What yacht owners want today.
Yacht owners today are demanding more and more of the home comforts be available on their yacht. The prospect of paying hundreds of thousands of dollars/euros for a yacht and being limited to having to rely on a noisy, expensive generator or having to hook up to shore power to enjoy these comforts is no longer an acceptable trade-off.
This demand has led to the installation of larger house battery banks to manage these loads.
Technology has enabled devices such as Air-Conditioning, Refrigeration, Water Desalinators and other electrical appliances to be much more energy-efficient. Battery technology is constantly improving to provide larger capacity batteries that are more capable of handling the power loads, and the high charge, and discharge rates that are needed. Lithium-Ion technology has evolved to a mature state, providing batteries that can provide much greater usable capacity, less weight and longer life. The commoditization of Li-Ion is driving the price down.
There are also available now, intelligent battery charging and management systems to optimize the use of these larger battery banks.
That endless battery discussion.
The battery discussion is a never-ending one. The yachting forums are full of threads related to battery choices. Which one is better? How to avoid common battery problems, how to charge batteries optimally, battery safety concerns etc. The aim of this blog is to provide enough information, without getting too technical, so that you, the end-user yachtie can make a more informed decision on:
- The right battery brand
- The right type of battery
- Size and type of battery management/charging solution
Today there are two main choices for batteries and there are many different battery types.
Lead-acid types are the traditional battery types and Lithium-Ion (Li-Ion) battery types. Li-ion is “newer” technology (if 10 years is new?). Both Lead Acid and Li-Ion have many different “chemistries” or types available. So let’s first look at the different types of lead-acid batteries and then let’s review the Lithium-Ion battery types. Then we discuss battery management and charging solutions.
How to choose the right battery.
This can be a very complex question. So let’s try to simplify this as much as possible without ignoring any key elements of battery choice. We are mainly concerned with the characteristics of a battery and choosing the right battery for your needs based on those battery characteristics:
- How fast a battery can fully charge
- How fast a battery can fully discharge
- What percentage of the battery capacity can I really use? (This is often referred to as Depth of Discharge (DoD)
- Does the way a type of battery is used, affect how long the battery will last?
- The number of charge cycles a battery can make before it becomes unusable i.e the battery will no longer hold a charge for a useful period of time.
- Price. The cost of a battery needs to be taken into account. NOTE: We recommend you consider this only after you have determined all of the above characteristics. Remember the old saying “Buy cheap, buy twice”. It is important that you weigh up the key facts to get the right price/performance from your battery purchase. Of course, sometimes you need to make a compromise due to your budget constraints.
Lead-Acid battery types.
There are many different types of lead-acid batteries. The goal of this blog is to provide a less confusing explanation of the different battery “chemistries”. We will discuss the main types of lead-acid batteries and what is the best use for each type of battery.
The many types of lead-acid battery all perform differently. If you choose Lead Acid over Lithium-Ion, It is important to pick the right battery for your particular use. Using the wrong battery type can significantly reduce the battery performance and in some instances do irreversible damage to the battery. This can result in a drastic reduction in battery life. It can also be a very unpleasant boating experience if you are unable to start your engine!
Generally speaking, Lead Acid batteries are broken down into two main categories; Flooded (or wet) Cells and Maintenance Free Sealed Lead Acid Batteries (SLA).
Flooded Lead Acid Batteries.
Flooded Lead Acid batteries are the oldest and most commonly found lead acid battery type and are widely used in the automotive industry. They provide the most cost-effective solution, as the least cost per amp-hour, of any lead-acid battery type. These are most commonly used as “cranking” or starting batteries.
The modern wet-cell comes in two styles; serviceable and maintenance-free. Normal flooded batteries require extra care and regular maintenance in the form of watering, equalizing charges and keeping the terminals clean. Flooded cells need to be mounted the right way up and can be susceptible to spillage.
Transporting Flooded Lead Acid Batteries brings with it its own challenges. Classified as “dangerous goods”, flooded lead-acid batteries require very specific transportation methods and can only be shipped with accredited dangerous goods certified shipping and courier companies.
Sealed Lead Acid Batteries.
