Battery weight isn’t easily adjusted. Once it’s in the car,
it’s in the car. In many cases, the rules dictate where
batteries can and cannot be mounted. In most cars, you
can’t mount the batteries between the frame rails with
the fuel cell and orient them in the standard side-to-
side fashion. In something like a small front wheel drive
conversion (for example a relatively common NHRA SS/
GT car) the trunk well is very small, further restricting
battery mounting options.
The most important factor is to mount the batteries
solidly. This is one of the primary reasons why most
chassis builders like to mount batteries between the
frame rails. The prevents a situation where batteries
come flying off the mounts. Battery mounts are no place
to look for easy weight reduction, but you can opt for
robust mounts that aren’t portly either.
Pro chassis builder Jerry Bickel typically mounts the
batteries side by side in the center of the trunk.
“We typically use AGM batteries in many of our cars,”
Bickel explained.
“Although plate migration isn’t really an issue, we still
mount the batteries with the plates parallel to the sides
of the car. This eliminates any chance of an internal
battery short.
“Given certain factors such as vehicle size, the choice
of equipment on a car, driver weight and so on, some
cars are heavier than others. Because of this, the battery
weight has a direct influence on the weight distribution
in the car.
“Mounting the batteries outboard with the fuel cell in
the center of the car is an acceptable practice. But in
a case where the car is heavy, you can’t remove one of
the batteries to compensate for the weight easily. This
would mess up the weight distribution.”
Mounting the batteries in the center has other
advantages.
“By mounting the batteries in the center of the car,
you have the option of removing one battery, and not
destroying the corner weights,” Bickel said.
“Mounting the batteries in the center of the car also
gives you option of moving them forward or back, which
can influence the weight distribution.
“I also feel a battery or a pair of batteries is safer when
mounted between the frame rails. In a crash, the fuel
cell has a better chance of withstanding an impact than
the batteries.”
batteries have to be moved upward,” explained Bickel.
“If you mount the b atteries too high, then the posts
or other electrical connections can touch the deck lid.
Pro deck lids are constructed from carbon fiber, and it’s
a good electrical conductor. This limits the mounting
location for the batteries.”
Dual batteries may not be necessary in cars with
a good charging system. But considering all of the
electronics in a modern drag car, a pair of batteries
can be a serious bonus. If you decide to run a pair of
batteries, hook them up in parallel. This effectively
doubles
their
individual
amp-hour
capacity.
To hook up the parallel circuit, route the “hot” starter
lead to one battery, then run a line from the positive
(+) post on one battery to the positive post on the
second battery. The second battery should then have
its negative post (-) grounded with a cable joining both
batteries’ negative terminals. The batteries should be
identical in construction and capacity. Do not mix a new
battery with an old battery.
Another consideration with rear-mounted batteries
is the battery shutoff switch. It’s mandated by the
sanctioning body rules. An easily accessible master
cutoff switch allows someone to turn off all electrical
power in the event of an accident. There are a couple of
different switch layouts available, but the most common
layout uses a switch mounted inside the trunk with an
external linkage/knob to turn the power on or off.
Some battery master cutoff switches are designed for
momentary “on” service, others have continuous service
There are almost 200 different cutoff switches available
at Summit Racing Equipment, several with continuous
ratings of over 300 amps.
Battery cables are important too. Runing 3/0-gauge
welding cable from front to back on your race car will
add weight; typically, 3/0 cable weights 0.65 pounds per
foot. Big cable is difficult to package too, especially if
you’re trying to route it through a rocker panel.
XS Power has a good solution. It’s cable kit for single
battery applications features 2-gauge lightweight
cable—16 feet of red power cable and 3 feet of black
ground cable. It also comes with 8 crimp terminals, a
pair battery clamps, heat shrink material, grommets,
wire clamps, and mounting screws. Summit Racing
carries it:
When mounting batteries, the overall height of the
package is also important. Battery access for charging is another important
consideration. If you have to mount batteries low in the
car and/or under sheet metal, battery jumper posts will
help big-time. Some designs allow you to charge the
batteries from the outside of the car without opening or
removing the trunk lid.
“In a Pro Stock style chassis for example, you have to
consider the tunnel clearance for the wheelie bars in
the trunk area. Because of this clearance criterion, the As you can see, there’s much more to batteries than
first meets the eye. In the end, think of safety first, then
weight.
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