All PS/2s use a battery, to power the CMOS memory that holds configuration information, and to run the internal date-and-time clock. This page summarises the different kinds of batteries in use, and gives the occasional hint on obtaining or fitting them.
Machines use batteries as follows; click on the FRU number for more information on that particular item:
PS/2 model name Model number Battery FRU Battery type
Model 25-286 8525 8509237 RTC module
Model 25SX 8525 33F8354 3v coin cell
Model 30-286 8530 8509237 RTC module
Model 33 (E) 9533 33F8354 3v coin cell
Model 35 8535 8509237 RTC module
Model 40 8540 8509237 RTC module
Model 50/50Z 8550 72X8498 6v pack
Model 55SX 8555 8509237 RTC module
Model 56 8556 33F8354 3v coin cell
Model 56 9556 33F8354 3v coin cell
Model 57 8557 33F8354 3v coin cell
Model 57 9557 33F8354 3v coin cell
Model 60 8560 72X8498 6v pack
Model 65SX 8565 8509237 RTC module
Model 70 8570 72X8498 6v pack
P70 Portable 8573 72X8498 6v pack
P75 Portable 8573 64F9987 6v pack
Model 76 9576 33F8354 3v coin cell
Model 77 9577 33F8354 3v coin cell
Model 80 8580 72X8498 6v pack
Model 90 8590 33F8354 3v coin cell
Server 85 9585 33F8354 3v coin cell
Model 95 8595 33F8354 3v coin cell
Server 95 9595 33F8354 3v coin cell
Server 95A 9595A 33F8354 3v coin cell
PC Server 500 86XX 33F8354 3v coin cell
This is a conventional coin-shaped 3 volt lithium cell; typical cost is about $3-$5. Equivalents are:
Duracell Ever Ready Panasonic Varta Sony
DL2032 ECR2032 CR2032 CR2032 CR2032
This consists of two conventional coin-shaped 3 volt lithium cells soldered to a small circuit board, attached to a 5cm red & black cable with a battery connector at the other end. A plastic hood covers the two cells. Currently, there is no known direct equivalent.
The lithium cells are 3 volt coin cells with two solder tags on one side. Typical cost is about $4-$9 each. Equivalents are:
An alternate approach is to use an AT-style battery pack, or anything else that will fit inside the case! AT replacement battery packs are rated at 6.0 volts, and generally contain a resistor which prevents charging and controls the voltage. They come with attached wires, a 4 pin connector and velcro mount, and fit nicely in the battery/speaker cavity. The velcro can be used to attach it to the bottom surface so that it doesn't move. The header pinout is correct, and even has the plug in the second hole to correctly polarize the header. Cost is around $15.
This is a 6 volt two-cell lithium pack. The original IBM ones are usually yellow, with black ends. Replacements are available as camera batteries; typical cost is about $10-$15. Equivalents are:
Duracell Ever Ready Panasonic Kodak Varta Ray-O-Vac Sanyo
DL223A EL223AP CR-P2 K223LA VL223 PC223 CR-P2
This is a Dallas self-contained CMOS RAM module with integral real-time clock and battery. The entire module must be replaced. The Dallas part number is DS1287, but this part is now obsolete. According to the Dallas Semiconductor data book, the DS1287 can be replaced by the DS12887 (the latter is pin compatible but has more RAM).
The DS12887 is not Year 2000 compliant, but of course PS/2s are compliant except that a manual reset of the date is required at the start of the year 2000. Do not be tempted to use the Year 2000 compliant upgrade to the DS12887, which is designated the DS12C887; it uses the century byte differently to a PS/2 and will apparently not work.
The DS1287 can also be replaced by the DS1287A, and the DS12887 by the DS12887A; the only difference in each case is that the part with the 'A' suffix has a pin which can be used to clear the RAM; this pin is unused on PS/2s.
Typical cost is $10-$15. Equivalents are:
Dallas Odin BenchMarq
DS12887 OEC12C887 BQ3287MT
DS12887A OEC12887A BQ3287AMT