Lester 24EL8 Operating instructions

Operating Instructions 101004C
DUAL MODE BATTERY CHARGER
TYPE 24EL8
TECHNICIAN DIAGNOSTIC AND SERVICE INSTRUCTIONS
To discourage end users from disassembling the
charger, UNDERWRITERS LABORATORIES and
CANADIAN STANDARDS ASSOCIATION require
that the internal replaceable fuses be omitted from the
Owners Manual wiring diagram and parts list. Those
parts are included in the enclosed service wiring
diagrams and parts lists.
Refer to the Owners Manual for installation, normal
operating procedures, and safety precautions.
FOLLOW ALL SAFETY PRECAUTIONS.
DUAL MODE CHARGER TEST PROCEDURES
Disconnect both the AC and DC charger cordsets.
Remove the screws on each side of the charger and
lift the cover off. Refer to the Service Parts List and
compare to the charger under test to locate the
described test points. Make sure that all the charger
internal connections are secure and tight.
TEST FOR CORRECT AC VOLTAGE AVAILABLE
AT TRANSFORMER
Connect the AC cord to a live outlet; move the power
switch to AUTO. Verify that AC line voltage is
measured across terminals P-P on the transformer
(110-127 for 120 VAC models; 215-245 for 230 VAC
models).
TEST FOR CORRECT AC VOLTAGE AT
TRANSFORMER AUXILIARY COIL
Verify that approximately 26-30 VAC is measured
across terminals 1-3 on the transformer. Unplug the
electronic timer assembly and verify this same
voltage across the control cable assembly electronic
timer edge connector contacts 4-6.
One half of this measured AC voltage should appear
across transformer terminals 2-1 and 2-3. With the
electronic timer assembly unplugged,the same
reading should also appear across plug contacts 3-4
and 3-6, and 7-4 and 7-6, as well as 9-4 and 9-6.
TEST FOR CORRECT AC VOLTAGE AT
TRANSFORMER SECONDARY
Verify that approximately 58-64 VAC is measured
across transformer secondary terminals 4-7. Half of
this measured AC voltage should also appear across
the transformer coil center tap and each end,
transformer terminals 5-7 and 5-4, as well as 6-7 and
6-4.
Transformer failure is indicated when the measured
AC voltages are significantly lower than specified.
TEST FOR COMPLETE CIRCUIT FROM CHARGER
TO WHEELCHAIR BATTERIES IN THE
WHEELCHAIR
Move the power switch to OFF and unplug the AC
power cord and connect the charger DC output plug
to the charging receptacle of the wheelchair under
test.
Remove covers from wheelchair battery box and
measure battery system voltage at the battery
terminals inside the battery box, about 24 VDC.
Make sure this same battery pack voltage, about 24
VDC, is measured across where the RED lead from
the thyristor assembly connects to the ammeter
(+, POSITIVE), and transformer terminal 5 as well as
terminal 6 (-, NEGATIVE). Refer to the wiring
diagram.
IF THE CORRECT BATTERY VOLTAGE DOES
NOT APPEAR INSIDE THE CHARGER, THEN
TEST ALL CIRCUITS UNTIL THE OPEN CIRCUIT
IS ELIMINATED.
Repair or replace: Wheelchair charging circuit wiring,
or wheelchair charging circuit fuses and/or
fuseholders, or wheelchair charging circuit breakers,
or wheelchair charging receptacle. Charger DC
cordset with charging plug, or charger DC fuse and/or
fuseholders. Charger control cable assembly if shunt
resistor tests as an open circuit, or charger ammeter if

Operating Instructions 201004C
the ammeter tests as an open circuit, until a complete
circuit is established to the battery pack and correct
battery pack voltage is measured across these
terminals.
Unplug the connector from the electronic timer
assembly. Inspect the plug contacts for distortion,
corrosion or any condition that would prevent
electrical contact with the pads on the electronic timer
assembly. Test all of the leads of the control cable
assembly to verify that none test as an open circuit.
Repair or replace the control cable assembly to
correct any deficiencies.
If all of the above test in good condition and the
charger still has not had output, then the only two
components remaining are the thyristor assembly and
the electronic timer assembly.
The complexity of the electronic timer assembly
prohibits field service and replacement with a known
good unit for test purposes is the only alternative. For
this reason, it is essential to have a spare electronic
timer assembly on hand when performing diagnosis
and repair.
The feedback control design of the charger makes it
possible for one of the thyristors in the thyristor
assembly to not function and the charger to still have
some output. This condition can be detected by
noting the temperature of the separate thyristors and
replacing the complete assembly if one of the
thyristors feels cold and the other hot. This condition
may also suggest its presence by continual melting of
the DC fuse.
The thyristors may be turned on one at a time to test
for failure. Use a 1.5 volt "AA" (Double A) penlight
battery. DO NOT USE A HIGHER VOLTAGE OR
LARGER BATTERY TO PERFORM THIS TEST OR
YOU CAN DESTROY THE THYRISTOR. Connect
the AC cord to a live outlet, set the power switch to
AUTO, unplug the electronic timer, and connect the
charging plug to a fully charged battery pack.
Connect a lead from the NEGATIVE (-) end of the AA
penlight to contact #9, or #7 or #3 of the electronic
timer plug. Momentarily touch a lead from the
POSITIVE (+) end of the AA penlight to contact #1
and then to contact #2. Do not continue this for more
than a few seconds as it is possible to damage the
thyristors and charger.
If the ammeter does not indicate current flow for each
thyristor, then one of the thyristors has failed and the
complete assembly must be replaced.
SERVICE NOTICE – JANUARY, 1987
There has been a change in the AC power fuse used in
some Type 24EL8 dual mode wheelchair battery
chargers. This change affects the models listed below
designed to operate on 120 VAC, 60 Hertz power.
Models affected: 12090 12160
12395 12620
12425 12630
The 5 amp, fast blow single element AC power fuse
(Lester Part No. 14359S, Buss MDX-5), used in these
charger models, was replaced by a 5 amp slow blow
dual element AC power fuse (Lester Part No. 16208S,
Buss MDX-5).
False blowing of the fast blow AC power fuse (Lester
Park No. 14359S, Buss MTH-5) has been reported.
Replacing this fuse with its slow blow equivalent
(Lester Part No. 16208S, Buss MDX-5) is intended to
eliminate this.
The replacement fuse is a round cartridge fuse, ¼"
diameter by 1¼" long. It is rated at 5 amps, is designed
for use in circuits with a maximum operating voltage of
125 volts, and is a slow blow dual element design.
Locally available replacement fuses with these
specifications may be used if you encounter a situation
where false blowing of the AC fuse is determined.

