Lithium-ion battery technology has revolutionised energy storage across multiple industries, offering unrivalled performance, capacity, weight and longevity advantages. But what are the cost implications of upgrading to lithium-ion?

Jeremy Peacock, co-owner of marine energy specialists Enertec, likes to illustrate the cost vs performance profile of the technology through examples, and stresses that not all lithium-ion batteries are created equal.


Using a 40-43ft vessel, this analysis is based on the following specs:

• Direct current (DC) electric refrigeration with a daily load of around 100-120 amp-hours (AH) per day

• Additional loads on the vessel (lights, electronics, inverter, pumps etc) using another 40-50 AH per day

• Total daily load of between 140-170 AH per day.

A typical lead-acid (flooded/AGM/GEL) battery bank for this size vessel is a 12-volt system of around 400 AH capacity. Two of the biggest issues with lead-acid battery technology are the small amount of usable capacity and the slow recharge ability.

Li-ion batteries have created a far superior alternative in both areas, along with a vast reduction in battery weight and size, better voltage stability and far greater cycle life. To accurately compare the two types of batteries, let’s first look at the differences between the two technologies.


All types of lead-acid batteries use the same chemistry, which limits the technology’s performance. One limiting factor is ‘usable capacity’. This refers to the percentage of the battery that can be discharged and recharged (depth of discharge – DoD) without seriously degrading the cycle life. Users are advised not to discharge the battery below 50% State of Charge (SoC).

Recharging lead-acid batteries is very slow – around four hours to fully recharge from 50% SoC. The slowest portion of the battery to recover is the last 15% which takes around three hours to recharge – no matter how powerful the charging system.

Away from the marina most vessels of this size rely on engine and/or solar charging. So, because of the time it takes to recover lead-acid batteries it is not practical (often impossible), to recover a lead-acid battery bank past 75% SoC when at sea.

Realistically this only allows for a usable capacity of approximately 35% of the total battery capacity (see Fig 1).

In our typical 40-43 ft vessel with 400 AH of house battery capacity, this equals around 140 AH of usable energy.

Li-ion batteries use a different chemistry which allows them to be discharged to a far greater depth than lead-acid batteries while still offering a vastly superior cycle life. They can also be charged much faster making it possible to recover them to 100% SoC from an engine alternator or solar. (See Fig 2.)

Using Juice PRO Series Li-ion batteries as an example, these can be discharged to 20% SoC and then fully recharged to 100% SoC in an hour – with the correct charge ratio. In most cases the vessel’s charging system will not be powerful enough to achieve charging this quickly, but even with a smaller system, charging will be considerably faster than for lead-acid technology.


While Li-ion batteries offer significant advantages in a house bank application, the cost vs advantages of swapping to cranking batteries to Li-ion is harder to justify. We usually advise the continued use of lead-acid technology.

With some Li-ion batteries, including the Juice PRO Series, it is still possible to charge both the cranking battery and Li-ion house battery from a single engine alternator. To achieve this the alternator is fitted with an external smart regulator and both battery banks are charged via an isolation diode. A typical emergency switch to allow cranking off the Li-ion house batteries (if the cranking battery fails) is still possible.

These two advantages allow Juice PRO Series Liion batteries to deliver 80% of their rated capacity as usable energy (see Fig 1).

In our typical 40-43ft vessel this would allow the installation of a single 12V 200 AH Juice PRO Series battery in the place of the 400 AH lead acid bank. This single 12V 200 AH Li-ion battery would provide 160 AH of usable energy, require less space and reduce battery weight from around 140kg to only 27kg.

The end result is a battery of half of the nominal capacity providing the same, and often greater, usable energy.


Cycle life refers to the number of times a battery can be discharged and recharged before it is degraded beyond viability.

Li-ion batteries offer far greater cycle life than lead-acid, allowing them to deliver considerably more energy during their service life (see Fig 3).

A typical lead acid AGM battery will have a cycle life rated at approx. 500 cycles to 50% DoD. Li-ion technology, like that used for the Juice PRO Series batteries, offers 3000+ cycles down to 80% DoD.

Combining their greater usable capacity and far greater cycle life, Li-ion batteries deliver around 9-10 times the energy throughout their life than conventional lead-acid technologies.

This launch - as well as the yacht at the beginning of this story - have made the switch to Lithium-Ion batteries.


There are low-cost ‘drop-in’ lithium batteries available with internal disconnects to protect the battery. But these can lead to much larger issues.

