It's really easy for us to spend your money. I'm not a big fan of all the bells and whistles, I like robust, as simple as possible, and as inexpensive as possible. This last one, inexpensive as possible, includes the long term costs of keeping the system running. I look at the cost over 10 years, not just the cost of putting a system in today. Those criteria, robust, simple, inexpensive, are highly dependent upon how one is going to sail. As
@Scott T-Bird stated above, his sailing style to be in port hooked to shore power for much of his boats time. As
@Ralph Johnstone has stated above, he mainly costal cruises and is often in port able to connect to shore power. Each of their stated systems work very well for how they sail. And the devices they recommend work very well for what they want to have for their boat.
You,
@GeneraiT001, stated your desired sailing use is long term cruising. That is also what
@dlochner has been doing. His responses have been directed towards that end.
I have setup my current sailboat also for long term cruising. When I bought my boat a number of years ago, I was working full time and did not have the spare time to delve into various aspects of setting up my boat for long term cruising - especially the conversion from lead acid to a lithium based based system. I am fairly knowledgeable about LA batteries and have been using those kinds of systems in sailboats for a long time. Many decades ago, I was taught how to maintain lead acid batteries by the head electrical engineer of the Hoover dam. Subsequently, I've had decades of practical experience running lead acid batteries on sailboats.
The single biggest cause of LA failures is sulfation. All of your lead acid battery chemistries are based on lead plates (or an alloy) and sulfuric acid (with various additives). The basic process is the metallic lead goes into ionic lead in solution (discharging) and then with a charging voltage applied the lead is redeposited as metallic lead back onto the plates (charging). However, there is a competing process where some of the ionic lead in solution combines with the available sulfur in the sulfuric acid solution and deposits onto the plates as lead sulfate. The lead tied up as lead sulfate no longer will participate in the charging/discharging cycle hence your battery looses capacity. Eventually your batteries are sufficiently degraded such that they no longer function. This process cannot be avoided, but it can be significantly reduced through the process of equalization. When do you need to do an equalization cycle? There is not a single answer to that - it depends on numerous variables. But a general rule of thumb is after any time your batteries have been discharged below about 75% of it's capacity. Now, how often is that on a sailboat?
Equalization should be done with both controlled voltage and current. A power supply that can control both current and voltage at the same time is difficult to build. I use a high end research grade power supply that can do both but that gets a bit complicated. There are a number of modern battery chargers that claim to have the ability to run all the different charging regimes ( see
@dlochner 's post #4 above). What he didn't mention was equalization - but you began this thread asking for "simple"... However, when I have looked at these so called "smart chargers" I have rejected considering buying one. The equalization cycle they run is typically based on time, and that time frame is typically somewhere between and hour and 3 hours. That is grossly inadequate for an equalization cycle. An equalization cycle should be run for about 24 hours.
Now, before a bunch of folk start getting their panties in a wad about that statement - here is a direct quote from the standard IEEE 450
IEEE Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications: "Note that an equalizing charge normally requires that equalizing voltage be applied continuously for 24 hours or longer." There is no way you are going to be able to properly do this in an offshore sailboat.
In my opinion, you should simply discard the idea of charging your LFP batteries through a LA battery. It is not the correct solution for your sailing desires.
Also, going to 400 amp hour LFP - your current alternator is inadequate. At a very minimum you need to convert it to an externally regulated system but you really would be better served by going to a larger alternator with a serpentine belt. Again, I'm going to recommend you get a subscription to Attainable Adventures by John Harries - he has just done an evaluation of alternators that you would really benefit from reading, along with the tons of other information that would be very useful for you....
dj
"switching over to LiFePo is feasible before sailing off into the wild blue yonder"
