LiPo (Lithium-ion Polymer) Batteries


Basic understanding of LiPo battery use and care for RC models

LiPos (Lithium-ion Polymer) batteries have become more and more useful in RC hobbies. This is because LiPo are able to charged up to over 100 times without losing capacity, this provides an ideal energy source to power RC models. It is more convenient and safer than using nitro/fuel as a source of power.

A typical LiPo battery consists of one or more cells with a connector power plug and a balancer port. Each cell of a LiPo has a nominal voltage rating of 3.7 volts and a maximum charge voltage of 4.22 volts (4.2V is standard), as such there is a "voltage-window" ranging between 3 volts to 4.2 volts. You can pack each cell together to increase your voltage or capacity linearly or in parallel, example 3S LiPo is 3x3.7 =11.1v (fully charged 3x4.2=12.6+v).

It is important to know that if a cell is discharged below 3 volts, this will cause irreparable damage to the cell and therefore a complete charge is no longer possible, giving your LiPo a short shelf life.

If you received one of our DM drone enabled model aircrafts, our typical flight controller we use has a voltage protection that prevents your LiPo batteries from falling below it's recommended level. Many Electronic Speed Controller (ESC) also has a built-in voltage protection.  Before the LiPo voltage reaches the critical range, your drone will either try to land or return to launch. At this stage, you can still fly for about 2 more minutes, but should only fly within your landing zone. After the second warning, you should discontinue flying with the same LiPo battery. If you should carry on flying, the cell voltage will fall below 3.0V and be damaged.

During each flight, the cells may discharged differently. For example on a LiPo with 3 cells, one cell can have 3.4V, the next 3.6V and the third 3.5V. This adds to a total voltage of 10.5V. To rebalance each cell, you can charge your LiPo with the balancer port connected during charging. You use the LiPo Balance Charge function provided by your charger.

You can also buy a little gadget LiPo Battery Monitor and Alarm for under US$3, listed below (What We Use), which will allow you to measure voltages before each flight and also acts as an onboard alarm, if left connected to your LiPo balance port.

If your model aircraft includes an On Screen Display (OSD) and you are flying with video, you can easily monitor your voltage. A good practice is to not fly below 10.5V with 3s LiPo and begin your landing protocol. The voltage monitor will fluctuate during flight, and a sudden burst may drop the voltage lower. You may also notice a higher remaining voltage upon landing. If you complete your flight with about 11.4V left upon landing, you can simply store them for future use without completing a LiPo Storage charge.

Storage:  A LiPo should be stored at about 3.8V per cell, if not used for an extended period of time.  Again, if you don't store your LiPo at the suggested voltage, your battery will get damaged too.  You should store your LiPo batteries in a fireproof containers or sand bags.

Disposing LiPo: When your LiPo batteries cannot be completely charge, a shorter flight time begins to take it's toll. The capacity of such a damaged LiPo can be reduce by 50% of the original capacity when used. To disposed a damaged LiPo, you can just fill a disposable container with table salt and water. Discharge the battery as much first, fully submerge your LiPo for a week, and you can then dispose it at a battery recycling centre or throw it out.  Remember a charged LiPo when crushed, will cause an intense burst of flames.

Understand your charger limitation:  You may have learned that a LiPo with a capacity of 5000 mAh, allows you to set a charge current at 5A, and that is theoretically correct.  However a popular IMAX B6 Charger is only a 50W charger. Using the formula P = U * I, you will get I = P / U for a 6S Lipo divide 50w/25.2V= 1.98A.  You can charge your 6S LiPo at maximum of 1.9A even if it is a 5000 mAh battery. If you try to charge it higher, as a safety, the screen goes black, and the entire unit shuts down until you disconnect your power. Some of the high-end IMAX chargers will automatically reduce the charge rate, if it determines it cannot charge at the rate you entered.

LiPo Battery Schematics:
There are different types of battery connectors used by different manufacturers on different batteries and battery accessories such as chargers and speed controllers.

We suggest you try to choose your own preferred connector type(s) and stick to those to ensure compatibility with all your own equipment and models.

The main picture shows a range of the most popular battery connectors and balance / charging plugs. They are labelled and listed as follows :

  • B1 - Deans (T) type main connector - Female & Male. Used for main connection to speed controllers and motors. Used for medium to high current draw. Suitable for up to 60amps
  • B2 - JST / BEC type main connector - Female & Male. Used for main connection to speed controllers and motors. Used for low current draw.  Suitable for about 5amps
  • B3 - Tamiya main battery plug usually used on Car and Boat batteries (NiCd / NiMh) - Female & Male
  • B4 - Bullet Connectors - Female & Male. Single wire connectors, available in a range of different sizes to suit current draw / load requirements from 2mm to 8mm
  • B5 - HXT Connectors - Female & Male. Available in 3.5mm and 4.00mm sizes. Used for main battery connectors for medium / high power applications
  • B6 - Traxxas Connectors - Male & Female. Mainly used on high current draw car and boat batteries
  • B7 - XT60 Connectors - Male & Female. Used for high current draw battery connections
  • B8 - EC3 Connectors - Male & Female. Used for high current draw battery connections
  • B9 - Flight Power / Thunder Power (FP / TP) LiPo Balance Charger plug - Female & Male
  • B10 - Hyperion / PolyQuest (HP / PQ) LiPo Balance Charger plug - Female & Male
  • B11 - JST-XHR (XH) LiPo Balance Charger plug - Female & Male
  • B12 - JST-EHR (EH) LiPo Balance Charger plug - Female & Male.  Good for 3 Amps.

By understanding the balance plug, it is a relatively easy task to cut off different plug types and solder / crimp on your preferred type, and leverage a secondary power source.

While it may seem to be a lot of information and responsibility for a LiPo battery, I am sure you will enjoy your hobby! :)

DIYdrone Lab
... behind the scenes Wednesday February 10, 2016
: LiPo Battery Monitor & Alarm
: LiPo Battery Monitor & Alarm
: What We Use

Reserved for Video #1
about video

tips couponNotes: While it is good to charge and store your LiPo batteries in fireproof bags, we actually have our little DM tip; add another base layer of silicone bake ware.  Yes, silicon have been tested and proven to be high-heat resistant up to 500F or 260C.  So, visit your kitchen, you may just have one handy.

Inspect your LiPo carefully after a crash, a punctured LiPo will begin to bubble at high temperature before releasing a thick smoke and burst into flames.

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Wednesday, February 10, 2016

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