Tech Report

IS IT TIME TO UPGRADE TO A LITHIUM HOUSE BANK? by Bob Osborn

WE’VE ALL HEARD THE HORROR STORIES of lithium batteries catching fire aboard planes, in cars and on boats. However, as so many parts of our world now rely on highcapacity energy storage and our boats become ever more energy hungry, it may be time to consider an upgrade to your electrical system.

I say “electrical system” as converting to a lithium bank is not as simple as pulling out those trusty lead acid batteries and plunking in lithium. There are considerations of how your boat is wired, possible increased loads and whatever is needed to ensure that the installation is up to code and safe.

Aboard our 2007 47-foot Aerodyne sloop, Pandora, our house bank was comprised of 4 8D Lifeline AGMs that were nearing the end of their life, so I had to do something. After two years of pandemic delays, making it difficult to even find a reasonable source for quality batteries, this spring we finally were able to move forward.

There are some fundamental differences between the basic characteristics of lead acid batteries and lithium, so it’s not as simple as looking on Amazon for the cheapest options, swapping out those old lead acid batteries, reprograming the charger and off you go. At first glance, it might look like you could take that approach but you will likely not achieve expected performance out of your new bank. Additionally, a “non-code” installation may make it impossible to secure insurance or worse, expose you to a major electrical problem or fire.

The American Boat and Yacht Council will soon issue guidelines for the installation of lithium batteries, an important development for safety and a milestone that now makes many more insurers willing to cover boats with lithium aboard when installed properly. Over the last few years, Pandora’s insurers changed their rules from “no lithium” to “lithium is ok as long as the installation is done to ABYC standards” an important development that gave me the confidence to move forward.

Two more important considerations are the source of the batteries and, equally important, finding someone to handle the installation or provide guidance, that knows the standards, ensuring that the job is done right. Do the batteries have the type of chemistry that are less prone to overheating and do they have a welldesigned BMS (battery management system)? I chose to go with batteries with lithium phosphate chemistry (also called liFeTO batteries), as they are considered to be the most stable and safest in a marine installation. Quality batteries come with a bewildering array of safety features, chips to monitor charging and discharging along with apps that will run on your smartphone or tablet to allow you to keep track of exactly what is going on “under the hood.” With this in mind, I decided to use four 210Ah, 12v “drop-in” batteries from Blue Heron Batteries, meaning that they are sized to fit into the same general space as the batteries that they replace. One of the principles, Hank George, who started the company, has a deep background in engineering so he was able to help design a system that would provide substantially more usable power to handle the substantial power needs of Pandora.

As a first step, I prepared a full inventory of my electrical system, engine alternators, solar controllers, charger inverters and any components that distributed power to my starter battery, bow thruster bank as well as my house bank to determine which components could be used or reprogramed to be compatible with lithium. Some components needed to be replaced but most proved to be reuseable, which was good news.

will soon have a new wind generator and I wanted to increase the usable kw/hrs available from the house bank with this upgrade. As I don’t have a house generator it was important to balance usage with the ability to put power back into the bank every day. As we spend the winter cruising season in the Caribbean, there is generally ample sun and wind to keep the bank up and fully charged. On the occasion when mother nature isn’t cooperating, I have a small 2kw Honda generator that has proven its worth over the years.

The original bank was comprised of four Lifeline 8DL AGM batteries each with 255AH at 12v, giving me a total of just over 1000ah or 500 at 24v when new. However, for practical purposes, I rarely used more than 25 percent of rated capacity as I wanted to extend the life of the bank as long as possible, giving me about 200 usable amp hours. Some folks suggest that a quality AGM bank can safely deliver about 50-tp-60 percent of rated capacity but this does have an impact on lifespan of the batteries. The new lithium bank is comprised of four lithium batteries, each rated at 210ah for a total of 840ah at 12v, giving me usable power capacity of more than 700ah a more than doubling of our power reserves given the fact that these batteries can be drawn down by 90 percent without substantially impacting their lifespan.

Additionally, there is a big difference between the weight of the old and new bank with the four lithium batteries totaling just under 250 pounds, a savings of nearly 400 pounds when compared to the AGM bank. This weight savings would be particularly valuable for the cruising cats that are becoming more popular. Pandora, built in Finland in 2007, is a 24v boat and the new system needed to integrate with my 12v starting battery and 24v bow thruster, both using AGMs that had plenty of life left in them, which complicated the installation considerably.

I am a pretty handy guy and do most everything aboard Pandora but in this case, given the complexities of the integration of 12v and 24v along with multiple battery chemistries, I decided to bring Pandora to a yard that is well versed in lithium and ABYC standards.

Additionally, most of us are not the first owners of our boats and over the years, especially on older boats, we really don’t know for sure if components installed prior to our ownership were done properly. In Pandora’s case, the installer discovered wiring and components added along the way that created safety issues that needed correcting and terminal corrosion, all too common on older boats, that had to be remedied.

As one example, I had a new inverter/charger installed about five years ago and it was discovered that the unit had not been properly installed, something that only the most experienced tech would have identified and never came up when the boat was surveyed last summer. reviews the real-world benefits of making the move to lithium.

Resources referenced: Blue Heron lithium batteries: American Boat and Yacht Council: ABYC certified electrical technicians:

All and all, the addition of the new lithium bank was a meaningful investment but for us having the additional power aboard an increasingly power-hungry vessel was an important upgrade that should pay dividends in the coming years.

I will be keeping track of how the bank performs this winter season and plan a followup article in BWS in the coming months that Bob Osborn is the president of the Salty Dawg Sailing Association and serves as port officer for Antigua, the primary destination of the group’s fall rally to the Caribbean. He is dedicated to promoting blue water sailing and the cruising lifestyle. He and his wife Brenda spend their winters afloat in the Eastern Caribbean aboard Pandora their 47-foot Aerodyne. He has been keeping a blog for more than a decade and writes regularly.