Very nice posts on the topic
I am in total agreement with most of the advantages of converting to lithium and I recognize that people like Scott have put a lot of thought into doing it with bundled packs. However, I feel that a good drop LiFeBo4 battery like the Battle-Borne brand has solved many, if not all, of the problems solved by well-designed systems with cells in bundled packs through complex design and sophisticated programming of the BMS.
Specifically, it is worth pointing out that each Battle-Borne battery comes with its own BMS and is protected against over and undercharge. In addition, because these batteries are connected in series-parallel configurations (for the 12Volt) and in parallel configuration (for the 24 Volt), each battery responds to its voltage and current individual conditions.
Because each of the batteries in a bank is slightly different from the others, as the battery bank is being charged, or discharged, not all the batteries shut down at the same time. For example, as the charging voltage approaches its max pre-programmed value, the battery bank current drops progressively from the max charging current to zero within a few minutes as each one of the batteries reaches its maximum degree of charge. This feature avoids the major inductive voltage that occurs when the full battery bank is shut down instantaneously by a single BMS. The combined behavior of the many BMSs in a bank also makes the need of adding an acid battery to the bank to protect against the problem created by a single BMS.
I believe that, aside from the extra cost and lower energy density of the drop batteries compared with the cells bundled packs, the drop batteries allow for a simpler system design and I would argue that they can be a very good alternative when converting to lithium.
I installed my 400 ah Battle-Borne bank more than 2 years ago and have had no problem with them. Other better-known boats living off the grid such as Delos and Sophisticated Lady, have used these batteries for much longer times without reporting any problems either.
Below is the list of changes I did to Ipanema’s electrical system to make sure the new batteries were safely installed and protected. Some of these changes were dictated by the specific needs of cruising in 60 Hz territory. The philosophy was to minimize the changes in the original electrical circuits and keep the design and operation of the system safe and as simple as possible.
1) I had already installed two solar panel arrays in parallel with individual solar controllers that I set with Lithium battery settings.
2) I had previously installed two Mastervolt battery chargers, 60 amp, and 100 amp, replacing the ones that came with the boat and had failed. This installation was very simple and did not require any new wiring. Both chargers work with 50 or 60 Hz and, although when I bought them I was not planning to switch to lithium, they could easily be set for charging Lithium Batteries. I think that based on cost I could have replaced the chargers with inverter-chargers if I had thought of switching to lithium then. However, retrospectively I realize that it turned out simpler and more efficient to keep the inverter separate from the chargers, particularly on cruising grounds where the AC can be 50 or 60 Hz, as will be clear below.
3) I had previously installed a 350 wat Superwind generator that came with a voltage controller preventing it to generate more than 18.8 volts. This is the max safe voltage recommended by Battleborn and is rarely reached for a long time.
4) The first thing I installed was the new Victron Smart Battery Monitor 712
5) My boat came from the factory with a 60 amp 24 volts alternator which also has its output limited to 28.8 volts.
6) Although I installed a Sterling Alternator protector I don’t think that it is needed with drop Battery banks since they have each its own MBS and never turn off simultaneously. I also installed a temperature sensor with an alarm that I monitor when using the engine for long periods of time starting with discharged batteries. So far temp has never been above 60 C.
7) I installed a 5 KW Victron Phenix inverter (24V-220vac, 50 Hz) in the space adjacent to the nav station and battery box. Although at a very short distance from the batteries, the inverter required heavy gauge cables with appropriate circuit breakers and switched by the main DC switches to the batteries. I did not have to change the cables between the switches and the batteries as they can handle well the 500 amps used by the bow thruster. This inverter allows running at the same time the water maker and two air-con, or the two washers, or the water heater or my Nespresso machine, or any combination of them. For example, I can run the watermaker from the inverter for one hour (240 liters) and then turn the generator to run the water maker and the battery chargers for another hour making a total of 480 liters with one hour of generator working close to max power and end up with a fully charged battery bank.
8) The power output of the inverter required a single and much smaller 3 wire 30 amp cable that was passed to the engine compartment to connect to the main AC input of the boat. This was done by adding one extra outlet to the US-version white box with two outlets: one for the 220 V and the other for the 115 V transformed to 220V. This connection gives power to all the AC outlets and appliances of the boat. The operation of this system is quite simple. You just connect the plug leading to the full AC system to the outlet of your choice depending on whether you have shore power or want to use the inverter output. A similar system could be accomplished with a proper rotary switch. By the way, independent of which outlet you are connected to, the automatic relay switch by AMEL still works and will disconnect the AC input power to the boat and connect instead the power from the generator. The only problem with this system was that if you use the inverter before and then run the generator and charge the batteries when you turn off the generator, the batteries will continue to be charged, but this time by inverter output from the batteries themselves, creating an infinite loop and all kinds of alarms on the inverter (not good). A simple solution was to add one NC relay to the line powering each of the battery chargers that were activated (opened) if the inverter power was connected. A full AC and DC circuits diagram was posted earlier
9) The previous owner had installed in the same place I installed the 5 Kw inverter, a 2 KW 50 Hz inverter that I kept as a backup and, connected to an extension cord, it can give 220 volt 50 Hz current to either of the 3 frequency sensitive appliances (washers and microwave).
10) I also installed the Victron CERBO GX that allows me full monitoring via the internet of temperatures, voltages, and currents and, in the future, to turn on and off the generator automatically (Project in progress)
11) I have been full-time cruising in the Caribbean since 2019 and tend to spend about 50% of our time on marinas with the rest of the time off the grid. To make sure that the batteries are not overcharged when the boat is left connected to shore power for long periods of time, I used the programable relay from the Smart Battery Monitor Victron 712 to control the AC input to the 60 amp battery charger. The relay is programmed so that shore power automatically charges the batteries up to 80% and stays off until the batteries reach 30% capacity. With this system, while in a marina, I can leave my fans, refrigerators, and freezers running with the lithium batteries without worrying about over-draining or over-charging them.
12) While off the grid, in the tropic dry season I have enough solar and wind power to avoid using the generator that I only run once per week to exercise it while making water and washing clothes
In summary, the use of Drop Batteries by Battleborn, allowed me to make the conversion to lithium minimizing the changes in original AMEL AC circuits and creating a system that is safe, easy to use, and reduced to a minimum our need of burning fuel using the generator.