I have been a bad boy and need help .

I have accumulated many chargers for numerous rechargeable devices, flashlights, etc. I tried keeping the device and charger together, I even managed to label a few, but somehow (those awful gremlins at work ) the vast majority of chargers are now in a big pile . Only a couple of them have the company imprinted, so the for most part I have no idea what charger belongs to what device .

So, do I have to match the output voltage exactly with the input voltage of the device? Can I use a lower output charger with a higher input device, if the plug matches? Can I simply match up the plugs that fit?

Pete