Overcurrent Protection at Batteries

[Kettlewell]

This question has cropped up before in other discussions, but I have never seen what I consider an "answer" to the question. What is appropriate overcurrent protection at the batteries, or is it even worth it? Many here seem to think so, yet ABYC says it is not necessary on wire intended to carry starting current between the batteries, the main battery switch, or the starter. I currently have both my house and starter bank fused, but I wonder if it is really worth it. I can see why ABYC says this. Let's say you want to protect the wire. You'll need at least 00 wire to get up to the ability to handle 200 amps. Yet, some folks find that a 200-amp fuse just doesn't cut it and will blow too often on the starting circuit. So they up the fuses to 300 or 350, which would require 000 wire or above to handle that level. I suppose you will get some protection using these fuses even if the wire coating lights on fire, because eventually the fuse will blow during a dead short even if the wire is still intact and red hot. The problem I see is the short that only lets 300 amps of current go through, still evaporating or lighting on fire your wire coating, but not having enough oomph to break your fuse. So, these fuses appear to only be useful for the very rare catastrophic dead short situation, while not doing anything for the more likely scenarios. And of course putting any fuse, connections, etc. in the line adds more potential places for a wire to come loose, or resistance to build up, possibly causing the sort of catastrophe you're trying to avoid by installing the devices.

By the way, what do folks think of Ample Power's suggestion to put the main battery fuses in the negative side of things? Their argument makes a lot of sense: no need to shield the fuse as it is ground, making it safer to work in the battery box with tools that might be conductive, and making it easier to change the fuse or disconnect it too, because you don't have to worry as much about grounding them. I know they aren't ABYC approved this way, but does it make sense?