No matter what boat you have there will come a time when you need to replace the batteries on board and with all the choices available today it may not just be a case of swapping like for like. There are now many varieties of marine batteries to choose from with startling differences that are worthy of further investigation.
We are all familiar with the typical lead acid battery that has been the staple of marine batteries for eons. Available as either a starting battery or as a deep cycle variety these ‘flooded’ batteries are by far the most common but are often found being used for the wrong application. Although a starting battery will work (for a short while) as a house battery it is really designed for the short but intense draw of power (75-400 amperes for up to 20 seconds) when the starter is energized. They are able to briefly take a high hit of energy and then be rapidly recharged in a short period of time by an alternator. Their burst of power is made possible by the higher amount of thin alternating positive and negative insulated plates that are found in their core. It is important that they are sized correctly and the marine cranking amps or cold cranking amps are adequate for the size of motor that is being started. A deep cycle battery or ‘house battery’ is made slightly differently, with less but thicker plates and it has the ability to be cycled or drained by a load over time and then be recharged from a lower state back to capacity. These batteries do well supplying energy for a boat’s electrical systems such as lighting, entertainment systems and more. In a pinch they also can act as a starter but are not internally designed to do so and if done too often will drastically shorten the life of the battery. When selecting a deep cycle battery it is important to have a bank that is capable of handling three to four times the required amp hours to achieve maximum life expectancy and not draw the batteries down too low. Within this range the batteries can work and charge optimally and battery life will be prolonged. Deep cycle batteries are available in different sizes with reserve power increasing with size. For marine use the most common, from small to large, are group 24; group 27; group 31; 4D and 8D. Not all batteries of the same size have the same capacity, so shop wisely. Another factor to consider when opting for starting and/or deep cycle wet cell of flooded batteries is the need for them to be adequately ventilated as they can produce harmful fumes.
The dual-purpose battery is a third lead acid battery, a hybrid of the batteries mentioned above. As with any hybrid, it is a bit of a compromise in that it will not have the comparable starting capacity as that of a comparable sized starting battery, and will not have the amp hours or deep cycle capacity as a comparable dedicated deep cycle battery. It will give you the capability of using it as a starter and to also draw it down like a deep cycle without damage. These batteries are particularly suited for applications such as in small boats that only have space for a single battery, or with small craft that need a two-battery setup with interchangeable batteries. With only a slightly higher cost than that of a standard wet cell battery, these provide a good all-around option for the small craft operator.
Rapidly becoming popular amongst boaters are the AGM, or Absorbed Glass Matt, batteries. These sealed batteries (requiring no water or maintenance other than charging) are made up of positive and negative plates just like standard batteries but they also have fine layers of porous fibered glass sandwiched between them that are coated in acid electrolyte. This configuration allows for an extremely efficient creation and transmission of power. What all this means is these batteries are more efficient, handle shock and vibration better and (when cared for correctly) are longer lasting than their wet cell brethren. They are completely sealed with special valves that regulate the internal pressure and because they are more efficient internally they can have more cranking power and more reserve power than comparably sized flooded batteries. They also charge faster than traditional deep cell batteries and drain less while sitting unused. These dual-purpose batteries are becoming the preferred battery of the discriminating boater despite their higher price tag and greater weight. Efficiency and longevity make them a good choice and increased value for most.
On the high end of the AGM spectrum is the TPPL, or Thin Plate Pure Lead, battery. These are AGM batteries with plates made up of almost pure lead that is rolled rather than cast, creating a highly efficient conductor. With this construction batteries can cycle longer, be drained more and have increased cycle life. These batteries are particularly good for long-range cruisers or battery users in remote locations. When configured properly they can charge quickly and provide increased power usage between charges. However, the cost of these batteries can be a drawback for boaters on a budget.
Gel cell batteries were the cream of the crop for many years, with the ability to be used in any position along with maintenance-free operation and very low idle power loss, but they have fallen in favor of the less expensive and highly capable AGM batteries. The high cost and need for chargers with specialized gel charging and regulating capability make them a choice for a limited few. Advantages of these batteries include manufacture to very high quality tolerances, suitable for mounting in areas subject to low expelled gases (all batteries expel some gases and should be ventilated), are submersible and can handle the highest amount of cycles of any of the above mentioned batteries.
The newest variety of battery on the market and also the most costly are Lithium Manganese batteries. These high end batteries are capable of double the cycles of even the best AGM batteries and can be drawn down an amazing 100% and be recharged, better than the best AGM batteries which can be discharged up to 80%, before being damaged. A relatively new technology, these batteries are just now starting to hit the market en masse. As manufacturing technology and efficiency improves and use of these batteries increases, the price will drop, but for now the cost is prohibitive for many boaters.
As with any marine equipment you generally get what you pay for. Understanding the differences and capabilities of different batteries, along with determining your needs and requirements, will ultimately get you the best battery within your budget.
Glenn Hayes is a freelance photographer and writer living in West Central Florida. Specializing in marine and location photography his work covers commercial, editorial and fine art work. www.HayesStudios.com