Commonly known as Valve Regulated Lead Acid (VRLA) or Sealed Lead Acid (SLA). SLA batteries are available in a few different formats. Their principal manufacturing process, including the number of plates and plate thickness, determines its designated end-user application. SLA batteries tend not to sulphate (When sulfation occurs, your battery goes dead) or degrade as easily as wet cells and are regarded to be the safest lead acid battery to use.
Two main versions of Sealed Lead Acid Batteries (SLA) are commonly found. AGM (Absorbed Glass Matt) and Gel Cell (gelified electrolyte).
AGM Sealed Lead Acid Battery.
AGM batteries are usually the least expensive in the Valve Regulated Sealed lead acid variety. AGM Sealed Lead Acid Batteries utilise an Absorbed Glass Matt (AGM) process which is superior to traditional flooded technology. Fine, highly porous, micro-fibre glass separators absorb the electrolyte, increasing efficiency by lowering internal resistance, which in turn boosts capacity. Lower internal resistance also means that the battery can be recharged much faster than conventional flooded or wet lead-acid batteries. AGM batteries provide much larger capacity in a smaller case size and are able to be mounted on their side and shipped using standard shipping processes.
AGM batteries have many uses and are commonly used in; telecommunications industries, golf carts, mobility vehicles, automotive, marine and much more. As always, it is important to ensure you are selecting the right AGM battery for your specific use. Although the voltage, capacity, dimensions and ratings may be very similar across a range, each AGM battery has a specific use that it is built for.
Gel Sealed Lead Acid Types.
A common misconception is that all “sealed” lead-acid batteries are GEL. Gel VRLA batteries contain a gelified electrolyte which differs to their AGM counterparts. Sulfuric acid is mixed with silica fume, which makes the resulting mass gel-like and immobile. This creates a completely maintenance-free, spill-free, lead-acid battery product. Unlike a flooded or wet-cell lead acid battery, GEL cell batteries do not need to be kept upright and can be shipped using standard shipping process.
GEL’s inherent design reduces electrolyte evaporation, spillage and subsequent corrosion issues that are very common in flooded or wet-cell batteries. GEL batteries boast greater resistance to extreme temperatures, shock, and vibration. They are capable of withstanding over-discharging, which typically causes irreversible damage to Flooded and some AGM batteries. They are ideal in uses where a constant current is required, such as yachts, golf carts, mobility, power bank and RV power bank applications.
GEL are generally much more expensive than their AGM and Flooded counterparts. They have a very low discharge rate (1% per month), but they require specific charging practices and need to be charged with a GEL specific battery charger.
Deep Cycle Lead Acid Batteries.
Deep Cycle Sealed Lead Acid batteries, as the name suggests, are specifically designed for deep cycling applications. They contain fewer plates than their cranking or starting counterparts. These plates are also much thicker. This reduces the total surface area, resulting in a battery that provides lower max current, but is capable of a much deeper state of charge.
Deep cycle batteries are typically discharged to 50% of their capacity and recharged again. This level of cycling is generally used where the battery is providing constant current for long periods of time. Such as golf carts, mobility scooters, power banks, RV power banks, Solar energy systems etc.
The basic formula recommended for a deep cycle Lead Acid battery is to suggest one with a residual capacity approximately three times the estimated daily use. It is also recommended to bring Deep Cycle batteries back up to full charge every few weeks to minimize loss of battery capacity. Failure to do so will reduce the battery’s life, and over time it will provide lower and lower capacity. Deep Cycle Lead Acid Batteries are usually categorized by their amp hour rating (AHr). Amp Hour is a measure of the battery capacity.
Deep Cycle batteries are available in both AGM or GEL variety.
Engine Starting or “Cranking” Lead Acid Batteries.
Generally Cranking batteries differ to their deep cycle counterparts as they have been specifically designed to produce a large burst of current in a short time frame. This is particularly useful in engine starting applications. Cranking batteries are generally rated based on their ccA (Cold Cranking Amps) rating. The larger the ccA rating, the larger the engine the battery can turn over. These batteries are NOT designed to provide sustained power.
