Determining Work Load

Can someone tell me if there is a multimeter test that can determine the work load in mAh for a device? I'm working on replacing battery packs in a cordless vacuum, and would like to calculate running time for the new batteries, but do not know how many mAh the vacuum uses.

Thanks,
MattSA

mAh is the product of mA and h (hours). Put your multimeter in Adc mode (might mean moving the test leads into different jacks). Connect the meter in-series between the postive pole of the battery (red lead to +) and the motor wire that normally connects to the + pole through the switch. The motor should run. Measure the running current. I'm guessing 1 to 2A.

Say you read 1.5A. That is 1500mA. If your battery stores 3000mAh (3Ah), you could expect the motor to run for 3000mAh/1500mA = 2h.