These batteries have huge limitations on the current they can deliver or be charged with. They can also cause damage if disconnecting themselves when being charged by an engine alternator. This will opencircuit the alternator and can lead to damage to the alternator and all other connected electrical equipment on the vessel.

The marine electrical regulations have been written to preclude these sorts of issues. Unfortunately, the majority of Li-ion batteries offered in the marine market don’t comply with these standards and at best will provide poor performance. At worse these are dangerous and can cause complications with insurance cover.


Misconceptions around safety issues with Li-ion technology have, in some cases, unfairly damaged their reputation. To set the record straight there are several points to cover.

The first thing to understand is that there are various Li-ion chemistries under the Li-ion umbrella. All have advantages and disadvantages and some are better suited to particular industries.

In the marine industry, Li-ion iron phosphate (LiFePO4) chemistry is typically used thanks to its chemical stability which ensures high safety standards. Different Li-ion chemistries used in electronic devices, toys and electric vehicles generally place a high value on greater energy density. But the type largely used in marine batteries is extremely safe and considerably more tolerant than other lithium chemistries.

As an example, Juice PRO Series batteries are tested to IEC standards which require them to be subjected to an over-discharge test,a forced discharge test, external short circuit tests, a thermal abuse test, crush test, nail penetration test and drop test. Through every single test the battery cells – while damaged and possibly unusable – did not cause any safety issues.

Based on this, it can be argued that the inherent safety of Li-ion iron phosphate chemistry coupled with a suitably-designed battery management system means that Li-ion batteries could be considered safer than traditional lead-acid batteries.

While the initial outlay for Li-ion (purchase plus installation) is higher than for lead-acid technologies, the performance advantages (more usable energy and much higher cycle life) make Li-ion batteries far less expensive per AH of energy delivered.

Add this to the savings in weight (and associated performance implications), size and better voltage stability and the argument for converting to correctly designed compliant Li-ion batteries stacks up. Basically, if finances allow, make the switch at your next battery change and enjoy the features this technology has to offer.

From a cost perspective, while a high-quality Li-ion battery will cost around two or three times as much as lead-acid variants, the cost analysis stacks firmly in favour of Li-ion batteries. No surprise then, that today nearly every industry sector reliant on stored energy uses Li-ion technologies.

Lithium-ion batteries have a longer service cycle - they can be discharged to a much lower level than conventional lead-acid batteries.


Full disclosure: changing from lead-acid to Li-ion batteries is not as simple as removing the old and dropping in the new. Installations in New Zealand or Australia must comply with the marine electrical regulations (AS/NZS 3004.2:2014). These specify the requirements for installing Li-ion batteries.

Among other things, these regulations require the battery to be able to disconnect the load (after a prealarm) to prevent it from over-discharge. It must also be able to disconnect all charge sources (after a pre-alarm) – preventing charging issues from damaging the vessel’s Li-ion batteries and wider electrical system.

When installing compliant li-ion batteries, the biggest variable is how the charge control side of the battery system will work. This feature allows the battery to disconnect charge sources in the event of any problems.

Some manufacturers require all the charging equipment (alternator regulators, AC battery chargers, solar regulators etc.) to be the same brand as the batteries. Others, like the Juice PRO Series, are designed to work with a variety of makes and models and don’t require specific Li-ion settings on the equipment.

This reduces installation time when swapping to Li-ion batteries and significantly lowers the overall cost of the changeover. The flexibility in controlling charge sources is achieved by using an integrated solid-state charge control relay on the battery, sending a signal to each charge source to switch off if there is a charging issue.

Although it takes longer to install compliant Li-ion batteries compared to traditional lead-acid batteries, a correctly designed Li-ion installation is relatively straight forward. Suppliers will advise on the best system design for your vessel and ensure compliance with the marine electrical regulations.


Smart lithium, smarter trolling

Lithium-ion batteries are often considered the ‘gold standard’ for trolling motors. They weigh a lot less than conventional batteries, offer twice the run-time and boast a life expectancy 10 to 20 times longer.

But there’s some confusion about the different types of lithium-ion batteries and their safety. And to get the most from them, they need to be installed and used correctly.

Lusty & Blundell, distributor of both trolling motors and lithium-ion batteries, asked Peter Sewell – electrical engineer and lithium battery specialist – to sketch the ideal trolling motor installation.

“LiFePO4 or lithium-ion phosphate batteries (used to power marine trolling motors) are nothing like the lithium-ion batteries in a mobile phone which have been known to catch fire and can be quite dangerous,” he says.

