Alternator not charging all the time

[Jerry Ward]

We have a 2008 Beaver Contessa and 2 times now, when we got ready to leave for our next destination, we had a low battery message on the dash.  A voltmeter reading at the batteries showed 12.5V. The first time, I disconnected the toad and plugged it back in hard and it started charging 14,7 Volts.  The last move, I had to start the generator, (it sounded like it didn't want to start). I don't know if the generator should show 14+ volts or not but it only showed 12.5 until I shut the engine (Cat 425) off and restarted it.  Then it showed 14.7 volts and the low battery message was gone.

We are getting ready to leave in the morning and I'm starting to get paranoid!  :-)

TIA

[Joel Ashley]

Are you dry camping with the toad still umbilicalled?  Some toads may parasite power while parked.  12v is a battery more than halfway discharged.  12.5 is pushing it.

The alternator should charge up the chassis to ~13.4v then switch to bolster the house set.  But never start the engine dry-camped without using the Generator first to get the house set to at least “Absorb” status, or you’ll risk ruining your alternator.  Most (but not all) gensets get their starting voltage from the chassis set.

It does kinda sound like your alternator may need checking, but start with being sure your connections are all uncorroded and tight…. batteries, alternator, and chassis grounds.

Joel

[Jerry Ward]

Thanks Joel.  No, we are plugged into shore power.

[Joel Ashley]

Perhaps the Big Boy’s contacts are not transferring inverter charger output as designed.  It’s not an uncommon issue reported here.

[Jerry Ward]

Thank you so much Joel!  Not sure exactly how or when the Big Boy Switch works, but definitely something to keep in mind.

[Steve Huber Co-Admin]

Jerry,
The Battery Boost switch on the left driver console forces the Big Boy solenoid to close, tying the chassis and coach batteries together to provide maximum current to what you are trying to start, usually the engine or generator.

It also closes under the control of the Bird system to keep your batteries charged. When you are on shore power the inverter should charging/maintaining your coach batteries. Once they reach 13.4V (full charge) the Bird system senses this and closes the Big Boy solenoid.  This ties the coach and chassis batteries together so the house batteries can supply a charge voltage/current to the chassis batteries.

When the engine is running, the process is reversed. The Bird system senses when the engine alternator has charged the chassis batteries to 13.4V. It then closes the Big Boy solenoid so the house batteries will receive charge voltage/current from the chassis batteries.

As Joel noted, it sounds like the Big Boy may not be closing and it could be due to corroded contacts inside the Big Boy. Sometimes you can clear the contacts by pressing and releasing the Battery Boost switch a few times. Also use the Battery Boost switch when starting the engine or generator as this will cause the contacts to close.
It’s also possible that you may have weak chassis batteries.

The Bird Big Boy manuals are on Coach Assist also.
Steve

[Joel Ashley]

As you are new here Jerry, you may not know that Coach Assist is under the “Technical” tab on the main BAC website.  Tap the large bold URL address at the top right of this page to get there.  You will need to sign in there if you decide to download any documentation.

Joel

[Jerry Ward]

Thank you so much Joel!

[Jerry Ward]

Thank you so much Steve!  I am going to have to bring myself up to speed!