How To Avoid Battery Explosions

Why do batteries explode and how can you protect
yourself from injury when your hood is up?
It helps to know a little bit about 12-volt lead-acid
batteries. They have six two-volt chambers, called
cells, that contain a grid of lead plates submerged in
sulfuric acid. Electricity is generated when the acid
reacts with the lead plates and water.
One byproduct of the process is gaseous hydrogen,
an element so highly flammable that it is used to
power rocket engines. Charging a battery also
generates hydrogen. And because heat drives up
hydrogen output, you can expect more trouble
generally in hot weather.
The danger is that hydrogen will explode if a spark
occurs nearby. One source of sparks can be the
battery itself.
As a battery ages, it loses water, leaving the top of
the lead plates exposed to the air inside the battery
case. Over time, this can lead to warpage of the
plates.
When the driver starts the engine, the heavy
demand for power can cause these already warped
plates to flex, touch and thus spark.
The most common cause of battery explosions upon
start-up is dirty battery posts and cables. The dirt
prevents a good connection and allows electrical
arcing. So it is a good idea to inspect and clean
battery posts regularly.
Improper jump-starting is another leading cause of
explosions. The mistake many motorists make is to
connect the jumper cables to another car's good
battery and then to the dead battery, a practice that
causes sparking. Always connect jumper cables to
the dead battery first, then to the good battery.
Another important safety precaution is to attach the
negative jumper cable for the dead battery to an
unpainted metal portion of the car frame, rather
than to the negative battery post. That allows any
sparking to occur far from the battery itself.
The potential for battery explosions may be greater
than it was 10 years ago. Some newer batteries are
sealed, preventing motorists from adding water to
keep the electrolyte (the mixture of sulfuric acid and
water) above the lead plates. But many
manufacturers have gone back to batteries with tops
that can be removed.
Another problem is that new cars have much larger
demands for electrical current, so batteries must
produce more juice but with the same physical
volume. One method used by battery makers to
increase current is to space the lead plates closer
together, but that only makes it easier for them to
short.
In any case, motorists should always exercise
caution when the hood is up, avoiding smoking or
anything else that can ignite hydrogen.