Sorry for the late post, but just wanted to mention that any corrosion on the terminals would lead to decreased current levels, not increased current levels. The batteries would be sourcing less current and would, in theory, last longer.
Second, you mentioned that these smoke detectors were "hard-wired", which I assume means that they normally run off the mains and only require the battery when the mains voltage is down? Is that the case? If so, why are the batteries being depleted at all? If the batteries are being depleted that quickly, maybe you have a problem with the mains supply. EDIT: Me no read entire thread. Me dum.
Also, mains-connected devices that have a battery fall-back built in will sometimes provide a "float" voltage to the battery to keep it topped off. Non-rechargeable batteries in general and alkaline batteries in particular do not like this. They will be angry with you. Do not do this. Check to make sure the smoke detector you are using does NOT attempt to float or recharge the batteries unless you want it to, and if you want it to, do NOT use alkaline batteries.
Finally, alkaline batteries have a different discharge profile than lithiums. An alkaline battery's terminal voltage will decline almost linearly as the battery is discharged, starting at around 1.6V and falling to 1.0V before most devices will stop working or will tell you that the battery needs to be replaced. Lithium batteries will maintain their terminal voltage at 1.5V-1.3V until just prior to being completely discharged. So your smoke detector may be discharging your lithiums just as quickly, but the low-voltage beeper has not yet kicked in due to the flatter discharge profile of the lithium battery. That, and the fact that a lithium AA battery starts out with a lot more capacity than an alkaline AA.
Last edited by sluggo
on Fri Mar 22, 2013 3:14 pm, edited 2 times in total.
This problem was caused by Windows, which was created by Microsoft Corporation.