Battery Isolator ~ Part Deux

[Razzman]

So i picked up one of the stinger battery isolators and the instructions for it say to install between the positive terminals of both bats (duh) with two fused leads. How important is it to have fused leads coming from each bat to the iso on a boat?

[chpthril]

I don't see a need to fuse those POS cables. I would run my cables in wire-loom though.

[spharis]

No fuse required, unless it's going in an auto.

[tarheeler]

yeah do not use a fuse that way if something happens it will melt the wire instead of blowing a fuse.

[spharis]

And how do you propose the wire would melt?

[Razzman]

Thanks SP, kinda what i figured but i just had to check with the resident expert

[tarheeler]

the wire might not melt but the weakest link would be destroyed with out a fuse. that is what a fuse or breaker is used for. properly-selected fuses (or other overcurrent devices) are an essential part of a power distribution system to prevent fire or damage due to overload or short-circuits.

[spharis]

We're talking about batteries, and charging systems, not electrical components that do require fusing. Look at your car or any other vehicle (as long as it's not a toyota ), and find a fuse on the charging system that isn't direct linked to the ignition, or other electrical component; as in the wire itself is fused.

Fusing of wiring in vehicles is done because the chassis is ground....if a wire cuts, it creates an closed loop to the battery, battery overheats, then wires melt, etc......so you fuse the wiring in a car.....in a boat, there is no chasis that is always grounded. I do not find it necessary to fuse wiring in boat applications, just components.

Besides that, fusing this isolator would be very bad business if the fuses both failed. The alternator would be without the conditioner, the battery, and it would likely fail as well, if that is a 3 lug.....I don't know what style Razz has.

[Razzman]

It's a Stinger SR80.

[tarheeler]

on the merc engines they have a 90 amp fuse between the battery and the starter, they must not know as much as you or they would quit using them. that would save them alot of money as they sell alot of i/o engines.

[spharis]

Right, on the starter.....I have a breaker on mine as well.

There's nothing on the charging system though; if a fuse blows on the charging system......could be bad for the alt. This would have the same affect as turning a battery selector switch to "off".....bye bye alt. If they did use a fuse there, then if it were my boat, I would be removing it.

Here's a good article on simple DC boat isolator and dual battery setups.
http://209.85.165.104/search?q=cache...lnk&cd=1&gl=us

[spharis]

It's a Stinger SR80.

That is actually an integrator, but it works better and you have less wiring to run.

[tarheeler]

Right, on the starter.....I have a breaker on mine as well.

There's nothing on the charging system though; if a fuse blows on the charging system......could be bad for the alt. [/url]

so, the big red battery cable, the only cable on the positive side, also has a fuse and then hooks to the starter is not part of the charging system?

[spharis]

You have a fuse inline from your battery to your starter, where does your alternator cable go, to the the starter lug?

[Razzman]

Obviously not because if it did i would not have smoked my altenator when i accidently reversed the polarity on the battery cables last week. I checked the fuse at the starter and it was intact. Had there been a circuit breaker inline between the battery and the starter that would not have happened. But again fuses at the isolator would not have prevented that.