Everything You Need To Know About LIPO Batteries
Lithium-Polymer batteries are better known under the term LiPo. The LiPo is a special type battery that requires more attention and maintenance than, for example, a NiMh battery. When flying a quadcopter offers a LiPo the required power to leave all electronic components to work.
The LiPo has several special features that distinguish it from other types of batteries. A LiPo is a battery that consists of 1 or more Lithium-Polymer cells. The LiPo is the ideal battery for a drone or quadcopter due to its high energy density, its high discharge capacity, and its relatively low weight.
A LiPo is made from one or more cells that are connected to each other in series. The number of cells per LiPo is indicated by the “S” sign. For example, there is a 4S LiPo for a 4-cell LiPo and a 5S LiPo for a 5-cell LiPo.
The nominal voltage of one cell is 3.7V. However, this is not fully charged or discharged
voltage per cell. The nominal cell voltage is approximately the middle between a safe full
fully charged and safely discharged LiPo. A LiPo can be safely charged up to a voltage of
4.2V per cell. The limit for a safe discharge per cell is around 3.5V. When your quadcopter is prepared for the use of higher voltages you can use a LiPo with several cells. The disadvantage of adding a cell to a LiPo is that the weight and size of the LiPo will also become larger and part of the extra energy will, therefore, be lost to it propelling the extra weight.
The name LiHV stands for Lithium High Voltage. As the name suggests, this is a LiPo that has a higher voltage per cell than a normal LiPo. This increased voltage per cell is possible due to a higher energy density per cell. The maximum voltage of a LiHV is 4.35V per cell. There are mixed stories about the use of LiHVs. On the one hand, they offer more energy, but on the other hand, the use of LiHVs shows that they lose their (discharge) capacity earlier as they get older.
The discharge capacity of a LiPo is indicated in a “C value”. The C value is one value stated by the manufacturer of a LiPo. The manufacturer specifies a continuous C value and sometimes also a “Burst” C value. The Burst C value is the maximum C value for a short duration, for example, 10 seconds. If we have the C value and the capacity (mAh) of knowing a LiPo we can calculate the maximum safe discharge capacity in amperes. The formula for this is LiPo capacity / 100 x C value. As an example, we take a LiPo with a capacity of 1500mAh and a C value of 75C. The maximum safe discharge capacity of this LiPo is then 1500 mAh / 100 x 75 C = 112.5 amps. The C value is an important factor when using a LiPo in a drone or quadcopter. Namely, if the C value is too low, the LiPo will not be able to deliver the requested capacity and the performance of a drone or quadcopter will therefore not be optimal.
THE CAPACITY OF A LIPO
The capacity of a LiPo is indicated in “milliampere-hours” (mAh). The mAh number gives how many milliamps you can discharge from a LiPo within an hour until it is complete discharged. Just as with the number of cells, it is also possible to have a LiPo with a larger one capacity to use in your drone or quadcopter, however, this effect is partially offset by the extra weight. The advantage of a larger mAh number at the same C value is that the discharge capacity becomes larger (for example 1000mAh x 50C = 50 amps, 1500mAh x 50C = 75 amps). The ideal operating temperature of a LiPo is between 30 and 60 degrees Celsius. When a LiPo is used in cold weather conditions, the (discharge) capacity drops drastically. It is advisable to first heat the LiPo in such weather conditions.
You can do this, for example, by using the LiPo a few minutes before you start using it in your
pocket to stop. The LiPo will then heat a good one due to body heat operating temperature.
INTERNAL RESISTANCE (IR)
Every LiPo cell has an internal resistance due to the materials used. This internal resistance
differs per cell. The higher the internal resistance, the lower the discharge capacity of a LiPo. The internal resistance increases as a LiPo gets older, when overloaded, overheated or physical damage. You can use a battery charger to measure the internal resistance which has this function onboard, for example, the SkyRC Q200.
WHAT TYPE OF PLUGS CAN BE FOUND ON A LIPO?
There are always two plugs on a LiPo, the power cable with the plug and the balancing plug which is removable or not. The power cable on the LiPo can be supplied with various plugs. The most used are the: XT30, XT60, XT90, and Deans plug. Make sure this plug always matches the plug attached to your drone or quadcopter. The balancing cable and plug are only used for the balancing phase during charging or discharged to a battery charger. The most common balancing plug is the JST-XH plug. The number of wires in a balancing plug corresponds to the number of cells in a LiPo. Sit like that with a 2S LiPo 3 wires in a balancing plug, with a 4S LiPo 5 wires in one balancer plug and so on. When you plug in or unplug a plug, you should never touch the wires but always on the plug itself.
