Lithium polymer batteries are expensive. How you handle yours will have a big effect on how long they last. Therefore, it is worth taking the time to learn about proper charging procedures.

Lets say you just finished using your lithium polymer battery. It can be charged again without delay, as long as it isn’t hot. If it is hot, you will need to wait until it has cooled down; preferably to below 35° Celsius (95° Fahrenheit).

Your battery isn’t hot, so let the charging begin. The first steps are to power up your charger and connect your battery charge cable to the charger. You should plug in the charge cable before connecting it to the battery, because charge cables usually terminate in exposed bullet / banana connectors, which are easy to short to each other directly or via anything metal (i.e. the charger). Now you can connect the battery to the charger via the charge cable.

It’s time to set the charger’s settings. Whatever the input method, there are two important settings: charge voltage and current. The correct voltage setting is determined by the lithium polymer battery you are charging. Most batteries say their nominal voltage, with the common ones being 7.4V and 11.1V. This number is calculated as

Correct Voltage Setting = 3.7V * Number of Cells in Series

On small to medium sized lithium polymer batteries, the number of cells in series is simply the number of cells in the battery. However, on large batteries, some of the cells are wired in parallel and as such do not contribute to the correct voltage setting. The standard for writing the number of cells in series is Xs. For a small battery, like the Thunder Power Pro Lite 3s 1320mAh, we see that X=3. For this battery, correct voltage setting = 3.7V * 3 = 11.1 V.

Correct voltage setting now determined, all that remains is current setting. Current setting is largely up to the user. The most common and always correct setting is:

Standard Current Setting = Battery Capacity / 1h

Continuing with the above example, the battery capacity is 1320mAh. Therefore, standard current setting = 1320mAh / 1h = 1320mA = 1.32A. This is known as a 1C charge, because C is defined as 1 / 1h.

Some like to charge slower than 1C to be gentle with their batteries. However, there is no scientific evidence of slower charging leading to longer battery life. There are also a few chargers that charge faster than 1C to save time, such as the Thunder Power 1010C. These chargers are usually very specific about when this fast charging is safe; please follow the instructions and warnings they come with.

With those two settings set, you are ready to start the charge. Once the charging process has started, the charger takes care of everything. It will end the charge when the battery is full, at which time you can use it again. There is no need to wait between the end of a charge and the start of a discharge.

There are two ways of increasing the safety of your charges. One is to use a balancer, such as the Thunder Power 205V or 210V. The balancer will fight cell imbalance, and provide some a warning if the cells are dangerously imbalanced. The other is to place your battery somewhere nonflammable. Ask yourself, if this battery ignites, will anything nearby ignite as well? Leaving the battery on a wood counter or in a wood airplane is more risky than isolating it on a bare cement floor.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
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As of December 6th 2006, Thunder Power produces 16 different cells, both in their Pro Lite and eXtreme series batteries, to meet the widely varying needs of R/C modellers. Whether you fly radio control airplanes, drive rc cars, or boats, there’s a Thunder Power cell for you. This article will help you choose between them.

Thunder Power’s 350mAh Pro Lite 18C cell is their smallest. Offered only in 2s (22g) and 3s (33g) packs, this cell is meant for the smallest indoor airplanes. Common all-up-weights for a 350mAh-powered airplane are 3-6oz. These packs are available with a JST connector or with bare leads. A balance connector is not available, so max charge rate is 1C.

The Thunder Power 480mAh Pro Lite 15C cell is just a little larger. Offered only in 2s (23g) and 3s (34g) packs, this cell is meant for small indoor airplanes. Common all-up-weights for a 480mAh-powered airplane are 5-8oz. These packs are available with a JST connector or with bare leads. A balance connector is not available, so max charge rate is 1C.

Thunder Power’s 730mAh Pro Lite 13C cell bridges the gap between indoor and outdoor airplanes. It’s small enough for an indoor plane, but large enough for an outdoor plane. Common all-up-weights for a 730mAh-powered airplane are 7-13oz. It comes in 2s (34g) and 3s (49g) packs, and is available with a JST or with bare leads. A balance connector is not available, so max charge rate is 1C.

