Battery Boost Held ON too Long - What Could Possibly Go Wrong?

[Frank McElroy]

I had an interesting PCB repair last week that I want to share with the group.

A member with a new to him 2007 Signature contacted me to have his Big Boy control board (PCB#6 in RRB) repaired. 

On the board, a copper trace overheated and separated.  In trying to find out why, I asked a bit about the history.  The new owner mentioned that the previous owner said he replaced his big boy with a new one that didn't work and that he would wedge the battery boost to stay ON for hours at a time.  That bit of information explained everything.

The battery boost switch is momentary for a reason.  It is designed to be held ON for minutes - not tens of minutes let alone hours.  In normal operation, the control circuit board pulses 12 volts to the big boy coil to in effect provide about 8 VDC to hold the coil engaged (Big Boy is NOT a latching battery isolator like the Blue Sea ML-ACR).  When you press and hold ON the battery boost, you are providing a full 12VDC to the Big Boy solenoid coil and over time it will overheat, fail AND also burn up PCB#6 in the Rear Run Bay.

Since these boards are becoming hard to find in salvage yards, the board was repaired and is now working just fine.

A word of caution - please don't hold the battery boost switch ON for more than a few minutes at a time.

[Jdw12345]

For the life of me, I can’t comprehend how anyone could ever think that holding down the boost switch is how to solve there issue! I just can’t understand that train of thought! 

[96 EVO]

11 minutes ago, Jdw12345 said:

For the life of me, I can’t comprehend how anyone could ever think that holding down the boost switch is how to solve there issue! I just can’t understand that train of thought! 

Don't know, but I've read of owners using different devices wedged under the switch!

Can't recall ever using the boost switch myself, but, I keep my batteries reasonably fresh!

[Frank McElroy]

12 minutes ago, 96 EVO said:

Don't know, but I've read of owners using different devices wedged under the switch!

Can't recall ever using the boost switch myself, but, I keep my batteries reasonably fresh!

Yes, over the years I've seen the same posts about owners using different devices to hold the battery boost switch ON.  A very bad idea - that's the main reason why I decided to post why not to do it.

As it turned out, the new owner had 2 boards from the previous owner with the same exact failure.  He now has 2 repaired boards.  One he's using and one as a spare for future use if ever needed.

[96 EVO]

My alternator bit the dust on my way south this winter! Luckily my BIRD / Big Boy is functional!

I just ran my generator the rest of the way, and replaced my alternator at my destination.

[Frank McElroy]

2 hours ago, 96 EVO said:

My alternator bit the dust on my way south this winter! Luckily my BIRD / Big Boy is functional!

I just ran my generator the rest of the way, and replaced my alternator at my destination.

Yes, that's a great example of understanding how all the systems in your coach work together and if there is an issue, how to solve the problem as you did.

Years ago, I got a call at about 10:30 PM from a person who I knew and I thought that there must be a problem so I took the call.  He was on the side of the road on a dark rainy night, with no headlights, dash gauges, or interior lights but with the engine running, and waiting hours for a tow.   His domestic engineer was very scared to say the least. 

Since I know he had a Kongsberg chassis multiplex coach, with the house batteries powering the dash gauges, headlights and interior lights, I told him that his Big Boy failed and to just jumper the chassis batteries to the house batteries to start the generator.

That's exactly what he did and a few minutes later, his domestic engineer was thrilled at getting back power to the coach - tow was cancelled and he drove home.

It's all about understanding how all the systems work together and what to do if there is a problem.

 

[amphi_sc]

Understanding BigBoy and control board....

Just curious if my system's operation is normal.  While the Big Boy engages and charges from shore or alternator (BB internal contacts cleaned periodically), I have noticed that after a couple of days on shore power and with the Magnum float charging at basically 0 amps and 12.6 volts the board will decide to disengage the Big Boy causing the chassis to slowly discharge over time (days) ... 12.4-12.3v at the chassis battery posts.  I've verified the house batteries at 12.6v at the battery posts. When I press the boost switch the BigBoy will click back on (temporarily) and the two banks are connected and charge together.  If I kill the shore power breaker, wait a couple minutes, then turn the main shore breaker back on the Magnum cycles into absorb charge around 13.3-13.4v and the BigBoy re-engages charging the chassis back.  If I'm parked for days on shore power this happens and the chassis will slowly drop.  Is the board dropping because the float voltage is too low and I should set a custom setting to raise the float voltage a little?  Otherwise every few days I just kill the shore power for a bit and top off the chassis. I have Lifeline AGMs and AGM-2 setting on the Magnum 2812.  BTW , it appears the AGM (1) setting floats at 12.4v vs the AGM-2 setting 12.6v.  A custom profile could be implemented.