LOADING AND DISCHARGING LIPOS
To properly control and manage the voltage of a LiPo during charging and / or discharging you must at all times use a battery charger that has a function to Charge and/or discharges LiPos. A LiPo battery charger has one for this balancer plug port into which you can plug the balancer plug of the LiPo. A LiPo charge or discharge cycle consists of a regular charge or discharge and then a balancing phase. In this phase, the battery charger will try to bring the voltage per cell as close together as possible so that each cell contains as much energy as the other cells. The charger also charges per cell in whether the maximum voltage does not exceed 4.2V. Voltage registration per cell and the balancing phase during loading is done via the balancing plug. Always keep an eye on the LiPo (s) during loading or unloading. After all, it is a LiPo flammable and various fires have developed in the past by igniting LiPos. As an additional safety measure, it is wise to load or discharge a LiPo in one so-called “LiPo Safe Bag”. These special LiPo bags are made from fire retardant material and will therefore also catch the first flames with an igniting LiPo. The number of charges and/or discharge cycles per LiPo is approximately 250 to 300 times. Rule of thumb is that when a LiPo can no longer deliver its discharge capacity and / or becomes bloated, that it must then be disposed of. The reason why a LiPo can get bloated is that Lithium-polymer in a cell causes a gas when physical damage occurs, the cell overloading or overheating. We recommend the following for loading and/or discharging LiPos to buy a good battery charger so that you always have the capacity and your LiPos are safely charged and/or be discharged. Before loading it is recommended to do this with a maximum C value of 2, for example, a 1500mAh 4S LiPo you have to charge a maximum of 3 amps.
HOW TO SAFELY STORE YOUR LIPO?
Because a LiPo is a flammable product, you should always be careful with a LiPo.
Preferably always store a LiPo in “Storage Mode”. In Storage Mode, the voltage is per cell
about 3.8V. This voltage is considered to be the voltage including the cell of a LiPo in the
best condition. The storage of a LiPo must be done in a metal lockable box (for example ammunition box) or a LiPo bag at room temperature. Whenever you need a LiPo having to store it for one day is allowed in a discharged state, but the strong advice is when this more than one day the LiPo can be stored in Storage Mode.
TRAVEL WITH A LIPO
Almost all airlines accept (a) LiPo (s) in hand luggage. Has every airline has its regulations, always check them. LiPos are allowed to never be taken in checked-in baggage. When you take (a) LiPo (s) with you during a flight always ensure that it is (are) in Storage Mode and cover the connector (s) from Finish a LiPo (s) with tape or a specially available cover cap. The best thing is you Put LiPo (s) in a LiPo bag, this will prevent possible discussions during the check-in your flight. Do not take damaged LiPo (s) with you at any time during a flight.
HOW TO DISPOSE of YOUR LIPO SAFELY?
If you want to dispose of a LiPo because it is defective, you can use the following methods:
when your charger can do this, the LiPo is completely discharged at low amperage (approximately 0.3 ampere) or discharged utilizing a special LiPo discharger. Methods with saltwater, piercing the cells, etc. are strongly discouraged! Be assured of it in any case that when you dispose of a LiPo there is no energy left in the LiPo.
HOW DO YOU CHOOSE THE RIGHT LIPO FOR YOUR DRONE OR QUADCOPTER?
Choosing the right LiPo for your drone or quadcopter is only possible if you know which drone
you want to buy or if you know which motors, Electronic Speed Controllers (ESCs) and propellers you like is going to use for your quadcopter. Below is a guideline for choosing the right LiPo for your quadcopter:
• 3 inch quadcopter: 450 – 850mAh
• 4 inch quadcopter: 850 – 1300mAh
• 5 inch quadcopter: 1300 – 1800mAh
• 6 inch quadcopter: 1500 – 2200mAh
• 7 inch quadcopter: 1800 – 3200mAh
With a drone you need to know what the maximum amperage will be that the drone will ask at a maximum load. With a quadcopter you need the maximum ampere consumption per motor multiply by 4 and hereby small consumers such as a flight controller, video transmitter (VTX), receiver (RX), et cetera. However, these small consumers are so small that we are here speak about 2 to 5 amps. For example: a quadcopter motor requires a maximum of 35 amps when you use a 5040 3-leaf propeller. The numbers specified by the manufacturer for the maximum power are in reality always lower because these figures are produced in a static “weir” test. In reality you can deduct 10 – 15% of this. You also need to keep in mind that you never have the maximum power of one continuously quadcopter engine you will ask, the majority of a flight requires 50 – 90% power. This yields the following calculation: 35 amps x 4 (4 motors) * 0.90 (90%) = 126 amps. When you use a 1500mAh LiPo you can then use the following calculation for the Burst C-value to be calculated: 125 amps / 1.5Ah (1500mAh / 100) = 83C. As a rule of thumb you can use it assume that the continuous C value is approximately 60% of the Burst C value, this yields the following calculate: 83C * 0.6 = 50C. When you have a flight style where you are more like the entire flight 50% gas gives it might be wise to have a LiPo with a higher C value than in the to take a calculation. There are many LiPo’s brands on the market, our advice is to always go for it a reputable brand because the unknown, cheaper LiPo’s brands are often not the capacity and C value with which they are offered.