House batts not charged by alternator

[Terry Melot]

My alternator charges the chassis batts just fine. However, yesterday, after 8 hours on the road, I noticed it was not charging the house batts while driving. The house batt voltage was down to 12.3 V by the time we stopped and plugged in.  The day before, it kept the house batts at 13.9 V. The day before that, down in the mid 12s.  Why charge the house batts sometimes and not other times?  I must be missing something.
Any suggestions?

[Bill Sprague]

Terry,

When did you read the 12.3 on the house batteries?  When driving?  When stopped, engine off and not plugged in?  Or, when stopped and plugged in?

Bill

[Edward Buker]

Terry,

Sometime when you think the alternator is not charging and you are getting the lower reading, stop at a rest area or at your campground and before you shut the engine down measure the voltage with a meter at your chassis batteries and see what the true charging voltage is at the bank. The dash gauge is susceptible to wiring harness voltage loss due to the distance from the battery and varying loads at the front end of the coach. That can give false readings regarding what is actually happening at the batteries which is what you really care about.

If you are 13.2V or above at the batteries I would not worry. If the voltage is less, then the alternator and battery bank should be checked out to see what is going on.

Later Ed

[Terry Melot]

Bill, reading the 12.3 on the Aladdin while driving. When we stopped and plugged into shore power, the amps going to house batts was 60-70 amp for about an hour.

[Terry Melot]

Ed, I don't have a dash gage that reads "house batts".  Only the Aladdin. It not only shows voltage but the amount of amps either going to the house batts or with a "Dis" showing the amps going away from house batts. When the voltage has been below 13.5 it always shows "Dis" for discharging (while not plugged into shore power or the gen running).  I understand that if the engine is off. But thought the engine alternator would keep the house batts charged while running.

[Joel Ashley]

Check that all your connections are tight on your BIRD, Terry.  (Perhaps I could have written that differently   ).

Theoretically at start up, when the chassis bank hits 13.3 volts, the BIRD (Bi-directional Isolator Relay Delay) lets the Big Boy feed alternator current to the house banks.  Then it makes sure the engine has sufficient voltage to keep running while on the road, but otherwise feeds charging current to the house set.  Seems a while back there were threads here where fellows had discovered loose wires on the BIRD.  That doesn't mean that's what's wrong, but it would be where I'd first look at this point.  If yours is like mine, I have to be careful, for example, when closing the fuse/Big Boy/BIRD access door that I don't pinch the BIRD's wires;  hanging from the access door, the BIRD's wires naturally droop down in harm's way, so you might check it out.

Joel

[Edward Buker]

Terry,

Within the limits of available current the alternator is certainly capable of bringing up the charge level of the house batteries if it is connected to them and they are not in a severely discharged state. I am not sure if the system that the coach uses to bring the current to them is disconnecting them from the alternator. It is not very common that alternators stop charging and then heal themselves and start charging again so my guess is that the alternator is probably O.K.

The second indication that you have that the alternator is probably O.K. is that you have not mentioned a failure to start due to low chassis batteries.

You can confirm the charging with a meter by looking at the chassis battery voltage when your house bank is reading low by the Alladin. If the chassis batteries are at 13.2V or higher and the house batteries are seeing low voltage like the Alladin has been showing in the 12.4V range then look to the system that connects them together as possibly being the issue (probably a Big Boy system or similar). There is some chance that you have a battery in the house bank that is failing and pulling a lot of current dragging the voltage down but I would think the current measurement, as measured by the Alladin would not go to discharge, it would be a higher current level then normal but still in charge mode.

Check all the battery connections and main fuse connections to see if they are all tight and corrosion free. The Big Boy/Bird if you have one is a solenoid switch which can have contacts that degrade with use so that could be possibly involved. That is the best guess that I have here from VT. Hope it helps...

Later Ed

[Terry Melot]

Joel and Ed, thanks for the info. I am learning more than I ever wanted to know about this MH. I intend to be in this one or another Beaver similar to it for the next 10+ years, so I guess I need to know these things. Recently had the Gas/elec frig replaced with all elect. So we have a bigger draw than before just driving down the road. I understood that we'd have less dry camp time but thought the engine alternator would have no problem with 5-8 amps 120 v (60-90amps 12 volt)

I'm guessing the Big Boy and the Bird are in the battery compartment?  I will check all wires in there for tightness.  I recently changed the chassis batts and could have disturbed something.  I could even have put a wire that should be on the positive pole on the negative pole. But that is the chassis side.  No problem with that.
The coach batts are older and one of them could be going bad.

