First off the alternator is there to maintain the battery not fully charge them. I would say yes to you need some type system to charge the battery pack. I no long have our RV , but when I change over from 10 battery system to a 4 lithium battery system it came with a charger. Within 3 months it fried. They install a newer one different maker and we ran it for another year without a issue. I do not know about the B to B charger that you are talking about. The one in my RV took up the space of 3 battery space. They put it in with a fork due to weight.
If you feel you do not need it don't put it in. If your system burns out then you will know you need one. The people who make these system should know what they need in it so it will work and last. I purchase my complete system from a place in Phoenix Az. Sorry I do not remember the name, all paper work went with the RV when sold. I do know that the system is still working due to the fact the new owner sent us a Christmas card letting us know everything is working well on the Coach.
This is one of the places that I contact and got info along with the one in Az. https://enerdrive.com.au/.
The one in Az is not showing up on my web search so out of business or change there name.
