250 amp fuse

[dabrooks]

We have a 2013 Tiffin 35 QBA. I wanted to carry all the spare fuses that we might need. On the QBA the main protection fuse between the house battery bank and the coach is 250 amps. On some units I have heard that they require up to 400 amp fuse. I found an exact match here MEGA Fuse - MEGA Fuses for Current Protection for less than $5.00 plus shipping.

[mrboyer]

When changing batteries, I did blow one of these large fuses. Bought two to have a spare. Haven't used it in 6 years, but it is low cost insurance.

[two-niner]

mrboyer: And you are still in one piece and breathing. LOL (but not funny)

[Tony Lee]

If the fuse hadn't been there things might have been different.

[RamGunner]

It's a really good idea to have spares for everything - especially fuses like that.

About two years ago I was working in a data center when a tech from Cox got a little careless installing a battery backup for an OC12 MUX. He bridged the connections on a battery (it may have been one of the individual 12's or the main 48, I didn't check). Even with a fuse, there was a big pop and a really big arc. It was enough to fuse the wires together, but the fuse blew and kept it from being really bad.

[mrboyer]

Actually, when I was changing the batteries, the lug at the fuse was loose and had heated to the point that the phenolic fuse holder had burned and the fuse broke not shorted, but it could have easily have done that. I build my own fuse holder with large heat sinks to prevent the problem which I not had any.

[TechWriter]

Instead of a fuse I installed a DC Breaker which also serves as a disconnect switch.

[Tony Lee]

Breakers are regarded as more reliable, lower contact resistance and faster fault clearing than fuses - but in my opinion, that really only applies to single pole breakers.
Sharing the load across 2 or three poles in parallel is a really bad idea.