Question: Does a replacement battery have to be the
same size as my old one?
Answer:No. If your old battery has reached the end of
the road and needs to be replaced, or if you think you need a
battery with a bigger amp capacity for easier cold weather starting
or to handle added electrical accessories (such as a killer stereo
system, driving lights, etc.), then there's no reason why you
have to install a battery that's the same size as your old one.
The word "size" may be a bit confusing here because
what we're really talking about is the battery's amp or power
rating, not the physical dimensions of its case.
A battery with a bigger case is not necessarily a more powerful
battery. Battery manufacturers can cram a lot of amps into a
relatively small box by varying the design of the cell plates
and grids. So two batteries with identical exterior dimensions
may have significantly different power ratings.
Batteries come in many different sizes and configurations
(which are referred to as "group" sizes) because the
vehicle manufacturers can't get together and standardize anything.
So when you're choosing a battery, you have to consider three
things: (1) the group size (height, width, length and post configuration),
(2) whether your battery has top or side posts, and (3) how many
amps will be needed for reliable cold starting and vehicle operation.
GROUP SIZES
Because there are 57 different group sizes, many aftermarket
replacement battery suppliers consolidate group sizes to simplify
inventory requirements. So some replacement batteries may not
fit exactly the same as the original. The battery may be slightly
shorter, taller, narrower or wider than the original. But as
long as it fits the battery tray and there are no interference
problems (too tall a battery may cause the cables to make contact
with the hood causing a dangerous and damaging electrical short!),
it should work fine.
Some replacement batteries come with both side and top posts
to further consolidate applications. Some also have folding handles
to make handling and installation easier.
BATTERY RATINGS
Though many replacement batteries are marketed by the number
of "months" of warranty coverage provided (36, 48, 60,
etc.), what's more important in terms of performance is the battery's
power rating which is usually specified in "Cold Cranking
Amps" (CCA) rating. The CCA rating tells you how many amps
the battery can deliver at 0 degree F. for 30 seconds and still
maintain a minimum voltage of 1.2v. per cell.
In the past, the rule of thumb was to always buy a battery
with a rating of at least one CCA per cubic inch of engine displacement.
But twice that is probably a better recommendation for reliable
cold weather starting.
At the very least, you should buy a replacement battery with
the same or better CCA rating as your old battery or one that
meets the vehicle manufacturer's requirements. For most small
four-cylinder engines, this would be a 450 CCA or larger battery,
for a six cylinder application, a 550 CCA or larger battery, and
for a V8 a 650 CCA or larger battery. Bigger is usually better.
Extra battery capacity is recommended if your vehicle has a lot
of electrical accessories such as air conditioning, power windows,
seats, electric rear defogger, etc.
BATTERY INSTALLATION
Most batteries are "dry charged" at the factory,
which means they're activated as soon as acid is poured into the
cells. Even so, the battery may require some charging to bring
it all the way up to full charge.
Most experts recommend charging the battery before it is installed
regardless of whether it is dry charged or not. This will ensure
the battery is at full charge and lessen the strain on your charging
system.
When the battery is installed, it must be locked down and
held securely by a clamp, strap or bracket. This will not only
keep the battery from sliding around on its tray (which might
allow the positive cable to touch against something and short
out the battery or start a fire!), but will also help to minimize
vibration that can damage the battery.
The battery cables should also be inspected to make sure they're
in good condition, too. If the cables are badly corroded, don't
fit the battery posts or terminals tightly, or have been "fixed"
by installing temporary clamps on the ends, the cables should
be replaced. At the very least, you should clean the cable clamps
and battery posts with a post cleaner, sandpaper or a wire brush
to ensure good electrical contact. A light coating of grease,
petroleum jelly and/or installing chemically treated felt washers
under the cable clamps will help prevent corrosion.
