LiPo Storage
In-Practice

by Bob Violett

   We have all heard/read about the various theories concerning the proper procedures for Lithium Polymer battery use and storage.  We now have "In-Practice" conformation that our EVF power batteries should be stored at their optimum storage voltage of 3.85+- .05 per cell.
 
   Tommy Wood of Lakeland, Florida flies his EVF 12 powered Electra alot, laterally about three hundred flights per year. Tommy's practice of faithfully storing the batteries properly between flying sessions has provided evidence that this procedure really works.
   Tommy has (2) two year old sets of ThunderPower (3) 45C 4S 2P 6500mAh packs with 120+ flights each that are still going strong.  They are flat, firm and produce close to brand new performance.  The chemistry in the 65C batteries from ThunderPower is measurably improved over the 45C series, so we can expect even better service life.
   

Appropriate Chargers

   The FMA PowerLab 8 and the CellPro 10XP have a "Storage Charge" feature.  We now know to use it.  It is BVM's practice to not leave the batteries fully charged for more than a few days and to store them at room temperature.

Internal Resistance

   Another important feature of these modern chargers is their ability to detect and record the internal resistance of each cell in a pack.  The "I.R." is the best measure of a LiPo battery's capability to deliver Watts.  We record these numbers when the packs are first put into use, then keep track of the number as we accumulate flights.  As the packs age, these numbers will creep upward but should remain fairly even cell to cell within a set of packs.

   If you are using the PowerLab 8 for fast parallel field charging, we have found it helpful to occasionally slow charge the batteries on the CellPro 10s or XP to verify the per cell I.R.

Tommy Wood is using:
Charger - (2) CellPro 10s
Storage Temperature - Room Temperature 75
-80
Number of sets of ThunderPower - 3 sets
Current I.R. of cells - 1.2-1.5

Note:  The CellPro 10s will bring batteries up to storage charge after a flight.  It will not discharge the batteries.


From ThunderPower

Storage & Transportation

1)    Store batteries at room temperature between 40 and 70 degrees F for best results

2)    If storing longer than one week; batteries must be stored at 3.8V/cell to 3.9V/cell (approximately 50% charged). This is easily accomplished using our PowerLab 8, PowerLab 6, or CellPro 10XP charger.

3)    Do not expose battery packs to direct sunlight (heat) for extended periods.

4)    When transporting or temporarily storing in a vehicle, temperature ranges should be greater than 20 degrees F but no more than 150 degrees F.

5)    Storing Lipo batteries at temperatures greater than 170 degrees F for extended periods of time (more than 2 hours) may cause damage to battery and possible fire.

 

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