Why is it so important to have a heavy-duty marine battery on board?
A marine battery is the most important electrical component in your on-board power system. When the engine isn't running and there are no other energy sources such as wind generator or solar panels available, the marine battery is therefore the only energy source to supply power to consumers in the on-board network. Since most boats and yachts are equipped with extensive, high-quality electronics, a complete battery failure is a veritable maritime emergency.
What types of boat batteries are available for use on board?
The types of marine batteries available are just as varied as their intended use.
Boat engine starter batteries
Batteries for starting the boat engine, also known as starter batteries or car batteries have to provide high current for a short time. Only a small amount of energy is drawn during the starting process and quickly recharged when the engine is running.
Boat consumer batteries
Batteries that are used to provide power to electrical consumers (lights, navigation instruments, fridges, etc.) are known as consumer batteries or 'house' batteries. In recreational vehicles or in caravans they are also called leisure batteries. Consumer batteries for boats are used cyclically. This means that they are regularly discharged more than a starter battery. They have a greater depth of discharge, also known as DOD.
Bow thruster & winch batteries
A bow thruster or winch battery supplies power to the bow or stern thruster or the winches on board. It has to provide a lot of power at short-duration and is therefore comparable to a starter battery. As the running times are longer with bow thrusters or winches than with starters, more energy is drawn from bow thruster/winch batteries. Bow thruster manufacturers define a minimum capacity that should be maintained.
Batteries for electric outboard engines
Electric outboards require no fuel and are powered by a rechargeable battery
Boat batteries for multiple applications
There are cases where there is no separate bow thruster battery or winch battery. In these instances, the bow/stern thruster or winch is connected to the boat's consumer battery. In other cases, bow/stern thrusters or winches are connected to the boat's starter battery. This must of course be taken into account when selecting the type of battery and battery capacity.
What different technologies are available for marine batteries?
Nowadays a distinction is made between lead acid and lithium technology for marine batteries.
Lead-acid batteries include traditional serviceable (flooded) and maintenance-free (sealed) wet batteries with liquid electrolyte (water-diluted sulphuric acid) as well as gel batteries and AGM batteries.
Lithium batteries have been tried and tested for use in small consumer appliances and power tools due to their high energy density and low weight. They are now also available as high-performance batteries based on lithium iron phosphate (LifePO4) and lithium nickel manganese cobalt oxide (LiNMC) technology.
Which marine battery is the best choice for my boat?
Maintenance-free lead/acid wet batteries - Ideal as bow thruster/starter or consumer battery
The wet batteries available from us are maintenance-free. Thanks to their lead alloys and sealed housing designs with a pressure relief valve, the batteries have such low water loss that they carry enough acid for their entire life cycle. If excess gases are produced during operation or charging, these can escape through the valve via a small vent in the upper part of the housing. Maintenance-free marine wet batteries tolerate greater heels/slopes without acid leakage. Nevertheless, they should be placed in an acid-proof battery box
and in a well-ventilated location. Our maintenance-free marine wet batteries can be used as starter/bow thruster and consumer batteries. To prevent premature battery wear, a discharge depth of ideally 35% to a maximum of 50% should be maintained. A deep discharge can lead to irreversible damage.
Gel batteries as consumer batteries
Gel batteries belong to the group of Valve Regulated Lead Acid (VRLA) batteries with a completely closed housing, in which the battery acid is thickened with kieselguhr. The gases produced during operation recombine to water inside the housing of the boat battery. Gel batteries are extremely low in gassing, leak-proof and can be used in boat or vehicle interiors regardless of position (but not overhead). There is no loss of capacity due to acid stratification/separation. The electrochemical processes in GEL batteries are not as efficient as in wet batteries, they have a higher internal resistance, with the advantage of very low self-discharge and very good storage capability. However, they are less suitable for providing high currents for short periods of time, for example to start the engine. Therefore they are ideal consumer batteries. The recommended discharge depth is 50%. Occasional deeper discharges are tolerated, but are at the expense of service life. A total deep discharge will also ruin a GEL battery.
AGM batteries as bow thruster, consumer or starter battery
AGM (Absorbent Glass Mat) is the most modern lead/acid boat battery variant, in which the battery acid is bound in a glass fibre mesh. Like gel batteries, they have a completely closed housing and are also valve-regulated, absolutely leak-proof and low-gassing, shock and vibration-resistant, can be mounted and operated in any position (except overhead) and have a low self-discharge rate. Compared to the GEL battery, the electrochemical processes in AGM batteries are much better. AGM has a lower internal resistance. This means that an AGM battery can absorb larger charging currents and also emit larger consumption currents. AGM can be used both as a consumer battery and starter or bow thruster battery. The recommended discharge depth is 50%. Occasional deeper discharges are tolerated, but are at the expense of service life. More than 80% discharge will cause irreversible damage. "Deep Cycle" AGM batteries are optimised in design and can be discharged regularly more than 50%, but never more than 80% (observe manufacturer's instructions!).