[Edward Buker]

Terry,

Try just before you leave the campsite for traveling to lower the demand of the frig thermostat for cooling or even shut it down for some duration of your travel. These refrigerators are well insulated and with a load of food and frozen goods already chilled they should do quite well for 6 to 8 hours if not opened much.

If your trouble seemed to start about the time the frig was changed then that may be the prime issue but should be able to be managed. Obviously if your battery bank is needing to draw charge and your refrigerator is pulling 80 amps along with the coach demand (fans etc) you are in a marginal place if the batteries are in need of charging also.

We traveled in a boat with a frig that had a compressor and between ports for 4 to 8 hours we just turned the unit off or to a minimum setting to save the alternators.

Later Ed

[Jerry Carr]

Terry, we have an all ele. coach 06 thunder, I don't have an issue with the frig, we only have 4 wet deep cycle Batteries on the house side and we do some dry camping I find that we can make it overnight with no APU running.  I think we have the inverter set to auto start at 12.7 The newer energy star frig is really very good on energy I doubt that it runs much going down the road.
  

[Gary Wolfer]

I would check the battery isolator. The alternator  passes current to the isolator then separates the current to the chassis battery and the house batteries Me thinks! The bird changes current from the house batteries overflow to the chassis batteries when the house batteries are fully charged. I would check the output from the isolator to the house batteries. I am just a novice not a tech but sounds logical to me.

[Joel Ashley]

Gary, your scenario is right when the inverter's charger is doing the work while plugged into post power.  But in this instance it is reversed.  The BIRD manages the distribution of the charge current regardless of voltage source.  When the alternator has worked to get the chassis bank up to 13.3 volts, which isn't usually long after startup, it then moves current to the house banks.

Terry, your BIRD, if it is like my '06, is a little black box device mounted on the inside of the main fuse compartment access door, and has several wiring connections along its bottom edge.  This compartment is gray, above your batteries, and between your two master battery switches.  Upon opening the door you will note the Big Boy (isolator relay) solenoid staring you in the face front and center.  But you want to carefully check that all the wires are snugly fastened to the BIRD's bottom edge connectors and that they are all free of corrosion and damage, and that none of the wires have been damaged by getting caught in the door somehow.

This may not be your issue at all, but is a simple thing to check.


This may be of some help:
http://www.beaveramb.org/PDF/PDF%20Manuals/intellitecbigboyandbird/BIRD.pdf

Be aware that the above reference doesn't show the one extra connection yours probably has for managing your genset's output.

Joel

[Gerald Farris]

Gary,
On a coach that is factory equipped with a "BIRD" system, there is no battery isolator. The engine alternator is tied directly to the chassis batteries, and the "BIRD" system uses the "Big Boy" relay to accomplish the same result that the battery isolator does on your coach. The "BIRD" system also replaces the Echo Charger that was used on SMC era coaches.

Gerald

[Terry Melot]

Joel, thanks for the info and the link.  Found the BigBoy and the Bird.  No loose connections.  All in that cabinet looks new. It has stayed nice and dry, and clean.  If I were in Bend I'd go see Jeff at Bend RV Service. I'm sure he could put his finger right on the problem. It still could be a bad cell in one of the house batts, as you or someone else suggested. They are older. Unknown how old. The date code tabs were not removed when purchased.

[Bill Sprague]

Bill, reading the 12.3 on the Aladdin while driving. When we stopped and plugged into shore power, the amps going to house batts was 60-70 amp for about an hour.

Terry,

You are getting good help here, so I can't add much, if anything!

It has been mentioned many places and you may already know this.  But, don't "over work" your alternator.  They are designed to quickly replace the energy used when a truck starts and then keep things running.  They were not designed to sustain high loads for long periods.  According to one long gone Monaco rep, the leading cause of alternator replacements under warranty was charging house batteries that were discharged from dry camping while driving home.

The Monaco rep suggested the long term load caused the alternator to heat up.  When hot, the bearing life is shortened which leads to early failure.  

The acid test is to touch it!  It will be normally warm to the touch, not hot.  

The Monaco rep's solution was to run the Onan for charging house batteries for the first hour or so if departing with discharged house batteries.

Marty Schenck recently replaced his Norcold with a Samsung on a 4 house battery system.  He paid attention to the differences in electrical load while driving and found it to be negligible.   He noted that there may be a marginal difference if the "Ecco" mode is selected on the Samsung fridge.  

Based on what Marty showed me, I doubt your fridge is creating an excessive charging load.  My hunch is that you are right about an old battery causing the situation.   Can you test the various cells with a hydrometer?   My second hunch, based on your suggestion the batteries are old, is you have dirty battery terminals.