Transcript Power Supplies And Batteries (3 point 3).

Power Supplies And Batteries
ARRL Book Section 3.3
Why Mobile First
• Many emergency responses may require you to
move around
• Another reason is that a radio needs power
– Most disasters take out electric power
– Keeping batteries charged and ready can be tough
– But your car keeps a battery charged most of the time
(when its working right)
• For people not using mobile you need to have
battery power available for when the commercial
power fails.
To Recharge or Not to Recharge
• Some batteries are one time use
– Carbon-Zinc batteries are not designed to be recharged (T4C08)
• Keeping rechargable batteries ready to go can be
challenge
– Batteries wear and leak their charge (even when they are not
used)
– You need to inspect your batteries regularly for damage,
store them in a cool dry place, and give them a maintenance
charge at least every 6 months. (T4C09)
• The best way to get the most energy out of a battery
is to draw the power steadily but as slowly as
possible (T4C10)
– This is one reason during practices to see how little power you
can use to reach other individuals you must communicate with
• Slow steady pace is also the best way to recharge
– If you charge or discharge a battery too fast it can overheat
and either explode or give off dangerous gas (T0A11)
Most Common Rechargeable
• Nickel-Cadmium batteries are rechargeable
standard
– Need several Ni-Cd batteries to run a radio –
standard radio runs on 12 volts, A single Ni-Cd
battery only puts out 1.2 volts (T4C07)
– Some handheld radios run on less than 12 volts to
avoid needing 10 batteries, but that also tends to limit
output power of the handheld
– Ni-Cd batteries have memory effect, if you charge
them every time they are ½ discharged soon you can
only use half the capacity
• Discharge a Ni-Cd battery completely and then recharge it.
Other Battery Choices
• Lithium-Ion Batteries offer the longest life (T4C06)
– They also offer the highest price and need a special battery charger
$$$$$$
• Lead-Acid battery (like in your car) is another choice
– Battery weighs like its made out of lead (oh it is) – not very tempting for
a hand held radio
– Can put the battery in your home and charge it but there are risks
• It contains dangerous acid that could spill or cause injury (or make you
need an underware change after seeing your kid or grandkid playing with it)
• Short circuits can damage wiring or cause a fire (seeing a short circuit
across 2 battery terminals is some pretty amazing fire works)
• Explosive gasses can collect if not properly vented (gas is hydrogen –
Remember the Hindenburg?) (T0A10)
• Not all Lead-Acid Batteries are created equal, a car battery is
designed for high output and then recharge (ie its designed to start a
car engine)
– Radios use little power but they keep using it and discharge the battery,
a car battery won’t last long on that kind of cycle
– Consider a Marine type or Deep Cycle Battery – they are designed for
small loads and being discharged before recharging
Radios Can Be Run Using
Household Power
• Lets you practice using regular power while
keeping your batteries outside of living space
– Radios do use 12 volt DC but lot of things have those
big plugs with transformers inside
– For a Radio you want to use a regulated power
supply to protect against voltage fluctuations. (T5A05)
• Picking power supplies
– Obviously want right voltage (usually 12 volt DC)
– Rated by Watts or Amps
• If its rated it Watts almost certainly to small
• Look at amperage your radio can draw on full power transmit
and pick a supply with that amperage
– Be careful Radio Shack 15 amp is cutting it kind of close
– My supply is a 35 amp Pyramid – but I run several radios at
once.