RC Helicopter - Battery Information and charging
NIMH Battery:
- The average charging time for the NIMH battery is about 1.5 - 2 hours (for Z400 stock battery is about 30 minutes ONLY). However, when you are charging the battery, please always pay attention to the battery charging. When the battery get WARM (NOT HOT), then it is fully charged. IMPORTANT: ALWAYS PAY ATTENTION TO THE BATTERY WHEN YOU ARE CHARGING THE BATTERY. DO NOT OVER CHARGE THE BATTERY - IT CAN BE VERY DANGER.
Li-Ion Battery:
- When you are charging the Li-Ion Battery (only use the charger supplied with the battery), please always pay attention when you are charging the battery. On the li-ion charger, there is a light on the charger, when the battery is charging, the light is RED, when you light turns GREEN, this indicates the battery is fully charged and you need to remove the battery immediately - DO NOT OVER CHARGE THE LI-ION BATTERY - IT CAN BE VERY DANGER.
Li-ion Battery Safety Instruction:
- Do not disassemble or reconstruct battery
- Do not short-circuit battery
- Do not use or leave battery nearby fire, stove, heated place
- Do not immerse the battery in water or get it wet
- Do not charge the batter nearby fire or under blazing sun
- Do not drive a nail into the battery. Strike it by hammer, or tread it
- Do not give battery impact or fling it
- Do not use the battery with conspicuous damage or deformation
- Do not make the direct soldering on the battery
- Do not reverse-charge or over discharge the cell(s)
- Do not reverse-charge or reverse connect
- Do not connect battery to the plug socket or car-cigarette-plug
- Do not use the battery for unspecified equipment
- Do not touch a leaked battery directly
- Do not use lithium ion battery in mixture
- Keep the battery away from babies
- Do not continue to charge battery over specified time
- Do not get unto a microwave or a high pressure container
- Do not use a leaked battery nearby fire
- Do not use an abnormal battery
- Do not use or leave the battery under the blazing sun (or heated car by sunshine)
- Do not use nearby the place where generates static electricity which will give damage to the protection circuit.
- Use the specified charger and observe charging requirement
- Charging temperature rage is regulated. Do not charge the battery out of recommended temperature range (0 - 45 degree)
- When the battery has rust, bad smell or something abnormal at first-time-using, do not use the equipment and go to bring the battery to the shop which is was bought.
- In case children use the battery, their parents teach how to use the batteries according to the manual with care. And also, when children are using the batteries, pay attention to use it according to that or not.
- Keep the battery out of the reach of children. And pay attention the children using or handling it.
- It the skin or cloth is smeared with liquid from battery, wash with fresh water. In may cause skin inflammation
ALWAYS PAY ATTENTION WHEN YOU ARE CHARGING THE BATTERY. VERY IMPORTANT.
For Li-ion battery, always use the charge come with the li-ion battery ONLY.
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Batteries are the equivalent of fuel for our electric planes. So just as there are several types of IC engine fuels (Glow, Petrol, Diesel mix) and expertise on knowing the right mixtures etc, there are several types of rechargeable batteries and much to learn of there use and care.
Introduction
Electric flight places very high demands on battery cells, drawing high currents and causing high temperatures to build up in our packs. In most flight applications the cells are being used beyond the manufacturers recommendations. This is because there are no batteries specifically made for electric flight, we end up using cells designed for applications such as power tools and cordless appliances.
Electric flight requires cells that can provide high amounts of current while maintaining a voltage close to the nominal value of 1.2v. A battery has several characteristics that can tell us if it suitable for use.
They are:
- Capacity (measured in mAh)
- Weight
- Internal resistance
By taking the capacity and dividing it by the weight you will end up with an energy density figure eg: A Sanyo KR600AE has a capacity of 600 milliamps/hour (This means if you discharge the cell at a rate of 0.6A it will last for 1 hour, sometimes referred to as a 1C rate) and a weight of 19 grams. Divide the two together and you get 31 mAh per gram. The higher the value the better, but this will need to be weighed up against the cells ability to supply the current you need.
The other parameter is the cells internal resistance. The higher the resistance the lower the voltage that will end up at your motor. Also the more heat that will build up in the pack as that energy has to go somewhere.
There are other factors but they are harder to quantify and have mainly to do with the cells chemistry. For example the Sanyo 1100AAU has a higher internal resistance than the smaller 600AE but will out perform it in voltage at the same current load.
NiCad’s
Nickel Cadmium cells are the most abundant and excel at providing high currents at high voltages. Most of the NiCad’s we use can be fast charged by automatic peak detect chargers. The following is a list of some typical cells and there suggested maximum charge currents and there maximum continuous current draws.
Model Max Charge Max Discharge
Sanyo KR600AE 2A 12A
Sanyo CP1300SCR 3A 25A
Sanyo CP1700SCR 5A 40A
Sanyo 1700SCR 5A 40A
The discharge curve of a NiCad is very flat meaning that it holds its power well until near the end of the curve where it rapidly declines. Cells will loose some of there charge if left unused for several hours. It is best to repeak your packs before flying them if you want to get the maximum capacity out.
NiMh
Nickel Metal Hydrides are a more environmentally friendly due to there lack of cadmium. They also have a higher energy density than NiCads. The down side is that they have a slightly lower voltage than a Nicad and they cannot handle as much current as the same weight NiCad. In the high performance cells the NiMh are also more expensive. NiMh cells should also be charged at a slower rate than there equivalent sized NiCad.
In use a NiMh is best used hot off the charger as the cell voltage will decay quite rapidly. Make sure your charger is compatible with NiMh cells before trying to charge them as the peak is not as pronounced as NiCad’s.
Here are some discharge curves for some typical cells
NiCad folklore
There's a tremendous amount of folklore about NiCads, most of it at least somewhat misguided, much of it just plain wrong. The worst advice ever given to a NiCad battery owner: discharge it completely. Discharging a NiCad cell is fine, and may even be useful if the cell was previously overcharged. Completely discharging a NiCad Pack, however, is never a good idea. Because no two cells are identical you run the risk of getting ‘cell reversal’ if a pack is discharged completely. Cell reversal usually results in permanent damage.
The NiCad ‘Memory’ effect is actually called ‘Voltage Depression’ and occurs when a cell is Overcharged. This overcharging of the active material in the electrode reduces the cells voltage. The effect is erased by discharging and recharging that portion of the active material which has experienced the extensive overcharge.
For the best performance in your NiCads you should peak charge your cells and throw away your trickle charger.
The bottom line - yes there is a memory effect, but it is very small and not worth worrying about. |