Battery Isolator clicking

[Tim Manninen]

Hi all,
Don't know if you remember me but we finally left Mi and now sitting in Laredo Tx. First trip with the coach and no issues until now. We are getting ready to cross into Mexico. We woke up this morning and heard a clicking thumping noise. After investigating I found the Big Boy Battery Isolator Relay is the culprit.
Is this something I should just order and replace or could the problem be something else? The house batteries are at 13.1 and the solar is 13.4 The chassie batteries are 12.4 I'm hooked to a 50 amp service.
Any help is greatly appreciated.
Tim Manninen
2005 Monterey

[Mike Shumack]

Your chassis batteries are about dead.

The BIRD controls the Big Boy. Have you checked for voltage on the correct BIRD terminals? Attached is the BIRD service manual.
The Big Boy solenoid has a large contact inside that can become pitted/corroded. There are a lot of posts on how to take it apart to clean or change the contact disc.

To check the Big Boy "internal contact", apply 12V to the small terminal to energize the solenoid (a.k.a. Relay) then measure the voltage drop across the large terminals (put Voltmeter on low scale for DCV (i.e. 2V) then put positive terminal on one large terminal and negative voltmeter lead on the other large terminal)
Below is from the BIRD manual:

If 12 volts is applied to isolator relay coil, check for voltage drop across the isolator relay
contacts.  If the drop is greater than 0.2 volts, replace relay.

[Tim Manninen]

Hi Mike ,
I'm aware of the thump when I plug in. I felt the Big Boy Battery Isolator and I feel it click so I believe that is the problem.
I assume the Battery Isolator switches from The chassie to the house Batteries. We just drove from Mi the Laredo so the chassie batteries should be fully charged.
Thanks for your reply.
Tim

[Mike Shumack]

Hi Tim, you read my post before I edited it. I see that you are talking about the Big Boy.

[Frank Bergamo]

Tim,
as Mike stated above, check voltage on each of the two big terminals of the Big Boy solenoid. They should both read the same or close to it, while plugged in or with coach running. If not the same, then Big Boy solenoid is not working properly. Sounds like to me the shore power is charging the house batteries, but not the chassis batteries. The Big Boy is bi-directional, it should charge both ways, shore power or with engine alternator. Hope this helps. This may help you understand system. http://beaveramb.org/forum/index.php/topic,8421.0.html

[Tim Manninen]

Thanks Mike and Frank,
I read something about cleaning contacts on the BIRD which I think is the black sq box located on the door.
Or should I replace the Big boy.
Also If I start the coach will the chassie battery charge? I started the coach with only 12.4 V fired right up.
I found videos on how to clean the Big Boy. Looks easy. The clicking stopped after running the coach and charging the chassie battery for 8 or 10 min. The battery this morning is at 13.9 all seems good.
Thanks to everyone for your help.
Tim

[Frank Bergamo]

Tim,
check my edit above. It should answer your questions.

[Bill Lampkin]

If you have a battery temp sensor connected to your inverter, unplug the temp sensor (telephone cord) from the inverter and see if the click, clunk goes away. Worked on my unit.

[George Harwell]

Tim,
     Your chassis battery voltage is not where it should be. After driving from Michigan and plugging in to 50 amp service you should be reading around 13.4 volts . Your big boy is clunking because it is switching back and forth between your house and chassis battery. You need to get the chassis batterys tested for serviceability. As for the big boy mine has been clunking for 15 years so I opened it up and found it was perfectly okay. No corrosion but I flipped the contact anyway. The clunking is like an upset tummy, comes and goes. Happy new year!!!

[Mike Shumack]

I get a new Big Boy, then take the old one apart and try to fix it for a spare.
Here's the instructions for disassembly and cleaning.
Okay - this site won't let me post the instructions (it's over 300 KB). E-mail me if you need them. They may be in the "Coach Assist" links section already.

