Lithium Polymer Batteries (LIPO)
It can sometimes be difficult to know which battery is best for your application, for R/C aircraft there is a huge variety of batteries available and while many may suit your application your ultimate goal is to purchase a battery pack that will:-
- Be within your budget
- Have a long cycle life
- Have the correct size and weight
- Give you the longest flight times
- Be able to deliver the correct voltage/amp (Power)
You may have noticed by now that batteries have different ratings, sizes, plugs, wire, charge rates and chemical makeup. Lets look deeper:-
This is usually the biggest number shown on the pack and is measured in mAh (Milliamp/hour). The capacity is the first indicator of the batteries size. To keep things simple, think of capacity (mAh) as the amount of fuel in your cars fuel tank. A higher capacity tank will run your car for longer. A 4,000mAh battery will run for twice as long as a 2,000mAh battery. So a 2,000mah battery will (in theory) run for 1hr if drained at a constant 2,000 Milliamps.
Discharge is the amount of power the battery can 'push' out and the number shown '20C' is an multiplication of the capacity. For example; A 20C battery can discharge at 20 x 2,000mAh which is 40,000mAh or 40Amps. This is an important number if you know your motor requires a certain power level. In addition to this, batteries have a 'Burst' rate, which is the amount of power the battery can discharge for a short period, usually 10 seconds. A typical battery label may show 20-30C, this would mean a 1,000mAh battery can discharge 20,000mAh constantly or give a sudden and short 10 second 30,000mAh (30A) burst of power.
Tip: A higher 'C' rated battery will last longer if run at a lower 'C' rate. Example: a 30C battery run at 20C maximum will have a longer cycle life than a 20C run at 20C each flight.
All lithium Polymer cells in any industry have a nominal voltage of 3.7v per cell. When fully charged a LiPoly cell should be 4.2v and when discharged it should never be below 3v. You will notice that LiPoly RC packs are made up of layers of multiple cells. If the battery's rating is 3S this means it is 3 x 3.7v which is 11.1v. It has 3 layers of 3.7v each. In other words, its a '3 cell pack'.
For a battery to be right for your model it must fit within the models battery compartment and also balance the Plane/Helicopter correctly. It's tempting to choose the biggest and most powerful battery your model can handle, but this will sacrafice flight performance and if your packs voltage is too high; destroy the ESC or Motor. Check with your ESC and Motor specification to ensure you have the right voltage pack then check the models CG (Center of Gravity) to decide on the right battery weight.
Always use a lithium Polymer battery charger and never charge the battery above 4.2v per cell. (example: 2S, never above 8.4v) Never leave a charging battery unattended. Never allow the battery's voltage to fall below 3v per cell. (example: 3S, never below 9.6v)
Lithium Polymer Battery Safety Guidelines
Warning! Procedures and Guidelines if not properly followed could cause failure of a lithium Polymer battery that can cause property damage, injury or even death
Handling and Storage
- Never alter, puncture or impact batteries or related components.
- Do not directly connect the terminals with metal objects. This will short-circuit batteries, resulting in heat and electrical discharge.
- Never store batteries together, the batteries terminals may contact one another causing a short circuit.
- Never expose batteries to extreme temperatures or direct sunlight. The temperature range must be between 40 - 120F or 4 - 49c.
- Always verify voltage of batteries that have been out of service for greater than six (6) months.
- Always charge/store batteries in a non-conductive, fireproof container or bag.
- For best results store batteries at approximately 1/2 of the capacity listed on the batteries label.
Before the First Charge
- Make a visual and physical inspection of the batteries for any damaged or loose leads or connectors, damaged packaging or other irregularities which may cause a short circuit and battery failure.
- Verify that the positive terminal of the batteries is connected to the positive terminal of the charger. Confirm polarity with a voltmeter if unsure.
- Check the voltage of batteries using a voltmeter to make sure batteries have the voltage of the capacity listed on the batteries label.
Always refer to your chargers manual for correct procedures and safety information. In addition to your chargers manual the warnings and guidelines should be followed to avoid possible propery damage and injury.
- Always use a compatible balanced mode charger, specifically designed for the chemisty of battery you are using.
- Always charge batteries in an open area away from flammable material, liquid and surface.
- Never charge batteries inside of the model.
- Never charge batteries that are hot to the touch (above 100 F). DO NOT handle batteries until they are cool.
- Always set the charger to the proper cell count and/or voltage listed on batteries labels.
- Always set the charger to the amp charge rate as listed on batteries labels.
- Never charge at a rate greater than 1C.
- Always check the voltage of batteries before each charge session in order to ensure they are at or above the minimum safe starting voltage. If starting voltage is below recommended levels then batteries have been over discharged or have experienced a failure and should NOT be charged.
- Never overcharge batteries beyond the capacity listed on batteries labels.
- Never discharge batteries at amperage rates higher than specified on batteries labels.
- Never allow the temperature of batteries to exceed temperatures advised by the manufacturer.
- Never discharge batteries to voltage below which they are rated by the manufacturer when measured under load (connected to the vehicle or a charger capable of discharging). Batteries discharged to a voltage lower than the lowest approved voltage may be damaged, resulting in loss of performance and potential fire when batteries are charged.
Additional Guidelines and Warnings
- In the event of a crash, always quickly and safely disconnect and remove batteries from the model. Then follow the previously listed safety procedure.
- If the internal contents of batteries come into contact with your skin, wash the affected area with soap and water immediately. If it comes into conect with your eyes, flush them with generous amounts of water for 15 minutes and seek immediate medical attention.
Bestviewedfromabove and its workers take no responsibilty of the instructions above, these are guidelines only and instructions on the actual batteries and chargers should be followed.