will this kill my Keymate??

I have recently used up the original batteries(LR44)on my KeyMate.I was playing around and realized that a peeled 21/23 cell contains 8 small button cells.If placed inside the plastic sleeve that is inside the battery tube of the keymate the 8 cells fit perfect and will power the light very brightly.It is too long to fit without peeling the cell first however the cells will fit when installed seperately.I have only ran it for a few seconds each time to check the output however at 12 volts I am afraid it may kill my little KeyMate.I was looking for a cheaper alternative to the LR44 cells and I have a few of these new 12 volt cells handy.Will this hurt my KeyMate and if not will the run time be about the same as the original cells?
This is a very bright light at first but it did not last very long at all with the original cells.

only the voltage drop save your poor keymate /ubbthreads/images/graemlins/wink.gif

but if you continue with this battery you blow the led in few hours

the LR44 aren't exepesive if you buy them in large quantities, for expample on ebay you can find 140 batts for about 10 cents each

also exist a 6V version of the 21-23A but is smaller and have less capacity