1) Shunt is required for a "good battery monitor" Hall effects work fine but require manual monitoring if your electrical bay is in a difficult place putting in a manual monitor will be difficult to use. I'm sure you can extend the wiring to place things where you'd like but Bluetoothing is the way to go for convenience.
2) Battery monitors are their own system within the system you don't have to be married to any brand of controller some may talk better within their own systems but certainly not necessary.
3)Bluetooth is great as you dont need to waste time putting your monitors in a place that is accessible and useable to be able to see whats going on from the battery monitor. signal is usually good for a 10-15 foot circle around the rv. Victron connect password is 000000 this will connect you to their devices immediately on startup.
4) Battery monitors are a pretty quiet usually misunderstood piece to the electrical puzzle, but absolutely essential to fully understanding and Knowing instantly if you have a battery problem.
There is no one place to learn but this is where I would start.
solar Solar education is ongoing and I started with Bob the solar guy and have moved on to Wills stuff that is pretty rock solid along with other forums including Wills to understand everything that is going on. 4-6 years ago trimetrics was all there was minus the marine market for rvs that is slowly changing.
5)Low cost hall effects and the picture above in the post of the Chinese BM are low cost for a reason. They do not bluetooth and require alot of chineglish to setup and get working correctly. They also require Manual monitoring to see whats going on. some not all dont record your day to day and only spot check whats happening right now. Its a hard pill to swallow but you did want the best and the bmv712 with bluetooth is it right now.
My own personal opinion is I wish I was doing my system today rather then 6 years ago when I started. Like em or hatem Victron solar controllers and all their gadgets like the bmv 712 and low voltage disconnect all registering in a nice handy little app on a smart phone is unparalleled with any other brand on the market. The data these provide is unreal its on demand its programmed with your fingers and you can switch to lithium as you wish without any further purchases.
My morningstar charge controller required a special cable that i had to rip out the bed to get to my controller and custom program the dip switches then download a program to program the custom settings that i had to sit and watch until i fine tuned it for several days with a laptop for lithium the Victron once installed is all done in the app.
To my knowledge Morningstar does NOT have a battery monitor only a small feature on the remote solar controller monitor that records AH in that is manually resetable for the day and TOTAL ah Only available with the higher end solar controllers. MSVIEW was a easy program to learn but the victron is a million times easier doing it on the PHONE APP!
Voltage based monitoring in solar applications is NOT accurate at all. Especially when the sun comes out and having no idea amp hours coming and going you can only rely on amp hours harvested through the morningstar remote meter to guess whats going on with actual SOC. Especially with SLA's or FLA's lithium is a little more accurate as they have little to no internal resistance.
All RV's with batteries are never fully disconnected from the load unless you pull the disconnect switch and wait 24 hours for the static charge to dissipate to find out your "real SOC" for this reason alone voltage based battery monitoring is a waste of time, but it is light years ahead of the really crappy 4 lights of death the rv manufactures put in.
Aside from super expensive highend marine monitors like the rv Tito one or the old school bogart trimeteric monitor the Victron is the lowest cost one.
If you dont care but want to dabble or on a low budget then the cheapy chinese BM or even the Hall effects will serve a better purpose then voltage monitoring your batteries. be prepared to spend time to learn how they work as the cheap droks monitor one way and you have to have 2 to monitor both ways in and out.
