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Auxiliary Batteries and wiring
Two Optima batteries added to power the camper, lights, air compressor, etc.

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Note: the electrical system and this page are under construction

The Batteries:

Campers, lights, and air compressors can deplete a starting battery leaving one unexpectedly setting in the woods. After some calculation, I concluded that a pair of 65 AH Optima Yellow Top deep cycle batteries would power my electrical needs. 130 AH of capacity would power the camper for at least a week, and could run for longer periods when boosted with the engine alternator or a small solar collector.

By saving the truck batteries for the engine only, starting should never be a problem. And if somehow the truck batteries died, I could always jump them with the two 750 CCA Optima's.

A pair ordered from a local accessory shop, arrived the next day.

Battery photo

These batteries are designed for cyclic applications and for use in vehicles with large accessory loads.

Battery Specs

Battery Mounting:

Unfortunately, the diesel Ram already has two starting batteries and little room for additional batteries under the hood, so another alternative was needed. There is room for one battery on each side beside the frame under the floor, but the batteries need to be protected from stones thrown by the front wheels.

Summit Racing Equipment manufactures a closed aluminum battery box that can be cut in half and turned on its side to fit one battery in each (now) open-top half.

Summit Logo

Summit Racing Equipment
PO Box 909
Akron, Ohio      44309-0909
1-800-230-3030    or    1-330-630-3030

assembled battery box DESCRIPTION: This aluminum box has a non-sealed design that can be configured for installation anywhere. Depending on how you bolt the panels together, your cables run through pre-punched holes in the back or the side, high or low. The box comes complete with its own assembly/installation kit including a heavy duty battery hold-down, two battery hold-down brackets, high grade bolts and nuts. Holds up to a group 27 battery.
The outside dimensions of the battery box are: Depth: 10 1/2 in. Width: 9 7/8 in.  Length: 14 5/8 in.
SUM-E890100   Natural finish aluminum battery box
SUM-E890101   Black finish aluminum battery box - cost was about $90 in 1999
The Summit battery box is huge and can be split in half, with each half turned on end to form a pair of open top optima boxes. The batteries still have their plastic wrappers in this photo. Box cut in half for two batteries
Each box half receives a pair of angle iron brackets. Four 3/8" bolts attach the battery box brackets directly to the frame beneath the cab, one box on each side of the truck.
It is difficult to reach the battery terminals after the batteries mounted under the cab, so standard battery cables run from the top to 3/8" SS terminal blocks mounted on the battery box. All power is distributed from the large terminal blocks. This adds an additional connection for each terminal, but it is more convenient than unbolting the battery box from the frame to add or remove a connection. box and battery ready to mount
This arrangement easily supports the 50 pound battery plus me hanging from the box. The driver side mount is more complicated because the parking brake cable must remain clear, and the fuel tank, brake line, fuel lines, and wiring are behind the frame rail - watch where you drill the mounting holes and be careful, the plastic fuel tank is behind the frame. There is enough room between the fuel tank and frame to install the bolts without moving the tank.

Battery Charging Circuit

An isolator is needed to prevent accessory loads from draining the starting batteries when the engine is not running. Isolators can be diode arrays or a an electrical solenoid switch. I prefer the solenoid because there is no voltage drop across a solenoid, it is reliable, and it easy to find a replacement when it fails. Number 8 wire feeds both 12V and ground from the main batteries to the solenoid, then to the aux batteries. The solenoid and a 40A circuit breaker are bolted to the air filter housing.

The winch will on the main starting batteries because voltage drop on the long run from the aux batteries would be too great.

Power Distribution

Each battery box has a surplus terminal block with three 3/8X24 stainless steel studs for large wire junctions. Fortunately I had a handful of 3/8x24 stainless nuts salvaged that had been salvaged from junk (3/8x24 hardware was commonly used for mobile antennas many years ago). Autozone Auto Parts had battery cables in various lengths.

I wanted a Ram underhood PDC from a junkyard, but was unable to locate one and settled for a PDC from a Dakota which is smaller and has fewer circuits. The Dakota PDC contains enough relays and fuses for the aux lights, camper, pre-luber, etc. The fuses and relays are the same as those in the Ram PDC and can be borrowed in an emergency.

A small fuse panel from a Chevy sedan provides the continuously hot circuits for the compressor and camper feeds. An ABS relay from a minivan is used for the power switching relay for the air compressor. These are mounted to the battery box under the driver side of the cab. A ground lug bolts to the cab mount and it is tied directly back to the main battery.

NOTE: This wiring is incomplete and will be reworked.

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This page was edited on: May 3, 2004