Circuit breaker at battery?

standfast

Well-Known Member
Joined
Jul 16, 2007
Posts
334
Reaction
113
Location
Abq, NM
Does anyone run a hi-amp resettable circuit breaker at the battery in case the main power cable across the whole car to the start relay and accessory power wires short? I was thinking about this the other day and realized I have no circuit protection on the biggest power wire I have. Will the alternator still charge back through a cicuit breaker? I don't see why it wouldn't.

Something like this right next to the battery.
http://order.waytekwire.com/productdetail2/M37/46989/HI AMP MANUAL RESET 150 AMP/
 

Co-Dog

Well-Known Member
Joined
Mar 13, 2007
Posts
612
Reaction
84
Location
La Mesa, CA
It is generally accepted that if the main cable is kept short and protected from physical harm, no protection is necessary. If the cable is run for more than a few feet, then you can't go wrong with some breaker insurance. Keep in mind that your starter will probably need a separate, unprotected cable. Most starters have current ratings higher than that of readily available DC breakers.
 

D-rek

Well-Known Member
Joined
Jan 20, 2005
Posts
557
Reaction
71
Location
Corona CA
I use one of those in my four seater works great no reliability issues and provides protection
 

jeff

Moderator
Joined
Apr 1, 2001
Posts
7,454
Reaction
352
Location
California
Website
www.performancelifts.com
AutoZone sells this style breaker. I purchased one at AZ for my boat and it was $24.00 bucks + tax. West Marine wanted almost triple for the EXACT same thing. The only catch is I got lucky and the AMP rating I was looking for was in stock and on the shelf. You might not get so lucky. I only use it for accessories and would not run the starter through it... assuming the AMP capacity of the breaker is high enough to support the starter draw it should work... but you might have to get the fans and accessories to shut down during the start cycle to prevent overloading the breaker.

Ripoff Alert ---> http://www.westmarine.com/webapp/wc...rue&storeNum=5002&subdeptNum=9&classNum=14180


Aloha
 

manicmechanic

Well-Known Member
Joined
Dec 11, 2005
Posts
964
Reaction
149
Location
Washington
The high amp breakers are great for 2 reasons. The red button opens the breaker in the event of a wiring emergency overheat/fire, that is not enough to kick out the high amp breaker. They must then be manualy reset. Great for "hidden switch"
AVOID!!! Thermal reset breakers they will keep energizing a shorted wire until it catches fire or melts into another wire even when properly sized.
As near the battery as possible for primary cuircut protection.
 

scottm

Well-Known Member
Joined
Feb 7, 2005
Posts
1,884
Reaction
559
Location
scottsdale AZ
Website
www.cemaz.com
I think a fuse or breaker on the batt cable should be in the tech rules. A bad wreck could easily move a piece of sheet metal or bend an exhaust pipe to the point that the positive cable is shorted out. I use an RV fuse on the battery ground wire in my race truck and rv. They are designed to keep a powerful battery bank from burning up an rv or boat. It is a heavy duty fuse block and takes 100 to 300 amp fuses. I have a 200 amp fuse in my 8 truck, and have not blown it yet, but I carry a 250 spare in case. And since I run it on the ground wire, I can always run the cable straight to the ground post if I dont have a spare fuse.

http://order.waytekwire.com/scatego...Amp Fuses And Fuse Holder/Circuit Protection/
 

Co-Dog

Well-Known Member
Joined
Mar 13, 2007
Posts
612
Reaction
84
Location
La Mesa, CA
High current fuses always worry me because they are expensive and you're not likely to find anybody with a spare. That's a good call on the ground cable. Less to worry about if you can easily bypass it. Another reason that I am not a big fuse fan is that troubleshooting the problem can leave you with 0 fuses of the right size pretty quickly.

One of the reasons that you don't see tech requirements for protection of the battery cable is that when the cable shorts out, the current varies quickly and over a large range. In other words, upon shorting there might be current of 600 or more amps, but in most cases it quickly vaporizes the strands of wire that are grounded, the resistance of the connection increases and the current drops until the connection is made again from the molten copper or steel. It's just like welding.. This all happens so quickly that the fuse may not even blow, depending on the size and type. The battery switch is supposed to be readily accessible and I'm not aware of any case where it wasn't sufficient to prevent catastrophe. Shorting a battery at the posts is where disaster strikes. The current is immeasurable, causing the acid to boil and spray everywhere as hydrogen is released which either ignites or explodes.

Don't get me wrong, what you are doing is perfectly acceptable and might just save your vehicle or your life some day. I'm not familiar with other sanctions, but SCORE rules are pretty specific about batteries and the disconnect switch, which has proven to be sufficient over time.
 

FABRICATOR

Well-Known Member
Joined
Apr 3, 2001
Posts
5,146
Reaction
108
Location
Ventura County, CA
There are sealed manual reset Klixon's too.

largeframe-p_pdlm-90.png
tcb-7855.jpg


IMHO, there is a fair chance that current protection in the starter circuit would not work as planned when the time comes.


.
 
Top