Big Boy Battery Isolator

[Tic Wilson]

Tell me what my next step should be.  We are parked connected to shore power.  We have noticed for several months that when we first get into bed and again about dawn, that we hear a knock sound.  Not multiple knocks, just a single knock.  Several minutes later there is another knock.  Shortened version; it is the Big Boy Battery Isolator.  Every two weeks, I top the water in the house batteries, since the solar panel keeps them charging.  The coach batteries I check every other month.
What is the most likely reason for the Big Boy to actuate?  What should I be looking for?
Thanks in advance for help!
2005 Beaver Monterey

[Bill Sprague]

The Big Boy and BIRD that comes with it are made by Inteletec.  A few years ago I located the instruction sheets and sent them to Tim.  He put them in the resources section.

It took some time for me to understand the instruction sheets, but the short version is that the Big Boy/Bird are their to make sure BOTH your house batteries and engine start batteries stay charged regardless of the power source.  The power can come from the engine alternator, shore power or generator.  If I recall, the solar panel was exempt. 

I never heard mine actuate.  But, actuation is supposed to be completely automatic.  When one set of batteries is lower than the other, the charge is switched.  I suspect what you are hearing is resulting from the normal drawdown of the engine start batteries due to how Beaver built it in a way that there is a constant drain to keep a few systems always running.

Since I never heard mine, noise loud enough to hear may indicate a problem.

[Tic Wilson]

Thanks Bill, I have found the documents and saved a copy.  Should be a Big Boy help!