Any more could cause the equipment to malfunction. If navigation or communications equipment such as GPS or VHF devices is connected to the battery, the ripple voltage should be no more than 100 mV (0.1 V). As a rule of thumb, the ripple current should remain below five per cent of installed battery capacity. The ripple voltage results in ripple current. To prevent this, the ripple voltage caused by a charger should remain as low as possible. The harmful effects of ripple voltage on batteriesĪ battery can become prematurely defective due to the ripple voltage produced by battery chargers. The after-charge phase phenomenon again does not apply to Lithium Ion batteries, which are charged much faster. In the second phase, also called the absorption or after-charge phase, the type of battery determines how much current is being absorbed, independently of the capacity of the battery charger. In Lithium Ion batteries, the efficiency is as high as 97 %.Īnother thing that needs to be kept in mind when calculating charge time is that the last 20 % of the charging process (from 80 to 100 %) takes around four hours with wet, gel and AGM batteries (this does not apply to Lithium Ion batteries). With gel and AGM batteries, the efficiency is higher – 85 to 90 % – so there is less loss and the charge time is shorter in comparison with wet batteries. This means that if 100 Ah are discharged from the battery, 120 Ah need to be charged in order to be able to extract 100 Ah again. In a standard wet battery, this is around 80%. The first consideration is the efficiency of the battery. The formula below is used to calculate the charging time of a Lithium Ion battery:Įff = efficiency 1.1 for a Gel battery, 1.15 for a AGM battery and 1.2 for a flooded batteryĪb = consumption of the connected equipment during the charging process Calculating charging timeĬalculating the charge time of a battery should take into account the following: ![]() The formula below is used to calculate the charging time of a Gel or AGM battery: Outside of these limits, the Mastervolt battery charger will continue to supply the connected consumers but not charge the batteries.Īdjusting the voltage to a higher or lower temperature is not required for Lithium Ion batteries. The compensation is at most 14.55 V for a 12 V system, and 29.1 V for a 24 V system.Īt very high (> 50 ☌) and low (<-20 ☌) temperatures, wet gel and AGM batteries may no longer be charged. We call this ‘temperature compensation’.īecause devices such as refrigerators are always drawing power from a battery, even while it is being charged, Mastervolt’s temperature compensation includes a maximum offsetting effect to protect the connected devices. This adjusts the charge voltage to the temperature of the battery, extending its lifespan. ![]() These battery chargers continuously regulate charge voltage and charge current.įor wet gel and AGM batteries, it is recommended to have a sensor for measuring the temperature of the battery. A battery charger with temperature compensation for optimal protectionĮnsuring the longest possible lifespan for gel, AGM and Lithium Ion batteries requires a modern Mastervolt battery charger with a three-step+ charge characteristic. For a 180 Ah battery, for instance, this means a maximum charge current of 60 amperes. However, to maximise the lifespan of the Lithium Ion battery, Mastervolt recommends a maximum charging current of 30 % of the capacity. Mastervolt Lithium Ion batteries can be subjected to much higher charge currents. ![]() The maximum charging current is 50 % for a gel battery, and 30 % for an AGM battery. This means that a 400 Ah battery bank and a connected load of ten amperes requires a battery charger capacity of between 70 and 90 amperes in order to charge the battery in a reasonable time. During charging, you usually continue to supply power to connected devices, and this power consumption should be added to the 15-25 %. Charge currentĪ rule of thumb for gel and AGM batteries states that the minimum charging current should be 15 to 25 % of the battery capacity. The float voltage is 13.5 V for 12 V and 27 V for 24 V systems. Lithium Ion batteries are charged with an absorption voltage of 14.25 V for 12 V, and 28.5 V for 24 V systems. The float voltage for this type of battery is 13.25 V for 12 V and 26.5 V for 24 V systems. These figures assume a temperature of 25 ☌.įor wet lead-acid batteries, the absorption voltage is 14.25 V for 12 V systems and 28.5 V for 24 V systems. The absorption phase is followed by the float phase (see 3-step+ charging characteristic on page 242) in which the voltage is reduced to 13.8 V for 12 V systems and 27.6 V for 24 V systems. Mastervolt gel (2 V, 12 V) and Mastervolt AGM (6 V, 12 V) batteries should be charged with a voltage of 14.25 V for 12 V systems and 28.5 V for 24 V systems.
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