Original request was where and what size of fuse to protect against short-circuits. 20A seems reasonable size considering differences in equipment between bikes. Location should be negative terminal of battery per my earlier post re direction of current flow. Fuse can be one-time or resettable circuit breaker type. I have only used the one-time (Buss, I think) style of long cylindrical fuse due to ease of mounting, cost, ease of replacement, etc... If anyone has found a good circuit breaker candidate, please let us know.
I'm sorry to contradict you, but the direction of current flow has absolutely nothing to do with the best location for the fuse.
Though your assertion that the electrons flow out of the negative terminal is true, they won't flow at all UNLESS they are flowing through a circuit that will also allow them to flow INTO the positive terminal. If you break that circuit with a blown fuse, at ANY point, current flow will cease.
Since nobody has brought it up yet..the best size fuse to use is based on wire gauge. Smaller gauge wire handles less current than larger wires. Find your smallest wire and Google what amount of current it can handle and take it from there.
While it is true that a large-value fuse in the battery feed line might not protect the thinnest wire on your bike, you really need to size the fuse for the maximum current that you expect to have flowing into or out of your battery.
Depending on your charging system(cutout or regulator) you may have as much as 15A or so into or out of the battery for short periods of time. For example, if I stop at a light and my headlight is on high beam, and I don;t keep the revs up, I will see a 12-15A battery drain. Even a slow-blow fuse will blow pretty quickly (5 seconds or so) if yu go over it's current rating.
The generator on the 6V bikes is rated at 15A, so it's possible you would have that much current flowing into the battery. That's why I suggested the 20A fuse (that, and the fact that my '64 FLH came to me with an owner-installed 20A fuse, albeit in the battery plus line....and it always did the job-never blew unless I did something stupid while I was working on the bike.)
The fuse we are talking about could be likened to the main breaker on your house electrical panel. a 100A or 150A breaker will certainly NOT protect a 14 gauge or 12 gauge circuit wiring. It's really there for catastrophic events. That's why the individual circuits that the panel feeds are each protected by a smaller breaker, rated for their capacity and wire size.
If you are really concerned about the smaller gauge wire in some circuits, the only real solution is to fuse those circuits separately, at a lower value.
You're right Andy...I know that but I guess my brain was in neutral when I wrote that....either that or I had to much stuff tumbling around in my old pumpkin to think clearly.
cdndewey wrote:You're right Andy...I know that but I guess my brain was in neutral when I wrote that....either that or I had to much stuff tumbling around in my old pumpkin to think clearly.