When you build a custom high quality stereo system, something to avoid is running your battery flat while listening to your sounds with the engine off. The last thing you want is your mum or significant other having to drive over and jump start your struggling charging system.

There are many ways to upgrade your power system, but they usually come with a consequence. First and foremost being the power loss to the vehicle. A few kilowatts will be lost due to additional electrical load imposed on the engine.

The required voltage your starter needs to start the engine is around 9.6 volts. Without this, the solenoid will not pull in. Instead you will hear a clicking noise from your starter, signifying the battery voltage is too low.

The best way to wire up a second battery is to use an automatic switch (battery isolator) which joins the batteries together when the vehicle is running, and then isolates one battery so that it can be used for electronic devices when the vehicle is off.

The best battery isolator I have found for the job is made by Capital instruments and can be sourced though any Auto Electrical store. It is called a Chargeguard Battery Isolator. It’s designed to be used in multi battery applications as a solenoid priority system to protect the starting battery from excessive discharge, while allowing the auxiliary battery to supply non-essential loads (such as car audio).

The Chargeguard monitors the voltage on the start battery, when this drops below 12.5 volts the solenoid will release separating the start battery from the auxiliary battery.

Once the engine has started the Chargegaurd monitors the start battery until it reaches 13.5 volts, indicating it is fully charged. The Chargegaurd will then close the solenoid connecting the auxiliary battery to the start battery and the charging system.

The Chargegaurd is ideal for car audio installations that can not tolerate the inherent voltage drop associated with a Diode battery isolator. The best part about this system is that it is basic to install.

This entry was posted on Tuesday, August 26th, 2003 at 5:22 pm and is filed under Tech Articles. You can trackback from your own site.