Mastervolt offers various types of maintenance-free batteries, each with its own specific characteristics. More information hereafter about the properties of gel, AGM and Lithium Ion batteries.
With flooded lead-acid batteries, which use a liquid electrolyte of water and sulphuric acid, the water is separated into hydrogen and oxygen during charging, mostly at the end of the charging cycle. These gases subsequently escape through the filler cap. This means water is used and distilled (battery) water needs to be added. The electrolyte in a Gel battery is a gel that binds the water with the acid. While the batteries are being filled, the gel is heated and liquefies.After the battery has been filled with the liquefied gel, the gel cools and solidifies. This process results in tiny hairline cracks in the gel between the plates. During the charging process, oxygen O2 is generated on the positive plate and hydrogen H2 on the negative plate. The cracks in the gel let the gases combine to create water. The gel then absorbs the water so that no water disappears from the system and no gases are produced.
Gel batteries are not a new technology and have been in use since the late 1950s. The most important applications are in emergency power systems, telecommunications systems, power supply and, for the last 20-25 years, as service batteries in various systems. Gel batteries come in two different versions. The 12-volt design is appropriate for regular use and available in capacities up to 200 Ah.
The second design is a 2-volt traction battery, available in capacities up to 2700 Ah and highly suitable for systems with frequent and significant discharging where a long lifespan is needed. For a battery of 12 or 24 volt, six or twelve Gel batteries need to be connected in series to provide the required voltage.
Major benefits of Gel batteries include very limited self-discharging, the possibility of a short charging time, and the lack of gas production under normal circumstances. All of this makes Gel batteries very suitable for heavy cyclical applications.
A different type of lead-acid battery is the AGM (Absorbed Glass Mat) battery. In this model, the electrolyte (water and sulphuric acid) is absorbed into an extremely delicate glass fibre mat. Just like with any other battery, charging generates hydrogen gas and oxygen, which are transported through the capillary tubes of the glass fibre mat. Once the two gases are recombined, water is once again obtained and subsequently reabsorbed into the glass fibre mat. The recombination process is then complete.
The glass fibre mat also serves as insulation between the plates, allowing the plates to be close together and leading to very low internal resistance. This means that a high discharge current is no problem. The charge current could be a little lower than with Gel batteries (approx. 30 %) because the glass fibre mat is also an efficient heat insulator, and heat generated by charging is gradually conducted to the outside of the case. This requires the charge current to be somewhat restricted and results in a slightly longer charging time.
AGM batteries are highly suitable for applications requiring a high discharge current, such as a bowthruster or winches and for medium cycle use. The AGM battery is entirely closed and therefore maintenance-free. If the AGM battery is overcharged, for instance due to the use of a (cheap) unregulated battery charger, a small amount of hydrogen gas is formed. This gas escapes through a special vent in the battery casing that is designed to prevent oxygen from entering the battery. Incorrect charging will reduce the battery’s lifespan.
Mastervolt’s Lithium Ion batteries are based on Lithium Ion iron phosphate, which has an energy density three times higher than that of lead-acid batteries. Although there are materials with an even higher energy density, these are generally considered less safe. The Mastervolt Lithium Ion batteries are therefore considered one of the safest batteries of their type. A unique feature is their built-in Battery Management System (BMS). The system monitors the cells and guarantees optimal safety. Mastervolt Lithium Ion batteries are MasterBus compatible, and up to 15 % more efficient compared to other Li-ion batteries available.
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