Recently, I encountered a REALLY annoying issue with my Mac Magic Mouse disconnecting every time it was bumped.
Sometimes when I listen to music I like to tap my desk and without realising, I tap my mouse as well (the Apple purists are probably shrieking reading that). Recently I put some new batteries into the mouse because the other ones went flat and then found I kept getting disconnected.
The issue wasn’t the batteries coming out, because letting the mouse sit and then tapping it would reconnect it to my Mac. The issue is actually the type of batteries that you use in your mouse and a subtle design flaw in the Magic Mouse battery compartment.
Even though the mouse takes double A (AA) batteries, it seems not all batteries are created equally. I was previously using Energizer branded AA batteries with no problem but ran out and only had some Eveready Super Heavy Duty batteries lying about which I put in.
Comparing the size of the older Energizer batteries with the Eveready Super Heavy Duty ones was immediately clear: the Eveready batteries were about 2mm smaller than the Energizer batteries.
The issue appears to be when the mouse is bumped one of the batteries actually seems to briefly lose contact with one of the terminals because of the smaller size and the mouse expecting a particular minimum length of the battery. Whether or not you can call this a design fault, it is annoying.
You might get the urge to fix the issue using aluminium foil to pad out the contact, but if you can afford to pay almost $100 for a Magic Mouse, you can afford $10 for a packet of batteries or the Apple-branded rechargeables which fit well.
After discovering this issue, I tested a few other batteries and discovered that Duracell batteries will be useable as well, but there was a tiny bit of play still. It seems the Apple Magic Mouse was designed with Energizer sized batteries in mind.
My advice would be to actually buy the Apple-branded AA batteries and a charger. They fit well and I think are actually Energizer batteries rebranded or made by the same company (I can’t confirm this though) comparing side by side, they appear to be the same size and thickness unlike other batteries compared.