Operating Instructions 301004C
WIRING DIAGRAMS
L2120S05
SERVICE PARTS LIST – TYPE 24EL8
120 VAC / 60 HZ
CHARGER DESCRIPTION
EVEREST &
JENNINGS INVACARE LESTER
#90483465 #1014758 #12610
MODEL NOS.
DESCRIPTION 12630 12620 12610
CASE ASSEMBLY 14358S 14454S 14432S
TRANSFORMER ASSEMBLY 12600S 12600S 12600S
THYRISTOR ASSEMBLY (SCRs) 14341S 14341S 14341S
CONTROL CABLE ASSEMBLY 14308S 14308S 14308S
ELECTRONIC TIMER ASSEMBLY 12450S 12245S 12245S
AMMETER, 10 AMP 13811S 13811S 13811S
FUSEHOLDER, AC AND DC, CLIP, SINGLE 10375S 10375S 10375S
FUSEHOLDER TAG, DC 14329S 14329S 14329S
FUSE, DC, 15 AMP, AGC-15 03838S 03838S 03838S
POWER SWITCH, SLIDE, SPST, 125 VAC, 6 AMP 15184S 15184S 15184S
FUSEHOLDER TAG, AC 13919S 13919S 13919S
FUSE, AC 5 AMP, MDX-5, 125V, SLOW BLOW 16208S 16208S 16208S
BUSHING, INSULATOR, 6N3-4, FOR CORDSETS 04275S 04275S 04275S
CORDSET, AC, 18/3, W/ MOLDED PLUG, 102" 14334S 14444S 14444S
CORDSET, DC, 14/2, 80", 2/ 30 AMP POWERPOLE 11687S - -
CORDSET, DC, 14/2, 108", BLACK & RED POWERPOLE -14421S 14421S
CORDSET, DC, 14/2, 108", YELLOW & WHITE POWERPOLE - - 14422S
CORDSET, DC, 16/2, 108", W/ CANNON PLUG - - 16221S
CORDSET, DC, 14/2, 108", W/ ALLIGATOR CLIPS - - 14538S

Operating Instructions 401004C
WIRING DIAGRAM
L2230S39
SERVICE PARTS LIST – LESTER MODEL 13770
TYPE 24EL8 230 VAC / 60 HZ
PART NO. DESCRIPTION
16273S CASE ASSEMBLY
13775S TRANSFORMER ASSEMBLY
14341S THYRISTOR ASSEMBLY (SCRs)
14308S CONTROL CABLE ASSEMBLY
12245S ELECTRONIC TIMER ASSEMBLY
13811S AMMETER, 10 AMP
10375S FUSEHOLDER, DC, CLIP, SINGLE
14329S FUSEHOLDER TAG, DC
03838S FUSE, DC, 15 AMP, AGC-15
16247S POWER SWITCH, SLIDE, DPST, 250 VAC, 6 AMP
15897S FUSEHOLDER, AC, CLIP, DUAL
16249S FUSEHOLDER TAG, AC
16268S FUSE, AC, 2.25 AMP, MDA-2.5, 250V, SLOW BLOW
04275S BUSHING, INSULATOR, 6N3-4, FOR CORDSETS
16243S CORDSET, AC, 18/3, W/O PLUG, 108"
11687S CORDSET, DC, 14/2, 80", 2/ 30 AMP POWERPOLE
14421S CORDSET, DC, 14/2, 108", BLACK & RED POWERPOLE
14422S CORDSET, DC, 14/2, 108", YELLOW & WHITE POWERPOLE
16221S CORDSET, DC, 16/2, 108", W/ CANNON PLUG
14538S CORDSET, DC, 14/2, 108", W/ ALLIGATOR CLIPS
16404S CORDSET, DC, 14/2, 108", 2/ SB-50 PLUG, GRAY