FAQs About Battery Isolators

Battery isolators are devices designed to divide direct electrical current (DC) into multiple branches. Once divided, the current can only flow in one direction along each branch. The purpose of using a battery isolator to divide direct current into branches is to charge multiple batteries from a single power source without connecting the batteries in parallel.

Q: Why is it best to not connect batteries in parallel?

A: It is best to avoid connecting batteries in parallel because if there is a weak or dead battery in the connection, it drains the power from the other batteries with which it is directly connected. This is avoided by using a battery isolator.

Q: Are there any disadvantages to using a batter isolator?

A: Battery isolators are not without disadvantages. Using an isolator in situations that call for multiple batteries adds to the cost of charging batteries, as one must buy the isolator. They range in price from less than $20 to $100 or more. Also, using a diode-type isolator, which is a common type of battery isolator, results in a loss of voltage between the power source and the batteries. The risk of having a weak or dead battery drain the power from a strong battery if the batteries are connected in parallel offsets the disadvantages of using an isolator.

Q: Where are battery isolators used?

A: Battery isolators are used wherever there is one battery dedicated to providing power to a starter and another battery to power accessories. Battery isolators are commonly found on boats, RVs, large trucks, utility vehicles and airplanes. The isolator insures that the main battery has enough charge to start the engine and recharge the batteries if the power load from the auxiliaries, such as navigation lights, has caused the secondary battery to drain. Cars with large, high powered stereo systems which require multiple batteries also use battery isolators.