives immediately upon high voltage condition, but stays activated
for approximately 30 seconds after the condition disappears.
HIGH DC SHTDN
Indicates that the charger has been shut down by the high output voltage shutdown circuit. Probable

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causes of a high DC shutdown are as follows:
a) The float or boost voltages have been increased above the pre-set shutdown voltage
b) The high voltage shutdown set point has been changed from the factory setting.
c) The charger has malfunctioned, and is not regulating properly.
There is a delay of approximately 5 seconds after the onset of the high voltage condition until the unit
shuts down. When a high volt shutdown occurs, the red HVS LED on the control board will illuminate,
along with the SHUTDOWN LED on the front panel.
If the high DC shutdown activates the charger will stay off until the batter
y voltage drops to approximately
nominal, at which point the circuit will reset and the charger will start. Manual reset of the shutdown is
accomplished as follows:
1) Turn off the AC input breaker. (Note that while the SHUTDOWN LED will extinguish, the
charger is still
locked out. This is because the shutdown LED is driven by the control board's power supply, which is
derived from the AC supply, rather than from battery).
2) Turn off the DC output breaker.
3) Wait for about one minute for capacitor voltage to decay through the capacitor bleeder resistor
4) Turn on the DC output breaker
5) Turn on the AC input breaker. If the charger is still in high DC shutdown, repeat steps 1 through 3,
waiting longer before turning DC and AC breakers back on.
The control board includes two sets of Form C contacts for high volt shutdown indication. Either one of
these can be used for remote indication of high voltage shutdown.
GROUND (optional)
This is a ground fault alarm. If either the charger’s positive or negative is connected to ground, even
through a high resistance path, this alarm will activate. LEDs indicate either positive or negative
grounding. The Form C contact only indicates that a fault has occurred.
Some applications require that ground be re
ferenced to either the positive or negative output. In this case,
the activated ground fault alarm will be a nuisance. The alarm can be safely disabled by placing the
ground fault jumper located on the alarm board (mounted on the charger’s front door) in the “disabled”
position. When pins 1 and 2 of J5 are connected together the ground fault alarm is disabled. When pins 2
and 3 are connected the ground fault alarm is enabled.
4
Adjustments
4.1 Output Voltage Adjustment
WARNING: Working inside the charger exposes you to dangerous AC and DC voltages. Do not
touch circuit breakers, filter capacitors, heat sinks or any other exposed metal surfaces
NOTE: Do not tamper with factory adjustments unless sure adjustment is necessary. Temperature-
compensated control circuitry automatically adjusts the output voltage depending on temperature.
Adjust the output only under these circumstances:
a) To correct a previous unauthorized adjustment
b) To adjust the charger for a different type of battery (e.g. from lead-acid to nickel-cadmium)
c) If your battery is consistently being over-charged or under-charged
NOTE: Unless authorized by SENS, any charger adjustment, including output voltage adjustment,
voids the warranty.
Procedure
1. Use a precision external voltmeter connected directly to the charger output terminals.
2. Set the charger’s front panel FLOAT/BOOST control to FLOAT.
3. Open the charger’s front panel and locate the control card. It contains two potentiometers labeled
“FLOAT” (R34) and “BOOST” (R33), both located next to one of the control transformers.
4. Adjust the FLOAT pot until the desired voltage is achieved.

