Microsoft word - lipo battery charging and safety.doc

3239 Old Cleveland Road Capalaba West Queensland 4157 Lithium Polymer (Li-Po) Battery Charging

Li-po batteries offer benefits over Ni-Cad and Ni-Mh batteries
in lowering weight and increasing power and run time. All
batteries should be treated with caution, but Li-Po batteries
even more so. There have been known cases of Li-Po batteries
catching fire. Usually this is due to poor handling, charging
and/or monitoring. When used correctly, Li-Po batteries are
really no more dangerous than many other things used in
daily life.
Cell Voltage
Li-Po batteries have a nominal charge of 3.7V per cell (3V at discharge and up to 4.2V at peak). A single cell Li-Po battery with a nominal 3.7V is usually used in micro RC applications. A double cell battery with a nominal 7.4V (also called 2S) is equivalent to a 6 cell Ni-Cad or N-Mh battery. These are often used in 2-3 channel RC equipment such as boats and cars. Three cell Li-Po’s (3S) are a nominal 11.1V and are common in small scale helicopters, planes and some cars. Four cells in series (4S) have a nominal 14.8V equivalent to using two 7.2V 6 cell Ni-Cad or Ni-Mh. Charging
Li-Po batteries need to be charged using a special Li-Po battery charger with a balance plug port. The balancing feature ensures that all cells are equally charged throughout the charging process. 3239 Old Cleveland Road Capalaba West Queensland 4157
When Charging
• Always charge on a non-flammable dry flat • Always monitor the charging cycle. If the battery swells or heats up stop charging immediately and monitor the battery from a safe distance. • Always use a flame retardant Li-Po charging • Never charge the battery inside the model. • Never charge the battery higher than the rated charge rate (specified on the battery) or 1C if no charge rate is specified. o 800mah battery = Charge at 0.8 amps per hour o 1200mah battery = Charge at 1.2 amps per hour o 3000mah battery = Charge at 3.0 amps per hour o 800mah battery = Charge at 4 amps per hour (5x0.8) o 1200mah battery = Charge at 6 amps per hour (5x1.2) o 3000mah battery = Charge at 15 amps per hour (5x3) • Never allow the peak to exceed 4.2V per cell. 3239 Old Cleveland Road Capalaba West Queensland 4157 Handling
• Always transport in a protective case away from liquids and sharp • Always check that the electronic speed controller on your model has a safety cutoff for Li-Po batteries and adjust the settings accordingly. • Never allow the battery to get wet. • Never reverse the polarity of the battery wires. • Never store the batteries in a hot place. 4-26oC is ideal. • Never allow the voltage to drop below 3.0V per cell. Dropping below 3.0V per cell will damage Li-Po batteries. New Batteries
Whenever you use the electrical components of your model you draw
power from the battery. The more electrical equipment (servos, motors
etc) you are running, the more power you will draw. A
“charge/discharge cycle” consists of charging the battery to capacity
and then running the battery on your equipment until it reaches the
minimum recommended charge. Never let your Lipo batteries drop
below 3.0 V per cell.
Li-Po batteries reach their optimum performance after around 10-12
charge/discharge cycles. During this time the batteries should only be
discharged at 7C or less. 7C is 7 times the battery milliamp
capacity / 1000
For example
If the capacity is 1800mAh, then 7C is 7 times 1800/1000
3239 Old Cleveland Road Capalaba West Queensland 4157 The safest way to test the discharge rate that is being drawn from the battery is to connect a watt meter to test how much current is being drawn. Models powered by electric motors can have a large current draw when you use the throttle because the motor requires a lot of power, so it is especially advisable to test how many amps are being drawn by the motor. It may be necessary to run the model at less than full throttle for the first 10-12 runs. You may be able to find out information on the current draw from the specifications on the motor, and once again you will need to adjust your initial running of the model to ensure that you aren’t drawing more than the recommended 7C (7 times mAh / 1000). Discharge Rate
After the break-in period above, the maximum discharge rate is
determined by the battery C rating. You’ll notice on the battery that it
will be marked with a figure like 15C, 20C, 25C etc. The maximum
discharge rate can be calculated in a similar fashion to the break-in
discharge rate, but using the actual C rating instead of 7C.
For example
Capacity 1800mAh 15C - maximum discharge rate is 15 times
1800/1000 (15 x 1.8 = 27 Amps)
Capacity 4000mAh 25C - maximum discharge rate is 25 times
4000/1000 (25 x 4.0 = 100 Amps)
3239 Old Cleveland Road Capalaba West Queensland 4157 Li-Po Battery Disposal
The safest way to dispose of your Lipo batteries is to contact your local
council for the nearest battery disposal depot.
If you don’t have access to a battery disposal depot and you do need to
dispose of a Lipo battery yourself, the following procedure should be
strictly followed…
The Lipo needs to be fully discharged for safety reasons before it is
thrown away. However if the battery is damaged it is NOT
RECOMMENDED to discharge them with a discharger.
1. Ensure the battery is cool before proceeding. 2. If the battery is damaged, skip to step 5. 3. Place the battery in a bucket of sand or other fireproof container. 4. Discharge the battery using a Lipo discharger and discharge until the voltage per cell reaches 1V or less. 5. Submerse the battery in a bucket of salt water with a lid. Do not use a metal container. Use ½ cup of salt per 4 litres of water. 6. Leave battery in the water for at least 2 weeks. 7. Remove the battery from the water and place it in the rubbish bin. They are environmentally friendly, unlike Ni-Mh and Ni-Cd batteries.


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