Thunder Power’s 910mAh Pro Lite 16C cell is for small outdoor airplanes weighing 9-15oz. It is available in 2s (46g) and 3s (65g) packs, and with a JST or bare leads. A balance connector is standard, so max charge rate is 3C.

The Thunder Power 1320mAh Pro Lite 13C cell can fuel a lot of very fun 10-20oz airplanes. The two 1320mAh packs are 2s (58g) and 3s (85g). A balance connector is standard, so max charge rate is 3C.

Thunder Power’s 2000mAh Pro Lite was released in early 2005. When it came out its performance eclipsed the competition. It had lithium polymer’s incredible energy density and revolutionary power density. It also premiered a second revolution: the balance connector. To this day, no one – not even Thunder Power – has been able to better it. More recent batteries do offer considerably better power density (higher voltages under higher loads), but that is at the expense of energy density (they weigh more for the same capacity). The 2000mAh Pro Lite cell remains the best choice for any model that has to run longer than 15 minutes, and a very competitive cell for 12-15 minute run times. Because of its performance, Thunder Power uses it in a huge range of packs, from 2s1p 2000mAh to 5s4p 8000mAh and 10s2p 4000mAh.

Some of us have seen electric aircraft with stunning performance. Key to this performance is a high C rating and high power density. Thunder Power’s take on this is the Pro Lite 2100mAh cell. Rated at 24C burst, this battery attracts attention from the glow crowd. It is available in 2s, 3s, 4s, and 5s; and in 1p (2100mAh) and 2p (4200mAh). A balance connector is standard, so 3C charging is available.

Thunder Power has developed a cell specifically for the T-Rex 450. It is the eXtreme Series 2070mAh, in 3s form. This cell unlocks the extreme performance possible with a T-Rex, and will do it over a long cycle life (the T-Rex is known for killing other cells faster than usual). The 2070mAh eXtreme Series cell is available in 2s, 3s, 4s, and 5s, all with a balance connector and 3C charge rates.

Thunder Power’s eXtreme Series cells – 2200mAh, 3300mAh, 3400mAh, 3800mAh, 3850mAh, 4500mAh, 4600mAh, and 5000mAh - are all about power. With 22-25C continuous and 50C burst ratings, these cells seriously perform in the most demanding applications, like electric ducted fans and 3D helicopters. eXtreme Series cells are available in 3s, 4s, and 5s packs, all with a balance connector and 3C charge rates. A few special 2s or 2p packs are available, too.

Packs with higher capacities than the above cells are made by combining 2 or more cells in parallel.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Lithium polymer batteries have made R/C flying more fun. The performance they offer is revolutionary and remarkable. But, they are susceptible to damage and need to be treated carefully. One important device that protects and maintains your lithium polymer battery is the balancer. Let’s examine how that is.

Lithium polymer batteries are damaged by:

• Mechanical deformation
• High temperature (above 60degC / 140degF)
• High voltage (above 4.2V/cell)
• Deep discharge (below 3.0V/cell in use, 3.3V/cell recovered, or 3.7V/cell storage)
• Rapid discharge (shorting cells or using above recommend discharge rates)

Of these, high voltage is the most difficult to control. Batteries made of lithium polymer cells wired in series will naturally, with time and cycles, become imbalanced. That is, each cell will be at a slightly different voltage.

This leads to high voltage while charging, as the charger can only read the average cell voltage. The charger will bring the pack to an average of 4.2V / cell, but one or more cells are above 4.2V / cell. Slight imbalance is always present -even in a battery that is new and balanced by the factory - and does no harm, but large imbalance does harm and is prevented by a balancer.

A balancer connects to a battery via cell taps. Cell taps are small wires soldered onto each cell’s tabs. The balancer thus has direct access to every cell, allowing it to adjust individual cell voltages by dissipating the energy as heat, or re-routing it to cells of lower voltage.