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Adjustment of the BOOST voltage is similar to adjustment of FLOAT, except that you adjust the
BOOST pot instead of the FLOAT pot. Be sure that the charger front panel mode switch is in BOOST
when you make adjustments.
Please note that the BOOST adjustment controls the level above FLOAT voltage, not the absolute
voltage. Therefore, whenever the FLOAT the voltage is changed, the BOOST voltage also changes.
4.2 Factory-Set Output and Alarm Voltages
NOTE: Output voltages are temperature compensated (vary with temperature). The factory settings
below are at 20 degrees C. The compensation is-0.18% per degree C. The alarm voltage settings are
NOT temperature compensated.Chargers set for sealed maintenance-free lead-acid battery
12 volt 24 volt 32 volt 48 volt 120 volt 240 volt
Float voltage 13.62 27.24 36.32 54.48 136.20 272.40
Boost voltage 13.80 27.60 36.80 55.20 138.00 276.00
Low DC alarm 11.00 22.00 29.33 44.00 110.00 220.00
High DC alarm 14.61 29.22 38.96 58.44 146.10 292.21
High DC shtdown 15.19 30.39 40.52 60.78 151.95 303.89
Chargers set for flooded lead-acid battery
12 volt 24 volt 32 volt 48 volt 120 volt 240 volt
Float voltage 13.32 26.64 35.52 53.28 133.20 266.40
Boost voltage 14.00 28.00 37.28 55.92 139.80 279.60
Low DC alarm 11.00 22.00 29.33 44.00 110.00 220.00
High DC alarm 14.82 29.64 39.47 59.20 148.01 296.02
High DC shtdown 15.41 30.83 41.05 61.57 153.93 307.86
Chargers set for nickel cadmium battery Multiply volts per cell times # of cells for actual voltage
Per Cell
Float voltage 1.43
Boost voltage 1.52
Low DC alarm 1.19
High DC alarm 1.61
High DC shtdown 1.67
Chart 4.2 shows relationshipsbetween charger output voltage, alarms and high volt shutdown Output
voltage is temperature compensated down to ten degrees C; compensation then ends.
To determine the charger’s voltage at temperatures other than 20 deg. C., multiply number of degreesC
difference between ambient and twenty C times .0018. Multiply that product times the factory voltage
setting (e.g. 27.24) and add it to the factory setting. Examples:
Example 1: Float voltage at 10 degrees C of a 24 volt charger set for 27.24 voltsat 20 degrees C:
20-10 (.0018) (27.24) + 27.24 = 27.73 volts
Example 2: Float voltage at 50 degrees C of a 24 volt charger set for 27.24 volts at 20 degrees C:
20-50 (.0018) (27.24) + 27.24 = 25.77 volts
CHART 4.2
Graph of Factory-Set Output, Alarm and Shutdown Voltages

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Degrees C
1.75
1.85
2.15
2.25
2.35
2.45
2.55 VRLA Float
VRLA Boost
Flooded Float
Flooded Boost
HV Alm VRLA
HV Shtdn VRLA
HV Alm Flooded
HV Shtdn Flooded
Low DC Alarm

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15
4.3 Forced Load Sharing
Chargers can be set up for forced load sharing when used in parallel with units of the same current
rating. Forced load sharing causes the chargers to share the load from light loading to full load except
when either charger is in BOOST mode (whether activated manually or via the AUTOBOOST system) or
if either charger is operating in current limit.
To set up, ensure that the DC output leads from each charger are identical in length and wire gauge.
Install a signal wire (18 or 22 AWG) between terminals on both control boards labeled “PAR”. Chargers
will share the load within+10% of each other.
5
Trouble-
shooting
5.1 Troubleshooting Table
If there is a problem and you suspect the charger is at fault, turn off the AC mains supply before
proceeding. Ensure that the following are correct: AC input wiring, battery and/or load connections
and PC card connectors. Ensure no foreign objects are in charger.
Symptom Possible Cause Test Corrective Action
No output /
Charge Fail
alarm
Control board failure Replace with known good
board Replace board,
DC Fuse blown Check fuse for continuity Replace if open
High DC Shutdown Check LED D30 on control
board If lit, see "High output Voltage" under Symptom
below in this chart
Power rectifier circuit
failure Test all power diodes with meter, perform SCR test on all
SCRs
Replace all shorted, open, or
bad parts
AC failure Check input supply Restore AC input supply
Shutdown due to
excessive output
voltage
Check whether LED D30 on
control board is lit Shut off AC and DC breakers for at least 2 minutes, then
restore
AC breaker
trips
repeatedly
Power diode, SCR, or
freewheeling diode
short
Check all power devices for
shorts Replace shorted device(s)
DC fuse blows
or DC breaker
trips
Control board failure Replace with known good
board Replace board, send bad board to SENS for repair
Freewheeling diode
short Check diode for short Replace diode
Low output
voltage / Low
DC alarm
Control board failure Replace with known good
board Replace board,
Misadjusted Float
Voltage pot (R34) on
control board
Adjust pot and see if output
voltage is affected Adjust R34 to correct output voltage
Overloaded charger Turn off DC breaker, check
voltage on INSIDE breaker
terminals
Check load for problems, and
check battery condition
Overheating Test all power diodes and
SCRs Replace bad devices
Check for obstruction of top
and bottom vents Remove obstruction(s)

F3 Series Charger Manual
16
Check for vertical mounting of
charger Mount charger vertically
Verity that room temperature is
less than 50 C Reduce room temperature
Verity that AC input voltage is
not higher than charger's
specified operating range
Contact utility company
Symptom Possible Cause Test Corrective Action
Check for failure of one phase Contact electrician or utility
company
Bad filter capacitor Disconnect capacitors one at a
time and check for change in
output voltage
Replace capacitor that
corrected output voltage
when removed
Line voltage less
that charger's
specified operating
range
Measure AC line voltage Use larger gauge AC wires or
contact utility company
High output
volts / High
DC alarm
Control board failure Replace with known good
board Replace board
Misadjusted Float
Voltage pot on
control board
Adjust pot and see if output
voltage is affected Adjust float pot to correct output voltage
Remote temperature
sensor failure Remove Remote Temp. Sensor connector on control board J6 Replace Remote Temp. Sensor
High ripple
voltage Control board failure Replace with known good board Replace board,
Excessive line
voltage imbalance Measure and compare the three AC phase voltages Contact electrician or utility company
Power diode / SCR
failure Test all power diodes with meter, perform SCR test on all
SCRs
Replace all open or bad parts
AC phase failure Check for failure of one phase Contact electrician or utility
company
AC line voltage too
high Check for AC line voltage over charger's specified operating
range
Contact utility company
Bad filter capacitor Disconnect capacitors one at a
time and check for change in
output voltage
Replace capacitor that
corrected output voltage
when removed
Alarms or
indicators not
functioning
Alarm, display, or
control board failure Replace each board in turn with a known good board Replace failed board(s)
5.2 Component Diagnostic Tests
Test #1: With transformer leads disconnected, energize the transformer with the normal AC supply
voltage. Measure entire secondary voltage. It should be 1.1 times the nominal battery voltage.
Test #2: With one or both leads disconnected from the inductor, measure the resistance across the
inductor terminals. If the resistance is near a short circuit condition, the inductor is OK.
Test #3: Power Diodes,units with SCR/diode modules
See the attached SCR/diode module troubleshooting table to determine module condition.
Test #3: Power Diodes, units with stud-mount diodes

F3 Series Charger Manual
17
Using a digital multimeter set to the diode testing function, measure the junction voltage across the
diode. A reading of between 0.4 volt and 0.8 volt in the forward polarity direction and infinity in the
reverse polarity direction indicates a good diode.
Test #4: SCRs, units with SCR/diode modules
See the attached SCR/diode module troubleshooting table to determine module condition.
Test #3: SCRs, units with stud-mount SCRs
Refer to Figure 5.2. Disconnect all the leads to the SCR and its heat sink. Connect a voltmeter across
the 1K resistor to measure the voltage drop. With the battery connected as shown, Vdrop should
read approximately 2.3V (Vsource-0.7V). Remove the voltage source to the gate, but keep it connected
to the 1K resistor and cathode. Vdrop should equal zero. Reconnect the gate and reverse the
batteries polarity. Vdrop should read zero volts. Readings other than these indicate a defective SCR.
Test #5: Due to the modest cost of the control circuit, we recommend that the entire unit be replaced
rather than attempting to repair it. If the trouble shooting guide has not revealed any defective
components (tests #1-4), the control circuit should be replaced as a unit.
Test #6: Remove all wires from the current shunt. Place a milliohmmeter across the two terminals. The
following formula should be used to determine the correct resistance:
Resistance in ohms should equal 0.5/Output current rating of the charger, except in 35 amp units when
resistance should equal 0.1 ohms.
If the resistance is more than 20% too low, the current shunt should be replaced.
FIGURE 5.2
SCR test setup
25 ž
approx. 3 volt source(2 "D"
batteries in series)
Cathode Gate
SCR
Anode
-
+
+
-
Vdrop 1 Kž

F3 Series Charger Manual
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INSERT DIAGRAM OF SCR/DIODE POWER
MODULE TROUBLESHOOTING INSTEAD OF
THIS PAGE

F3 Series Charger Manual
19
6
Theory of
Operation-
Control
Circuit
6.1 Introduction
This section provides information on operation, setup and adjustment ofthe SENS three phase, six
pulse battery charger control circuit. Schematics are included in the back of the manual to assist the
reader in understanding the circuits as they are discussed.
6.2 Power Train Format -General
Each power phase utilizes a single phase, full wave half controlled bridge rectifier with two power
diodes and two power SCRs (silicon controlled rectifiers). Firing circuits are of a modular format which
allows identical circuits to be used for a three phase-six pulse power train.
6.3 Control Circuits -General
Electronic loop control circuits are utilized for output voltage and current control. A quasi loop control
circuit is used to cross couple the voltage and current control loops to maintain close tracking for fast
control transfer from one control mode to another.
6.4 Alarm and Special Function Circuits -General
A soft start circuit allows the charger output to rise slowly when power is turned on.
Battery temperature compensation is standard. Temperature sensing is either local (sensing element
located on charger control board), or remote, depending on whether the remote sensor is connected to
the control board. The remote sensor is optional.
A load share circuit allows multiple chargers to share output current equallywhen operated in parallel.
A charge fail alarm is activated when there is both a loss of current and a low control bus which then
activates an alarm on the display board.
The high voltage shutdown circuit operates when battery voltage is too high. An alarm light on the
control board is illuminated, the charger firing circuits are shut down, and an LED on the display board
is activated.
6.5 Board Power Supplies -Detail
Control Circuit Operating Supplies-Detail
Operational amplifiers and other circuits require positive and negative 12 volts DC. A DC voltage of 5-
6 volts DC is required to set the magnitude of SCR firing pulses. Negative 2.5 and 5.5 volt reference
voltages are used for the current and voltage loop controls. Circuitry for each phase requires a control
transformer to provide supply voltages, synchronization and timing for SCR firing. A 24 volt center
tapped winding is used.
12 Volt Supplies-Detail
Refer to schematic No. 00198a. Control transformers T1, 2 and 3 are each full wave rectified with
common negatives and common output from positives. The positive and negative bus peak charges
the capacitors to a +/-17 VDC. Regulators VR1 and VR2 regulate the voltages to positive and
negative 12 VDC. Tantalum capacitors are used to filter high frequency noise. These positive and
negative lines supply operating power for all PC board electronic circuitry
Negative 2.5 and 5.5 Volt Buses-Detail
A resistor drops the -12 volts to-5.5 VDC and-2.5 VDC through a temperature sensor zener (LM335)
and a band gap zener (LM285). The bandgap zener provides a very stable -2.5 VDC reference which is
used to derive the reference voltage for the output voltage control and the current limit circuitry. The
temperature sensor zener(LM335) is used to create a -5.5 VDC temperature compensated reference
voltage.

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6.6 SCR Firing Circuits -Detail
Each power phase requires a firing circuit to fire the rectifying SCRs at precisely the right time for
rectification and output control. Since all firing circuits are identical, one phase will be discussed.
Ramp and Ramp Reset Circuits-Detail
The control transformer secondary voltage is rectified to a full wave pulsating wave form. The signal is
fed to an op-amp negative input where it is compared to a DC level of 450 mV (millivolts). When the
rectified voltage drops below this level, the output goes high to turn on a transistor. The collector
drops to near ground, discharging the capacitor across collector to emitter. As the rectified wave form
rises above 450 mV, the capacitor charges up thus creating a ramp that is synchronized with the phase
voltage.
Firing Pulse -Detail
At a comparison amplifier, the ramp signal is compared to the DC control bus voltage. When the ramp
signal rises above the DC control bus level, the output of the op-amp goes high. This turns on an npn
transistor which turns on the SCR firing circuit.
SCR Firing -Detail
During the half cycle when SCR anode is positive, a firing pulse will be generated and applied to a
MOS-FET. If the MOS-FET gate is positive biased, the positive anode voltage will flow through the
MOS-FET and out to the SCR gate, thus turning on the SCR. There are six pulsing circuits, two for
each phase. Each circuit has a blocking diode to avoid current flow through the MOS-FET during the
negative half cycle of the AC wave form.
6.7 Voltage and Current Control Loops-Detail
The loop control circuits consist of the voltage control circuit and the current control circuit. The DC
output must be carefully controlled and adjusted automatically for battery temperature variations to
prevent overcharging or undercharging the battery. Output current must be limited to prevent
excessive charge rate which can shorten battery life, as well as to protect the charger from overload
conditions.
NOTE: Refer to the “Special Function and Alarm Circuits”, later in this discussion, as they are an
integral part of the operation of the control loops.
Voltage Control -Detail
The voltage control amplifier compares the scaled down output voltage to a precision temperature
compensated reference voltage. When the output is higher than the reference level, the control
amplifier generates a DC control signal which is coupled to the control bus and in turn is fed to the
firing circuits to determine SCR firing angle. An increasing control bus voltage causes a delay in firing
and reduced output. As output is reduced to the correct voltage, the control bus voltage and firing
angle stabilize, and output remains constant.
Loop controls require a feedback signal from the function being controlled. Since the positive DC
output is the system ground or circuit common point, feedback is taken from the negative output. The
output is scaled down to approximately-5.5 VDC. Control loop stability is maintained by a type I
compensation loop.
Float/Boost /Autoboost -Detail
Chargers are equipped with two charging modes, float and boost. AUTOBOOST automatic equalize
operation is an option. Float mode charges the batteries up to their normal charged voltage, while
boost mode will charge the batteries over their normally charged voltage. The purpose is so that the
individual cells in the battery will equalize, thus improving battery performance. However, extended
time in boost mode can resultin battery damage due to overcharging and consequent electrolyte loss.
The float/boost/autoboost function is controlled either by a manual rotary switch or a timer. When the
timer is on, the charger is in boost mode. When time runs out the charger reverts back to float mode.
By changing the -5.5 VDC reference voltage different output voltages can be obtained. This is done