All, Speaking of where to mount the breaker... This has been discussed a lot in the past, which is in the archives.... Since you never, ever, never, want the traction wiring in the cabin with you, the breaker is located under the hood, and for the "Oh SH$@" emergency cable, I use a heavy duty PTO cable (power take off). BB -- Suck Amps, Dave "Battery Boy" Hawkins Check out our website! http://bbevs.com/ Like us on the Facebook! https://www.facebook.com/batteryboyevs
> Date: Thu, 27 Jun 2013 10:32:07 -0500 > From: Lee Hart > > David Kerzel wrote: >> The concern about a DC high current circuit breaker is the maximum >> interrupting current at the operating voltage. If a fault or a turn-off >> happens under load there will be an arc. The speed the contacts open, >> possibly a magnetic arc deflector all determine if the arc will maintain or >> be broken. If it is maintained the circuit is still closed by plasma inside >> the breaker. >> >> If the short circuit current of your battery system is less than the maximum >> interrupting current the breaker, preferably less than half, and the nominal >> voltage is under the breakers rating, it is properly applied. > > I.e. it WILL successfully open, and stop the current, as long as it is > operated within ratings. > >> Unlike a relay, there is a lot of opening and closing force in a circuit >> breaker and they are designed to protect the circuit even if they are >> destroyed. > > Yes. A good circuit breaker is designed to ALWAYS fail open, even if it > is destroyed in the process. A switch or contactor can fail with its > contacts welded closed. But a circuit breaker (or fuse) will always fail > open. You pay big money for them to guarantee it! > > However, this rule is broken if you ask it to interrupt too much voltage > and too much current at the same time. The exact border is somewhat > fuzzy. As you go higher in voltage, you have to considerably reduce the > current it is asked to interrupt. > > By the way: You may not think your batteries can supply over 1000 amps. > But remember that they also have significant capacitance. You also have > many thousands of microfarads of charged low-resistance capacitors in > the controller. These capacitors can supply much higher peak currents > than the batteries alone. So the peak current for a few milliseconds can > be extremely high. > > When a breaker or fuse interrupts it maximum current and voltage (like > 160vdc at thousands of amps!), all hell breaks loose inside it. Much of > the insides are vaporized, and white-hot plasma shoots out of every > opening. Do *not* mount them in a location where this plasma can set > fire to surrounding materials! > >> Always remember Murphy's Law: A fuse will only protect something only if the >> fuse costs more than what it protects. > > Ain't THAT the truth! :-) > > -- > For every complex problem, there is a solution that is simple, obvious, > and wrong. -- H.L. Mencken > -- > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