Cranking batteries are not designed to be deep cycled or discharged. They are designed to turn over an engine and sit on “float” charge (a charge that is slightly higher than the batteries maximum voltage) which is usually provided by an alternator. Discharging a cranking battery will start causing irreversible damage to the battery. This will ultimately reduce its performance, total life span and in some cases cause complete failure.
Best of Both Worlds.
Known by a few different names, but most commonly as Hybrid. These batteries are designed for both engine starting and deep cycling. This is particularly useful in marine and RV use where a large cracking current is required to start an engine, as well as cyclic ability to power onboard devices and appliances.
The use and popularity of lithium-ion, (li-ion) batteries has grown significantly in recent years. They offer some distinct benefits over the lead-acid battery.
However, like all technologies, lithium-ion batteries have their good points and some drawbacks.
To gain the best from the li-ion battery technology, it is necessary to understand not only the advantages but also the limitations or disadvantages of the technology. In this way, they can be used in a manner that plays to their strengths in the best way.
There are many benefits of Li-Ion include:
- Usable Capacity: 50% more usable energy than traditional flooded, AGM, or GEL lead-acid batteries of the same rating (aH).
- Weight: They typically weigh as little as one-third of a similarly rated lead-acid battery.
- Space: Take up to 70% less space.
- Efficient: They provide lower resistance, allowing them to be charged much faster, with minimal losses. Lead-acid batteries lose power quickly during discharge.
- More Hours of Power: Li-Ion batteries provide realistically usable 90% of their rated capacity, regardless of the rate of discharge. Lead-acid batteries typically provide less usable energy with higher rates of discharge. Lead Acid types are usually limited to 50% of the rated capacity to prevent diminished life.
- Ultra Long Life: Can be recharged many times more than lead-acid (3 to 10 times depending on use). Higher rates of discharge minimally affect cycle life. Higher levels of discharge greatly reduce cycle life of Lead-acid batteries.
- Value For Money: While lithium-ion batteries may cost more upfront, the long-term savings are good. Li-Ion batteries deliver greater performance and longer life than lead-acid batteries. This means lower replacement and labour costs, and less down-time.
- Self-discharge: One issue with many rechargeable batteries is the self-discharge rate. The rate of self-discharge for Li-Ion is much lower than that of other rechargeable cells. It is typically around 5% in the first 4 hours after being charged but then falls to around 1 or 2% per month.
- Low maintenance: There are no complicated charging regimes to follow to maintain performance PROVIDING the Li-ion batteries are monitored by a good Battery Management System (BMS).
- No requirement for priming: Some rechargeable cells need to be primed when they receive their first charge. There is no requirement for this with lithium-ion cells and batteries. However, ALL battery banks of more than 1 battery need to be carefully balanced. Ideally, all batteries in a bank should be put into service at the same time and discarded at the same time.
- Variety of types available: There are several types of Li-Ion battery available. This advantage of lithium-ion batteries can mean that the right technology can be used for the particular use needed.
Lithium Nickel Manganese Cobalt Oxide (NMC).
NMC has two major advantages as compared to the other batteries. NMC has high specific energy. This means you need less weight to deliver more power. The other is its low cost. It can be optimised to either have high specific power or high specific energy. This type is widely used in the Marine industry to power electric marine engines or for marine battery banks for yachts. Modern NMC batteries that are specifically engineered for marine use are very safe.
Lithium Iron Phosphate (LFP).
Is the most common of the Li-ion battery types. LFP has only one major disadvantage when compared to other types of li-ion batteries and that is its low specific energy. Other than that, it has a moderate to high rating in all the other characteristics. It has high specific power, offers a high level of safety, has a high lifespan and comes at a low cost. The performance of this battery is also good. It is often employed in marine and other applications that require a long lifespan and a good level of safety.
Marine Specific Batteries
A marine battery can be cranking, deep cycle or a combination of both. The critical factor that allows this battery to be used in the marine environment is its construction process.
Marine conditions place a lot of stress and excessive vibration on a battery. Batteries can also be subjected to temperature extremes which will significantly reduce the battery lifespan. Using a standard deep cycle and/or cranking battery for these purposes will produce normal results in the short term. However, in the long term, harsh marine conditions, excessive vibration and wear will damage the delicate lead-acid battery, ultimately resulting in a battery that has lasted considerably less than its manufacturer rated lifespan.
