Chassis Battery

[richmelcole@sbcglobal.net]

I found out that my chassis battery was dead after trying to start my coach.  We have a 2002 Monaco 40 PST and the 8D battery is only about a year old.  Unfortunately we store our coach without power and have to start the genset to charge batteries couple times a month.  I do have solar panel for the house batteries charge but found out the line going to the chassis battery didn't have a fuse installed.  Any ideas to reduce the parasitic draw of the battery?  Rich Cole

[Tom Cherry]

Some variables that I don't know or not totally aware of....

When you run your Genny, HOW do your charge the Chassis Battery?  Based on that year, I don't think there is a reliable system.  The Blue Seas ACR that Van has recommended is a GREAT investment.  OK....quick FIX.  Put Jumper cables from the House to the Chassis when you run the Genny.  That will take care of at least recharging.  Simple and inexpensive....

Take your dead 8D to a distributor....like the Interstate Distributors.  The one in Raleigh has several chargers that can actually recharge or bring back a dead battery.  I had a Vette Battery go dead from lack of use.  I tried recharging with a old beat up 6/12 VDC 10 Amp unit.  NOPE.  The Interstate guy said we can fix it.  They either really ran it down or they have a charging system like your Magnum and they souped it up.  It lasted for many MORE years.  SOME of the sealed batteries can be "opened"  If you still have electrolyte, you are good to go.  If the battery "Cooked" or was over charged....that is actually MORE detrimental.  That is why the Magnum chargers are designed NOT to overcharge or evaporate the electrolyte.

AGAIN....my fix....if you don't have a battery distributor.  Run the Genny with the Chassis in parallel with the House.  You might be pleasantly surprised what high amperage (typically in the 90 range) can do.

There is NOT a lot you can do on the Chassis side.  The ECM pulls power and drains.  UNLESS you want to disconnect the ECM, then there is not (to the best of my knowledge) you can do.  The Chassis Battery Switch does NOT kill the ECM drain.  Remove all phone chargers from 12 VDC outlets.  The Radio's memory is fused...but it typically is fed from the House.  Unless you have some phantom drain....there is not much on that side.  You can use a Clamp On DC Ammeter and check the milliamp draw.

NOW....as I write this....it HIT ME.  Check the Drain (on the battery).  If it exceeds say 25 - 30 Milliamps....you have a PROBLEM.  One of the MOST common problems for battery drain down, per Bosch (and also Leece Neville).....  BAD DIODES.  I had a boat that would kill batteries.  It did NOT do it when new.  I finally used a hand held VOM with an LOW (100 MA and 1 Amp) selection on the switch.  I found that I had about 175 Milliamps of DRAIN.  BINGO.....that killed that sucker every 3 weeks.  Had the Alternator rebuilt.  The folks swore UP AND DOWN....they put in new one.  I took it back.  They checked the boat themselves and saw the drain.  They pulled it apart.  The tech had tested....not replaced.  They fixed and reinstalled.  i could go several months.

NOW....the ECM pulls more....so someone should tell you what a normal ECM drain is.  If you are say 25 Milliamps over that....you MAY have bad diodes in the Alternator.

On the Chassis side...  Unplug or put a power strip or surge supprssor on each TV and HEC and Sat receiver.  Even in STANDBY, these drain power.   

That is my shotgun approach....  Good Luck... 

[richmelcole@sbcglobal.net]

Thanks Tom for responding to my post.  For me to charge my chassis battery when the genset is running I disconnect the generator wire from the BIRD and that closes the relay.  I was looking at the Intellitec BDX Battery Disconnect System as a possible solution.  The relay would isolate the battery by pushing a switch and would eliminate the manual disconnect switch in the electrical compartment.

[Mel S - '96 Safari]

2 hours ago, richmelcole@sbcglobal.net said:

I found out that my chassis battery was dead after trying to start my coach.  We have a 2002 Monaco 40 PST and the 8D battery is only about a year old.  Unfortunately we store our coach without power and have to start the genset to charge batteries couple times a month.  I do have solar panel for the house batteries charge but found out the line going to the chassis battery didn't have a fuse installed.  Any ideas to reduce the parasitic draw of the battery?  Rich Cole

Richard Cole

To eliminate parasitic battery draws: Disconnect/Unplug/Turn Off everything, (and anything), "battery powered" that is not being used or is not needed.

[Tom Cherry]

54 minutes ago, richmelcole@sbcglobal.net said:

Thanks Tom for responding to my post.  For me to charge my chassis battery when the genset is running I disconnect the generator wire from the BIRD and that closes the relay.  I was looking at the Intellitec BDX Battery Disconnect System as a possible solution.  The relay would isolate the battery by pushing a switch and would eliminate the manual disconnect switch in the electrical compartment.

I have the most recent version of the Intellitec system.  A 200A Big Boy and the BIRD D2.  If something were to go wrong.....I could probably fix it.  BUT, I think that putting in the Blue Seas ACR and be done with it.  Van is sharp and others chimed in.  

The Blue Seas contacts and such are better engineered than the Intellitec.  So, my fix might be to just install that.  

Your call....but my unsolicited opinion.  

I STILL think that if your Chassis got killed....you have a BAD diode or something pulling it down.  I still think you might salvage the 8D....but you need to find the culprit.  Monaco was pretty good about NOT loading up the Chassis.  So unless somebody did some wiring to get 12 and used the sneak Chassis, you can't do much.

