Battery Isolators

Battery isolators - charging several batteries at the same time.

With multiple battery groups in the on-board electronics, it is important to isolate them from each other so that they do not affect each other. This includes, for example, keeping the consumer and starter batteries separate so that the starter battery is not accidentally discharged by the electrical equipment. Otherwise, the voltage could drop to the point where the engine won't start. The systems should also remain separate during the charging process. Nevertheless,

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to be able to charge several batteries at the same time with only one power source such as the alternator, you need a charging current distributor. Here in FraRon's online store, you can find the component for up to three battery banks.

3 ways to separate batteries from each other

To prevent several batteries in the on-board network - for example of boats - from discharging each other, three different components can be used: simple isolating diodes, isolating relays or charging current distributors. Isolating diodes are semiconductor components that regulate the current so that it can only flow in one direction. This means: charging is possible, discharging is not. The disadvantage of diodes is that 0.7 volts of voltage are lost when they are used, due to their design. This reduces the charging voltage arriving at the battery by this value. A full charge, which is necessary for the service life of the batteries, can therefore not take place. Such isolating diodes with 0.7 V voltage drop were installed in the past and are usually no longer used today.

Cut-off relays are electromagnetic switches that work like diodes but mechanically separate multiple batteries. Their advantage is that there is no voltage loss. However, they require a pulse, which usually comes from the D+ alternator terminal. Disconnect relays controlled by D+ are usually factory installed by motorhome manufacturers. In FraRon's range, we offer modern voltage-controlled relays that no longer require D+. The charging current distributor can be seen as a further development of the isolating diode. The built-in electronics bypass the diode during charging so that the voltage does not drop. As a result, both the required charging voltage and the maximum current reach the batteries.

What is the difference between a charging current distributor and a battery cut-off relay?

A battery disconnect relay connects all batteries in parallel that are to be charged. When the alternator is working while driving, the relay connects the batteries. If the starter battery is already full, the supply battery continues to be charged up to the charging end voltage of the alternator. When stationary, the batteries are disconnected again so that they do not discharge each other. Simple battery disconnect relays are coupled to the D+ signal of the alternator, which signals the control voltage to them. More modern models operate with electronic voltage monitoring. The most important difference with the charging current distributor is that it distributes the current optimally to the batteries without coupling them to each other for this purpose. As a result, it charges all battery banks simultaneously.

If the coupling of the battery banks is realized by relays, a consumer that is more powerful than the charging source can discharge all coupled batteries. This is prevented with the charging current distributor.

Different models of charging current distributors

The Victron Energy charging current distributors in our range are available in different variants. They are available for up to 100 or 200 amps and for two or three battery banks. The manufacturer distinguishes between two types of its charging current distributors: Argo diode battery isolation and Argo FET battery isolation. Argo diode technology is characterized by low voltage drop, which can be attributed to the use of high-efficiency Schottky diodes. In contrast, there is virtually no voltage drop with FET isolation: less than 0.02 volts at low current and an average of 0.1 volts at high current. That's why you'll only get the more advanced Argo FET models from FraRon.

Do I need a charging current distributor for my motorhome?

Charging current distributors are not usually used in motorhomes. This is because there is typically only one starter battery and one body battery bank in the motorhome. An isolating relay or a charge booster are more suitable as a disconnecting and connecting link. The charging current distributor technique is useful for boats with multiple battery banks. This gives you the advantage that your starter battery and supply batteries are separated from each other and cannot discharge each other. In addition, all batteries can be charged at the same time without voltage loss. If you have any questions, please do not hesitate to contact us. Just give us a call! We can also advise you on the dimensioning of the battery cables so that you benefit from short cable runs and sufficient cross-sections. In addition, we offer you support with the installation of the charging current distributor with our installation service.