battery question

[Loren]

rama777,

Wire is sized safely to carry the highest current that the system will deliver. In your case, this is 60 amps. That requires 4 gauge wire.

If your batteries are dead, your converter/charger will try to deliver its maximum rated current, which is 60 amps. 10 gauge wire is usually rated to carry only 30 amps. Do you want to run 60 amps through 30 amp wire inside your trailer? I don't.

In practice, your converter will almost never produce that amount of current, since your batteries will almost never be discharged enough to take it, but it's possible. Don't install wiring that is too small.

Loren

Edit: I have found (on McMaster-Carr's web site) some wire smaller than 4 gauge that will carry 60 amps, so it's possible to use something smaller. Just be sure that whatever wire you choose will carry the 60 amp load from your converter.

[Loren]

Contrary to "common knowledge", fuses are not installed in a circuit to protect equipment. At least, they are not installed in the wired part of the circuit. Each piece of equipment attached to electrical power should have its own built-in protection, either in the form of a fuse or something else.

A fuse is installed in a circuit to protect the wire. Here's how it works:
If your circuit consists of 15 load centers, each of which draws 2 amps, it will be wired with a certain wire size, depending upon the maximum number of loads that are expected to be on at the same time. Let's say that the designer expects a maximum of 10 simultaneous loads in this case. He would install wire capable of carrying 20 amps, typically 12 gauge wire. He would also install a fuse rated at 20 amps to protect the wire from overload.

Obviously a 20 amp fuse is not much protection for a device that draws only 2 amps during normal operation since the device would probably be smoking by the time it is drawing only 10 amps. That 20 amp fuse is to protect the wire.

If all 15 loads were turned on simultaneously, the load would reach 30 amps, which would be dangerously high for the 12 gauge wire and which could cause a fire. Before this occurs, however, the 20 amp fuse would blow.

Uwe has the right idea. Use wire that’s large enough and install a fuse to protect it. Using his example, if he is using 6 gauge wire, he should have about a 40-50 amp fuse, depending on the specifications for the wire he is using. If his converter is rated at 60 amps, he could expect the fuse to blow on occasion.

Loren