Find the problem....a cheap VOM has the posts or ports for milliamp draw.  If you want to do some testing.  Hook up the vom for the 1 or 2 amps range.  Test.  Then disconnect the battery terminal at the starter or wherever the alternator is in the circuit. GET the alternator OUT of the circuit.  If you have the same.....not a diode.  BUT, if it drops off to say 25 milliamps or lower, then you know where it is.

I may be off slightly in the ECM....the Diesel may be a little higher. 

[richmelcole@sbcglobal.net]

Tom,  Is the ECM the electronic control module for the Cummins engine?  What I was thinking about the Intellitec disconnect was to install it just to isolate the chassis battery from drains like the  ECM.  Where you suggesting the Blue Seas ACR for the same application? 

Quote

 

 

[Tom Cherry]

Sorry for the confusion.  Monaco has done many things.....some mid year running changes.  The info that I provided is for a traditional system.

You have a BIRD (whichever model) that controls the Battery Boost (typically 200 Amp) Big Boy  Solenoid.   They have uses Trombettas and others also.   The solenoid serves two purposes.  First, when you push the battery boost switch, it fully closes and you get 12 VDC to the coil and the 200A contacts close and then you have an "electro/mechanical" jumper cable.

Second....the BIRD device or controller monitors both voltages on each battery and then energizes (full 12 VDC) the Big Boy is held at that voltage for around 20 - 30 seconds and all the "parameters" in the BIRD device are met.  This has voltage limits so that a depleted battery will not drain the other.

Then the BIRD switches to a lower voltage (3 -5VDC - mine and others runs in the mid to low 3's).  That then allows the Big Boy's coil to remain closed and you have BiDirectional Charging.  OR BIRD.  IF one of the batteries over charges or is getting weaker and will not hold a charge....then the BIRD signal opens and there is no "Big Boy Jumper Cable"

Typically, the cost of the two modules can run upwards of $300.  The Blue Seas ACR will, based on Van's comments, totally replace those components and it also will act as a "Boost" Solenoid.

I have NOT chased the circuits, so I don't know the wiring diagrams.  The Blue Seas unit is probably a bit more robust....

CURIOSITY.....  I measured my Big Boy "BIRD Solenoid Current".  Now I DO not have a clamp on that goes that low....but interesting....  I read 1.4 Amps....  Now the BS ACR says that it keeps a continuous draw of 0.156 (156 mA).  THAT in itself would be sustanctional.

You have not described your system.  IF you have a BIRD that keeps the Big Boy engaged when you have CHARGING (and typically, they don't.  The BIRD has to sense charging current or perhaps VOLTAGE.....then that would be quite a draw.  You need to be more specific about what you have and how it works.

As to the ECM.  nary a clue.  BUT, you can only PULL the fuse for the ECM to disconnect it and I know not where that is.  

All in all....the BS ACR is more efficient.  The continious current rating is about the same.  SO, I would say....if (and this probably does NOT apply to you), some folks are using a 110VAC trickle or maintainer that has (or needs) about 2 amps.....the BIRD/Big Boy would eat up MOST of that.  SO, you would need about 4 -6 amps of charging current.  The OLD rule of thumb...2 amps EACH EITHER the house or the chassis.  Folks that have NO Chassis charging should be (my opinion) using a 2 amp trickle charger to keep the Chassis up.  If you have a BIRD Big Boy that connects them, then odds are your inverter is taking care of the coach and the 1.4 amps of draw for the Big Boy to keep the Chassis charged is not relevant.

Give me more info.....as I am about "guessed" out....  Hope this helps you to understand what you are dealing with.  

Chassis Drain....if above something like 20 mA means you have something OTHER than the ECM drawing current....and odds are, it MIGHT be a bad diode.  OK....a bad diode will not mean that the alternator is not working.  If will work fine....but it will drain down a battery that is not being used.  THAT, you can take to the bank...

[lusgi]

When storing rig for any length of time i make sure the batteries are charged and then disconnect them.

[Tom Cherry]

4 hours ago, lusgi said:

When storing rig for any length of time i make sure the batteries are charged and then disconnect them.

Works great.  Some folks MAY not realized that the Battery Disconnect Switches are not that.  They are PARTIAL disconnects.  On MOST rigs, the inverter and some other things are cabled BEFORE the House Disconnect Switch.  Same thing for the Chassis...  The ECM is always connected or if it is a non-ecm, then you have other issues.  The Alternator is a common issue where the diode "leak" and you get a drain.

BUT, if you disconnect the positive cables on each bank (house and chassis), then that solves that....

Memory also says that the Allison will "reset" the TCM....in that if you have driven a certain way....the TCM learns that.  Sometimes the TCM learns bad things from gentle acceleration and the first things the Tech does is to PULL the power and let it sit for a while.  THEN...it is reconfigured to FACTORY and your driving habits are then "learned".  Along those same lines, the Allison reps at the gathering say to do a ROMPIN' STOMPIN' drag racer start every once and a while to prevent the TCM from getting a bit "lethargic" and it underperforms.  One full throttle start on every trip will not seriously impact your economy and the TCM will shift more like it is supposed to.  That is what we learned from that session...