Intelligent Battery Management Systems are important to ensure that the user does not have to think too much about battery maintenance. A good Intelligent battery management system, such as the Integrel System, will ensure you get maximum life and performance from your battery bank.
Batteries that are designed for marine use will be specifically labelled as Marine Grade. Ask your retailer if the battery you are buying is designed to be used in marine conditions. If not, then these are best avoided. Marine batteries can be flooded, Gel, AGM or Lithium-Ion.
Battery Management Systems (BMS).
The right battery choice can soon become a bad choice if the correct battery management and charging systems are not in place to charge and protect your battery bank.
A good battery charging and management system need to perform the following tasks:
- Intelligently inform the user:
- When the battery bank needs to be charged, and
- How long exactly it needs to be charged.
- The remaining time for a battery to be charged when it is undercharged.
- Rapidly charge a large battery bank to the right voltage and intelligently know when to reduce the charging voltage to sustain a battery at the optimum charge level (This is called the “Float level”.
- Provide a safety buffer to cut off non-critical electrical devices BEFORE they run below the battery’s low charge thresholds.
- Selectively disconnect loads so that you can decide what load is a priority. I.e Disconnect the air con if the cooker and Air Con are taking more than the maximum allowable load. When the cooker is off.. restart the Air Con.
- Preventing complete battery shutdown. Nobody wants to be dead in the water, unable to start their engine. In the case of some lithium batteries, if they are fully discharged you need to return them to the factory to get them reset!
Lead Acid batteries are for the most part, just dumb storage devices. Therefore it is easy to overcharge, undercharge or to exceed maximum charge or discharge rates. So a good battery management solution is important whether you choose Lead Acid or Li-Ion.
Who provides Battery Management Systems?
Many, or should we say, most good li-ion batteries come with an embedded BMS. These are generally proprietary and can only be used with the batteries themselves. These are a good “first line of defence” to provide different levels of battery charge balancing and safety warnings and eventual cut off to prevent potentially dangerous situations of:
- Overheating. As a result of poor ventilation, incorrect battery placement or whatever reason the batteries have been located in other than a cool, ventilated environment.
- Overcharging. Which can also cause overheating.
- Too rapid discharging. Which can also cause overheating.
- Fully discharging the battery to the point where it either:
- In the case of lead-acid, sulphates.
- In the case of Li-Ion. Shuts down.
The most technically advanced battery charging and management system for Marine and RV application is the Integrel Solution. The Integrel generator, unlike any traditional or even high energy alternator, provides a very high rate of charge (up to 9kW continuous). This is combined and managed by the Integrel Controller which monitors and adjusts the charge rate based on:
- Engine speed.
- Engine load.
- The rate of charge that a given type of battery can accept.
- Battery temperature and other environmental signals that Integrel monitors. The system also provides careful management of the batteries to ensure they are charged optimally. There is no other battery management solution on the market that can match the Integrel solution for performance and safety features.
Best practices for batteries on your yacht.
All batteries, but particularly li-ion, are sensitive to temperature. It is essential that the batteries are positioned in the coolest possible location in the boat and there is plenty of air circulation around them. Li-ion batteries will automatically disconnect if their internal temperature exceeds a given limit which may be as low as 45°c. If prolonged operation in high ambient conditions is required, careful attention must be paid to the manufacturers’ operating limits and battery choices should be made accordingly.
Lead-acid battery spaces must be vented to the exterior. If in doubt about the effect of the battery weight on boat trim, consult a naval architect.
Routes for cabling need to be identified as part of the survey, bearing in mind that cable lengths should be kept to a minimum to reduce cable losses. Details of recommended cable sizes can be found here.
Most vessels have conduits for major cable runs and these should be used where possible.
Please note: the positive and negative power cables should be run together to reduce stray magnetic fields. These should always be kept clear of bilge areas. Data cables, AC power cables and DC cables should be run separately if possible. Correct and safe cable dimensions can be found here.