“In fact, I’d much rather have a LiFePO4 battery on board my boat than a conventional lead-acid battery. They are safer, almost impossible to make catch fire (even by overcharging) and, if they are in a fire, they don’t sustain it.”

Sewell has designed and built lithium-ion battery systems for cars, farm vehicles and aircraft for over 20 years and has used LiFePO4 lithium batteries on his own launch for six years. “They’re ideal for a boat – lightweight, safe and quick to recharge – the best combination of weight and safety.”

Lithium Battery Expert Peter Sewell (left) and Surtee's Cliff Schnick

L&B CEO, Mark Milburn, says many users don’t realise that lithium-ion batteries shouldn’t be charged while in use, and that when charging, they require a specialist charger. “Although some people try to get around the latter by installing an AC charger on board, this is actually against the electrical regulations and could cause serious problems.”

He points out that, as a general rule, electric trolling motors should only be run at 80% of their available power, not flat out, or that once the battery’s charge drops beyond a certain level, many of the motor’s advanced functions, such as anchor lock and auto trim will cease to work.

To address these concerns, the L&B team has designed an effective, reliable, and powerful solution. “It became clear we needed an easy-to-understand and simple-to-install system to protect the motor and the battery, meet all the regulations and ensure the owner got all the benefits,” says Milburn.


• A Sterling Power AMPS lithium-ion battery
• A DC-to-DC lithium-ion charger that enables the trolling motor battery to be charged while the vessel is underway, either en  route to a fishing spot or moving between spots
• A dedicated battery switch that means the battery can either be used to operate the motor or be charged – but not both
• A Victron smart shunt that acts like a fuel gauge for the battery, precisely showing how much power has been used/is      available (via cable to the MFD screen or via Bluetooth to a mobile phone or tablet)
• A battery-to battery charger for use with a normal shore-based AC charger (this tops up the lithium-ion battery once the vessel’s engine and house batteries have been fully charged). The system was recently installed in this year’s Hutchwilco NZ Boat Show’s Grand Prize, a 7.5m Surtees 750 Game Fisher fitted with an 87-inch Minn Kota trolling motor.

“It’s a really great system,” says Surtees operations manager Cliff Schnick. “The lithium-ion battery only weighs 13kg versus 35kg for a conventional battery. That’s great for the boat’s ride and performance. Not having to drag all that extra weight around will save the lucky winner a heap of fuel!”

Milburn sees the new charging system becoming the default solution for those wanting to add a trolling motor to a new boat or to retrofit one. “It’s an enhanced, elegant system that meets all the regulations, safely provides on-the-go charging and lets users know how exactly much power they have left.

“Combined with an AMPS lithium-ion battery, it will also save unnecessary weight in the front of the boat, reduce fuel consumption, deliver twice the run time and many, many times the life expectancy of a lead-acid battery. “And for those switching from a conventional battery to lithium-ion, the AMPS footprint is identical. No need for a redesign or rebuild of the battery locker.”


Fitting energy-efficient technologies brings a multitude of benefits to your electrical system and boating experience – not least boosting performance and reducing your environmental footprint. Story by Jo Reeves.

Because we all love to boat in style and comfort, the increasing list of power-hungry products that provide this means energy efficiency is high on the agenda.

From induction cooking and coffee machines to heating, cooling, lighting and desalination, these home comforts are reliant on energy – and plenty of it. Combine this with a desire to stay off-grid for longer and we’re looking at a challenging ask for many boat owners. Luckily, new technology can help.

Enertec Marine co-owner Jeremy Peacock has seen a sharp increase in demand for energy-efficient products to boost the running time of customers’ on-board electrical systems. “New developments in technology offer more efficient ways to power our boats – reducing running costs, fuel emissions and the carbon footprint we leave behind,” he says.

“We’ve sourced, and in some cases manufactured, technologically advanced, energy-efficient products in response to this demand. Not only do they boost performance, in many cases they save money in the long run.”


Li-Ion technology provides greater energy density, far better performance and longevity and offers huge advantages for boaties.

“We saw a great opportunity for Li-Ion batteries that complied with the New Zealand and Australian marine regulations and provided better functionality – and decided to make our own. We took our ‘Juice’ brand batteries all the way through R&D to market and we’re confident we now produce the best batteries on the market.”

