disconnect switch amp rating

[rod7515]

I have a 66 Dart that I plan on racing a few times a year. Nothing serious but will be needing a disconnect switch since I will be moving the battery into the trunk. I see that there are disconect switches ranging anywhere from 20 amps to 300 amps. How do I know which one I should be using and what regulates me to those amps? I plan on using a 2 post switch. I plan on placing an order this weekend for some parts and will be getting an NHRA rule book included in this order so I dont know what factors into this.
Thanks
Rodney

 

[crackedback]

It depends. You can get a 180 amp switch for around $30. IMO, It will be capable of doing the work you need as long as you don't run starter loads through it..

A 20 amp is OK for just switching other relays on/off. The load in the car from most things downstream is likely going to be greater than 20 amps.

Depending on how you plan to set up the system, I'd look for a switch in the 80+ amp range just to be safe sans the starter loads. There is the minimum standard for a cut off that will make the car legal, then there are improvements. How you plan to isolate the alternator, alternator type, whether you want the big starter cable hot all the time, lots of choices to consider. Pick your method and go.

 

[skykeith]

Go to Summit and order MOR-74101 or MOR-74102 if you want the alternator cutoff feature. They'll handle all the starter load you can throw at them and last forever.

 

[bOb shingler]

why doesn't a battery in the engine compartment not need a cut-off switch?

 

[nm9stheham]

In a few racing bodies, lke FIA rally, they are required wherever the battery is located. It is there to cut-off the battery in case of wreck/fire/etc. So, for racing safety considerations, it should be there regardless.

The heavier amperage rating is a good idea because if you do get into a wreck and the + cable is being pinched and shorted, you will have to break a lot of current; a lighter current cutoff may just arc over the contacts and weld itself closed with a shorted battery load in it. Besides the inconvenient fact that the 20A rating won't carry the battery currents you need in the first place.......!

 

[ntsqd]

A battery kill switch should be rated for an intermittent load (i.e. starting) that is far higher current than their continuous duty current rating. For instance the [ame="http://www.amazon.com/Cole-Hersee-7590401-Master-Disconnect/dp/B001FQNI20/ref=sr_1_1?s=automotive&ie=UTF8&qid=1398005561&sr=1-1&keywords=Cole-Hersee+75904"]Cole-Hersee 75904[/ame] is rated for 125A continuous and 1000A intermittent ([ame]http://www.colehersee.com/home/item/cat/209/75904/[/ame]). If the switch that you're considering doesn't list the intermittent load rating I'd look for a different switch. The 75904 switch also has silver laminated contacts which are far less likely to 'spot-weld' together and not release when they need to.