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Rechargeable Lithium-Polymer Batteries
Lithium-Polymer batteries are often confused
with Lithium-Ion or non-rechargeable Lithium batteries. They
differ from Lithium batteries in three major ways: LiPos are
rechargeable, they have non-standard shapes and a nominal cell
voltage of 3.7 volts.
The main difference from Lithium-Ion batteries
is that LiPos have a non-liquid dielectric and are (sometimes)
capable of higher discharge rates of 20C and greater. The dielectric's
thick consistency means that LiPos do not have to be encased
in a container.
LiPos come with a few "Cautions"
attached, mostly due to the fact that they can catch on fire
if improperly charged or if discharged higher than their rating.
Never charge LiPos at a rate greater than 1C and don't leave
them unattended while charging. A lot of these warnings are
due to the conditions under which LiPos are most commonly used:
to power electric motors in R/C airplanes at or near their highest
discharge rate for extended lengths of time. QRP rigs don't
discharge batteries at this rate or duty cycle. The same precautions
exist for the Li-Ion batteries in your cell phone.
Although LiPos are initially expensive, they
are rated for 300-500 charge/discharge cycles. My sources for
these batteries are listed at the bottom of this page.
Three small LiPos discharged at a 300
mA rate - the 250 mAh battery is absolutely tiny &
weighs the same as 7 US pennies! A LiPo battery charger
typically costs $30-$50. Battery prices, weights and cost
per cycle (including $50 charger and assuming only 300
cycles):
Battery |
Cost |
Weight |
Cost/Cycle |
250 mAh |
$24 |
0.7 oz |
$00.24 |
450 mAh |
$26 |
1.3 oz |
$00.25 |
900 mAh |
$34 |
2.1 oz |
$00.28 |
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| Also discharged at a 300 mA rate, this
is the LiPo equivelant of an 8-cell pack of AA alkaline
batteries - except that this LiPo weighs less, lasts longer
and has a flatter discharge curve.Despite its small size,
this battery has a safe continuous discharge rating of 30
amps! It weighs 4.9 ounces, costs $64 initially and $ 00.38
per cycle to use. |
Informative Links
Lithium-Polymer
Info | AeroMicro
| Atlanta
Hobby
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