What happens when the plastic cover is removed from rechargeable AA NiMH batteries?

Question

Since rechargeable AA batteries are bigger than non rechargeable, I had to remove plastic cover on battery so it could fit in wireless keyboard. I only had to remove it on one of the two batteries used. I now have 4 of these batteries without the cover on it. But here is the part I really want to understand...

I used one covered (normal) aa rechargeable nimh battery and one coverless aa rechargeable nimh to power a bluetooth wireless mouse. Now the Belkin bluetooth mouse will only power up and work with the same combination of batteries. The coverless one has to be in the left slot. The covered one goes in the right.

What did using a coverless aa do to cause the mouse to not be anylonger compatible with two covered nimh's? I have never tried to use two coverless ones. Would it be unsafe to do so? Is it unsafe to use a coverless battery?

Answer 1

It's not safe to remove the plastic cover from batteries.  The whole case is the negative connection.  This includes the sides of the battery.  The positive connection is the little button on the top and of course it's insulated from the case.  If you have a stack of batteries, such as in a multi-cell flashlight, the bare cases can short against the case.  You could have caused some damage to the mouse.  An AA battery is a specific size, or is supposed to be.  If you bought a very cheap brand, their quality control coult be lacking.  Like anything, battery sizes have tolerances.  The link below leads to a battery size site if you're interested.

Answer 2

That is weird. I really have no idea. But i dont see why it wouldnt be safe to remove the cover. I just always thought that it was there to advertise the battery brand anyway.