Thanks

[Tom Cherry]

14 hours ago, 96 EVO said:

Don't know, but I've read of owners using different devices wedged under the switch!

Can't recall ever using the boost switch myself, but, I keep my batteries reasonably fresh!

BEN….a definite NO NO.  Read the manual for your system.  We have the NON FULL 12 VDC Big Boy.  There is a device on the swing out door in the rear run bay (the one with the knobs).  It is a Intellitec BIRD Diesel2 module.  It senses the voltages on each bank.  It then controls the Big Boy.  It sends out “Pulsed” voltage.  Measure it….it will be 3 - 4 VDC.  But, if you put it on a “scope”, it is a PURE 12VDC.  But the length of the Pulse or the time ON is only 1/3 or about 3 - 4 VOLTS, averaged.

BUT, if you push or HOLD the BOOST switch, there is a signal sent to the relay that drives the Big Boy and you get a FULL 12 VDC. Hold that down for maybe 5 minutes or shorter….Heat builds UP.  Fries the coil.  

The specs on the Big Boy list CONTINUOUS current or full 12 VDC for maybe 30 seconds….don’t hold me to a precise number….the manual warns you.  BUT, when the BIRD D2 Module kicks in….INSTANTANEOUS 12 VDC….that locks in the coil.  Then after, say a second or so, it drops back and then the control circuit is the Pulsed voltage.

You do NOT have the board (#6) on a 05/06 Dynasty and above that this post is about.  

NOW…..there were….on older models…..a 100A Big Boy.  OK to have full 12 VDC.  There were other “types”, misidentified as a “Big Boy” (Trombetta and White Rogers and others) that WERE full 12 VDC rated.  

The PURPOSE of this response is to WARN FOLKS.  Never EVER put a stupid Golf TEE under a later model Monaco boost switch……you’ll damage the 200A Big Boy and/or “COOK” your Chassis Battery….when you are ON AC or GENNY.

Thanks for bringing it up so we can get the word out….AGAIN….
 

[96 EVO]

5 minutes ago, amphi_sc said:

Understanding BigBoy and control board....

Just curious if my system's operation is normal.  While the Big Boy engages and charges from shore or alternator (BB internal contacts cleaned periodically), I have noticed that after a couple of days on shore power and with the Magnum float charging at basically 0 amps and 12.6 volts the board will decide to disengage the Big Boy causing the chassis to slowly discharge over time (days) ... 12.4-12.3v at the chassis battery posts.  I've verified the house batteries at 12.6v at the battery posts. When I press the boost switch the BigBoy will click back on (temporarily) and the two banks are connected and charge together.  If I kill the shore power breaker, wait a couple minutes, then turn the main shore breaker back on the Magnum cycles into absorb charge around 13.3-13.4v and the BigBoy re-engages charging the chassis back.  If I'm parked for days on shore power this happens and the chassis will slowly drop.  Is the board dropping because the float voltage is too low and I should set a custom setting to raise the float voltage a little?  Otherwise every few days I just kill the shore power for a bit and top off the chassis. I have Lifeline AGMs and AGM-2 setting on the Magnum 2812.  BTW , it appears the AGM (1) setting floats at 12.4v vs the AGM-2 setting 12.6v.  A custom profile could be implemented.

Thanks

Sounds like you may have a charging problem.

12.6V isn't float charging, and is too low for the Big Boy to engage.

13.3-13.4V is float charge voltage. Absorb charging should be >14.0V!

[Tom Cherry]

4 minutes ago, amphi_sc said:

Understanding BigBoy and control board....

Just curious if my system's operation is normal.  While the Big Boy engages and charges from shore or alternator (BB internal contacts cleaned periodically), I have noticed that after a couple of days on shore power and with the Magnum float charging at basically 0 amps and 12.6 volts the board will decide to disengage the Big Boy causing the chassis to slowly discharge over time (days) ... 12.4-12.3v at the chassis battery posts.  I've verified the house batteries at 12.6v at the battery posts. When I press the boost switch the BigBoy will click back on (temporarily) and the two banks are connected and charge together.  If I kill the shore power breaker, wait a couple minutes, then turn the main shore breaker back on the Magnum cycles into absorb charge around 13.3-13.4v and the BigBoy re-engages charging the chassis back.  If I'm parked for days on shore power this happens and the chassis will slowly drop.  Is the board dropping because the float voltage is too low and I should set a custom setting to raise the float voltage a little?  Otherwise every few days I just kill the shore power for a bit and top off the chassis. I have Lifeline AGMs and AGM-2 setting on the Magnum 2812.  BTW , it appears the AGM (1) setting floats at 12.4v vs the AGM-2 setting 12.6v.  A custom profile could be implemented.

