Originally Posted by Perfect Switch
But, solenoids used as battery isolators - unlike solenoids used for say, winching or golf carts - aren't generally switching very much current, so the contacts do last a very long time in normal use. A couple of decades of daily use without a problem is not uncommon.
Very true regarding diode-type isolators.
What separate the men from the boys is performance at elevated current levels.... where most alternators will periodically create healthy output...say 150 to 250 amps.
With solenoid-type isolators though, the solenoid is usually switched on before there is a heavy load applied, so it's not like a solenoid isolator is going to do a lot of switching (and contact arcing) of 150 or 250 amp loads.
It's also pretty rare to see an alternator putting out that much amperage. It takes a heavy load on the bus to draw that much - a welder (as mentioned by Rando), a winch or BigAss(TM) inverter could do it...but again, the solenoid wouldn't be switching those loads, just (possibly) carrying them.
Battery charging won't draw anything near that. 5a-10a usually, 30a sometimes. Depends on the battery and whatever other loads happen to be running (lights and radios, etc.).
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