Lithium Ion Batteries, Part 1: What You Need to Know Now

The Basics

Most boaters are already aware of what lithium-ion batteries are, and that they are pricey compared to traditional lead-acid batteries.  But, are lithium-ion batteries or other lithium-based products worth the price?

It depends on the application.

First, a Quick Overview

Like most wet cell, gel, and AMG batteries, a lithium-ion battery is made up of an anode, cathode, separator, electrolyte and two current collectors (positive and negative). The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator.

It’s worth explaining that a lithium-ion battery is a “secondary-cell” unit made up of multiple smaller batteries in a pack, not the sort of single lithium solid-state battery found in disposable lithium AA and AAA batteries you buy in the grocery store. These are “primary-cell” batteries, which means they cannot be recharged once empty, while lithium-ion batteries can be recharged thousands of times over several years.

The movement of the lithium ions creates free electrons in the anode that create a charge at the positive current collector. The electrical current then flows from the current collector through whatever you want to power to the negative current collector. The separator blocks the flow of electrons inside the battery.

A “lithium-ion” battery is a category of battery, not to be confused with Lithium Iron Phosphate batteries, which are lithium-ion batteries with a specific chemistry.

Other types of lithium-ion batteries include Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Nickel Cobalt Aluminum Oxide (NCA). Both have high energy production, but are more unstable and more expensive than Lithium Iron Phosphate batteries.

That’s all about the same as with your old standard battery.

Advantages of Lithium-ion Batteries

The primary advantage is known as “energy density.” Battery energy density is the amount of energy a battery contains compared to its weight or size. It’s possible to measure a battery’s energy in watt-hours (watts per hour, the equivalent of using one watt for one hour). We can then divide a battery’s watt hours (wh) by its weight or volume to get a designation called “energy density.”

• Lithium batteries win big here, weighing 1/2 to 1/3 as much as conventional batteries, per watt hour. Viewed another way, you can have 2 to 3 times as much DC energy aboard with no added weight penalty by switching to a lithium-ion battery.
• Lithium-ion batteries have a low “shelf-discharge” rate, about 2% per month versus 5% to 8% for lead-acid.
• Lithium-ion batteries can be discharged 80% or more without harming performance and they are rated for about 50% or more cycles compared to conventional batteries.
• Lithium-Ion Batteries can be charged much faster than conventional ones. Quick-charging lithium units can cut recharge time 50% to 75%. Particularly in chartering or commercial operations, that can add to a significant savings in generator fuel, not to mention a noise reduction
• A corollary to faster charging is the reduction of generator time to recharge, saving fuel.
• The overall battery life for most lithium-ion batteries is two-to-four times that of conventional batteries.
• But weight savings or a much slower “storage” discharge rate, deep cycles and the number of cycles in a battery’s life along with other attributes are not critical in many applications.

Appropriate Applications for Lithium-Batteries

• Electric boats and electric outboard motors of all types.
• Bass boats — where prolonged use of trolling motors is common.
• Any boat that has batteries that can be recharged overnight.
• Small boats with limited space below decks.
• Small boats loaded up with electronics and other amenities
• Boats with batteries in a location where replacement is difficult.
• Boats with air conditioning but not a generator.
• Boats left on moorings for long periods of time
• Boats using solar power as a primary source of recharging
• Large boats with a high nighttime power drain
• Hybrid-powered boats
• Catamarans with limited space
• Boats in isolated locations where a dead battery could spell trouble

Most lithium-ion batteries have 5-year warranties but some are guaranteed up to 11 years. Conversely, most lead-acid manufacturers offer warranties between one and five years. So, when taking the long view, lithium batteries can end up being more economical than conventional batteries, particularly when taking inflation into consideration.

Unlike lead-acid batteries, lithium-iron-phosphate batteries do not get damaged if they are left in a partial state of charge so you don’t have to stress about getting them charged immediately after use. They also don’t have a memory effect, so you don’t have to drain them completely before charging.

Last but not least, lithium-ion batteries don’t leak acid or discharge potentially explosive fumes as lead-acid batteries sometimes do. However, there is a slight chance that lithium-ion batteries can have an internal fire, in which case special fire-fighting foam is required.

Applications Where Lithium Batteries are not Needed

• Engine cold-cranking batteries
• If you run a heavy displacement boat, added battery weight is not a big negative.
• If you have a generator aboard to recharge when needed.
• If your batteries are easy to access and servicing and replacement are no problem.
• If you don’t intend to keep your boat more than a few years, the added cost of the lithium-ion battery won’t amortize itself.

Boaters have been living quite happily without lithium-ion batteries for a long time. If conventional batteries are properly fulfilling their function, then use of a lithium battery may not be indicated.