An electric device which splits direct current into several parts or branches, but allows current only to pass in one direction in each of these branches is called a Battery Isolator. This arrangement enables to chargebatteries, instead of one battery at a time from single source of power not necessarily connecting battery terminals parallelly.

Purpose of Battery Isolator

Atleast one battery isolator is found on trucks or any other vehicles as they prevent drains and ensure that starting battery is charged enough and perfect to start the engine. Battery isolators are also used for utility and recreational vehicles, large trucks, airplanes, and boats. The batteries have different purposes; One battery is used for starting and running the engine while other batteries are used to run accessory loads such as instruments, winches, radar, compressors, lights and more. Silicon diodes are used to make battery isolators, which acts like check valves. These diodes allows the current to pass from batteries, but do not allow to pass back from a charging source.


To start the engine with starting battery, it should have enough power supply, which is ensured by battery isolator as well as batteries recharge is taken care of, in case overloads or fails of auxiliary batteries such as; navigator lights or refrigerators. Other than these, battery isolators are also used for large and high power stereos of car and adapts high current loads for off road vehicles.

Battery isolators are useful, as they save a dead or weak battery drains from strong battery charging, when connected together directly, but they are costly and little complex.Moreover, a voltage drop is experienced in circuit between the batteries and charging sources, if a diode type isolator is used.

Safety with Isolators

                Having a battery isolator helps in interrupting power before starting to work on a vehicle’s wiring. Sparks are produced when one gets a bare contact which may cause fire. Isolators are operated by simply inserting a key into a slot and is turned clockwise, that locks isolator in place and closes the circuit and turning key anticlockwise opens the circuit. Battery isolators differs in capacity, say, a battery isolator intended for a small car cannot handle more load, thus, before fitting isolator, confirming and matching its specifications relevant to the circuit and battery of vehicle is necessary.