Search
Member Login

LITHIUM BATTERIES FOR THE CRUISING BOAT - IS DIY AN OPTION?

Written by Hank J George, Blue Heron

Some of the first lithium/LiFePO4 batteries were installed in boats 14 years ago.  The lithium iron phosphate chemistry is now widely accepted, the preference for refits, and becoming the standard on many new boats.  With an extremely long life, the ability to deeply discharge without damage, faster charging rates, and 1/3rd the weight of lead acid, it is a natural for the cruising boat.

The first steps are: selecting your the lithium battery capacity; deciding how simple or advanced you want your battery monitoring system (single battery monitor vs. Victron Cerbo); dealing with your alternator (multiple options – some simple, some expensive); determining which charging devices need adjustment; and choosing the quality level for your batteries: cheap (warning – they can only last 1-3 years), moderate quality and price (last 5-7 years), or high quality (true 10 to 15 year battery).  With those decisions behind you, the next question is who should do the install.  Many think “Heck! Why not do it myself?”  But be careful – there are some critical steps that are often best left to the professional.

Critical Safety Issues

Here are the most critical factors I have seen affecting safety and long battery life:

  • Clean, secure, coated electrical connections – Fires continue to occur in boats, and fiberglass boats once ignited, burn hot, with thick smoke and are difficult to extinguish.  The most common cause of boat fires is overheated electrical connections, due to being loose or corroded.  All heavy power connections, new and old, should be double checked to be clean and torqued well, and then checked with an IR temp gun when charging at high current.  And, when finished apply a coat of Boeshield for long lasting isolation from oxidation.  Professional installers know how to do these steps well.  If one chooses to do this step themself, I would definitely recommend having a professional inspect and test your work, and do an inspection of older connections too.
  • High quality batteries from a US company vs. cheap on-line listings – There are no great deals in buying a lithium battery - sorry.  If priced cheaply, they are made with cheap cells (used, reject, or by a low-quality manufacturer), and cheap BMS.  Often, warranties are not supported, or if you are sent a replacement, it only lasts a few months and they decline any further replacements, saying you abused the battery.  US companies are more responsive and responsible and have QC inspectors check their pallet load of cells or batteries before leaving the manufacturer’s plant to be sure of what they are getting.  A Chinese company shipping from a warehouse in the US is not a US Company.  We’ve opened and tested (by engineers) lots of cheap batteries and none had good cells or BMS.  And the so-called on-line testing gurus don’t do extensive tests – Ever see one test internal resistance, the key to determining used or low-quality cells?

Don’t rely solely on claims of “Grade A.”  That just means the cells met the manufacturer’s specs, but that cell manufacturer’s Grade A cells might only last 3 years, compared to another’s that last 10 or 15 years. Grade A is not a uniform quality standard across all manufacturers.

  • Robust BMS – Cheap batteries have small BMS circuit boards, much fewer parameters monitored, overly stressed MOSFET components on the circuit board (use too-few to share the thermal load properly) and have undersized heat sinks.  A robust BMS monitors more parameters for safety, has double the number of MOSFETS so they aren’t stressed and will last a long time, and has large heat sinks.
  • Quality Charging Equipment – In your installation, don’t go for cheap chargers.  Stick with well established brands like Victron, Mastervolt, Xantrex, and Magnum, and preferably units that are UL approved.  Runaway charging is a prime driver of overheating cells and leading to thermal runaway.  We want redundancy – a quality charger with redundant safety circuits to minimize the chance of overcharging (UL certification does this), and a robust BMS with redundant circuits and sensors to interrupt over-charging.
  • Mount securely – Lithium batteries, to maintain their internal integrity, need to be mounted securely, such as with blocking at the base, and tie-down clamping with threaded rods. 

As a Salty Dawg Sponsor, our tech support team stands ready to answer any lithium questions from Salty Dawg Members – contact [email protected] .

Author – Hank George is a lifelong sailor, having logged 200,000 miles.  He holds multiple engineering degrees; has guided hundreds of lithium upgrades over the past 14 years; is owner and chief engineer for Blue Heron Batteries; and is past President of the SDSA.