[Steve Huber]

Tim,
As George points out, your issue is not with the Big Boy or BIRD system. The BIRD monitors both sets of batteries and closes the Big Boy when one set reaches 13.3V. It opens when the voltage drops to 12.8V. This is why you are hearing the thumping/clicking. Your house set cannot maintain 13.3V, either due to a bad house battery or a bad chassis battery that is dragging the house voltage down when the Big Boy closes.
At 12.4v, your chassis batteries are not being charged. Also, on shore power, your battery charger should be able to maintain the house batteries around 13.3V.
Suggest you check for a bad/weak battery. As George observed, I'd target the chassis units first.
Steve

[Larry Dedrick]

Tim
      Big Boy will make more noise as the corrosion on the inside becomes greater. Disassembly and cleaning should bring it back to normal operation. Thats assuming you have a corrosion build up. Once I cleaned mine the noise from the Big Boy was much less. Also it is normal for the big boy to cycle between battery banks. When on shore power the House batteries have priority and when the Chasis batteries drop below a certain voltage the big boy will close and charge both banks. When ignition is on and engine running, then Chassis batteries have priority and if house batteries drop to a certain voltage the big boy will close charging both battery banks.
      This cycling continues 24/7. I did have a case where the house batteries were not being charged while driving and found my BIRD to be malfunctioning. Once i fixed that all operation was normal. The ground wire on the BIRD was being temperamental.
        I realize you were concerned about the noise, and you should be able to hear the big boy cycle, but the louder it becomes the more likely you have a good corrosion build up inside the Big Boy.
        Hope this helps

[David T. Richelderfer]

In Tim's first post: "The chassie batteries are 12.4 I'm hooked to a 50 amp service."
In Tim's second post: "We just drove from Mi the Laredo so the chassie batteries should be fully charged."

I don't know the length of time elapsed between these two posts.  But you are correct, after a few hours of leaving MI, the chassis batteries should have been showing fully charged during the whole trip from MI to Laredo.  Fully charged and while stopped at a rest area, for example, the chassis batteries should show 12.6-12.7v without being plugged into shore power, without the generator running, and without the coach engine running.

When stopped traveling and after plugging into shore power or with the generator running, the inverter will, after a time, charge and maintain the coach and chassis batteries to 13.1v to 13.4v.  The inverter will go through three stages of charging - bulk, absorption and float - starting with bulk charging showing over 14v on the charge-status equipment.  As the batteries become charged, the invertor will switch to absorption charging showing a reduced voltage, and finally switch to float charging where the batteries should show 13.1v to 13.4v on the charge-status equipment.  Upon disconnection from all charging, the batteries should show 12.6v to 12.7v.  This explanation works only IF the invertor charging system and BIG BOY/BIRD systems are working properly.

[Tim Manninen]

Hi All,
You folks are fantastic. Thanks for all the replies. I am in a bad area for connecting to my hotspot so it takes awhile for me to respond.
The coach started last night with only 12.4 volts. It fired right up. I ran it for 8 or 10 mins and watched the battery charge to 13.9. We didn't hear and clunking all night and this morning the chassie battery was at 13volts. I like the thought the big boy is like a tummy ache it comes and goes.
Off to Mexico in a few days.
Thanks again for all your help.
Tim, Elke and 3 Aussies

[Joel Ashley]

Tim, a word of caution.  Your alternator was not designed to charge sets of very discharged batteries, even from dry-camping one night.  Many an owner have had their alternators burn up trying to catch up all the batteries afterward.  If you’ve been plugged into power that’s one thing, but otherwise use your generator to get past the bulk-charge phase (as shown on your inverter’s control screen) before starting your engine.

You should’ve seen more than 12.4 volts if you’d been plugged in for much time.  If you saw that number on your inverter screen, it was for the house batteries;  your chassis set may have actually been closer to 12.5 -12.8 volts. Keep in mind that, believe it or not, at 12 volts on your screen your house batteries are half discharged.  The genset will take them to 13.4v before the BIRD and Big Boy switch the charging to tackle the chassis set.

Joel