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July 2005

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July 2005

By Staff

FMA, Inc.




This document is a work in progress.
New information will be added as it becomes available.
Check the FMA Web site (
www.fmadirect.com
) for updates.


Latest revision: July 24, 2005

Document provided by
FMA, Inc.
Distributor for Kokam Lithium Polymer Cells
5716A Industry Lane
Frederick, MD 21704 U.S.A.
Phone: (800) 343-2934
Fax: (301) 668-7619
Web:
www.fmadirect.com

Contents

Safety.........................................................................................................3

Charging....................................................................................................8

Chargers....................................................................................................................... 9

Charging through a protective circuit ........................................................................... 9

Safety Guard specifications ................................................................................. 10

FMA Cell balance charging very simply measures the voltage of each individual
............... 11

cell in the pack as it charges and applies a sophisticated charge control algorithm that:
....... 11

Charging in series or in parallel.................................................................................. 12

Discharging.............................................................................................13

Li PoCalc .................................................................................................................... 15

How to use Li Po batteries effectively ........................................................................ 16

Gas Gauging using the discharge curve data............................................................ 18

So, what do I need for my bird, since it isnt a Tu-4?............................................... 19

Li Po power suggestions for various electric aircraft types and sizes ................. 21




The Kokam USA Lithium Polymer Battery System 3

Safety

FMA, Inc. battery packs are designed to protect against in-the-field risk of unwanted chemical
reactions and other electrical and mechanical malfunctions for rechargeable sources that power
mission-critical portable and handheld equipment as well as remote control electric aircraft, cars,
boats, and robots. The FMA Li Po systems comply with all safety requirements and test guidelines of
the IEEE-1625-2004 standard. EP Kokam / FMA provides statistical analysis and sample testing of
cells for each production lot to confirm that cells perform to manufacturers' specifications. Tests
verify that Li Po packs operate properly for their respective 0 to 45 degree C charge range and 20 to
60 degree C discharge range.

The safety record for Lithium cells in radio control applications is excellent, particularly considering that:
Both manufacturers and modelers were learning how to use and handle the cells.
Many modelers use the cells with no protective circuit during charge or discharge.
Many chargers and charging methods are used.

There have been reports of cells damaged by overcharge. We call them silver sausages because of their
shape. In a very few instances, there has been venting with flames. In almost all cases, the cause has been
known or was deduced from analysis of the situation. Nearly all these problems were related to charging.
One non-charging incident involving a Lithium pack of unknown manufacture occurred because the
modeler crashed an airplane and placed it in his car without removing the pack.

Potential cell damage causes include:

Overvoltage during charge.

Use of chargers not designed for Li Po chemistry.

Unbalance of a cell(s) in a pack. Unbalance will be defined later.
Sudden peak surge voltage from the charger when disconnecting.
Charge current set too high for the cell.
Incorrect selection of charge voltage.
Excessive discharge rate.
Use of aluminum soldering paste that deteriorates the tabs and causes a short circuit.
Unreliable chargers. In some chargers with FET switching, the FET shorts when it fails and full supply
voltage is applied to the cell. This can be avoided if appropriate crowbar protection
1
or foldback
2
is
designed into the charger.
Cell failure that creates an instant unbalance in the pack.
Fundamental risk of lithium ignition with lithium is exposed to air entering through a damaged cell
envelope.
Faulty pack assembly.
Physical damage and abuse.

All high energy density cells, including Li Po cells, are safe when handled, interconnected, charged and
discharged according to manufacturers recommendations, accepted industry practices and common sense.
FMA provides a set of precautions in the package for use of the cells and packs it sells. The precautions
are listed below, and are also provided on the FMA Direct Web site.




1
This is an overvoltage protection circuit which rapidly places a low resistance shunt across the power supply output
terminals if a predetermined voltage is exceeded.
2
A power supply output protection circuit whereby the output current decreases with increasing overload, reaching a
minimum at short circuit. This minimizes internal power dissipation under overload conditions. The Kokam USA Lithium Polymer Battery System 4


WARNING
Safety precautions
for Lithium Polymer and NiCd cells/packs stocked by FMA Direct

1. Nev er f ast-charge any batt ery ty pe unatt ended.
2. Nev er c harge LiPo c ells/ pack s at any rat e unatt ended.
3. Only c harge LiPo c ells/ pac ks wit h a c harger designed specific ally f or lit hium polym er
chemistry. Ex am ple c hargers include t he Kok am USA, LI PO 402, LI PO 102 and
LI PO 202; Bis hop Power Products Apac he S1215 and S1500; Great Planes T rit on;
and Sc hulz e c hargers wit h lit hium c harging c apability.
4. LiPo c ells c an ignit e bec aus e of unmatc hed cell c apacity or v olt age, c ell dam age,
charger f ailure, inc orrect c harger s ett ings and other f act ors.
5. Alway s us e t he c orrect c harging volt age. LiPo c ells/ pac ks may ignit e if c onnect ed t o
a c harger s upplying m ore t han 6 v olts per c ell.
6. Alway s ass ure t he c harger is working properly.
7. Alway s c harge LiPo c ells/ pac ks where no harm c an res ult, no m att er what happens.
8. Nev er c harge a c ell/ pack in a m odel. A hot pack m ay ignite wood, f oam or plastic.
9. Nev er c harge a c ell/ pack inside a mot or v ehic le, or in a v ehicles engine c om part-
m ent.
10. Nev er c harge a c ell/ pack on a wooden work benc h, or on any f lamm able m at erial.
11. If a c ell/ pack is inv olv ed in a cras h:
a. Remov e t he c ell/ pack from t he model.
b. Caref ully ins pect t he c ell/ pack f or s hort s in t he wiring or c onnect ions. If in doubt,
cut all wires from t he c ell/ pack.
c. Dis ass emble t he pack.
d. Ins pect c ells f or dents, c rac ks and s plits. Dis pos e of damaged c ells (s ee below).
12. Dis pos e of c ells/ pack s as f ollows:
a. Dis c harge: wit h t he c ell/ pack in a s afe area, c onnect a m oderat e resist anc e across
the t erminals until the c ell/ pack is disc harged. CAU TI ON: c ell/pack m ay be hot!
b. Dis c ard:
NiM H: plac e in regular tras h.
NiCd: rec ycle (c admium is t oxic).
LiPo: punct ure plast ic env elope, im mers e in s alt wat er f or s ev eral hours, plac e
in regular t ras h.
13. Handle all c ells/ pack s wit h c are, as t hey c an deliv er high c urrent s if s hort ed. Shorting
by a ring, f or exam ple, w ill rem ov e a finger.
14. Alway s st ore c ells/ pack s in a s ec ure loc at ion where they c annot be s hort ed or han-
dled by c hildren.
15. When c onst ructing a pac k, us e only c ells of the s ame c apacit y (mAh).

FM A, I nc. and K O K A M US A, its successors, heirs an d assigns are not resp onsi ble
in any way for a ny and all bo dily inj urie(s) and/or pro perty da ma ge that may occ ur
fro m the use of or caused by in a ny way the lithiu m Poly m er an d Ni C d cells/packs
stocked a nd or distrib uted by F M A, Inc. an d K O K A M US A.
FMA, Inc. 5716A Industry Lane Frederick, MD 21704
Sales: