NRS ELC-12/20-D Service manual

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*31318*
NATIONAL
RAILWAY
SUPPLY
Installing, Operating and
Service Instructions for the
12/20 Solid State Charger
MODEL ELC-12/20-S and ELC-12/20-D
BATTERY CHARGER
PLEASE SAVE THESE IMPORTANT SAFETY AND OPERATING INSTRUCTIONS
For correct operation of the equipment, it is important to read and be familiar
with this entire manual before installing and operating the charger.
DO NOT DISCARD THIS MANUAL AFTER READING.
LOOK FOR THIS SYMBOL TO POINT OUT SAFETY PRECAUTIONS. IT MEANS:
BECOME ALERT—YOUR SAFETY IS INVOLVED. IF YOU DO NOT FOLLOW THESE
SAFETY INSTRUCTIONS, INJURY OR PROPERTY DAMAGE CAN OCCUR.
1. IMPORTANT SAFETY INSTRUCTIONS
a. Before using the battery charger, read all the
instructions and caution markings on the
battery charger, the battery, and all of the
products using the battery.
b. Do not touch the uninsulated parts of the AC
input or the DC wires, the charger's binding
posts, or the battery terminals, as there is a
possibility of electrical shock.
c. Batteries produce hydrogen gas while
operating, which can explode if ignited.
Never smoke, use an open flame, or create
sparks in the vicinity of the battery. Ventilate
the area well when the battery is charging in
an enclosed area.
d. Batteries contain caustic material which may
cause burns. Do not get in eyes, on skin, or
clothing. If the gelled or liquid content of the
batteries contacts the skin or clothing, wash
the area thoroughly with water. In the case
of contact with the eyes, flush immediately
with clean water for 15 minutes and obtain
medical attention.
e. Only qualified personnel should program or
service this equipment.
f. De-energize all AC and DC power
connections before servicing this unit. If
injury does occur, apply standard treatment
for electrical shock and, if necessary, consult
with a physician.
g. The charger is not for outdoor use. Do not
expose the charger to rain or snow.
h. Do not operate the charger if it has received
a sharp blow, been dropped, or otherwise
damaged.
i. Do not disassemble the charger. Have the
charger examined by a NATIONAL
RAILWAY SUPPLY service agent. If the
charger is assembled incorrectly, damage to
the charger and the batteries or an electrical
shock may result.
2. DESCRIPTION
The NATIONAL RAILWAY SUPPLY charger, model
12/20, is a convection-cooled, solid state, SCR
regulated charger that provides either a constant
current or constant voltage output. The charger can
be set to charge batteries within a voltage range of
10.00 to 17.00 volts for gel-cell, liquid lead-acid,
nickel cadmium, nickel iron, and starved electrolytic
batteries.

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3. THEORY OF OPERATION
When the charger is connected to the desired AC
voltage source (115 or 230), the transformer creates
auxiliary voltages for the electronic control module.
The electronic control module controls and monitors
the charger so it will perform properly. The
transformer also supplies the power output used for
charging the batteries and provides electrical
isolation between the charger's output and the AC
source.
The charger's output current flows through a shunt
and is sensed by the electronic control module along
with the charger's output voltage. These values are
converted into drive pulses for the SCRs by the
control module. This pulsating charge current (a
pulse occurs each time an SCR is on) is then filtered
by a large capacitor and the batteries to provide a
smooth output.
The charger has an "IE" profile which is: (a) High rate
constant current, and (b) Constant voltage. When
the charger is first started, the SCRs will conduct for
a certain portion of the sinusoidal anode voltage to
provide the required charging current at the low level
of battery voltage. In this start region, a constant
current is applied to the battery. The SCR
conduction will then increase as the battery voltage
increases in order to provide a higher output voltage
while maintaining a constant charging current.
When the battery voltage reaches the float voltage,
the SCRs will start to decrease their output. This
causes the charger to automatically change from a
constant current charge region to a constant voltage
charge region. As the batteries become fully
charged, the output current decreases. A continuous
constant float voltage will be supplied to the batteries
to maintain their charge.
Another feature of the charger is temperature
compensation, which keeps the batteries from
getting under- or over-charged. TEMPERATURE
COMPENSATION ONLY OCCURS WHEN USING
A TEMPERATURE PROBE. The red LED on the
front of the charger will be off when using a
functional temperature probe. If the LED is on, either
a temperature probe is not being used, or the
temperature probe is working improperly.
Temperature compensation uses a temperature
reference of 77°F (25°C), a voltage reference of 2.23
volts (the voltage of a standard gel-cell battery at
77°F), and a compensation value of 3.0 mV per °F).
The equivalent equation for the compensated voltage
is:
Vcomp = V – k (t - 77°F)
Where V is the voltage of the battery at 77°F, t is
the temperature in °F, and k = V (.003 / 2.23).
The control module has a temperature
compensation range between 32°F and 95°F ( 0°C
and 35°C) that does not allow charger voltage to
increase or decrease beyond the calculated values.
Example 1:
If a 13.38 volt battery is charging and the
temperature increases to 95°F, then the output
voltage decreases to 13.06 volts.
13.38 - .018 (95°F - 77°F) = 13.06
Example 2:
If a 14.50 volt battery is charging and the
temperature increases to 95°F, then the output
voltage decreases to 14.15 volts.
14.50 - .0195 (95°F - 77°F) = 14.15
Example 3:
If 15.61 volt batteries are charging and the
temperature decreases to 32°F, the output voltage
increases to 16.56 volts.
15.61 - .021 (32°F - 77°F) = 16.56
4. RECEIVING AND INSTALLING THE CHARGER
Proper installation of the charger is important in order
to achieve good charger performance and to prevent
damage to the charger and batteries. When a
charger is received, a check for possible in-transit
damage should be made. If any damage is found, it
should be reported as a claim to the carrier. To
permit free air flow for convention cooling, allow
three inches (3") minimum between the charger
sides and other equipment and four inches (4")
minimum on top of the charger.
WARNING: NEVER PLACE ANYTHING ON
TOP OF THE CHARGER WHILE OPERATING.
DAMAGE TO THE CHARGER OR BATTERIES
COULD OCCUR.
WARNING: THE CHARGER MUST BE SET UP
FOR THE PROPER USER SPECIFICATIONS
BEFORE STARTING THE INITIAL CHARGE.
5. AC ELECTRICAL SUPPLY
The charger must be connected to a single-phase,
50/60/100 Hertz AC power source, which can be
either 115 or 115/230 VAC depending on charger
type. Use an 8 AWG wire for the AC power input.
Quarter-inch (1/4") ring terminals are required for
proper connection to the AC input and ground
binding posts (A.A.R.) located on the front of the
charger. Open the small door cover on the front of
the charger by pulling out on the push tabs. Connect

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the AC power terminals on the two posts on the right,
as marked on the panel behind the posts. Connect
the AC ground to the terminal lug provided.
WARNING: FAILURE TO PROPERLY
CONNECT THE AC VOLTAGE CONDUCTORS
COULD CAUSE SERIOUS DAMAGE TO THE
CHARGER. BE SURE TO SET THE VOLTAGE
SELECTION SWITCHES ON THE FRONT OF THE
CHARGER TO THEIR PROPER POSITION.
WARNING: DO NOT OPERATE THE
CHARGER WITHOUT PROPER GROUNDING.
IMPROPER GROUNDING CAN RESULT IN THE
RISK OF AN ELECTRIC SHOCK.
6. DC OUTPUT
The DC output wires are connected on the two left-
most binding posts as marked on the panel behind
the posts (positive on the left and negative on the
right). The DC cables should have quarter-inch (¼")
ring terminals for connecting them to the binding
posts. Check to make sure the polarity of the DC
output wires are the same as those connected to the
battery. The charger will not operate in a reversed
polarity condition. WHEN CONNECTING THE DC
WIRES TO THE CHARGER WITH THE AC POWER
DISCONNECTED, A SPARK MAY OCCUR. This is
caused by the output capacitors being charged by
the batteries. If the DC polarity is reversed, a circuit
breaker will protect the charger from internal
damage. Correct the reversed wires and push the
circuit breaker button back in. Close the door cover
on the front of the charger after tightening all of the
binding post nuts.
WARNING: DO NOT TOUCH THE
CHARGER'S TERMINALS OR AN ELECTRICAL
SHOCK COULD OCCUR. A VOLTAGE IS
PRESENT ON THE DC TERMINALS EVEN AFTER
THE AC IS DISCONNECTED BECAUSE OF THE
ENERGY STORED IN THE CAPACITOR.
7. TEMPERATURE PROBE
The external temperature probe is an optional way of
extending battery life by using temperature
compensation. One end of the temperature probe
cable has a three-pin plug, which plugs into a
receptacle labeled TEMP PROBE on the front of the
charger. The other end of the cable has the
temperature sensor sealed either in a terminal or
small metal box.
WARNING: IT IS IMPORTANT TO MOUNT
THE TEMPERATURE PROBE ON THE
BATTERIES FOR PROPER TEMPERATURE
COMPENSATION. IF THIS CANNOT BE DONE,
LOCATE THE PROBE AS LOW AS POSSIBLE IN
THE BUNGALOW OR CABINET.
Terminal-Type Probe
The terminal-type probe should be attached to the
negative (-) battery post near the center of the
battery pack. If the threaded stud is long enough
above the battery jumper nut, attach the probe with
another nut. Torque this nut to proper specifications.
If the stud is too short, the nut holding the jumper
wire will need to be removed. Open or remove the
load and charging circuits to the batteries. Remove
the nut holding the jumper and add the probe, then
torque the nut to the proper specifications. Then
close or connect the load and charging circuits back
to the batteries.
Box-Type Probe
The metal box has a high performance contact
adhesive tape for attaching it to the battery. To
attach, clean a spot for the probe on the middle
battery about three inches (3") down from the top of
the battery. Make sure the spot is free of all dirt and
oil or the probe will not adhere properly. For proper
adhesion, the battery surface must be cleaned with
isopropyl alcohol. Ideal application temperature
range is between 70 and 100°F. Initial application to
surfaces at temperatures below 50°F is not
recommended. Under cold conditions, the surface
should be warmed before application. Once properly
applied, low temperatures will not affect the bond
strength.
Remove the adhesive's protective strip and press the
probe firmly against the battery to ensure good
adhesion.
Securely fasten the temperature probe cable to
protect the probe from being torn from the
battery. Secure the probe's cable to a fixed object to
ensure the probe will not be pulled loose. Use a
cable tie mount on the battery or on the adjacent
battery, if necessary.
8. OPERATION
The battery charger is adjustable with the three
rotary switches on the front of the charger. The
switches (settable between 10.00 and 17.00)
determine the float voltage for the batteries. SET
THE FLOAT VOLTAGE TO THE BATTERY
MANUFACTURER'S SPECIFIED VOLTAGE FOR
77°F. The charger will then electronically charge the
batteries to the voltage specified on the switches. To
set the switches, use a small screwdriver and turn
the switch so that the arrowhead on the slot is
pointing to the desired number. Set the switches in
the following manner: If the desired battery voltage is
13.38 volts, set the top switch to 3, the middle switch

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to 3, and the bottom switch to 8 (see the figure 8.1).
This will provide you with the proper charging
voltage. The tens digit is always a one (1) and
cannot be changed. BE SURE EACH SWITCH IS
SET ON A NUMBER AND NOT BETWEEN
NUMBERS. If a switch is set between numbers, the
output current will go to zero and the yellow charging
LED will flash.
The charger does not have a power switch. When
the AC power is applied to the charger, the DC
output will start and the yellow LED will be on. To
turn off the charger, disconnect the AC power
source.
Figure 8.1
9. MAINTENANCE
The battery charger requires minimal maintenance.
It should be kept clean and all connections are to be
periodically tightened. BE SURE THE CHASSIS IS
SECURELY GROUNDED. If any problem cannot be
resolved, consult the nearest NRS service agent at
1-800-357-3572.
10. SERVICING
If the battery charger operates improperly, follow the
steps below.
a. Begin by checking the voltage switches to
verify their settings against the specifications
of the batteries.
b. Check the AC voltage selection switch for
the proper setting.
c. Check the fuses to make sure they have not
blown.
d. Check the circuit breaker to see if it has
opened and push it in to reset it, if
necessary.
e. Check the polarity between DC output and
the battery and make sure their connections
are tight.
f. Remove the small cover on the front of the
charger and make sure all of the binding
posts nuts are tight.
g. If the steps above do not solve the problem,
contact your local NRS service agent at 1-
800-357-3572.
11. CHARGER SPECIFICATIONS
AC INPUT VOLTAGE:
115 Vac (108-128) or 230 Vac (216-256)
ELC-12/20-D
115 Vac (108-125) ELC-12/20-S
AC INPUT CURRENT:
6 amps for 115 Vac (full power)
3 amps for 230 Vac (full power)
AC INPUT FREQUENCY:
50/60/100 Hertz (single phase)
AC LINE REGULATION:
For a constant output current at 2.23 volts/cell
+17% for 6 cells
AC FUSES:
MDA 4 or equivalent ELC-12/20-D
MDA 8 or equivalent ELC-12/20-S
POWER FACTOR:
Percentage at 20.0 amps DC current
56% at 13.38 volts
DC OUTPUT:
Voltage range 10.00 – 17.00 + 0.1 volts
Current Maximum 20.0 + .5 amps
DC OUTPUT RIPPLE (at battery terminals):
0.25V p-p at 20.0 amps, 12.0 volts
0.1V p-p at 2.0 amps, 13.38 volts
TEMPERATURE COMPENSATION:
3mV per °F per cell
WEIGHT, NET:
30.2 lbs.

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12. PARTS LIST
The following is a list of parts found in the NRS Model ELC 12/20-D (Dual Voltage) and –S (Single Voltage). When
replacing a part, USE ONLY ORIGINAL FACTORY REPLACEMENT PARTS of the correct size and rating.
PART NO. QTY. DESCRIPTION
22305S 1 TRANSFORMER ASSEMBLY (12/20-S)
22295S 1 TRANSFORMER ASSEMBLY (12/20-D)
18696S 1 SHUNT ASSEMBLY
31306S 1 CONTROL MODULE (W/ ELECTRONIC BOARD #21505)
31104S 1 CONTROL MODULE MOUNT
31179S 1 CONTROL CABLE
31102S 1 BASE ASSEMBLY (12/20-D)
31329S 1 BASE ASSEMBLY (12/20-S)
31128S 1 COVER ASSEMBLY
05322S 2 FUSEHOLDER ASSEMBLY
15834S 2 FUSE, 4 AMP (12/20-D)
31304S 1 CIRCUIT BREAKER ASSEMBLY
31177S 1 AC SWITCH ASSEMBLY (12/20-D ONLY)
27317S 1 AMMETER, 25 AMP
14197S 4 BUSHING, 1"
14123S 1 TEMPERATURE TRANSDUCER, 10' (BOX W/ ADHESIVE)
14124S 1 TEMPERATURE TRANSDUCER, 20' (BOX W/ ADHESIVE)
14126S 1 TEMPERATURE TRANSDUCER, 30' (BOX W/ ADHESIVE)
29741S 1 TEMPERATURE TRANSDUCER, 10' (W/ TERMINAL)
29742S 1 TEMPERATURE TRANSDUCER, 30' (W/ TERMINAL)
31344S 1 HEATSINK ASSEMBLY, W/ SCR
26769S 1 SCR ASSEMBLY, 22 AMP
14417S 1 OUTPUT CAPACITOR, C, 10,000 UF, 50V
14786S 1 DIODE ASSEMBLY, D
18796S 1 CAP ASSEMBLY, W/ DIODE ASSEMBLY
14759S 1 VARISTOR ASSEMBLY, VR2, 130V
31171S 1 TAP STRIP ASSEMBLY (12/20-D)
31309S 1 VARISTOR ASSEMBLY, VR1, 320V
31327S 1 TAP STRIP ASSEMBLY (12/20-S)
31301S 2 DOOR LATCH, BASE
31302S 2 DOOR LATCH, STUD
19623S 1 FUSE, 8 AMP (12/20-S)
The adhesive used on the temperature probes (#s 14123S, 14124S, and 14126S) is 3M Scotch #Y-9473, which is
a thermally conducting, two-sided adhesive tape. If a replacement adhesive is needed, use this type of tape or an
equivalent adhesive.

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13. WIRING DIAGRAM