good quality LiPo packsLiPo battery calculator

 

The battery (LiPo pack) is one of the biggest expenses in our hobby - at least for the electric guys. Unfortunately the C rating (the indicator of the performance of the battery) printed on the LiPo packs are not very "accurate". Due to the lack of standardisation the manufacturer can print more or less what they want on their batteries.

 

To be able to compare the performance of different brands of Lipos, Mark, Wayne and John developed the The Lipoly Objective Performance Database. The database builds on the "true C rating" of LiPo packs calculated by the internal resistance and the capacity of one cell of the pack. The mainspring of the database is their great LiPoTool which does the calculation. We added some values to the calculator and put all of it below for your convenience. Please support their awesome work and put your results in their database.

 

KEEP IN MIND: The calculator is based on empiric values as well as theoretical assumptions. The iR of a battery changes depending on temperature, discharge rate and dynamic and even depends on the method used to measure it. Therefore the results can just be seen as a rule of thumb and are without any guarantee.

 

Details about the calculator

 

The calculator utilizes the values of one cell of your LiPo pack. To get the real life C rating of your packs you need two values.

The first one is the capacity in mAh of the cell which is easy because it is simply the capacity of the pack itself (i.e. 5000mAh).

The second one is the internal resistance (abbr. iR) in milli Ω of the cell. You have to measure this value. Unfortunately this is not possible with a standard multimeter but most of the chargers (i.e. iCharger) are able to measure the iR of the pack and the cells. An even more accurate way to measure the internal resistance is to use an ESR meter. Wayne builds a great ESR meter which is perfect for our hobby. You can order it directly from him.

 

IMPORTANT: To ensure best comparability and accuracy leave the LiPo pack at room temperature for at least one hour before measuring the internal resistance. 

 

About the values of the calculator

 

capacity [mAh]: The cell's capacity in mAh. Nowadays this is equal to the capacity of the LiPo pack itself.
cell iR [mΩ]: The measured internal resistance of the cell.
If you want to calculate the C rating of the whole pack measure each cell of the pack and use the highest value.
cell count: This value is just needed to calculate the total voltage drop. Depending on the result you want to get you can enter the cell count of the pack or the whole setup (i.e. 14 for a 14S helicopter).
continuous
C rating:
The "true C rating" or "real life C rating" of the cell, respectively the pack, based on the iR and the capacity.
It is a conservative calculation to limit the possibility of damage due to overheating during discharge.
FOM: FOM is the abbreviation for Figure of Merit. It is used to compare the performance of LiPo packs with different capacity.
The bigger the FOM value the better the performance of the pack. Here you can find more information about the FOM.
continuous current [A]: This is just another way to express the "continuous C rating".
Therefore it is the recommended average current the cell/pack may support without getting damaged or destroyed due to overheating.
voltage drop per cell [V]: The voltage of the cell drops by this value when the continuous current is drawn compared to its voltage with no load.
total voltage drop [V]: The voltage drop of the whole pack/setup. This value is useful to predict the voltage drop during load in flight.
For example a 12S setup with 5000mAh packs and an iR of 2 leads to a total voltage drop of almost 3V when drawing the continuous current. So even with fully loaded packs (4.20V per cell) the ESC just gets 47.4V instead of the nominal voltage of 50.4V.

  

LiPo calculator

 

You have to enter the capacity of the cell/pack in mAh.

To calculate the true C rating enter the cell's iR in milli Ω and click "Calculate C".

To calculate the cell's internal resistance enter the C rating in "true C rating" and click "Calculate iR". 

If you enter the cell count of your setup/pack as well the total voltage drop of the setup/pack is calculated when drawing the continuous current.