L40 Battery Life Guide (44K)
Cells in Battery Pack with Rechargeable AAs
Testing the Battery Pack
8543 without battery
Testing Quick Charger
AC and Car Adapters
and transformer specs)
79F0197, FRU 79F0994
Ni-Cd10.8v, 2.4 AH
Not Using the Rechargeable Battery for a Long Period
It you do not use the rechargeable battery for a long period, remove it
from the computer and keep it in a cool place. The rechargeable battery
should be charged at least once every 6 months to extend the battery
Peter has some horrid flashbacks and recalls:
Normally there is one cell of the whole block on the last
leg. I disposed a large number of L40SX battery packs when my office
in '96. Today I'm a bit sorry about that - I use to part out the case
fill it with "industrial standard" cells of a particular size.
The main problems:
a) the cells are NiCd, which are prone to "memory"
b) the charger circuit is crap.
c) Users operated the L40SX permanently on the AC adapter
and maybe for a few minutes on batteries ... then putting it back to
charger. That causes the memory effect and cooks the battery in the
d) The temperature sensor in the battery in most cases
is not properly attached to one of the innermost cells that heat up
when charge reaches the endpoint. Thermal coupling is rather poor and
cells are permanently overcharged and overheated. Poor design to begin
IBM had various ECAs on the L40: LCD brightness,
lifetime, Serial and Parallel port power, battery lifetime again,
battery chargers, isolation problems in the DC/DC converter circuit
fire hazard, shot fuses in charger circuit, runtime on batteries and
to save energy and extend the runtime on batteries. (These were the
I recall after the many years ...)
1. Remove the keyboard.
2. Set the rechargeable battery in place without connecting any
3. Measure the voltage between terminals 1 (+) and 2 (-) and note the
4. Using the AC adapter, apply external power to the
Make sure that a charge arrow appears in the system-status
5. Measure the voltage again between terminals
(+) and 2 (-).
If the voltage is not greater than
measured in Step 3, replace the AC adapter. If the voltage is greater
the one measured in Step 3, go to the next step.
6. Remove the rechargeable battery from the computer.
7. Measure the voltage at the battery terminals.
Pin Voltage (Vdc)
1 +8.5 to +12.6
If the voltage is not correct, the rechargeable battery
or defective. If the voltage is correct, go to the next
8. Using a low-power ohm meter, measure the resistance at the
terminals between 2 (T) and 3 (-). The resistance must be 4 kilohms to
30 kilohms. If the resistance is out of range, replace the rechargeable
8543 run without a battery installed?
Rick Ekblaw replies:
Yes, the L40SX will happily run from AC only with no
installed. If you don't insist on being "color coordinated", an
5140 (PC Convertible) power supply will work on the L40SX, the "big
have the same power rating (15VDC, 2.7A, center positive). Don't
bother with the little "Battery Charger" wall-wart for the 5140, it
puts out 200mA, and it won't even charge the battery in the L40SX, much
less run the machine. A decent electronics store should be able
supply you with a suitable generic power supply, but they may have to
order it because their usual "stock" supplies will max out at either 1A
A semi-rare item for the L40SX is the automotive
adapter (part number 79F1013, FRU 79F1039).
PN 79F0986 Panasonic Lithium BR-2/3A 3V. Original backup battery is
listed as 3V, 1200 mAh. I have also seen 65F0231 listed for this
battery, YMMV... Used to maintain stored-data (such as configuration
information, date, and time) after powering off. This battery is not
LITH 2/3A 1200MAH W/TAB - BR-2/3AT2SP
Do NOT solder directly on a Lithium battery! Use a tabbed version like
this! There are other versions with solder eyes instead of just plain
tabs. Digikey lists a few different versions of this size.
1. Remove the keyboard and the top cover.
2. Measure the voltage at the connectors of the backup battery.
Pin Voltage (Vdc)
1 +2.8 to +3.2
If the voltage is not correct, the backup battery is
discharged by a
short circuit or is defective.
PN 65F0225 Ni-Cd DC 3.6v 45mAH Panasonic KRM 11/16 CF. Goes on top of
blue battery shield in the little "fence" on top.Supplies power to the
computer during replacement of the rechargeable battery. However, the
standby battery is not charged at the time of shipment. It takes 48
hours to automatically charge it using the AC adapter. Therefore, do not
replace the rechargeable battery in Suspend Mode during that time.
NOTE: The charging time required is
1. Remove the keyboard and the top cover.
2. Connect the AC adapter to the computer.
3. Disconnect the standby battery connector from the system board and
measure the voltage at the connector of the standby battery as
+3.0 to +4.5
If the voltage is correct, perform the failing operation with
standby battery to isolate the problem.
If the voltage is not correct, continue.
4. Measure the output voltage at the connector on the system
If the voltage is higher than measured in Step 3, the standby
is discharged or is defective.
If the voltage is the same as measured in Step 3. or less than +3.0
Vdc, replace the standby battery. If the problem remains,replace the
PN 79F0193 FRU 79F0995
Input- 100-240v ac, 50/60Hz 0.5-0.3A, 35W Output 13v 1.3A
There is no deep discharge function built into the Quick charger.
If a noise can be heard from the operating quick charger, replace
1. Perform steps 6 through 8 in 'Testing the Rechargeable Battery',
to verify the rechargeable battery for correct operation.
2. Plug the quick charger into an electrical outlet. If the amber power
indicator does not turn on, replace the quick charger.
3. Install the rechargeable battery. If the green charging indicator
is not blinking, replace the quick charger.
AC and Car
1. If a noise can be heard from the AC adapter when it is plugged into
line voltage, replace the AC adapter. If a noise still comes from
the AC adapter, suspect the computer.
If not, the AC adapter has a problem.
Replace the AC adapter with the original one, then go to the next
2. Measure the output voltage at the plug of the AC adapter
Pin Voltage (Vdc)
If the voltage is not correct, replace the AC
The A/C adapter plugged into the L40, but the
indicate that the battery is still being drained. The A/C adapter
is plugged into both the wall and the L40. Do I have a bad
There is a third connection to double-check: the plug from the
L40 to the A/C adapter. It may have worked its way loose.
Ah ... it is 15V DC, 2.7 Amps, center positive, outer
diameter 1/4" (6.25mm), inner diameter 1/8" (3mm).
Peter, that's very close - the size is 6.3mm outer, 3.0mm inner
(it's a standard plug which I think is available at Radio Shack here,
if not then it can be ordered online from them). The original AC
adapter is FRU 79F0993.
The L40's power use falls within the Energy Star's guidelines
An application is suspended by closing the clamshell
the power switch on. When the clamshell is opened, the
resumes at the point it was suspended. During suspension system
are automatically powered off except for the real time clock and
memory. The system can be set to resume at a specific time of
Internal backup battery
the battery pack without disrupting the application.
Trickle Charge trickle
occurs during AC operation.
Manual vs. Automatic Mode
You can use the "A-M" switch on the left side of the top
cover to select manual or automatic mode. In automatic mode, the
hardware initiates low clock speed operation during idle periods.
In manual mode, the processor runs at the default clock speed set by
user when the system is configured. The clock speed settings are
20, 10, and 5MHz.
Sleep mode conserves battery
power during idle times between clock cycles and key strokes by putting
system components in an idle state resulting in low power usage.
Sleep mode is not operational when an external display is
This function is exploited by DOS and OS/2 Application,
operating system, and environmental characteristics will affect actual
battery duration between recharges.
When I get my L40 back together, I'll have to check these out-