The finished setup looks pretty good, and, best of all, it works like a charm. When we're not at the track, we can remove the actuator arm and seal the hole in the taillight with a small rubber plug. We can also still use the master disconnect switch as a trunk-mounted kill switch to slow down thieves. In addition, having this weight over the right rear of the car will help gain extra traction.
The overall weight of your hot rod is important, and where that weight resides is just as critical. Extra pounds hanging over the nose of the car won't help performance-whether you're drag racing or road racing-and the factory battery location for most cars is in exactly the wrong spot. It's generally mounted as far forward as possible, and relatively high (to make service easier). Since we're eking the most out of the Fairlane for drag racing, we want to reduce the overall weight and put as much of what remains at the rear, for better traction. The good news is that moving your battery to a better position isn't rocket science. The trick is locating it properly, and wiring it to provide trouble-free operation.
Increased room in the engine bay for other vitals is another advantage to moving the battery to the trunk. As a bonus, it looks cleaner. There are some items you need to think about if you're going to tackle this project. The most important thing is passing tech the next time you go to the track. According to the NHRA (see sidebar for regs), you'll need a few extra steps if you have a trunk-mounted battery and want their blessing. Other racing bodies, like the SCCA, have their own rules, so it pays to get familiar with them before beginning this job.
The main player in our story is this 24-pound Odyssey Battery by EnerSys (PN PC925, $132.69), which is rated at 925 amps (similar-sized lead acid batteries are rated far less). This battery is a dry-cell, so you don't have to worry about damage from corrosive acid. It's also compact, at about 6 1/2 inches long by 7 inches wide by 5 inches tall. | 
We found this lightweight welded battery tray (PN HDW-925, $54.95) at West Coast Batteries, where we also found the SAE terminal adapters for $12.95. We picked up this memory retention module from American Auto Wire (PN 500778, $26). If you have devices requiring constant battery power for memory circuit retention, this is the ticket. It passes 1 amp of continuous battery power, even when the master disconnect is off. |
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Stuff You'll Need:
* Drill and bits
* Stepped drill bit for making larger holes
* Rubber grommets
* Self-tapping screws
* Basic wrench and ratchet set
* Electrical connectors
* Zip ties
* Heat gun
* Shrink wrap (sized for 10-gauge wire), or electrical tape
* 10-gauge wire (around 20 feet)
* Welder or hardware to bolt down switch and battery tray
NHRA Regulations for Relocated Batteries
8.1 Batteries
All batteries must be securely mounted and may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch (.6 mm) steel or .032-inch (.8 mm) aluminum (including package tray) required when battery is relocated in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch (.6 mm) or .032-inch (.8 mm) aluminum, or FIA-accepted polybox. If sealed box is used in lieu of rear firewall, box may not be used to secure battery and must be vented outside of body. Strapping tape prohibited. A maximum of two automobile batteries, or 150 pounds (68 kg) combined maximum weight (unless otherwise specified in Class Requirements) is permitted. Metal battery hold-down straps mandatory. Hold-down bolts must be minimum 3/8 inch (9.53 mm) if battery is relocated from stock and other than stock hold-downs are used ("J" hooks prohibited, or must have open end welded shut).
8.4 Master Cutoff
A master cutoff is mandatory when battery is relocated, or as outlined in Class Requirements. An electrical power-cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car. This cutoff switch must be connected to the positive side of the electrical system, and must stop all electrical functions (including magneto ignition). The external control switch for this cutoff switch will be clearly indicated by a red flash inside a white-edged blue triangle, with a base of at least 12 cm. The positions must be clearly indicated with the word "OFF". If switch is "push/pull" type, push must be the action for shutting off the electrical system, pull to turn it on. Any rods or cables used to activate the switch must be a minimum of 1/8 inch (3.2 mm) in diameter. Plastic or keyed switches prohibited. Switches and/or controls must be located behind rear wheels on rear engine dragsters.
This battery relocation kit from Moroso (PN 74055, $99.88) comes with most of the stuff you need to get the battery in the trunk and wired. It includes 20 feet of 2-gauge copper cable, four terminals, 8 feet of cable with top-post terminals, rubber-lined D-clamps, grommets, and heat-shrink tubing. Moroso's super-duty switch (PN 74102, $59.88) has a rating of 2,000 amps intermittent, and 300 amps continuous. | 
Here's what we started with: battery acid had destroyed the factory tray, and the battery was held in place by a bungee cord. It's unsafe, would never pass tech inspection, and weighs 48 pounds (24 pounds heavier than our new Odyssey battery). |
The NHRA doesn't care if your battery is an old-school wet-acid type or a new dry-cell variety. If it's in your trunk, it needs to be sealed off with a battery box or a rear bulkhead. This battery box by Moroso (PN 74050, $96.88) includes mounting hardware and vent tubes, and is the only plastic box that has the NHRA stamp of approval. If you use a box, make sure you secure it per NHRA regulations. The yellow arrow points to a factory plug in the trunk floor. This is where we're running our ground cable to the frame. | |