IBM ThinkPad T40 battery Description Type:  Li-ion
Capacity:  4400 mAh
Volt:  10.8 V 
Size:  205.12 x 59.10 x 21.10 mm
Color:  Black
IBM ThinkPad T40 battery Compatible original Battery Code:

08K8192
08K8193
08K8194
08K8195
08K8196
08K8197
08K8198
08K8199
08K8201
08K8214
2P1013
92P1011
92P1060
92P1061
92P1071
92P1073
92P1075
92P1077
92P1087
92P1089
92P1091
92P1101
92P1102
93P5002
93P5003
ASM 08K8192
ASM 92P1076
FRU 08K8193
FRU 08K8214
FRU 92P1069

IBM T40 battery Fit with below:

ThinkPad R50
ThinkPad R50 Series
ThinkPad R50(6600MAH)
ThinkPad R50e
ThinkPad R50e Series
ThinkPad R50e(6600MAH)
ThinkPad R50P
ThinkPad R50P(6600MAH)
ThinkPad R51
ThinkPad R51 Series
ThinkPad R51(6600MAH)
ThinkPad R52
ThinkPad R52 Series
ThinkPad R52(6600MAH)
ThinkPad T40
ThinkPad T40(6600MAH)
ThinkPad T40P
ThinkPad T40P(6600MAH)
ThinkPad T41
ThinkPad T41 Series
ThinkPad T41(6600MAH)
ThinkPad T41P
ThinkPad T41P(6600MAH)
ThinkPad T42 Series
ThinkPad T42P
ThinkPad T42P(6600MAH)
ThinkPad T43
ThinkPad T43 Series
ThinkPad T43(6600MAH)
ThinkPad T43P
ThinkPad T43P(6600MAH)