I once heard of a sailor who prided himself on sailing “pure”—no motor, no electrical, just wood and canvas. How he could dock and undock his lengthy craft, threading it in and out of the marina on sailpower alone, was a source of mystery and admiration to me. But the truth is, most of us mere mortals happily rely on the technological convenience afforded by a trusty engine and robust electrical system. It’s that latter part I’d like to talk about today, because there’s a revolution underway in how we power our boats.
To continue reading this article or issue you must be a paid member. Sign in
Join Practical Sailor
Get full access to Practical-Sailor.com – more than 4,000 articles – for just $34.
Join today and save 42% off our full price.
Not only our insurance cover stipulates professional installation, but comprehensive fire-protection, specific to Lithium (Ion and LiPe04), is also required. That’s quite a specialised market (AVD is one – Aqueous Vermiculite Dispersion extinguishers); also several manufacturers have gas suppression systems built-in (SOK is one brand).
Which insurer? Ours does not (State Farm).
All insurance binders have a general duty clause that says something to the effect that improper repairs or modifications can void the coverage. Following ABYC is one common way to avoid this clause.
Thanks for the comment, Richard. Building on what Drew said, neither does my insurance provider (Aviva) does not stipulate a professional LFP install. Rather, they exclude from coverage “The cost of making good faulty or improper material [and] faulty or improper workmanship.” So, as Drew mentioned, following ABYC code (and being ready to demonstrate the quality of your work through plans and pictures) is a sure way to stay within fair bounds. That said, you raise a good point and I heartily agree that everyone should check their policy fine print before embarking on a self-install!
I cover safety precautions, including the importance of lithium-specific fire extinguishers, in part 2, so stay tuned. It should be published soon. While there is no NFPA rating for lithium fires (yet), there are some emerging standards like NTA8133. Look for that mark on the extinguisher of your choosing. For now, AVD is what you want, and I expect we will see more extinguisher options and standards coming to market in the next few years as the lithium space matures.
Fair winds!
Many boats have automatic battery switches, replacing the 1-2-Both switch. It’s my guess that there cannot be a direct connection between a lithium and a lead-acid battery. The banks must be completely separate, with the DC-DC charger moving energy from the lead-acid start battey to the lithium house bank. That means the battery switches (auto and manual) need to be replaced with two On-Off switches, one for each bank.
The engine alternator, shore battery chargers, solar, wind, etc. are usually connected to the house bank. For a lithium install, these sources must be moved to the start battery. All charging sources go to the start battery, while only the DC-DC charger supplies current to the lithium house.
True or am I mistaken?
You are correct!
ABYC E-11 stipulates each lead-acid battery or battery bank over 800 CCA (or 100Ah capacity if CCA is unavailable) should have its own isolation switch. On the lithium side, ABYC E-13 mandates a switch if the battery or battery bank is greater than 500Wh in capacity. So, in practice, just give each battery its own switch. The switches should be connected as close as possible to the positive terminal of the batteries and rated appropriately.
And correct–you don’t want to wire an alternator into your lithium system directly or run lithium and lead-acid in parallel. Your alternator should be connected to a lead-acid starter battery, which is in turn connected to your lithium house bank via a DC-DC converter. Preferably, a bidirectional converter. Stephen Burnage wrote a good article that covers exactly this: https://www.practical-sailor.com/marine-electronics/lithium-batteries-for-small-boats-install-guide
There is one exception to the rule of separation: emergency situations. Burnage recommends retaining a manual combiner switch between your lead-acid and lithium batteries so that you can still power critical loads if your lithium system goes down. This is the only time the two systems should be directly connected. I recommend checking out the schematic diagram in Burnage’s article.
Hope this helps.