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Lithium-ion battery swap: a few issues to consider

Ed Sherman, vice president/education at the American Boat & Yacht Council, writes a regular column in Marine Electronics Journal called Ed’s Electro-Tech Tips. The purpose is to keep electronics dealers and installers up to speed on a variety of electrical issues related to their work. While most of the information is very technical, Ed’s recent comments about lithium batteries are more general. Since we’re seeing more and more of the technology work its way into the marine world, we thought you’d like to tap into the conversation. Here’s how he introduced the topic to MEJ’s trade readers: 

I’m getting a lot of queries lately about switching to lithium battery technology and I’ll bet that many of you are too. The question is, how to advise your customer about this battery option. Is it safe? Do I need to do anything beyond swapping out the existing batteries? They are expensive, but will they significantly outlast my current collection of lead acid batteries? Are there any ABYC or ISO (International Organization for Standardization) standards that apply to this technology? Are boat builders using this technology as original equipment?

I’ll start with the easy answers first. As of this writing there are no specific ABYC or ISO standards in place addressing lithium technology batteries. That said, ABYC has been working with a group of experts from the lithium sector to develop a technical information report. I’m told that ISO is now working to develop a standard as well. 

As for OEMs (original equipment manufacturers) using the technology, the only installs I’ve seen to date were on very custom boats that were built as requested by their owners who were typically engineering types who wanted the latest and greatest. Last fall, however, I entered the Jeanneau booth at the Annapolis Sailboat show and snapped the lead photo for this article. Turns out Jeanneau was offering an option for lithium tech on their new boats. When I asked the sales reps what additional upgrades came with the option, they weren’t exactly sure what was involved, but they were certain there were additional modifications involved in the upgrade. That was comforting, because as I’ll discuss here, upgrades are needed if this is going to be a successful change.

The operative phrase to associate with lithium battery technology is "current density.” The bottom line is lots of battery amp-hour capacity for the physical dimensions and weight. Additionally, lithium tech batteries have a significantly higher recharge acceptance rate than any other technology available to us in the marine field these days. This translates to rapid recharge of the batteries when depleted. Additionally, all the vendors I’ve queried tout the deeper level of discharge these batteries can take without reducing cycle life, 80% vs 50%. 

Ok, so what are the negatives to this technology? For a customer that simply wants to swap out their existing batteries, they are many. Early adopters have learned the hard way that the alternator that helps to recharge the batteries when the engine is running is going to be working hard. It’s going to need to be of a heavy-duty variety and equipped with a temperature sensor that shuts it down when things get too warm. On one of the installations I’ve inspected, the builder added a forced fresh air cooling system aimed right at the alternator to help keep things cooled down. 

Management system is essential

Additionally, whatever battery you select MUST be equipped with a battery management system (BMS). This is imperative to ensure proper cell balance and even discharge and recharge levels. We’ve seen lithium tech for sale at places like eBay and Amazon from unscrupulous vendors that are not properly equipped. The BMS is a minimum safety requirement that the ABYC group developing our tech information report all agree on. 

Selecting name brand equipment could make a difference as well. The process for manufacturing the cells that make up a lithium battery requires hospital-level cleanliness to ensure inherent safety of the cells. Dirt or other contaminates in the cells are known to trigger what is known as thermal runaway, whereby the battery catches on fire and the fire can’t be put out with any known current extinguishing agent. I’ve seen lithium installations where the builder had installed halon or equivalent extinguishing systems in the battery storage compartments thinking this might actually do something. Well, that system might slow down the boat from catching fire, but once those batteries go into thermal runaway, they are going to burn until all the fuel is consumed. The only way we know of to extinguish these fires is with plenty of cold water. This is of course counter-intuitive with electrical fires. Several builders I’ve checked out have installed the batteries in dedicated compartments whereby if the batteries were to go into a runaway mode, they would literally burn their way right through the bottom of the compartment and fall into the ocean. These were multi-hull boats and the compartments were located between the hulls. This of course would be a bit difficult to design for a monohull. 

New standards that apply to batteries in general apply here as well. Over-current protection for the battery bank is now required. The August release of ABYC E-11 outlines the new requirements. Finally, in addition to the alternator issues already mentioned, the installed battery charger may be an issue. How programmable is it? Does it have a lithium setting? Can it be calibrated to match the battery vendor’s recharge specifications? In many cases the answer here is ‘no’ and this would necessitate replacement.

So, to sum this all up, lithium technology is great, but a simple swap with your existing batteries may not be the answer. To maximize both safety and cycle-life, your customer may need to upgrade their alternator and battery recharging systems to maximize the cycle-life needed to get the maximum amp-hour per dollar from this technology.

In addition to his work at ABYC, Ed Sherman writes a blog called Ed’s Boat Tips—click HERE for a look.

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