What is this device on my battery?

[tony_cliffy]

I assume it is some kind of circuit breaker, but not sure. It is called a 'shortstop' and says "20A" as it if it is a fuse.<br /><br />Is it an auto-reset? Or do I have to replace it if it blows? I think that positive lead is my alternator (charging) lead so this thing is a fuse on the battery?<br /><br />

 

[Silvertip]

Re: What is this device on my battery?

That is a circuit breaker. It is not the charging lead for the battery. Charging occurs through the larger battery cable from the engine. Follow the red lead to see where it goes. It is very likely for a bilge pump, live well pump, trolling motor (most likely), etc.

 

[tony_cliffy]

Re: What is this device on my battery?

Charging occurs through the battery cable?

 

[demsvmejm]

Re: What is this device on my battery?

The typical circuit design Upinsmoke is referring to is where the alternator output terminal connects to the starter Battery connection and then the charge current flows back to the battry. This effectively shortens the run of the alternator output circuit to just from the Alt to the starter. From there it uses the higher amperage capacity battery cable to complete the circuit, thus lowering cost, weight and complexity.

 

[demsvmejm]

Re: What is this device on my battery?

Tonycliffy, unless "shortstop" is a tradename like Thermos(bottle) or Crescent(wrench) I would suspect that your itme is a diode that prevents damage to a sensitive or important (thus expensive) electronic component in case of a reverse connection. With only ring terminals and color coded wires to guide you, a reverse connection after a winter's storage could zap a computer, regulator, fishfinder or such. The 20A does indicate is is a fuse so it may very well be a double duty device. Good question though. If you find out for certain let us know.

 

[tony_cliffy]

Re: What is this device on my battery?

I found out from another message board that it is a circuit breaker - brand name Bussman. It goes into a large wire bundle so will be hard to trace. I can try lifting it and seeing what stops working. I do have a fuse panel running just a couple items off the starting battery (although most things runoff the house battery) so this must be my feed to that panel. Now I'm wondering why I have one hot wire but two separate ground wires!

 

[Gone]

Re: What is this device on my battery?

Bringing separate grounds back to the battery's negative post aids in noise suppression for some applications. A common ground bus with a cable back to the battery is often noisy.<br /><br />BTW, your picture looks like a headlight circuit breaker used in cars a few years ago. Yes, they reset themselves....for a few cycles.

 

[jch7450]

Re: What is this device on my battery?

SHORTSTOP® Circuit Breakers - Series 120<br />Auto, Manual, & Modified Reset Circuit Breakers<br />Specifications:<br />Ratings: 8A to 50A; 12VDC; 24 VDC<br />Operating Temperature: -23°C to 65°C<br />Storage Temperature: -29°C to 93°C<br />Applications: Battery chargers, trucks, buses, RV's, trolling motors, etc.<br />Approvals: Complies with SAE Standard J553.

 

[Salmonseeker]

Re: What is this device on my battery?

My boat came from the factory with one of these for the trolling motor. It was a 40 amp though. It is an auto reset circuit breaker. It will cut out just a fuse would blow. Once it cools down it will reset itself.

 

[Silvertip]

Re: What is this device on my battery?

If this is a 20A breaker it is very likely the positive feed to the fuse/breaker panel at the console. One of the ground wires is for the negative buss on the fuse/breaker panel. The second ground wire may be for the bilge pump, stern light, or a livewell pump.