Smart Battery - BBB Rating
Any LFP battery with an internal BMS & contactor
that lacks external communication to the DC charge system for proper safety shut downs, should really be avoided for use on board a boat.
Also, please check with your insurer before making any conversion to LFP.
Simple questions:
Let's say your alt regulator or inverter/charger have a hiccup or programming glitch and push the LFP battery to a disconnect/open circuit while charging.
What happens to everything on your DC bus, including navigation equipment, when the voltage transient, caused by an open circuit load dump, shoots your DC bus through the roof?
I know of no regulation circuitry that can react fast enough, with a charge source at full bore, to eliminate the possibility of a voltage transient causing damage to your gear. This includes alt regulators, inverters and other charge sources.
What happens when an unbalanced or out of balance cell (most "drop-in" batteries use lots of cylindrical cells) causes an end board temp sensor to shut one battery down under a high load or during charging? Are the remaining low amperage safety switches capable of handling this load?
What happens when the now different SOC battery automatically re-engages with the rest of the bank? Manual resets of any type of safety type breaker are an ABYC requirement so sealed batteries that re-set, on their own, already don't meet parts of the ABYC standards..
There is a reason the ABYC is working on a standard to address high capacity lithium-ion batteries.This work has been on-going since 2014..
"
Drop in" Lithium-ion batteries, or batteries that
lack external communication, communication that can
properly shut down charge sources BEFORE a disconnect occurs, is just one of the issues of "drop in" batteries.
Look into how Victron, Mastervolt & the OPE-Li3 / Lithionics LFP batteries all do their BMS systems before you consider a drop-in LFP battery. These batteries are all designed for marine applicable use. LFP batteries should not be purchased based on price, in fact this is the worst way to buy them. Of the three brands mentioned above the OPE-Li3/Lithionics battery has passed the most third party safety testing.
A sealed LFP battery that can't externally communicate is simply sales guys trying to get into your pants like a cheap prom date. These "boxes" were initially designed to work on the sides of telephone poles in China to run solar lighting, hence the very low BMS safety switch current ratings. The fact that someone slaps a
marine sticker on it does not make it such nor does it make it safe for a marine use installation.
Ask yourself what happens when the ABYC standard is finalized and your "
drop-in" battery does not meet the minimum safe design and installation requirements?
If you want LFP then at this point Victron, Mastervolt or the OPE-Li3 systems from Bruce Schwab/Lithionics is the way to go. I do know some "drop-in" companies claim to be working on external communication but I also know this is a ways out.
If designed properly, used properly & installed properly LFP can be great but like many things is is NOT just a battery is it a complete system approach in order to do this correctly.
This may help give some more background.
LiFePO4 Batteries on Boats