Protection for multiple batteries.

Battery Isolator

Our customers continue to add electrical content to their cars and trucks.  The more electronics they add, the more current they consume.  This is especially true when you are adding powerful stereo systems with sub-woofers and high-wattage amplifiers.  A lot of our customers will add multiple batteries to their electrical systems to increase the available power.  To add multiple batteries safely and get the most reliability out of them, we always recommend adding a battery isolator between them to that they charge and discharge safely.  This post is going to go through the details of battery isolators and why they are critical to multiple battery systems.

In most cases, you want to have a battery in your car or truck that powers all of the main functions.  These functions include your ignition, starter, lighting, fans, fuel pumps, horn and turn signals.  You also may want to add a second battery just to power the high-wattage demand of your stereo.  This second battery would power the amp and sub-woofer.  You may also want this second battery to power any other A/V equipment like TV’s and gaming consoles.  This way you can take your car to a show or take it tailgating, use your stereo and not risk running down the main battery that starts the car.  The problem is that in some cases, two batteries wired together can cause problems.  If one battery is weaker than the other, it can rob charge from the stronger battery.  This picture shows how this happens.

One battery can deplete the other

Example of two batteries wired in parallel with no battery isolator

A weaker battery can drain a healthy charged battery in your vehicle.

The simple solution is to add a battery isolator between the two batteries.  Examples of good battery isolators are manufactured by Littelfuse and Bussman.  These can be purchased at companies like Del City and Waytek Wire.  This picture shows the battery isolator wired between two batteries.

Both batteries are isolated from each other

Dual battery system with a battery isolator

The battery isolator stops current from flowing between the two batteries while allowing both to charge safely from the alternator.

This picture shows how most battery isolators are wired between the alternator and the bank of batteries.

Battery Isolators are Key to A Safe Multiple Battery System

Example wiring diagram for a dual battery system with a battery isolator

When you’re using our Infinitybox system, that is going to get powered from the primary vehicle wiring.  All of your accessories like amps, sub-woofers, inverters and winches will get their 12-volt power from the second battery.  If the accessories drain the second battery, this drain will not pull down the primary battery.

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