Lipo Batteries

LiPo Battery

Just like the motor and the ESC, the LiPo batteries used in this project are widely used for Radio Controlled Models. These are rechargeable batteries of lithium-ion technology using a polymer electrolyte instead of the more common liquid electrolyte. A LiPo battery is defined by:

  • its cell number (also referred as “S”: a 3S battery having 3 cells) which define the voltage (see bellow)
  • its voltage, determined by the number of cells. Tere are a few common voltage measurements worth noting:
    •  Charged: the voltage of a fully-charged LiPo cell is 4.20V. A fully charged 3S pack is 12.60V. Please note that charging above this will damage the cell.
    • Nominal: this can be considered a sort of “half-charged” voltage, as it is 3.70V, in between charged and discharged.  Nominal voltage is what manufacturers use when describing the voltage of their batteries. For example, a 3S battery is marked with its nominal voltage of 11.1V (3.70V*3 cells).
    • Discharged: the voltage of a discharged LiPo cell is 3.00V. But we consider that discharging below 3.3V will definitely damage the cell.
    • StorageWhen you want to store you battery for a few weeks or months, I strongly recommend to charge or discharge each cell to approximatively 3.80V which is the most stable state of a cell.
  • its discharge capacity, exprimed in with an integer followed by “C”. The C rating of a battery tells you how many amps can be safely drawn from the battery constantly. By multiplying the C rating’s coefficient by the capacity of the battery in Ah, you can determine the sort of amperage you can draw.  In the case of a 3S battery with a capacity of 5000mAh (5Ah) and a C rating of 20C, I can multiply 20*5 and get the max constant output of my battery, which is 100A. You will want that this max constant output is equal or above the max amps rating of your motor.
  • its capacity, measured in mAh (milliamp hours). This basically tells you how long you can expect the battery to last on a charge.  A 5000 mAh is equal to 5Ah (amp hours), which means that the battery can discharge at 5 amps for one hour, 2.5 amps for 2 hours, etc.

I will recommend a list of batteries for this project and the adapted chargers BUT using LiPo batteries requires special attention and misuse of these batteries (such as complete discharge, shock, hazardous storage, etc.) can lead to a start of fires and serious injuries.

I strongly recommend to read this safety guide and to check this guide to learn more about Lipo batteries.

Note that you can use for this project one 6S LiPo Battery or two 3S batteries in Series.

Plugging two batteries in series means that you will double the cells and so the voltage for the same Amps capacity, in contrary to the parallel wiring that double the amps capacity for the initial number of cells (or initial voltage).

 

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