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House Batteries Don't Charge While on the Road


johnfr
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It has came to my attention that the house batteries of our '07 Cayman PDQ are not charging when we are traveling on the road. I know that I can not expect the alternator to charge house batteries that are deeply discharged. However, having been connected to shore power just prior to hitting the road, by time we get a few hours down the road the house batteries are not at full charge leading me to believe that the alternator charge is not reaching the house batteries. Our coach has a Battery Boost switch that allows connecting house batteries to chassis battery via a high amperage (Big Boy) relay in emergency situation of chassis battery becomes discharged.

I am trying to determine how the house batteries get connected to the alternator while on the road. I haven't found any kind of battery isolator. Does the battery boost relay activate to connect house batteries for charging? I have attached a couple photos showing the boost relay. Also a pdf file showing a similar 12V DC wiring diagram for a 2006 Thunder coach.

Anyone out there have any idea how the house batteries are connected to alternator for charging while on the road?

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06 Patriot 12 V distribution-large.pdf

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2 hours ago, johnfr said:

It has came to my attention that the house batteries of our '07 Cayman PDQ are not charging when we are traveling on the road. I know that I can not expect the alternator to charge house batteries that are deeply discharged. However, having been connected to shore power just prior to hitting the road, by time we get a few hours down the road the house batteries are not at full charge leading me to believe that the alternator charge is not reaching the house batteries. Our coach has a Battery Boost switch that allows connecting house batteries to chassis battery via a high amperage (Big Boy) relay in emergency situation of chassis battery becomes discharged.

I am trying to determine how the house batteries get connected to the alternator while on the road. I haven't found any kind of battery isolator. Does the battery boost relay activate to connect house batteries for charging? I have attached a couple photos showing the boost relay. Also a pdf file showing a similar 12V DC wiring diagram for a 2006 Thunder coach.

Anyone out there have any idea how the house batteries are connected to alternator for charging while on the road?

IMG_0800_A.jpg

IMG_0798_A.jpg

IMG_0799_A.jpg

06 Patriot 12 V distribution-large.pdf 204.35 kB · 4 downloads

Johnfr, my understanding is the Trombetta relay you took the pic of is not making a connection. When the engine batteries reach a certain charge level the Trombetta closes and attaches both banks together. The older Trombetta relays are known to be copper and get a green gunk inside of them that keeps them from making a connection. You can drill the rivets out and clean the insides of it and bolt it back together and reuse it. Or, as I did, I ordered the silver plated version (same item number as the copper but the last 3 digits are 020 instead if 010) and simply swap it out. 

 

I had this same problem several years ago and I just swapped the old one out. I did take the old one apart and cleaned it to have as a spare. It did have the green gunk inside. Hope this helps and it's understandable.

 

Chad Y

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Chad Y -- Thanks for the comments. I was suspecting that this Trombetta relay might have a dual purpose as when I traced the wiring between chassis and house batteries it seemed to be the only common point between the two. I will see if I can find one with silver plated contacts.

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I was able to confirm with volt meter this morning that the relay is bad.  With engine running chassis battery was at 14.1 volts while house battery was 13.1. I confirmed that 12V was being applied to the control terminals of the relay.  Have a new one on order from Amazon.

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5 hours ago, johnfr said:

I was able to confirm with volt meter this morning that the relay is bad.  With engine running chassis battery was at 14.1 volts while house battery was 13.1. I confirmed that 12V was being applied to the control terminals of the relay.  Have a new one on order from Amazon.

Good deal Johnfr. I had the exact same situation. That should fix you up. Good luck on the swap out!

 

Chad

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  • 2 weeks later...

I was able to get out to the storage site yesterday and replace the relay. That took care of the problem. House batteries now charge when the engine is running.

Thanks for you all's help.

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I cleaned my Big Boy once, and when it needed it a second time, I replaced it (and the BIRD circuitry) with a Blue Sea ML-ACR. A much better solution that costs less than a Big Boy Relay. 
 

This is a simple device that does one thing: connects or disconnects the house and chassis batteries.

 

The features I like about it are

- will charge both sets of batteries from the alternator or output from the inverter/charger

- auto mode as well as manual off and manual combine override via the remote switch or on the relay itself

- LED status indicator on the remote switch that replaces the Battery Boost switch in the dash/side panel

- takes no current to hold it in either position, so does not run hot

- has high current ratings

- sealed from the elements

- senses charging on either bank of batteries to combine in Auto mode

I had previously replaced the diode based isolator and battery boost relay with the ML-ACR on our 1994 Signature and it operated well.

I have helped Vanwill replace the same setup on his 2000 Dynasty and another friend on his 2002 Signature.

In those cases the ML-ACR replaces the isolator, the Battery Boost Relay, and the Lambert style or Trik-l-Amp or Trik-l-Start solution to keep both sets of batteries charged.

For our coach the ML-ACR replaces the Big Boy relay and renders the circuitry that drives the Big Boy unnecessary.

Mechanically the ML-ACR is a similar size as the Big Boy relay and we used 1/8”x3/4” copper bar to connect the ML-ACR to the existing wiring.

We also ran a pair of wires from the RRB to the dash for the remote switch. We could have run one wire and reused the existing wire from the Batt Boost switch.

The switch also needs fused power and ground which we picked up from the FRB.

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  • 2 months later...
  • 3 weeks later...

We also are experiencing the proble of the house batteries not charging while going down the road. Many post mention the bird and the big boy, I have not seen or read any mention of these with our 2002 Windsor. Where would we look to find if we have them? Some mentioned the switch on the dash that connects the 2 sets of batteries (house and chassis), might kick start the alternator to start charging the house batteries but I tried that and it didn't seem to work.

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