|Tech: Powering your 4x4 Vehicle Electrical Accessories||Short Cuts|
By: Dan Eddleman - 02/11
Fairly often questions arise on the best method to power the various electrical accessories commonly found in our 4x4 vehicles. Connecting into the complex wiring of today's vehicle wiring system can be challenging and there are pros and cons of operating either off the ignition switch accessory position or, a fused connection to the battery. The ChargeGuard® Automatic On/Off Switch, designed to solve this very problem in public safety and police vehicles, is a very clever solution to the same issue in 4x4 vehicles.
The particular dilemma that led to my discovery of the ChargeGuard switch was finding an acceptable solution for powering my onboard GPS system. Initially I had wired the GPS to operate from the ignition switch accessory position. On road trips, with the ignition being cut off at gas, food and other stops, the GPS track data was being broken up into a large number of small chunks of information. This became a nuisance when the data was later downloaded into a computer mapping application. My ham radio installation, originally powered by a fused connection direct to the vehicle battery, has an automatic timer built in to shut itself off after so many hours of operation. But this was not entirely satisfactory either, since it would turn off sometimes without my awareness.
Both commonly used practices of either connecting through the ignition switch, or a fused connection to the battery can be inconvenient. There may be circumstances where you want to use the electrical accessories, but not leave the key in the ignition for security reasons. With the direct battery connection, there's always the risk of a dead battery due to forgetting to turn off the accessory.
I began searching for a better solution and was very happy to find the ChargeGuard Automatic On/Off Switch, a reasonably priced solution to this problem. This unit is available from several contact sources listed at the bottom of this article.
|ChargeGuard Features and Operation|
|ChargeGuard Model CG12D||View Inside the Unit|
The ChargeGuard unit provides protection for the battery against excessive discharge, yet the convenience of having your CB radio and other electrical accessories operable when you need them regardless of whether the ignition switch is on or not. The unit contains 5 features to protect your battery from excessive discharge and additional protection especially important for electronic accessories.
|Installation on Interior Fire wall|
Per the ChargeGuard installation instructions, while the unit can be mounted inside the vehicle including under the hood, it is recommended that it be installed inside the passenger compartment where more moderate conditions exist. If installed under the hood, it needs to be in a dry and moderately cool location.
The electrical connections needed are a properly fused connection to the vehicle battery, connection of the unit's ground lead to a suitable ground, and connection of the electrical accessories to be controlled by the unit. Follow all instructions in the ChargeGuard general instructions for a safe, reliable installation.
In particular, ALWAYS provide proper fusing for any electrical connection made to the vehicle battery. Failure to do so would put your vehicle at risk of an electrical fire. Any wiring attached to the vehicle battery must have a fuse in series with the wiring, located at the battery (as done by the manufacturer for the OEM wiring) as shown below to protect the entire length of attached wire.
The electrical wiring to be used should specifically be for use in an automotive application. Automotive electrical wire uses insulation material suitable for high temperature applications and is more resistant to abrasion and corrosive environments. Fine stranded conductors are used to withstand the normal vibration present in automotive applications.
For optimum performance especially with high current draw electrical accessories, the wire gauge used should be chosen to not only handle current requirement, but also to minimize voltage drop. While most people's familiarity with wire gauge size and acceptable current loads probably comes from the National Electrical Code specifications, it should be remembered that those ratings are largely based on the acceptable temperature rise of the insulation materials used and should be viewed as the minimum size wire requirement. In low voltage systems, wire gauge must also be chosen based on consideration of the potential voltage drop. This will be application dependent based on the accessory current draw and length of the wiring used. Using wire one and sometimes two sizes larger than the minimum requirement may be needed to minimize voltage drop. While the maximum 35 amp fuse limit recommended by the manufacturer of the ChargeGuard unit could be handled with 8 gauge wire, I used 6 gauge to further minimize voltage drop to my mobile ham radio system. The connection terminals on the unit are suitably sized to handle the larger gauge wire.
Fuse sizes in my installation are based on a combination of the gauge of wiring used and the fuse sizes called for in the installation instructions of the attached electronic components. The main fuse at the battery is a 30 amp fuse, which is within the maximum 35 amp fuse specified in the ChargeGuard installation instructions and provides more than adequate protection of the 6 gauge wiring from the battery to the unit. Each device attached down stream of the unit has it's own fuse, sized as specified by the device manufacturer, and with appropriate gauge wiring.
|Fusing at Battery||Hi-Temp, Abrasion Resistant 6 Gauge Automotive Wire Used||Existing Grommet in Fire wall Used for Wire Entry|
|Operation and Observations|
At present time I have my GPS unit and ham radio system powered through the ChargeGuard. I have set the unit to shut off power 4 hours after the ignition was last switched off. This setting works nicely with the GPS set to accumulate track data only when the vehicle is in motion. The idle current power draw of both units is low enough that I can leave them switched on without any significant draw down of the battery.
If additional electrical accessories are added later, I plan to use a small fuse sub panel located adjacent to the ChargeGuard switch for more convenient attachment of the additional wiring.
|Garmin GPS-III+||Ham Radio Remote Unit|
ChargeGuard® is a registered trademark of ChargeGuard, Inc