Catastrophic Fuse?

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Apr 18, 2019
Hello everyone. I am trying to determine if I need a Cat fuse. My Motor Home is a 1999 Nat'l Dolphin 33' Rv with 30 amp service. I just updated my converter with a 60 amp Pro-logic/w Wizard  and two 6v 225 amp agm batteries hooked in series to make them 12v. If I do need one, how do I determine what size to use???? Thank you for any helpful input.
It is always a wise installation. Protecting direct shorts between the positive and negative of a battery bank is important. Install it as close to the battery bank as possible. The other safe guard is to be sure your batteries are fastened properly in the battery compartment.
Sizing is a little tricky. It should be sized about 25% higher than the max load possible on the bank. Max load includes your engine starter. This assumes you have the ability to combine your starting battery and house bank for starting the engine.
  While it would likely be more expensive, you may consider a ?resettable? breaker. Our 5th wheel came with that type of system. We?ve never had to do a reset, but if you were away from a fuse could merely do a reset, once you determined the cause of the trip!
A resettable breaker offers a couple of things. It allows an easy way to get the circuit back online and because of that, can be sized closer to the max load calculations which will offer additional safety. Starting a large engine can initially draw up to 400 amps and will settle in at under 200 amps. Many things will determine the exact load for each starting attempt. That load would not be found on the house batteries very often but it is possible depending on the condition of the starting battery. I have not checked any of the recent products out there but if you can find one that will absorb the maximum initial amp draw and size it for what the maximum constant draw will be, You will have a good functioning safety fuse.
I thank everyone for your quick responses and suggestions. Gary I'm going to take your suggestion of getting 150 amp fuse. I had already thought about doing this and was thankful too hear you suggest it as well. If it happens that I find that it is not large enough then i will upgrade to a larger one. Once again, thank you everyone. By the way! If anyone out there has a Nat'l RV such as mine and may have any questions that they might have about technical things I don't mind sharing what I have learned if it pertains to anything I have done on mine.
  I think it is a good call on your part to install a fuse.  All rv?s should have similar. If a direct short occurred, on one of the battery cables, it would be a potential fire in the making!
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