Why is it worth updating your boat electrical equipment now

Recently, equipment of boats with lithium batteries has become more and more widespread. New quality cruise boats such as the Arcona are equipped with them during construction.

Racing boats also keep up with this issue. Be it the best yachts IMOCA 60 and Fast 40 or small IRC yachts participating in the RORC offshore races.

The main advantages of this focus on lithium batteries are their small size and weight, as well as radically increased number of charge-discharge cycles. Typically, the best lithium boat batteries last four to five times the number of cycles compared to deep cycle lead acid batteries.

All of the above are important factors in reducing long-term costs. However, it is important to understand that they will not pay off immediately, but within five to six years, when the service life of ordinary boat batteries will also come to an end.

Please note that a lithium boat battery will not completely replace lead acid batteries. You will need to carry out a comprehensive and unified update of the boat battery management systems and regulation of all charge sources in order to exclude the possibility of thermal runaway, which poses a threat of a self-sustaining fire.

Yet the economic benefits of installing lithium batteries are not the only motivation for boat owners. They are just more suited to modern, complex yachts with high power consumption.

In addition, lithium batteries can, for example, allow the air conditioner to be left on overnight without shutting down the generator. And also switch from gas cooking to induction or from gasoline to electric.

An added benefit of these conversions is improved safety as they eliminate potential sources of ignition.

Although the chemistry of a lithium boat battery is more reactive than conventional batteries, it can create thermal runaway with subsequent uncontrolled fires.   

Of course, such a development of events has a very low degree of probability. But, you always need to be aware of the danger and take the necessary proactive measures.

Safe systems

A properly designed installation will have three comprehensive lines of protection against thermal runaway. The system is based on the fact that the individual cells of each battery have electronics that maintain charge balance between adjacent cells and initiate cell isolation in the event of overheating.

At the next level, each battery module also has a more sophisticated built-in battery management system that can also shut down the device. In theory, monitoring the battery level and battery level is an adjunct that should never be used.

Each battery module also interacts with the boat's overall battery management system, which is the first line of defense. This comprehensive system should alert the user if they are approaching operating limits and automatically reduce the rate of charge or discharge to reduce the load on the battery. It also isolates certain battery modules as required.

Fast discharging, like fast charging, can cause problems. Therefore, all elements of the charging system must be part of the battery management system. For example, standard alternator regulators are rated to charge at 14.4V (or 28.8V for 24V marine systems), but a 12V rated lithium ion phosphate battery reaches 12.8V when fully charged - it consists of four 3.2 V cells instead of six 2.2 V cells for a standard lead acid battery. Thus, standard charging will overcharge the lithium blocks, which can lead to overheating and potentially shorten their lifespan.

This is why a system-wide approach is needed that includes power management, charging, and monitoring. All elements must be designed from the outset to be compatible with lithium energy storage and be sized to fit each installation.

Considering the importance of adhering to the above conditions, as well as the fact that standards for the installation and use of lithium-ion batteries on ships have not yet been developed, it is still better to purchase equipment from reliable suppliers.

Although, inexpensive, unbranded cells can be purchased in online stores that do not have built-in security or control systems.

Some clarifications regarding lithium boat batteries

To prevent damage to batteries when stored in a fully charged state, many manufacturers allow a maximum charge of no more than 90%. Likewise, many do not allow discharging below 10-20% of total capacity, which partially reflects the battery's self-discharge rate during storage, which can reach 3% per month. Therefore, in practice, you should expect that you can only use the 70% of the rated capacity of a lithium-ion battery.

This is, of course, much better than conventional lead acid alternatives where only 30% of rated capacity is available in real-world conditions, but not with as much headroom as some lithium boat battery suppliers might suggest.

In terms of battery chemistry, we will most likely see Lithium Ion Phosphate (LiFePO4) batteries - a chemical product that was discovered in the late 1990s and advertised for battery maintenance or startup. They are great for this purpose and generally have a good price tag.

