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Safely Adding Electrical Upgrades or Dual Batteries


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This is one that should be common sense, but i have seen vehicles where the owners overlook this. Whenever you upgrade the alternator output to a vehicle, or change to higher amperage batteries, or even set up dual batteries, always watch where the wires are run very closely.

 

When i wire everything up, i used heavy gauge wire, with insulated clamps to mount the wires to the inner fenders, away from anything that would cause an issue with it, and run the wires for the dual batteries through the firewall to the switch in a short piece of conduit bonded to the firewall.

 

If you wire through a hole drilled in the firewall, with no additional insulation of any kind, the wire's insulation can rub through and cause it to catch the vehicle on fire. This can be easily prevented by using a readily available rubber grommet to insulate that one wire where it goes inside the cab.

 

I have worked on many vehicles in the past where people don't pay attention to things that could cause an issue later on down the road. Safety should always be first and foremost in any vehicle repair or upgrade of any kind.

 

On my 1994 Dakota, i have switched dual batteries, with the switch inside the cab, for ease of access, a higher output alternator, 1200 watt two channel amp, electric over hydraulic Meyers plow, 4 combination driving/fog lights on the front, hard wired 1800 watt power inverter in the cab, and all of the wires under the hood are run through PVC conduit that is attached to the truck with insulated hard rubber/metal clamps. The wiring in the cab is run through double layer flexible plastic, like the manufacturers use, that way i never have to worry about a fire, or a wire shorting out at the wrong time. I know running conduit isn't always practical in some vehicles, but even flexible tubing, and rubber grommets, are better than exposed wiring everywhere.

 

And, no matter what you are wiring, from aftermarket lights, to stereo systems, to winches, plows, whatever it may be, zip ties are a very inexpensive and valuable addition to any toolbox.

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You bring up good points, biggman100.  Wiring can be risky business if the "down the road" effects are not thoroughly considered.  This means vibration, shock, heat, twisting, flexing, sharp edges, poor connections, bad connector choices, improper mating of wires, improper wire gauge, insufficient insulation, bad soldering technique, improper use of heat shrink or tape, and poor grounds.

 

At the very least, emulate OEM quality, gauge, insulation method, connector type and safe wire routing...If upgrading, know amperage loads, wire types, wire gauge requirements and insulation types.  Outfits like Painless Wiring provide guidance and "kits" for a variety of rewiring chores and upgrades.  You can get ideas here.

 

Member questions on wiring safety are welcome!

 

Moses

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Really valuable point, RareCJ8!  Relays are the common way to switch high amperage circuits, and your suggestion is important.  By simply using high-amp load relays, activated by lower amp wiring circuits and switches, you can keep all of the heavy amp circuits under the hood, or at least use shorter cable leads. 

 

Relays are used in winches, for activating starter motors, for switching gangs of lights, for wiper motors, for just about every circuit in a modern vehicle.  The first wide use of relays was on European cars and trucks, driven by Bosch's fascination with power boxes and circuit relays.  Today, all contemporary vehicles have a Power Distribution Box with rows of relays and fuses.

 

For those curious about the relay circuits on a stock vehicle, take the lid off the power distribution box/panel of your modern car or truck.  (For a Jeep, there are usually as many relays as fuses.)  The use of CAN-bus may change this relationship, but the idea is clear.  And for high amp circuits like biggman100 and RareCJ8 describe, review the wiring and relays used in Warn winches or even your vehicle's starter circuit.  The magnetic starter solenoid (a relay) gets activated by lower amperage wiring from the key/start switch. 

 

Relays simplify wiring and shorten the length of higher amperage-carrying cables—and this reduces resistance load.  Going through the firewall with heavy cables becomes unnecessary, as lower amperage switches and lighter gauge wiring can trigger a high amp relay or starter motor type solenoid elsewhere—like beneath the hood as RareCJ8 suggests. 

 

The heavy cabling is simply from the battery to the remote relay and from the relay to the heavy draw device...The classic "Ford type" solenoids have been popular for a variety of aftermarket accessories since the flathead V-8 era!  There are a variety of high-amp relay designs available for automotive and marine use.  Painless Wiring is a good source, again, for ideas and products.

 

Moses

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  • 2 weeks later...

One more thing i want to add to this, after an experience i had today. I would never recommend that anyone run a single heavy gauge wire from the battery through the firewal, and then branch off from there. I saw a vehicle today where someone had done this, and my first thought was he was hoping for a fire, so he could collect on the insurance. He had the main single wire run inside the vehicle, then using a branch block, ran heavy duty wires to 2 sepearate high wattage amps, one capacitor, which i would never place in the open in any vehicle, and two different sets of neon under vehicle lights.

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