Tab Electronics Guide to Understanding Electricity ... - Sciences Club

320 Chapter Eleven
refrigerator (not a freezer!). Batteries being used in vehicles that are left
outside in the sunlight should be removed and brought indoors, if
possible.
Secondary batteries should be maintained in a charged state. Lead
acid and gelled electrolyte batteries need to be recharged about once
every 3 to 6 months if not used. Nicads, on the other hand, have a selfdischarge
rate of about 1% per day! For optimum performance, they
need to be left on a trickle charge continuously when not in use.
A Few Words of Caution
Some types of batteries contain very potent acids, caustic substances, or
highly poisonous materials. These materials include mercury, lead,
hydrochloric acid, and other substances so toxic that the EPA (U.S. Environmental
Protection Agency) classifies them as toxic waste. If you want
to experiment with chemistry, buy a Gilbert Chemistry Set, but don’t
attempt to mess around with this stuff.
Don’t try to recharge a battery that is not designed for recharging. It could
explode. And if the explosion doesn’t do enough damage in itself, toxic
waste can be sprayed in the eyes and mouth. Even rechargeable batteries
can explode if recharged too fast, or if overcharged.
Lead acid batteries can produce enormous current flows. An accidental
direct short, with a lead acid battery as the power source, can literally
blow up in your face; this could result in eye damage, or fires. Large batteries
should be fuse-protected right at the battery terminals.
Recharging Batteries
The recharging of secondary batteries is not a complex process, but there
are a few rules to follow. Nicad batteries should be completely discharged
before trying to recharge them. They should not be discharged too
quickly, however. One good way to discharge them properly is to connect
them to a small incandescent lamp rated for the same voltage as the
battery. When the lamp goes out, they’re discharged. Of course, other
types of resistive loads will perform this function as well as a lightbulb,
but they won’t provide a visual indication of when the discharge has
been completed. As stated previously, it is destructive to discharge any
battery too quickly. Nicads, however, are the only secondary battery type