The tangible benefits of this include:

• Stronger performance throughout the battery’s life
• Longer battery life (more cycles)
• Ability to eliminate one cause of cell combustion, namely cell over voltage while charging due to imbalance

Though every brand and model of cell balancer works a little different, the general procedure for their use is: Connect the balancer to the battery before charging, charge, and remove balancer when charge is complete. Regarding frequency of use, a balancer can be used with every charge, though this isn’t necessary if the battery is in good condition. Most users feel the extra effort of using a balancer with every charge is worth the added safety features.

Examples of good commercially available balancers are the 205V and 210V from Thunder Power.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Lithium Batteries are found in many modern electronic devices, such as laptops and cell phones. They are significantly lighter than NiMH or NiCD batteries, and have higher capacity for the same size. Over the last five years they have worked their way into the hobby market, for use in electric RC helicopters, boats, cars, and particularly rc model airplanes. Their light weight and high capacity make them ideal for long flight times, while also providing more power.

Voltage, Cell Count And C Rating:
The nominal voltage of each cell is 3.7V, but can go down to 3.3V during discharge, and up to 4.2V when fully charged. A battery pack is usually composed of two or more cells put together in series for increased voltage, or in parallel for increased capacity. The C rating denotes how quickly a battery can be discharged (a rating of 1C continuous would mean that a 2000mAh battery should not be discharged any faster than 2000mA or 2A, which would take one hour). A 2000mAh pack rated at 12C continuous would be able to discharge at 12 times its capacity (12 x 2000mA = 24000mA or 24A) at which rate it would discharge in 1/12th of an hour. If you know how much continuous current you will be drawing and the capacity of the pack you want to use, you can easily determince what C rating you require. If you are drawing 5A from a 1320mAh pack, just take the current and divide by the capacity: 5A = 5000mA, 5000mA / 1320mAh = 3.8C. Using a pack with a higher C rating than you require will leave some headroom, and extend the life of your battery. Batteries are also given a C rating in terms of burst, which is how quickly the battery is able to discharge for a short period. A burst rating of 20C would mean a 2000mAh battery could supply 20 x 2000mA = 40000mA or 40A for a few seconds at a time.

Naming Conventions:
Lithium Batteries are also know as LiPo, Li-Po, LiPoly, or Li-Poly. The pack configuration is denoted by the number of cells in series and the number of cells in parallel. A 3s2p pack would have three cells in series, and 2 cells in parallel, using a total of 3×2=6 cells. A 4000mAh 3s2p pack would have a capacity of 4000mAh, and a voltage of 11.1V (3 x 3.7V). It would internally consist of six 3.7V 2000mAh cells. The cells would be doubled up (the 2p part of 3s2p) to get 4000mAh, and there would be three in series (the 3s part of 3s2p) to get 3 x 3.7V = 11.1V.

Which Battery Is Best For Me?:
To select a battery, you first need to know what voltage you require and how much current you will be drawing continuously. If you have a motor that works with 11.1V, you would need a 3 cell battery. If you need to draw 20A, and you would like to have a 10 minute (1/6th of an hour = 6C) flight, you would need a battery with 20A / 6 = 3.3A = 3300mAh. This means you would need a 3s 3300mAh battery with a C rating of 6 or higher.

Safety Precautions:
Never charge a lithium battery if it is below 3.0V per cell, puffed up, or damaged. Always place on a fire-proof surface when charging. Only use chargers designed to work with Lithium Polymer batteries. Never leave your battery unattended while charging.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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Due to popular demand we have created 7 more images and a 2-minute movie of the Firefly micro remote controlled helicopter. We took the Firefly for a spin around our office and had a blast with this easy to fly indoor r/c helicopter. Get one for yourself! Or save $10 if you buy a package of two.

Go See the new pictures and movie»

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
RSS: www.rctoys.com/pr/feed

Gizmodo, a “technology weblog dedicated to everything related to gadgets, gizmos, and cutting-edge consumer electronics,” features the Draganflyer X-PRO and gives it a rave review. “[The X-Pro is a] flyer with four rotors and an electronically stabilized mechanism that makes it sturdy enough for video surveillance work. Use your imagination here…” Read the full article at Gizmodo’s Web site»

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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