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 below.

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.

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.
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”)
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.
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.
“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.
“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.
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.
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.