|
PRODUCTS:-
|
SAFETY
INFORMATION and HANDLING PRECAUTIONS
Introduction: Modern Lithium Polymer batteries (LiPo, Li-Poly) are a
preferred source of power for flying models because of their ability to
store and deliver large amounts of energy from light-weight packs.
Performance wise, these new batteries have much more in common with model
aircraft fuel than with any previous battery technology and they deserve
similar respect: For safe handling it is useful to Think of Lithium
Polymer Batteries as Fuel.
Treated with respect in knowledgeable hands, Lithium Polymer batteries
have been proven world-wide to be a controllable, practical and enjoyable
power source for model aviation.
What can go wrong:
Fire can be caused by: ‘Overcharging’ (wrong charger or charger
setting, unbalanced battery load, charger fouled by poor power supply),
charging a damaged cell or pack and short circuit (including crash
damage).
Cells or packs can be damaged by: Over discharging (running ‘too flat’
and/or too hot, discharging an unbalanced battery load), short circuit and
crash damage.
The definitions of ‘overcharging’ and ‘too flat’ are detailed in
the do’s and don’ts section overleaf.
With the exception of a very small number of fires that have resulted
directly from crash damage at the flying field, fires have almost always
occurred during charging. These fires have been almost exclusively
permitted by avoidable human error. Therefore the main purpose of this
information is:
A. To provide information that can help you actively avoid a dangerous
charging situation.
B. To provide some standard precautions to limit loss or injury in case a
fire results anyway
Some Lithium Polymer Jargon Explained.
&Mac183; 3s1p - means a battery pack containing 3 cells in series, 1
cell in parallel. 5s2p means a battery pack containing 5 cells in series,
2 cells in parallel and so on.
&Mac183; Cells in series “s” add to the Voltage (V). For every
“s” add 3.7 Volts (nominal). Parallel cells “p” add to the
capacity of the battery in mAh. A “2p” pack made from 2500mAh cells
will become a 5000mAh pack, “3p” 7500mAh and so on. The choice of
single or multiple “p” packs is a feature of LiPo (for NiCd and NiMH
packs the term “p” is redundant as these packs are invariably
“1p”)
&Mac183; For LiPo packs made with the identical kind of cells, a 3s2p
pack can deliver twice the current for roughly the same duration as a 3s1p
pack, or the same current for roughly twice the length time.
&Mac183; In our 3s1p / 3s2p example, note that the 3s2p will be about
twice the weight and size. For maximum power-to-weight performance in a
model, we would generally choose the 3s2p only when the required current
approaches or exceeds the discharge “C” rating of the 3s1p.
&Mac183; “C” is a 1000:1 ratio of the capacity of a cell or pack
in mAh to a given current in Amps. It is normally used to define maximum
current-handling capabilities for charging (e.g.1C) and discharging. A
large “C rating” for discharge permits high currents from smaller
packs, for instance a 10C continuous rated 5000mAh pack is able to deliver
50 Amps continuously.
&Mac183; “nominal voltage” is 3.7V for LiPo chemistry. The actual
voltage per series cell will increase when fully charged to about 4.2V and
decrease to 3.0Vat full permitted discharge.
&Mac183; 4.25V is a maximum, charging at higher voltage is dangerous.
3.0V is a minimum, continuing to draw current (Amps) when the cell has
reached 3.0V will cause overheating and damage.
&Mac183; For charging set-up we are principally concerned with the
number of cells in SERIES. A 3s2p pack MUST be charged as a
"3-cell" lithium polymer (LiPo) pack. We must also limit the
current during charging to a maximum of 1C, for instance 5 Amps for a
5000mAh pack. An appropriate LiPo charger will prevent overcharging if
this data is entered correctly.
Lithum Polymer Do’s and Don’ts
To actively prevent a fire:
Do Always use a correctly specified Lithium Polymer charger [mandatory]
Do Always double-check that your multi-function charger is set in LiPo
mode [extremely important]
Do ensure that your charger has a clean power supply such as a car battery
that is not itself on charge
Do Always set the charger to the total series cell count “s” of your
pack (or packs if charging in series)
Do read the battery label to confirm the cell count for charging shown
e.g. “charge as 3 cell”.
Don’t Ever allow charging to continue above 4.25V per “s” series
cell [definition of overcharging]
Don’t confuse the total number of cells in a pack (e.g. 6 for 3s2p) with
the series cell count (3 for 3s2p)
Don’t set the charge current limit above 1C. 1C = 3.2Amps for a 3200mAh
pack, 0.83Amps for an 830mAh pack and so on. Chose an available charger
setting below the 1C value for your pack.
Don’t charge dissimilar or un-matched packs in series or with any
difference in cell type, cell capacity, pack capacity or charge state (+/-
0.03V per cell). If in any doubt, charge separately.
Don’t permit your pack to be discharged below 3.0V per cell (hint, use
monitoring and timing or a Lithium-safe ESC, land immediately in case of
noticeable power drop, over-discharge = overheating)
Don’t charge any pack containing one or more damaged or swollen cell.
Do handle and transport carefully to avoid piercing, deformation or short
circuit with other objects
Do Disconnect batteries fully from ESC’s with BEC to prevent slow
over-discharge.
Do Ensure connectors are insulated correctly to prevent short circuit in
handling or storage
Don’t charge batteries unattended, always remain alert and monitor the
charging process
Do not attempt to force extra charge into a battery, note new batteries
are part-charged.
Do not permit the battery to run in excess of 90ºC let the battery cool
down before charging
Do short-hop-and cool-off “conditioning” cycles with a new pack, packs
have been known to improve and run cooler after the first two or three
cycles.
To limit the consequences of a potential fire hazard:
Charge in an isolated area away from flammables and valuables and avoid
charging batteries in the model. If you decide to charge in the vicinity
of other property, equip your charging location with a dry extinguisher or
fire blanket. Never charge in a moving vehicle where the dangers of fire
and smoke can be compounded by the risk of a road accident. If the battery
is crashed in a model, place the battery in an open space for observation,
never directly into a vehicle, clubhouse, garage or home. If at any time
you observe a cell or pack that has started to balloon or swell up, place
in a safe area for observation. If swelling occurs while charging,
disconnect immediately and place in a safe place for observation. If the
wire leads accidentally short out place battery in a safe place and
observe for 15 minutes.
By purchasing this battery/batteries, the buyer assumes all risks
associated with Lithium Polymer batteries. If you do not agree with these
conditions, return the battery immediately before use for a full refund.
Flightpower Warranty
Product warranty is limited to original defects in material and build; it
does not cover collateral damage. Due to the nature and use of this
product there is no term warranty. Misuse, abuse incorrect charging and
discharging and all other inappropriate use of this product is not covered
under warranty
|