Now in the automotive industry, batteries with the following chemical composition are used: lithium-nickel-manganese-cobalt. This makes them more responsive to high charging and discharging rates, which also makes them the best choice for electric propulsion on water.

Since Torqeedo alone has supplied over 100,000 electric drives for use at sea, including a huge number of outboard electric motors, LiMNC batteries make up the bulk of lithium boat batteries used afloat. Storing LiMNC batteries in a fully charged state will shorten their service life, so charging regimes must take this into account. As the automotive industry continues to drive down the cost of LiMNC batteries, we are likely to see more use of this chemistry in the future.

The temperature characteristics of the batteries are also important. While car batteries have heating and cooling systems (usually powered by the car's AC system) to keep the cell temperatures between 0 ° C and 45 ° C, this is not the case with other types of batteries. Even in temperate climates, engine room temperatures can easily reach 60 ° C in summer; while cold winter temperatures can prevent the battery from starting the engine.

Charge and discharge rate

Whatever the chemistry of the battery, it is important that it be matched to the charge and discharge modes. If you need to quickly charge batteries from a large alternator, they must have a fast charge acceptance rate.

Likewise, when operating under heavy loads (for example, an air conditioner running at night), check that the indicated battery discharge rate is correct or that the maximum power consumption of your air conditioning system is exceeded at start-up.

When upgrading an existing electrical installation, do not fall into the trap of replacing like with like in terms of available power. One of the benefits of switching to lithium boat batteries is the ability to handle a wider range of power hungry appliances, so consider additional equipment you might want to add in the next few years: for example, coffee machines, induction cookers, freezers, water installations, diving compressors, etc.

The larger battery pack also allows for better use of flexible battery charging methods, such as when driving in calm weather, which reduces the number of times the main engine or generator set has to run to charge the batteries.

At METS last year, Ken Whittamore, managing director of Triskel Marine, which developed the ultra-efficient Integrel charging system, told the audience that 20 years ago, a typical cruise yacht used about 1 kWh of electricity per day. Today, his Hallberg-Rassy 42, equipped with electric kitchen equipment, a water heater and a tender outboard motor, consumes 5-6 kWh per day.

An air-conditioned boat of similar size could double those numbers. The air conditioners of multihull 50-60 'yachts can consume 20-30 kWh per day. For comparison: the average house in Northern Europe uses an average of about 10-12 kWh per day.

Proof of the efficiency and variety of charging systems currently available is that such high energy consumption can often be achieved without the use of a generator. This, in turn, makes cruising yachts more resilient in terms of reliability and their ability to remain self-sufficient longer without the need for refueling.

Looking ahead

In recent years, manufacturers have tried to increase the energy density and thus the capacity of the batteries, without increasing their size and cost.

Thomas Wiedemann, Vice President of Program Management, Torqeedo, given the difficulties of introducing the latest lithium technology, predicts that short-term benefits over the next two to four years can be achieved by optimizing the way lithium boat batteries are charged, including more efficient and economical forms of charging in the process. work. Solar energy, for example, continues to fall in price, while a wider range of companies now offer panels in custom sizes and shapes that can be adapted to the available deck or roof space.

Looking ahead, it can be said that the automotive industry is making tremendous efforts to increase the overall battery life. Today, car manufacturers typically warrant their electric vehicle batteries for 200,000 km (125,000 miles), or eight years. However, a recent Economist report showed that there are already three companies - one in China and two in North America - planning to release a serial battery that will last one million miles. This is a metric needed for buses and electric trucks, but this technology can also become indispensable for yachts, and last as long as the vessel itself.

Lead acid batteries are not yet scrapped

Lead-acid batteries are too early to be discounted. This technology has also evolved in recent years, as there are many more boats that such batteries are suitable for. In addition, they help to avoid humanitarian and environmental problems associated with the extraction of cobalt. And recycling them is pretty easy and economical, unlike lithium-ion batteries.

08.12.2020