Battery Disconnect Issues

[bt1013]

I have a 2018 FR3 29DS. Recently the batt disconnect just stopped working. Its lamp is lit all the time, no matter the position of the toggle. And when toggled, there is no "clunk" heard when switching on or off. Doesnt make a difference if shore power is on or off. Then after I pulled batt cables off, and reconnected cables, at some point the disconnect switch started working again like it should. Now after the RV has sat a couple days... same thing, the swith is not connecting/disconnecting, and its lamp is always lit. Any ideas about this ghost?

[bubbles]

Sounds like it may be a bad disconnect relay or possibly a loose connection on the switch. This Georgetown diagram identifies the rocker switch wires and their function interconnected to the BCC. It's not an FR3 BCC drawing but the disconnect switching is the same. It may help.

[bikendan]

Moved thread from the Tech and Repair section to the FR3 sub-forum for better help from other FR3 owners and factory support.

Sent from my SM-G781U using Forest River Forums mobile app

[bt1013]

Thankyou!

[ForestGump34DS]

Originally Posted by bt1013

I have a 2018 FR3 29DS. Recently the batt disconnect just stopped working. Its lamp is lit all the time, no matter the position of the toggle. And when toggled, there is no "clunk" heard when switching on or off. Doesnt make a difference if shore power is on or off. Then after I pulled batt cables off, and reconnected cables, at some point the disconnect switch started working again like it should. Now after the RV has sat a couple days... same thing, the swith is not connecting/disconnecting, and its lamp is always lit. Any ideas about this ghost?

I had a similar problem with a Thor motorhome....no "clunk" when pushing the disconnect switch. I replaced the 5 amp (blown) fuse and it worked for several cycles, then blew again. I replaced the disconnect relay and that solved the problem. I believe you will find the fuse & disconnect relay in your battery control center (in battery compartment) under the BCC cover.

Another symptom I had was with no shore power hook up, the 12 vdc house lights would still work, meaning the disconnect relay was always in the "connect" position.

Good luck....

[bt1013]

Thankyou. I had accessed the BCC and checked all fuses (all good). I recall a black component on the BCCs motherboard. Its a square block about 1.5" square. Im assuming that may be the relay. I will look again.

[rk06382]

Originally Posted by bt1013

Thankyou. I had accessed the BCC and checked all fuses (all good). I recall a black component on the BCCs motherboard. Its a square block about 1.5" square. Im assuming that may be the relay. I will look again.

Please go to RV Custom Products web site & download the Forest River SDC-107 BCC Test Procedure (pdf).

My SDC-107A died a few years ago. See: My coach batteries stopped charging from the alternator. (Bad SDC-107A).

See SDC-107A Battery Control Center Schematics below:





I was also able to call tech support. (562) 921-8353

[ForestGump34DS]

Originally Posted by bt1013

Thankyou. I had accessed the BCC and checked all fuses (all good). I recall a black component on the BCCs motherboard. Its a square block about 1.5" square. Im assuming that may be the relay. I will look again.

I took a couple of pic of my BCC....trying to identify the disconnect relay for you (and for myself) and believe it is located behind the circuit board on the right hand side of the bus bar. Notice on the black cover it shows the "Coach Disconnect" on the right side. If you decide to take things apart to check that relay, I would advise taking pictures and labeling the wires !!!

[bubbles]

Originally Posted by ForestGump34DS

I took a couple of pic of my BCC....trying to identify the disconnect relay for you (and for myself) and believe it is located behind the circuit board on the right hand side of the bus bar. Notice on the black cover it shows the "Coach Disconnect" on the right side. If you decide to take things apart to check that relay, I would advise taking pictures and labeling the wires !!!

You have the new BCC and not the same as the OP's.

Originally Posted by bt1013

Thankyou. I had accessed the BCC and checked all fuses (all good). I recall a black component on the BCCs motherboard. Its a square block about 1.5" square. Im assuming that may be the relay. I will look again.

Tyhere are 2 relays under the board. Here they are.

[bt1013]

Thankyou!

[Rescue.Dogs]

Where can I find this and similar schematics for other models, specifically 2023 30DS?

[rk06382]

Originally Posted by Rescue.Dogs

Where can I find this and similar schematics for other models, specifically 2023 30DS?

I received the FR3 Battery Control Center Schematic 5-31-16 117963A.pdf from Forest River in 2017.

[bubbles]

Rescue.Dogs This would be the BCC that you have. Haven't seen a schematic (wiring diagram) for it yet. It uses 2 BIM's and is much simpler than the previous SDC-107A BCC. When you click on it it will appear right side up.

[Rescue.Dogs]

Originally Posted by bubbles

Rescue.Dogs This would be the BCC that you have. Haven't seen a schematic (wiring diagram) for it yet. It uses 2 BIM's and is much simpler than the previous SDC-107A BCC.

Thanks Bubbles. It will be good to have all this information when going over the coach pre-delivery.

I will try and hit up Forrest River for complete schematics of the whole coach. Not sure how far I will get.

The Precision Circuits 8421 in the newer coaches is a lot more opaque than the SDC-107A in older ones. Precision Circuits website gives almost no information about what the product does. I had to study the ample documentation for SDC-107A provided by Custom RV Products to understand what SDC-107A did, and then assume that the new device does basically the same.

On the plus side, the Precision Circuits BIM (Battery Isolation Manager) look quite robust. I wish I did not have to resort to reading their patent to understand what was special about them and how they worked. To their credit, their patent is one of the most well written patents I have seen.

Regards.

[bubbles]

Originally Posted by Rescue.Dogs

I had to study the ample documentation for SDC-107A provided by Custom RV Products to understand what SDC-107A did, and then assume that the new device does basically the same.

From my limited vantage point that would be my assessment.

[Rescue.Dogs]

Originally Posted by bubbles

From my limited vantage point that would be my assessment.

Thanks for the confirmation.

"Basically the same" is good enough to get the big picture assessment and to debug simple problems. But it is a dangerous trap if you have a complex failure.

I have been bitten with that one a few times in my almost 40-year engineering career.

On the plus side, after the last post, I wrote an e-mail to someone who was looking for a simple latching contactor for a project, telling him about the Precision Circuits BIM. Doing a bit more research and writing about it has me convinced that it is a SIGNIFICANT improvement over the "standard" latching contactors on the market. But I am assuming that the excellent concepts described in their patent are backed by at least good engineering.

Another gem from my nearly 40 years: An incompetent designer can turn the most elegant concept into the most unreliable product. Unfortunately, I have seen that one more times than I can count

Regards

[disoswam]

After buying new batteries 3 times I finally put the battery disconnect on the wire coming from the coach battery so it actually disconnects EVERYTHING. I installed a disconnect relay that automatically disconnects when battery voltage drops below 12V if I forget to hit the disconnect button.

[bubbles]

Originally Posted by disoswam

I installed a disconnect relay that automatically disconnects when battery voltage drops below 12V if I forget to hit the disconnect button.

A typical rv battery disconnect relay is a latching relay (12Vdc applied momentarily to energize in one condition and 12Vdc applied momentarily in reverse for the other condition) which does not present a load to keep energized. Your disconnect relay is a continuous duty (continuous load when energized) relay that requires power applied to keep energized.