Thanks

My advice….PM @Frank McElroy.  He is the expert.  You should set your battery type to the proper configuration.  There is a file ….use Magnum as the key word in the search box.  Then click on everywhere and select FILES.  I wrote it as an aid.  You can also call Magnum.

Frank will have to address the strange behavior, but I, the slightly informed novice, think you have an issue with the board. MOST Big Boy coils, I THOUGHT, hum and or get hot….most of the time…

[96 EVO]

Here's a pic of my Magnum charger / Inverter panel, float charging at 13.7V, with 0 DC amps.

It's been sitting in my driveway, plugged into shore power for close to 2 weeks!

Reason it's at 13.7-13.8V is the battery temp sensor is on, and outside temps got down to mid 30's overnight.

[Tom Cherry]

8 hours ago, 96 EVO said:

Here's a pic of my Magnum charger / Inverter panel, float charging at 13.7V, with 0 DC amps.

It's been sitting in my driveway, plugged into shore power for close to 2 weeks!

Reason it's at 13.7-13.8V is the battery temp sensor is on, and outside temps got down to mid 30's overnight.

Ben….

First….  Your system, which is the same as mine, works as you described….. and that is normal. And the only issue that I expect is to clean the Big Boy.  I actually carry a spare.  So….that is the way, in “theory”, that the Intellitec system was designed to work. As an aside, our Big Boy “sees” less than half the voltage….so when it gets hot and hums….it is totally different from the Dynasty or the system in Al’s Patriot thunder.  His Big Boy will be more than HOT….you usually can’t keep your hand on it as it is HOT..not warm.  And it is twice as loud when engaged or the HUM is pronounced.  That is the way that Intellitec designed BOTH systems….and is normal…..lots of folks are not aware of this…

But…if you go back and read Al’s post about his Patriot Thunder (basically same as any 05/06 Dynasty and up, @amphi_sc does not have “our” system.  He has a dedicated #6 PCB for charging and boost and maybe one other function.  His is not working, it appears, like it was designed.  In theory….from a concept, the two systems should function the same.  But in reality, his system is radically different and more complex than ours and  Frank and Paul are two, perhaps we have others, of the best here, as well as in the country, that can repair the “out of production” board and reprogram it.  It is simple for them as they have the “rig” to test…but when they replace the chip, which is probably 90% of the failures, they have to reprogram the new chip….sort of like reformatting the hard drive on a computer and installing a new OS.

From experience, after a lot of “educatin” by Frank, I know how it works….and can assist in determining whether it is a board or Big Boy issue…but then hand off to someone else if it is a defective board.

You probably already know this, but your comment provided a post to explain it so others with our system or the newer Dynasty can understand the differences.

Thanks….

[amphi_sc]

I did some more research on my untypical low float voltage.  Digging back through my notes on Lifeline batteries I found the suggested voltages. 

 

Then I also came across the Magnum charging profiles.  And then I remembered reading someplace Lifeline had upped there recommendation for the float voltage vs what Magnum had explicitly defined as the AGM profile thus why I moved to the AGM-2 profile. 

But my voltages aren't those.  But Ah-Ha, let's consider the temperature compensation chart.

Okay, what does my remote think about the battery temp.  50°C ... Really!  That's pretty warm so I open the compartment door and feel the batteries.  Nope ... feel pretty much ambient temp not the slightest bit warm to the touch.  I unplug the BTS from the inverter and rechecked the remote.  Float charging voltage is where I would expect it 13.5 not the 12.6/12.7 I was seeing with the -.75v temp compensation.  With no BTS plugged in the remote doesn't compensate.  So I must have a bad BTS thermocouple.  For now I'll leave it unplugged until I see about routing a new one through all the bays/ceiling etc.  What a pain but at least it makes sense. 

Continuing my internal debate. Any thoughts on the old AGM-1 profile vs AGM-2 profile knowing that neither one is no longer recommended by Lifeline.  AGM-2 sets higher voltages that exceed recommended vs the old Lifeline specific AGM profile is a tad too low.  Will AGM-2 risk "boiling'?  Would the old AGM-1 profile not float them high enough?

 

Edited April 26 by amphi_sc
Tried to logically get the pictures on the right inline flow

[96 EVO]

That's better!

Gota love those $0 fixes 👍!