What do you need?
Just as there is no standard size of battery for an RV, there is no one size fits all for battery management either.
Typically we build a set-and-forget system that prevents over discharge and over charge, but most people like to see the state of their battery and we provide the means to do this.
However, a very simple logger can also be used as a battery monitoring system (we can't call it management, because that becomes your job in a simple system)
A BMS can refer to either battery monitoring, or battery management.
With battery monitoring, you become the manager.
Battery management, in varying degrees, can do the whole lot for you. Some give you warning signals and want you to do something, some just do it and don't tell you. Some are a combination. Depending on the quality will depend on what you get and how well it will work for you. You can spend quite a small amount on a battery management system, but we urge caution on saving money on the system that has the job of protecting your investment in your battery.
We can install a monitoring system where an alarm is sounded if a cell goes outside its safe (ie; avoiding cell damage) operating range, and the operator is left to determine the next course of action. eg; stop charging or turn off the load. This works fine as long as someone is there to monitor the system and knows what to do when an alarm sounds.
The next level will stop the charging to protect the battery from damage and sound a warning alarm if the cell voltage goes higher or lower than the safe range. Again, this requires the operator to be there to hear the alarm.
A full control system - the system that we strongly recommend and most frequently install - controls the charging, gives a warning if the charging voltage goes out of range if something has failed, gives a warning if more than 80% of the battery capacity has been used. If nobody is there to hear that warning, the next level disconnects the battery to save the battery from damage. You may lose the food in your fridge, but it will be somewhat cheaper than replacing your battery. Our full control system will also automatically stop charging when your battery is full.
You can save money on many things, but be very wary of saving money on your battery management system.