Lithium Batteries Installation in Boats

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Due to increased power demands of today’s cruising yachts, Duncan Kent investigates lithium boat batteries in detail to help ensure safe and hassle-free systems.

Blue water cruising yachts needing additional electrical capacity can benefit from installing a lithium-ion battery bank as a modern solution to increasing electrical demand, particularly if one plans on ditching LPG as cooking source.

Lithium-ion installations, however, can be complicated and tricky; improper execution could even pose an immediate fire hazard.

Lithium-Iron Phosphate (LiFePO4) cells are widely recommended as safe alternatives to using Lithium-ion batteries onboard boats, commonly referred to by its acronym LFP.

These cells have been extensively tested by fire authorities across countries to demonstrate that they are fireproof in themselves; however, as with any battery they could still cause fire if installed or used incorrectly.

Lithium-ion battery packs containing elements such as nickel, cobalt and manganese should not be used aboard boats as these types are more likely to spark thermal runaway and cause fires if they should fail.

Used car batteries cannot be recycled since their complex protection systems cannot easily transfer over.

Electrically propelled yachts often utilize higher voltage systems (48V, 72V or 96V) that requires an intricate control system for optimal operation.

Lithium Cobalt oxide cells may seem attractive for this task; however, their implementation would require professional design and installation; furthermore they would likely prove very costly.

Why risk having such an installation installed if it can’t even be insured against?

Why choose LFP batteries?

Now the question is, What are the problems with lithium batteries in boats? LFP batteries offer several key advantages over conventional Lead-Acid (LA) ones: fast recharge times with high current charging, almost empty discharge capacities without being recharged back to 100% State of Charge as often, and more convenient replacement.

Actually, LFP batteries tend to perform best between 20%-80% SoC most of the time. Even complete discharge without harm will not have an adverse impact; most built-in Battery Management Systems (BMSs) typically shut them off around 12V which corresponds to around 10% SoC.

Once they are fully charged, their BMS should automatically turn off their charging source at around 14.2V to prevent overcharging and prevent overheating of batteries.

LFP batteries offer many more charge cycles than their LA counterparts and, what’s more, are significantly lighter for sailing yachts compared to any type of LA battery – making a noticeable difference to balance and performance.

Converting to LFP Batteries

Since LFP batteries can accept and discharge high currents, their wiring and circuit protection must meet this challenge in order for proper functioning and tailor-fit protection to exist.

All LFP banks require an inclusive Battery Management System with features including reverse polarity protection, individual cell balancing, charge voltage/current limitation/management/disconnection management as well as temperature sensing for alternator monitoring purposes; as well as discharge current restriction/management with visual/audible alarms for maximum productivity and emergency disconnection protection.

Notably, many brands of so-called drop-in LFP batteries (those equipped with an internal BMS) might make it challenging to connect more than two in series or parallel for use as part of a larger bank.

If your capacity needs are greater, building your own bank of individual 3.2V cells and attaching one external BMS can often provide the best solutions.

If you plan to assemble your battery bank from individual cells, new, grade A cells must be purchased.

Many budget buys online from China involve pre-used batteries taken directly out of data storage banks’ Uninterruptible Power Supplies (UPSs).

Although you might get lucky and return the batteries easily enough, returning them could prove nearly impossible. ideal If the cells had been capacity tested prior to purchasing them then their voltage levels will probably match, though you still must balance them before use for optimal results.

Although possible, LFPs should not be relied upon to start engines or power anchor windlass and bow thruster operations. Most won’t even work effectively because their instant heavy current draw can frequently exceed their BMS’ output threshold threshold value.

Concerns related to LFP installations often center on how best to safely charge their systems.

As with anything related to boats, personal decisions must also be considered when making choices and decisions relating to size and type. Many decisions will depend on your boat being larger or smaller in terms of size or style.

LFP batteries possess extremely low resistance compared to their Lead-Acid (LA) counterparts, enabling faster charging/discharging rates – up to 1C (1x capacity or 100Ah batteries). These features enable LFP cells to maintain longer cell lives than lead acid batteries (LA) batteries. However, they must only be charged between 0.5C-1.0C until their charge current drops to within 0.0015C-0.03C so as to prevent overcharging of cells. Charging should then cease so as not to overdischarge.