Battery disconnect switch - how many amps?

[SC74]

I've been wanting to install a master battery disconnect in the crawler. I have to order a couple parts from Summit and figured it would be something else to get and justify shipping cost.

How many continuous amps do I need? I am running 5.0 with exploder alt and stock starter. I see them from 20 - 300 amp ratings.

 

[Viperwolf1]

If you use the battery to start the engine you'll want that 300 amp one.

 

[Steve83]

Depending on exactly how you wire it in, you can get away with a relatively small one.



You don't actually have to break the starter feed to prevent cranking - if you kill all the OTHER power, then the starter relay can't be energized. Look at the lower R of that diagram.

 

[SC74]

I was going to wire te negative straight off of the battery through it. My battery sits where the heater used to be so cable runs will be short to the dash.

 

[Steve83]

That's risky, and it puts the MAXIMUM possible load on the switch, requiring the biggest & most-reliable (most-expen$ive) switch you can find. If the switch ever fails while the engine is running, it could take out the alternator, which could take EVERY electrical/electronic device with it. It's much safer to put it on the positive side.

 

[patterdale]

You want to be able to cover whatever amperage the battery is capable of putting out.

 

[burntfish]

I going to be using one of these for cutting the ignition and fuel off in a emergency and when in town with the top off. Its a 300 amp.


sent from my stupid phone using craptalk.

 

[bronconut73]

I going to be using one of these for cutting the ignition and fuel off in a emergency and when in town with the top off. Its a 300 amp.


sent from my stupid phone using craptalk.

I used the same switch. I installed it between the battery and solenoid. I have the radio memory wire straight wired to the battery so I don't lose my stations when I flip the switch off.
I also have one to manually keep my dual batteries separated until I need both for something. Has worked flawlessly for about 3 years. Simple and effective.

 

[bmc69]

I going to be using one of these for cutting the ignition and fuel off in a emergency and when in town with the top off. Its a 300 amp.


sent from my stupid phone using craptalk.

We used that exact switch for a couple years in our race trucks (cutoff is required, one for the driver and one accessible to support crew outside). Very unreliable......very. Eventually scrapped those in favor of the much more robust type sold by Moroso.

And as another poster noted..a fully in-line cutoff switch should have a capacity matching the cranking amp capacity of the battery. Any less and it essentially an expensive in-line "fuse".

 

[xcntrk]

I use one of those HD remote battery disconnect relays which is then controlled by a switch in the cabin. I can cut all power with a flip of the switch from the driver seat - upside down if necessary!

 

[SC74]

I was going to get the moroso. It has 1,000 surge amps and 175 continuous. I'll go with a higher continuous to be safe.

 

[SC74]

Also something to consider is that my mega fuse between the alt and battery (from BC Broncos) is 175 amp rating.

 

[Steve83]

None of that matters if you put the switch where it carries only the load it needs to. It doesn't need to carry the starter load, or the alternator output.

 

[JWMcCrary]

I've been using one of these for 7 years.

http://www.summitracing.com/parts/sum-830050/overview/