Batterty Isolators - Is there a consensus?
There's another thread on battery isolators, and here is a quote from that thread on testing a diode type isolator: "Should be around 14 at the outer lugs and around 14.7 at the B+ lug" Presumably, ...
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MEXICOWANDERER wrote:
I have seen dozens and dozens of can type constant duty solenoids fail because the owner did not connect the switch power source wire to IGNITION "B". An ignition switch has two "ignition" positions: The fist is for "the ignition" including fuel pump. Ignition "B" is connected to accessories like wipers, heater blower, radio, etc. The poor solenoids could not handle the massive current sent from the house battery bank over to the starting battery to assist it. Connected to Ignition "B" the isolator solenoid plays possum while the engine is cranked.
Hmmmmm. My RV, built in 1973, still has its original (constant duty) can-type solenoid installed. It's wired to parallel the engine battery and the RV batteries. I can lock it down for charging, press it momentarily to help only with starting, or disable it to isolate the engine and the RV.
I would estimate that at least 90% of the starting cycles (and probably more than 95%) in the last 40 years were with that solenoid engaged to assist the engine battery during starting. Many, if not most of those starting cycles, the engine battery was marginal for starting, so the solenoid was carrying a hefty current. The solenoid has gotten lots of use - we're on our third engine in the chassis.
I looked up the number of the solenoid, and it wasn't anything particularly fancy. I think it was a Delco (400A short duration) rated for continuous duty at some lesser current, but don't hold me to those numbers. Part of the reason I asked for comments was because I thought I should carry a spare, but wondered if I might want to modify the system to something more modern.
