Hung makes a good point. The problem he describes depends on the spring force holding the battery in place, the weight of the battery, and the metals used on the battery and flashlight contacts. All batteries I've seen use nickel plated contacts as do all the small fuses, although there might be some really cheap batteries that don't. Inexpensive flashlights might use any metal for the contacts -- the best ones use gold plating and other good ones use nickel. I've never had this problem with quality flashlights and NiMH batteries. (I highly recommend Eneloop brand NiMH batteries.)
Electrical contacts are a science in themselves. Basically, you need to have metal-to-metal contact, so the pressure has to be enough to break through any oxide layer and form a gas-free seal area. If the gas-free seal is broken by vibration or other movement, the contact area can oxidize (extremely quickly if one or both materials are something like tin), causing poor contact. This is actually much more of a problem with low current low voltage (so-called "dry") contacts than others. When higher voltages and currents are involved, tiny hot spots can form that burn their way through the surface contamination.
If these problems occur with a fuse, you'd see blinking lights, static-like motion related radio noise, or other intermittent problems. In cases of high currents, you might see signs of heating at the fuseholder terminals or arcing or burning at the fuse terminals, and a fuse might fail prematurely due to the extra heat. But relatively high currents, nickel plating, adequate spring pressure, and light weight all help maintain the contact integrity and seem, in my airplane at least, to be enough to prevent problems.
Roy
![[Linked Image from eznec.com]](https://eznec.com/images/States_Landed_In.jpg)
