
Everything you need to know about boat batteries
After cold winter months, the new sailing season begins every spring! Before you set sail, however, the boat should be maintained and spruced up. Winter is therefore the right time to plan, order and install new purchases. This includes, for example, new batteries that may have lost power over time. But what are boat batteries anyway, what are the different types and which battery do you need for your own boat? All the answers are here.
Advantages and disadvantages of lead-acid wet batteries
Lead-acid wet batteries are considered inexpensive batteries for use on boats. The batteries are maintenance-free and can be installed without any problems, even at greater inclination. Therefore, they are particularly suitable for sailing yachts. Lead-acid wet batteries can provide continuous power as well as short and high energy output for starting.
However, they should not be stored for long periods without trickle charging. For installation, you should note that during use and charging, gases are generated and escape from a valve. Therefore, lead-acid wet batteries should always be placed in well-ventilated places and are unsuitable for narrow or poorly ventilated boxes.
Advantages and disadvantages of gel batteries
Gel batteries are similar to lead-acid wet batteries, but are treated with thickener to give them a gel form. This prevents them from leaking and makes them suitable for use anywhere on board, except overhead. The batteries have a high internal resistance, so they can be stored for a period of time without being charged.
But again, batteries should not be deeply discharged, as this can cause damage. Gel batteries are often used as service batteries for the vehicle electrical system and its consumers. They are unsuitable as an engine battery, as they are not particularly good at delivering short or high currents. Therefore, gel batteries should rather not be used as an engine battery.



Advantages and disadvantages of AGM batteries
"Absorbent Glass Matt" means that the acid is absorbed and bound in a glass fleece. AGM batteries have become popular on boats because they combine all the advantages of gel and lead-acid batteries. This is why AGM batteries can be installed in any position, are maintenance-free and shock-resistant. At the same time, they hardly discharge themselves and the charging process works very quickly. AGM batteries, unlike lead-acid or gel batteries, can be discharged deeper. In addition, the popular boat battery is ideal for use as both a starter and a consumer battery. Since AGM batteries provide continuous power up to a deep discharge of up to 50 percent, you can also use them for electric drives.
If you want to discharge AGM batteries above 50 percent as an exception, you have to expect that this will significantly shorten their service life. A discharge over 80 percent even leads to battery death.
Advantages and disadvantages of lithium batteries
The most expensive, but at the same time the best solution are the lithium batteries. Lithium batteries are not only extremely light, but also have a high energy density and have extremely high capacities. The output voltage hardly drops, if at all, even at low charge levels. At the same time, lithium batteries can be charged quickly and are especially popular in modern electric boats. You can fully charge a lithium battery in just one to two hours.
However, even these high-quality and expensive batteries can suffer damage from overvoltage or deep discharge. Therefore, battery management systems (BMS) are installed by manufacturers to protect against application errors as well as short circuits. In addition, they continuously measure the charging currents, condition and battery temperature.
How long does a boat battery last?
High quality boat batteries can last up to ten years. On average, however, you should expect them to last around three to five years.
Häufig gestellte Fragen - FAQs
Was ist eine Bootsbatterie?
Die Bootsbatterie ist speziell für Boote konzipiert und unterscheidet sich deutlich von anderen Batterien: Diese kann lageunabhängig eingebaut werden kontinuierlich über einen längeren Zeitraum Strom für das Boot liefern.
Wie werden Bootsbatterien noch genannt?
Bootsbatterien werden auch „Marine Batterien" oder „Bordbatterien“ genannt.