Released on Aug. 03, 2022
Lithium polymer batteries, better known as LiPo, have high energy density, high discharge rate and low weight, making them excellent candidates for RC applications. This can only be dangerous if you don't follow the safety rules.
Improper handling of LiPo batteries can cause a fire. Please take the time to read these safety rules before handling/charging batteries.
- Place the lithium polymer battery on the body and not on the cable: the cable may be removed from a weak solder joint.
- Charge safely: It is very important to find a fire-resistant place to charge your battery. Using a lipo-safe bag is a good option, and some people even build a bunker for it. Ammo boxes are a cheap but effective solution.
- Do not charge the battery immediately after use; wait until it has cooled down completely.
- It is recommended that the battery be charged at or below 1°C.
- Do not charge the battery unattended: check the battery periodically for heat or expansion. In such a case, stop charging immediately.
- Do not use or charge a damaged battery: Do not charge it when it is swollen or otherwise visibly damaged.
- Make sure the number of cells and battery type in the charger are set correctly to match the number of cells and battery type.
- Do not overload the charger, although this is usually done by the charger. However, it is recommended to check the battery voltage regularly.
- Do not leave the battery in the sun or in a hot car.
A very good rule to follow here is the "80% rule". This means never download a Li-Po pack that is less than 80% of its safe capacity (in other words, 80% downloaded). For example, if you have a 2000 mAh LiPo package, no more than 1600 mAh (80% x 2000) should be taken out of the package. This means a healthy package which also has a total capacity of 2000 mAh (as the packages age, they will have less capacity).
This is where the computer charger pays multiple times, so you can see how much battery is needed, thus allowing you to adjust the flight time accordingly to stay within the 80% rule to utilize it. If you don't have a computer charger to confirm capacity, another good indicator is to measure the open circuit voltage (not including charge voltage) of the pack or individual cells immediately after the flight/drive with a digital voltmeter or other measurement method similar to the digital voltage of the device.
An 80% LiPo battery will provide about 3.73 to 3.75 volts open circuit voltage. Therefore, a 3S LiPo pack will show approximately 11.22 volts when discharged at approximately 80% after flight, while a 6S pack will be in the 22.44 volt region. The longer you take care of it in flight/in the car, the less accurate this tension method will be for determining 80% discharge, as the open circuit voltage at idle can easily recover on its own when the pack is sitting after flight, maybe even something like 3.78 - 3.80 volts. LiPo, LiIon and LiFe batteries obviously have very different characteristics compared to conventional RC rechargeable batteries.
Therefore, proper charging of LiIon batteries with a charger designed for them is critical for both battery life and safety.
Maximum charge voltage and current
A 3.7 volt LiPo RC battery is charged 100% when it reaches 4.2 volts. Further loading will significantly reduce your life expectancy. In fact, the cell phone industry has studied the effect of fully charged LiPo voltages on cycle time. These tests were performed under ideal lab conditions, obviously at lower phone download speeds, and of course, 80% depth was respected. The results are as follows.
- A charge to 4.1V allows more than 2000 cycles.
- Charge to 4.2V for about 500 cycles.
- Charge to 4.3V for 100 cycles.
- Less than 5 cycles to 4.4V.
People in the RC world have also reported an increase in life cycles. One ongoing example seems to indicate that if you set the maximum charge voltage to 4.15 volts per cell (if computer charging offers this option), you should definitely be able to get longer battery life (if using the rule that LiPo is religious). point" for performance and RC life cycle. Most RC chargers do not offer this feature, but if they do, you may want to consider it.
One caveat I should mention is the new generation of "high voltage" lithium polymer batteries. Several manufacturers are producing LiPo batteries that can withstand up to 4.35 volts and maintain a 500 cycle life.
Regardless of your maximum charge termination voltage, when I first started talking about balancing RC LiPo batteries, keeping each cell in a LiPo RC pack at the same voltage is another important rule, so keep that in the back of your mind right away.
Here are the top seven factors that can lead to shorter LiPo battery life.
1. leaving the LIPO fully charged for several days
2. Physical damage (such as dropping, using too strong Velcro, too tight straps, prying open the cell, etc.)
3. Excessive discharge
5. Insufficient balance
6. OVER CHARGING (voltage and current)
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