Mystery thump in battery bay.

[jeffprupis]

I thought I posted this a while back but can't seem to find the thread. We have an intermittent "thump" coming from the battery bay (actually the box which holds the Big Boy and BIRD). It starts as a very low wining sound followed by a thump which can be heard in the bedroom or when sitting outside on the curb side.  After turning OFF the charger (RS2000 Inverter/Charger) at the System Control Panel it seems to stop. Battery charging drops from 13.6V to 12.5V. Any ideas as to problem and or solution would be appreciated. Also, If I turn off the charger, I assume my chassis batteries are not getting charged. TIA

[Bill Lampkin]

I had the same thing; I fixed it by doing a 'reset' on my inverter. Unplug from shore power, make sure the gen is off and won't start, turn off inverter switch at the inverter, open house disconnect. Wait a few minutes, then reverse the procedure. Fixed my battery charging and got rid of the 'thump.' I think what you are hearing is the 'Big Boy' checking for battery voltage. Anyway, I found the inverter reset procedure in my Beaver manual, and it worked!

[jeffprupis]

Thanks Bill I seem to remember your reply last time. Would you happen to know where or how you found it in the manual. I have a PFF of mine so I can do a word search. TIA

[Bill Lampkin]

Jeff, I must have found it in the inverter section. I do remember I found it strange that the reset procedure did not appear in the Xantrex manual for my inverter, so when I found it in the manual, that caught my eye. Hope it works for you, it did for me!

[Mike Shumack]

It is interesting that resetting the Inverter would have any effect on the operation of the Big Boy solenoid (assuming the noise is coming from the Big Boy). The Inverter is not connected to the Big Boy (other than it provides chassis' battery charging when coach is plugged into Shore power).

Jeff, are you sure the trumping sound is coming from the Big Boy solenoid and not just sound transferring from somewhere else?

I often get a loud thump from my Transfer Switch when I plug into shore power. My transfer switch is in the rear basement compartment which is next to battery compartment. My inverter is located in the same compartment just a foot or two from the Transfer Switch.

It is normal for the Big Boy solenoid to make a whining sound.

Is the thump you are describing the Big Boy "contacts" slamming shut? I would not think those contacts are large enough to make a thump sound. There is nothing else in that compartment to make a sound like you describe. AFAIK.

Just want to understand what is going on in case I experience the same thing.
Good luck.

[Bill Lampkin]

Mike, The thumping sound I heard may well have been from my transfer switch, there was also a loud high frequency hum, source unknown. I do know that by resetting the inverter, both sounds went away. Its a mystery, but in my case, it worked!

[Mike Shumack]

I have that high frequency hum too - it comes from the Big Boy solenoid and is normal. I posted/asked about that humming a while back. 

[George Harwell]

Yes Mike, it is the big boy thumping. Been dealing with it for years. Comes and goes a couple of times each year. I have done the inverter reset and that helps but started again recently so I turned on the ignition switch for about a minute. Stopped the thumping. My coach is 16 years old so plan to pull the big boy relay this spring for some preventive maintenance.

[Dwight Wilson]

I had a similar issue last year , about the same time I was having some problems with my batteries. I installed new batteries and the problem went away. It might be something to do with a bad battery affecting the charging system operation? Just a thought in case your batteries are getting old?