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Friday, October 23, 2009

Isolator Issue

I changed my alternator from a 130-amp to a 200-amp. My battery isolator is only a 160-amp. What is going to happen to the isolator? Will I have to change the isolator? Will it go bad if I don't change it? It is a Sure Power Model 1602 rated at 160 amps. Thanks!
Jim, (Brackney, PA)


Yes Jim, it will be necessary to upgrade the isolator to one rated higher than the output of the alternator. It would also be a good idea to check the amperage rating of all the conductors in the charging system as well. While it’s a very good idea, especially for those I like to call “serious RVers” to upgrade to a higher output alternator, the entire system must be in balance; all parts must be able to carry the additional current. Think of it as the “weakest link” theory. The system is only as strong as its weakest link. You may have a high output alternator, even a properly sized isolator, but if the conductors or terminals are undersized, they become the weakest link.
It’s my policy to have the charging source, in this case the alternator, be the lowest rated component in the system. All the other components should be sized accordingly to more than carry the entire output current rating. Running with an undersized isolator will eventually burn out one or both of the diodes in the isolator, thereby ceasing any charge current going to that particular battery bank. I’d recommend a 240-amp, dual battery isolator, using the schottky-type diodes for your application.

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