50 Amp Circuit breakers & trailer plugs
Submitted: Monday, May 31, 2010 at 21:26
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Mark
Hi Guys
I am installing some 16mm2 cable from a smart isolator in the engine bay to a 12 Pin flat trailer plug to connect to charge a second battery in a camping trailer.
1. The Trailer manufacturer recommends a 50 amp breaker near the isolator. I have seen several types but the cheaper auto reset type seem flimsy & i'm worried about voltage drop. Are there any other alternatives for 16mm2 cable? (the trailer manufacturer recommended 8 B & S but i'd rather use the heavier stuff).
I have used a 75 amp (resettable) breaker from Jaycar in the past but found that it had a .5 volt drop from the input to output.
2. Does anyone know the max cable size for a 12 pin Britax B48 trailer socket (trailer has a B47 plug). I guess I'm going to have to step down the cable size at the socket. I'll be splitting the load across two pins which are 35 amp each.
3. Is it best to earth the return close to the trailer plug on the vehicle chassis or run a second 16mm2 cable back to the engine bay and as close to the alternator as possible. In other words would decent copper wire provide lower resistance than the vehicles steel chassis.
Thanks
Mark
Reply By: drivesafe - Tuesday, Jun 01, 2010 at 12:24
Tuesday, Jun 01, 2010 at 12:24
Hi Mark, it’s not uncommon to get a voltage drop across an unloaded set of contacts like a relay or circuit breaker.
But if you got a reading like that across the circuit breaker with even a small load of say 10 amps, you probably got an incorrect measurement because even at 10 amps, the amount of heat that needs to be generated to create a 0.5v voltage drop, your circuit breaker would literally glow in the dark.
Try measuring again, with a decent load and see what you get.
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