The batterys connected to the 4-pin header are 3.6V lithium. Used to be little black boxes with wires for the header.

Something like this should work for you:

http://www.cyberguys.com/templates/searchdeta … ?productID=1746

Edit - No manual but I did find some info on the jumper settings:

1SUPERMICRO
2
3P55CMA, P55CMS (REV. 2.0)
4
5Processor             Pentium
6Processor Speed       75/90/100/120/133/150/166MHz
7Chip Set              Intel
8Video Chip Set        None
9Maximum Onboard       128MB (EDO supported)
10Memory
11Maximum Video Memory  None
12Cache                 256/512KB
13BIOS                  AMI
14Dimensions            330mm x 218mm
15I/O Options           PS/2 mouse port, parallel port, serial ports (2),
16                      32-bit PCI slots (4), floppy drive interface, IDE
17                      interfaces (2), cache slot, VRM connector, Legacy
18                      connector, IR connector
19NPU Options           None
20
21[Image]
22
23                                CONNECTIONS
24
25  Purpose                  Location    Purpose                  Location
26
27  VRM connector               J1       External battery           JP30
28
29  Chassis fan power          J18       Turbo LED                  JP32
30
31  Power LED & keylock        J32       IR connector               JP68
32
33  IDE interface LED          J34       Serial port 2              JS1
34
35  Reset switch               J35       Serial port 1              JS2
36
37  Speaker                    J39       Parallel port              JS3
38
39  IDE interface 1            J70       Floppy drive               JS4
40                                       interface
41
42  IDE interface 2            J71       32-bit PCI slots         PC1 - PC4
43
44  Legacy connector           J85       Cache slot                 SL1
45
46  PS/2 mouse port            J96
47
48  Note: J18 may not be present on all boards.
49
50                        USER CONFIGURABLE SETTINGS
51
52               Function                    Label           Position
53
54  »   Factory configured - do not           J28             Closed
55      alter
56
57  »   Factory configured - do not           J37        Pins 1 & 2 closed
58      alter
59
60  »   Factory configured - do not           J41          Unidentified

61      alter
62
63  »   CMOS memory normal operation          J42        Pins 1 & 2 closed
64
65      CMOS memory clear                     J42        Pins 2 & 3 closed
66
67  »   Factory configured - do not           J43              Open
68      alter
69
70  »   ISA CLCK = PCI CLCK/4                 J67        Pins 2 & 3 closed
71
72      ISA CLCK = PCI CLCK/3                 J67        Pins 1 & 2 closed
73
74             DRAM CONFIGURATION
75
76     Size          Bank 0        Bank 1
77
78      8MB        (2) 1M x 32      None
79
80     16MB        (2) 2M x 32      None
81
82     16MB        (2) 1M x 32   (2) 1M x 32
83
84     24MB        (2) 1M x 32   (2) 2M x 32
85
86     32MB        (2) 4M x 32      None
87
88     32MB        (2) 2M x 32   (2) 2M x 32
89
90     40MB        (2) 1M x 32   (2) 4M x 32
91
92     48MB        (2) 2M x 32   (2) 4M x 32
93
94     64MB        (2) 8M x 32      None
95
96     64MB        (2) 4M x 32   (2) 4M x 32
97
98     72MB        (2) 1M x 32   (2) 8M x 32
99
100     80MB        (2) 2M x 32   (2) 8M x 32
101
102     96MB        (2) 4M x 32   (2) 8M x 32
103
104     128MB       (2) 8M x 32   (2) 8M x 32
105
106  Note: Board accepts EDO memory.
107
108                CACHE CONFIGURATION
109
110           Size                      SL1
111
112          256KB            256KB module installed
113
114          512KB            512KB module installed
115
116               CPU SPEED SELECTION
117
118  Speed      J27       J29       J31       J40
119
120  75MHz      Open     Closed    Closed     Open
121
122  90MHz      Open     Closed     Open      Open
123
124  100MHz     Open      Open     Closed     Open
125
126  120MHz    Closed    Closed     Open      Open
127
128  133MHz    Closed     Open     Closed     Open
129
130  150MHz    Closed     Open     Closed    Closed
131
132  166MHz    Closed     Open     Closed    Closed
133
134          CPU VOLTAGE SELECTION
135
136       Voltage               JP11
137
138        3.3v          Pins 2 & 3 closed
139
140        3.4v                 Open
141
142        3.5v          Pins 1 & 2 closed

OK, so I head down to my friendly neighborhood Micro Center, pick up a new 3.6v CMOS battery, and plug it into the battery header of my Supermicro P55CM, which has a soldered-on NiCd that is quite dead. I flip on the machine, and I still see the "CMOS battery low" message as soon as I start up, and the BIOS is not retaining my settings.

I tested the new battery and it's putting out between 3.66 and 3.68 volts depending on the tester.

Any ideas on why the battery header might not be working?

Thanks in advance....

You better remove the NiCd battery or it will sooner or later kill your board (stuff coming out). (Or did it already?) Maybe that also solves your problem. Did you test the battery while it was connected to the board? Did you switch on your computer a second time?

please don't make new threads while the topic is still the same

HAL, the old NiCd had a little bit of white corrosion on one end, but nothing terrible -- I clipped it off and brushed off what little of the corrosion dust had reached the board -- is it possible the corrosion could make it so the board won't recognize any battery anymore? Even one that attaches to a different header???

Did you try reversing the 4pin connector for the external battery? Without a motherboard manual, it's hard to know which pin goes where.

Did you save the CMOS settings and switch the computer off and on? The battery bad bit was still set on your first attempt. If there aren't any corroded tracks it shouldn't be too bad - but make sure there is none of the stuff left on the board.

jthieme, the board header has a "+" sign on one end, where I connected the red wire. I'd only reverse it after I'd exhausted other options.

HAL, I connected the battery, turned the computer on and off and saved CMOS settings in almost every possible configuration. I then tried using the clear CMOS jumper for about 30 minutes then tried again, still no change. On the motherboard, there are no tracks that look badly messed up. I suppose it's possible that there's just enough corrosion to block the signal, but I'm trying every other option before I scrap the board -- it's a great board and I'd like to save it if possible.

Maybe there's a jumper to choose the batteries?

Check the J42 jumper. It may be in the wrong position, or missing.

HAL, the only jumper settings I have to go on are the ones in the text file posted above. I have no manual and Supermicro doesn't have any either (their tech support guy is very nice, but so far hasn't had any helpful info for me). There are quite a few "factory configured / do not alter" jumpers -- not sure I want to go experimenting with them, though.

Zup, J42 is positioned for "normal cmos operation." I did change it to clear the cmos settings, hoping that it would correct the problem. No such luck.

Did you test the battery while it was connected to the board?

Are there still 3.6V when connected?

Should I test it with the computer powered up?

Thanks,
Stuart

Nope computer off.

Is this your auction? If not there's 2 of you out there with the same issue..🤣:

http://cgi.ebay.com/SUPER-MICRO-P55CM-Rev-2-M … 1QQcmdZViewItem

HAL -- tested with the battery connected -- 3.68v

jthieme -- that's not my board -- same problem, but WAY more corrosion on that battery than on mine.

ok, just noticed that they had jumper settings listed farther down in the auction listing. Not sure if it is the same as what I found earlier or not, I didn't compare.

jthieme, I should say that is not my exact board. That is my make and model of board. However, the corrosion on that battery is all over the battery, contacts, and has even spread over to the adjacent screw hole. I don't have anywhere near that amount of corrosion on mine.