Salt Batteries CATL Naxtra Drop-In – Some Thoughts Before You Buy

[Dan Corcoran]

We’re likely to see new “drop-in” batteries on the market before January. Before anyone rushes to upgrade in Spring, maybe because your batteries didn't make the winter, here are a couple of points worth keeping in mind.

1. Class Rules

Our class rules need to be updated to keep pace with new battery technology. This is something we should address as a club before members start fitting these batteries.

2. Not a Drop-In!

As I’ve said in previous posts, don’t assume “drop-in” really means drop-in. Even though these batteries are advertised that way, are the same form factor as lead acid batteries, and are not lithium they can still create problems.

Yes, you’ll find YouTube videos of people driving screws into them or cutting them with saws to “prove” how safe they are, our boats’ electrical systems aren’t designed for them. While lead acid batteries fade slowly when overworked, the internal Battery Management Systems (BMS) of new battery types shut down suddenly, which can damage some electronics in addition to leaving you suddenly without power.

3. Naxtra, likse LiFePO₄ , needs battery redundancy or a mixed chemistry setup (one new battery with one lead acid, and a DC-DC charger between them)

The LiFePO₄ batteries others are using today are excellent, but they still need proper system design. That means redundancy, larger fuses (ABYC requires bigger fuses to manage short-circuit fire risk), upgraded charging systems, accurate battery monitors, improved battery switching, and an extra cable to isolate the starter and alternator which right now typically share a single cable on a 109.

4. Why Owners Will Look at Naxtra

LiFePO₄ became attractive because it could be charged rapidly closer to full (around 95%) far faster than lead-acid (which slows at about 80%), which reduces engine hours and wear. It also stores more power per pound and, if you do the installation yourself, can be cheaper over the life of the boat. It also appears to weigh less, if you forget to count in the weight of the upgrades needed on a 109. It can actually weigh 50 lbs less if you equip your boat today with far more battery than the 150Ahr class rule minimum, e.g. fill your battery compartment with 3 big lead acids totaling 600Ahr like the former owner of my boat did.

5. The comparisons will be confusing

You may read that Naxtra isn’t as good as lithium batteries. For boat use, they’ll be nearly as good, with the main drawback being slower charging unless you install two in parallel to soak up all our alternators can put out. They’re not as energy-dense as the lithium in your phone, but when compared to LiFePO₄ (the standard for marine use), the difference in energy density is minor. Some claims can also be misleading, for example, Naxtra is marketed as safer because it’s less prone to thermal runaway like when a smartphone has a manufacturing flaw, but marine battery LiFePO₄ is already very safe in that regard. In short, there’s no reason to rip out a properly installed LiFePO₄ system to switch to Naxtra.

The real differences are price and perception. Naxtra will likely cost about about the same as a premium lead-acid. At that cost, faster charging / less run time on your engine, more capability fitting in your battery compartment for lower weight, and a projected 20-year lifespan, they’re appealing, but only if the rest of your electrical system is properly set up. Like all types of lithium's and TPPL, you want to have the upgrades to protect you from an electrical short becoming a fire with Naxtra as well.

6. Already have a drop-in?

If these drop-in concerns are new to you and you’ve already installed a LiFePO₄ battery without upgrading your electrical system, please take the time to read the articles posted on this board, especially those in MarineHowTo are excellent, and those on this site more specific to our 109's. If you run an additional battery sized cable from your switches to your engine, isolating the starter from the alternator sharing a cable, you can then follow the advice in more general articles. If you look at my proposed class rule, that provides additional focus on what to look for to compliment your drop in battery. I wrote now and before to help you protect yourself from fire, injury, and long-term damage to your boat’s electrical system. [Bill insert the best location to jump to here. Can you jump to a middle of a thread?]

7. Class Rules

Finally, a reminder: until the class rules change, it’s still lead acid for all J/109 events. If you agree it’s time for an update, join me at the class meeting and support updating the rules on October 22nd 7pm ET. https://j109.org/event/j-2025/?instance_id=702

[Dan Corcoran]

Never mind, new information, early 2026 will not have 12 volt product. First out is 24 volt batteries for heavy equipment.