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Richard Ritchie

Good to see progress. Interestingly, I see no sign of an external communication port on their batteries in the picture. Maybe they are indeed relying on Bluetooth …

Conor Smith

There is a Hub that connects to each battery with bluetooth. That hub monitors each battery SOC, charge rate, balancing status, ect and aggregates the data. It connects with CAN, N2k, and bluetooth to other devices, including having programable relays to set off various alarms or trigger contactors.

Mike G

Panbo seems to have more detail on the system than is publicly available from Dragonfly. Here’s a quote from the article: “The Hub allows connectivity to other devices via BlueTooth, NMEA 2000, RV-C, Victron’s VE.Bus, and Ethernet.”

What isn’t clear is how the batteries connect to the Hub. A Dragonfly video indicates a wireless mesh.

There is no plan to make all of their existing batteries interoperable with the new system.

Conor Smith

I agree there is little published about the system and the details are still being worked out.

Search for: Dragonfly intelLIgence Hub. The best source, although relatively brief, still appears to be this PDF:

Maarten & Marga Selkie

good point.

I think there is (quite) some confusion about BMS’s and the role they play. In simple terms, an internal BMS protects the individual battery and manages some processes (like cell balancing). An external BMS protects the battery bank (multiple) on system level and manages some other processes, including things like charging to SOC levels, allow/disallow (dis)charge, etc.

Communication from a battery (internal BMS) gives data to the external BMS and the rest of the system (solar chargers, alternator protect, inverters, etc) how to behave so the whole systems works as designed. An internal BMS in a system with multiple batteries can’t manage this as it works on battery level. For a simple system you might not notice the lack of function without external BMS. But systems on boats are often already complex with multiple sources of charging (solar, motor, gen, wind al together). Without external BMS the system becomes inefficient at best and wonky around the design edges or simply unreliable. That integration is a lot harder if your battery doesn’t communicate what’s going on till it simply switches off!

For example. In a system without integration a charger uses an algorithm (read assumptions) on charge voltage, current, etc. In a Victron system, the smart battery tells the BMS what charge current/voltage it actually needs. The charge algorithms are disabled and the chargers use the same voltage etc throughout all chargers to optimize charging as efficiently and safe as possible based on what the batteries say they can handle instead of a charger thinking: “well, I think it should…)

For protection, an internal BMS should be seen more as a last resort fail-stop (again of the battery only). It’s like not having brakes on your car and relying on the ABS to avoid an accident.
An external BMS will protect the system, incl batteries, on system level, including things like warning for load dump, stop discharging at a % SOC to extend battery life, temperature control, etc.

Having a battery that “can communicate” is not enough. The key is that is can be understood by a BMS. E.g., I would look first and foremost if a Batle Born communication is compatible with the external BMS or something else that manages the system. Nice graphs on a smartphone are not very useful if the rest of the systems doesn’t understand the protocol. (Even if it’s NMEA2k.) CANbus beats Bluetooth in my opinion. But Bluetooth seems to work as reliable so far as well if you can’t wire it.

The key is to design the electrical system as a whole. Not to just drop in a Li-battery for more power and cross your fingers. Not even if it is a smart battery used in a not-so-smart way.