yeah so the battery in my wireless mouse went dead no biggie... i pop it open and find the mouse is acting fine on one battery for the last 6months think its just a paralell circuit so your batteries don't need to be replaced longer or is there a demon possessing my mouse?

3/12/2008 8:43:30 PM

yea, common..

3/12/2008 8:48:37 PM

If it's a relatively new mouse (the ones with the advertised 6-9 month battery lives) then it's not surprising. They're able to run longer because they operate at lower voltage and with the batteries in parallel. This helps because as batteries age their internal resistance increases in addition to the obvious effect of their stored energy being spent. The increased internal resistance across the batteries makes it so that a system with 2 1.5 volt batteries in series is going to see the increased internal resistance of those batteries summed. Not only does this mean ohmic heating (wasted power and increasing inefficiency) it also means a drop in voltage across other circuit components.

The mice that are able to run with 2 1.5 volt batteries in parallel have huge advantages because their resistances add as the inverse of the sum of reciprocols- basically means that the resistance in parallel is going to be 1/2 the individual resistance and 1/4 the series resistance. Not only does this mean less loss of efficiency as the batteries age, but also less change in the voltage applied across other circuit components. Also, if one of the batteries happens to be a dud and die really fast the mouse will keep working until the other one gives out. Since it's only a single battery though it's going to be used up more than twice as fast (not only half the stored energy but you also lost the benefits of putting the internal resistance in parralel.)

It's such a painfully simple change and massive increase in battery longevity I have to wonder if the people making the first optical mice just didn't think about it or just couldn't make optical mice that ran at 1.5volts. It's cool that you end up getting more than 4 times the battery life out of this design change.

[Edited on March 12, 2008 at 11:24 PM. Reason : ]

3/12/2008 11:23:45 PM

^long and hard to read but thank you. I'm guessing the first optical couldn't run that low is my guess.

3/13/2008 2:22:22 PM

optical wireless trackman FTW

though it only uses one AA battery, so i don't know what that means...

3/13/2008 2:38:38 PM