So we have carefully thought about the tradeoffs after reading this chapter (where I cut through all the fanboy crap to what really matters), and decided that lithium batteries are the way to go for our offshore voyaging boat.
And we have figured out how much usable battery capacity we need and which charging sources and output power are required to keep up with our usage, as well as whether our system will be 12 or 24 volt, all covered in earlier chapters in this Online Book.
Now what? What gear should we actually buy?
Sure, we can dive into a hundred YouTube videos, but most are by someone who has never, or rarely, been offshore voyaging, and, worse still, many of the presenters could not explain ohms law1 if their lives depended on it—being a great presenter can mask truly stunning ignorance.
Or we can read who knows how many manufacturer web sites, reviews, and/or videos claiming that one particular lithium battery and BMS is best, or best for the money. But how do you decide who is making sense and who is full of shit and/or just trying to make a sale?
And even if we can figure that out, there is no best, there is only best for each of us.
To solve these problems I’m going to explore how each of us can develop our own set of buying criteria so we can cut through the noise to find and buy the best system for us.
The key points that are vital to understand are in the blue (tip) and pink (alert) boxes; that said, it will make more sense if you read the whole article carefully.
Also, I have used photos of various equipment to illustrate the article, but that does not mean I’m specifically endorsing that piece of gear.
What Matters To Us
The absolute number-one thing we need to fix in our minds before we go any further down this lithium-battery system selection road is that the needs of offshore voyaging boats are different and more stringent than pretty much any other usage case except aircraft.
Don’t Look To RVs (Campers)
For example, a system designed for a recreational vehicle (RV) is useless on an offshore voyaging boat because:
- Lithium-battery system load dumps on an RV don’t result in the power steering shutting down (think autopilot), the headlights going dark (think nav lights), and the dials blinking out (think plotter and instruments) in the middle of the highway.
- RVs generally spend a lot more of their time under power and have more room for solar panels in relation to their needs—an RV is more like a motorboat than sailboat.
- Most RV campers spend a lot more time on shore power.
RV lithium-battery systems do not supply mission-critical safety systems (driving), offshore voyaging boat systems do.
It’s also important to understand that RVs are a far bigger market for lithium-battery systems—for example, less than 10% of Wakespeed WS 500 alternator regulators are sold to boat owners—so most of the documentation and suggested configurations we find on the internet do not apply to us.
Compare Against a Benchmark
Next we need to compare against the long-proven solution, a well designed and installed lead-acid based system, and be realistic about what we are taking on when we leave that behind:
- Installing a lithium system that increases the chances of an electrical blackout is bad seamanship.
- If you doubt that, please read this before going further.
- Lithium systems are way, way more complex and intrinsically less reliable and fault tolerant.
If we install a lithium-battery system that’s anything less than done right, we will have taken a huge step backward. The ocean doesn’t give a shit how cool our electrical system is, it only cares about how functional and reliable it is.
Good News, Bad News
The good news is that today we can build a lithium battery-based electrical system that’s makes the offshore voyaging boat grade, and even do that at a relatively reasonable cost.
The bad news is that it’s on us to figure out how to do that in a seamanlike way, since there are no turnkey systems specially designed for our needs.
Actually, there are from Ocean Planet Energy, but even if we decide to buy the whole system from Bruce and his good folks (highly recommended), we still need enough understanding to know what he’s talking about, and to install and maintain the system right; yes, even if we pay someone else to do the actual work.
Why I’m Writing This
But, before I dig into the technology, this article and how it will unfold was, as happens so often, inspired by a member comment:
Right now my hang-up is why LFP communication with the Alternator Regulator is necessary, and I have heard no reasonable technical explanation from anyone yet.
I have to say that when I first read that I was a little put out. After all, I have written a complete Online Book, much of it explaining just that in detail. If you are too lazy to read it…yada, yada, yada…
But then I realized Rick has a point:
- I need to explain this more simply and in one place, rather than scattered throughout the Book.
- I also need to come up with a solution for those who don’t want to go that far or already have lithium batteries that don’t communicate; often, but not always, called “drop in”.
And then, once we have covered that off, we need a simple, or as simple as it’s possible for me to make it, list of criteria we can use as we buy stuff.
By the way, if you were wondering why there was no article or tips last week it was because I spent a ton of time researching for this article—this stuff is still complicated!
Let’s do that.