Installing these batteries significantly reduces the weight and size of a house battery bank. They also outperform conventional lead acid (Flooded, AGM or GEL) batteries, with greater useable capacity, the ability to run high loads from inverters without voltage sags, longer service life and faster, more efficient charging.

Charging Juice batteries illustrates the most noticeable difference. Unlike conventional lead acid batteries which need around eight hours to charge from 50% DoD (Depth of Discharge) to fully charged – irrespective of the size of the charging equipment – Juice Li-Ion batteries can be charged from 80% DoD to fully charged in one hour.

In practice, many boats don’t need to push the charging curve that hard and most opt for a ratio that will allow complete recharging in 2-3 hours. This significantly reduces the daily generator/engine running hours used to recharge house batteries. And that means vastly increased freedom to stay out on the water for longer.


Solar panels have also become an integral part of a boat’s electrical system.

“High-efficiency, flexible, long-life solar panels can revolutionise your boating experience,” says Peacock. “While a panel is rated at a maximum output – say 150 watts – it’s actually the efficiency of the cells which determines the amount of solar radiation required to achieve that. The higher the efficiency of the cells, the less solar radiation needed to achieve the panel’s rated output.”

Juice flexible solar panels, he says, have an efficiency of 2324% compared to many panels on the market with efficiencies as low as 15-17%. Less efficient panels need considerably more solar radiation to deliver a given output.


Many onboard consumers are also embracing technologies that place less demand on the vessel’s energy system. One example is watermaking.

Installing a watermaker or desalinator has become increasingly popular given both the desire to make water on demand rather than carry tons of water around (which increases fuel consumption/costs) and the scarcity of fill stations.

Many traditional watermakers are energy-hungry, requiring a generator for power. But manufacturers such as Spectra Watermakers and Katadyn have focused on increased efficiency, reducing energy requirements to a point where it is now possible to run the units directly from your battery bank.

Spectra Watermaker’s energy recovery technology re-uses energy in the watermaker, allowing it to use only a third of the power compared to conventional systems. One of the spinoffs of this new technology is improved performance in cooler seawater temperatures.

While conventional systems have their output rated at a seawater temperature of 25°C (with a significant output reduction with lower temperatures), Spectra models allow full output of water in seawater temperatures as low as 2°C. In Auckland, for example, at a seawater temperature of 14°C a Spectra watermaker uses only one-third of the energy of a conventional system, while producing around 50% more desalinated water.


In many cases the integration of energy-efficient products aboard means a generator is no longer necessary – reducing fuel and maintenance costs, though running an air conditioning unit or a device with a high energy demand may still require a genset. The good news is that there are energy-efficient generators.

“We distribute Fischer Panda generators because we believe they’re the best on the market,” says Peacock. “They use permanent magnet, variable speed technology for a smaller, lighter, quieter and more fuel-efficient generator.”

The permanent magnet technology allows the generator to vary its rpm based on load. It runs at low rpm at low load, and higher rpm at heavy load. This significantly improves fuel consumption and reduces exhaust emissions compared to fixed-rpm generators.

The alternators used in this technology are around twice as efficient as conventional units, producing less heat for their electrical output. And because the permanent magnet alternators are smaller than conventional versions, they can be powered by a smaller engine. The end result is a compact and lightweight generator set that not only performs better but reduces overall vessel weight, improving fuel economy.

No one wants to boat at the expense of the planet – but we all want to achieve optimal performance from our vessels. With the right technology these goals are not mutually exclusive. The only decision left to make is where to drop the anchor on your next off-grid adventure.


Pachoud Yachts – builder of Voodoo Power Catamarans – has focused on improving energy efficiency aboard its boats. This is driven by strong demand from customers wanting to reduce the environmental impact of their boating.

While the vessels are equipped with all the mod-cons expected in a luxury vessel, more effective power technology has resulted in more efficient electrical systems.

The Voodoo XF60 is fitted with Enertec’s Juice Li-Ion Pro Series batteries and Juice flexible solar panels. For larger consumers needing an extra boost of power, a Fischer Panda ‘i’ series generator has also been installed. This package completes a streamlined electrical system that reduces the carbon footprint, maximises performance and reduces running costs.

“At Pachoud Yachts and Voodoo Yachts we aim for our boats to be as efficient as possible, to give our clients an unmatched experience while simultaneously achieving their goals of a reduced environmental impact,” says owner Mitch Pachoud.

“A very energy efficient electrical system from top to bottom is a big part of this – resulting in our boats being some of the most efficient in the market, and kinder to the environment.”