Details about the Winnebego Battery Interconnect Manager.

[FilterGuy]

Folks,
I recently did an upgrade on a 2015 Winnebego where I had to learn a lot about their 'Battery Interconnect Manager' and 'Boost button' I thought I would share what I learned here in case any of you run into this. (From what I can tell, Winnebego had the same setup for several years.....for all I know, they still do).

The Battery interconnect manager is a system that has a relay that connects the Starter and House batteries under the following conditions;

1) Relay is turned on if:

a) Ignition is on for 20 seconds &​

i) 2 minutes have passed since Relay last turned off​

ii) & Coach Battery voltage low and needs charging Chassis Battery has a charging voltage​

ii) & Chassis Battery is Less than 15.5V & Generator is off ​

b) Ignition is off &​

i) 10 minutes have passed since Relay last turned off​

ii) & Chassis Battery voltage low and needs charging & Coach Battery has a charging voltage​

iii) & Coach Battery is less than 15.5V​

2) Relay is turned off if:

a) Ignition goes from on to off state​

b) Relay has been on for 1 hour (prevent overcharging and allow to view separate voltages)​

c) Anytime Ignition and Generator are both on.​

d) Anytime either Battery goes above 15.5 volts for 30 seconds.​

The RV had Lead Acid batteries for both the starter and house batteries so this was a nice way to have the alternator charge both and if you had a charger on the house battery it would also charge the starter battery.

All of the above is controlled by a module made by Precision Circuits (Manual Here)

Separate from the control module there is a button on the dash called a 'boost' button that will energize the relay. This lets you get a 'pushbutton' jump start from your house battery if your starter battery gets drained.

The following diagram shows how it is all hooked up.




(This diagram is a modified version of an incomplete diagram provided by Winnebego.)

The above works great when the house and starter batteries are both lead acid but if you want to change the house battery out to LiFePO4....not so much.
* Having the alternator directly charge the LiFePO4 is a good way to burn out the alternator
* A LiFePO4 charge profile is not the best thing for a lead-acid battery.
Consequently, the Precision Circuits control module needed to be disabled. I came up with two ways of doing this.
1) Completely remove the Precision Circuits control module
2) Fool the module into always staying off by wiring a constant 12V to both the Gen-set pin and the Ignition pin of the control module. (See 2C of the functional description above)

For this build, we opted to completely remove the module and did not try 'fooling' it.... but I do not see why fooling it would not work. The result looked like this:



Notice that since the boost button can energize the relay independent of the control module, the jump start function still works.


Here is a pic of the control module after it was removed.



Notice that the control module mounts directly on the primary and secondary wiring posts of the relay.

FYI: The Coach Disconnect and Chassis Disconnect in the above diagrams are latching relays that allow you to disconnect the coach and chassis batteries from the system while not in use. This helps prevent parasitic loads from draining the batteries. Since they are latching relays, it requires no power to keep them either on or off.

FYI 2: We also installed a Victron Orion TR smart to charge the batteries from the alternator in a controlled fashion. That had its own set of issues that are discussed here: https://diysolarforum.com/threads/victron-orion-engine-shutdown-detection-is-it-worth-it.45125/

 

[pvdude]

Thanks for posting that!
I had no idea the circuits were so complicated.
(Guessing our 2017 Winnebago is similar).
So far, the only modifications I have made in that area were to replace the coach batteries w/ Trojan T-105AGM's, and install an "Amp_L_Start" to keep the chassis battery charged.
I leave the coach power switch on all the time, park where the Sun can find the solar.
The Victron SmartSolar MPPT 100/30 works great to keep all charged.
The Trojan AGM and the Mercedes "gel" chassis battery seem to coexist OK.
When the 4 year old Trojans require replacement, I would like to investigate a more advanced battery technology, but not sure if the complexity of all the mods would be worth the added $$$ and effort for us.

 

[FilterGuy]

When the 4 year old Trojans require replacement, I would like to investigate a more advanced battery technology, but not sure if the complexity of all the mods would be worth the added $$$ and effort for us.

The complicated part was figuring it all out. We were getting strange behaviors on the system that had us scratching our heads. Once we understood how it worked it was not very complicated to understand what to do. It is a bit of a pain to get out, but once the controller module is removed everything is a lot simpler and works as expected.