I used a Li-BIM in my '00 American Tradition. I have a pdf write-up of the project with some images and diagrams but it seems it is too big to post here. The images may not apply to you anyway so below is the summary I have completed explaining why it was needed and it's benefits. I am sorry if it didn't copy clean.
Integration of a Li-BIM 225 into an Intellitec BBC Model 00-00578.
The Li-BIM 225 is a battery isolation manager to monitor and maintain a connection, as necessary, between chassis battery banks and coach battery banks. It is advised for Lithium coach battery banks over 300AH.
1.) Boondocking - The higher voltage curve of the LiFePo4 would result in the coach bank being above the >13.3v BCC requirement and keep the banks combined virtually all the time. Not an ideal use of coach battery capacity if off grid. The Li-BIM keeps the banks separate unless the chassis is <12.5 and the coach >13.5. Then it connects to charge for an hour and disconnects and repeat as necessary.
2.) Shore power - Again this would result in the banks combined full time by the BCC. This would lead to an improper charging profile (higher voltage than spec) and potential damage to the chassis bank. Resolved by the Li-BIM the same way as #1 above.
3.) Driving - BCC would combine banks for charging which is okay on the surface. However, if the coach bank is sizable (400 AH+) and is significantly depleted, the ability for Lithium to accept massive current with little resistance would cause the alternator to be overworked and could result in the alternator overheating (and possibly worse, read alternator fire). The Li-BIM would cycle the bank connection to 15 min connected/charging to 20 min disconnected and would repeat so long as coach bank was <13.3 (otherwise keep disconnected). This would have the added benefit of lightening the load on the alternator.
Kevin & Kara
2000 American Tradition 37TRS, Spartan MM chassis, Cummins ISC 315
2018 Ford Fusion Energi (Demco Dominator tow bar)