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Old Feb 07, 2013, 04:35 PM
Jimob23 is offline
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United Kingdom, England, Ware
Joined Aug 2012
180 Posts
Lipo c ratings

Not intending to start a "Which is the best Lipo" or preaching to the converted but recently purchased a new lipo rated 50C and I was doubtfull regarding the claim .
I think we are all aware that the C rating is always in question as the manufacturers never states as to how they arrived at the figure .
Posted an question on the battery forum where ended up getting a PM from a very informative fellow who it turned out has done extensive testing of lipo performances .
Gave me a good basic insight and directed me to this Excel sheet

http://www.jj604.com/LiPoTool/

A simple entry of the cells internal resistance or IR gives the actual C rating.
By use of a watt meter , fixed load of a vehicle head lamp bulb and Ohms law arrived at the IR of some packs .
Results were disturbing where the recently purchased branded 5000ma 50C pack was only actual at 22C
Splashed out on a dedicated meter that gives accurate total pack IR along with individual cell IR
Again discovered some packs where they were showing a balanced voltage but cells within the pack having very differing IR readings .Start to load up the pack the cell with higher resistance will heat up doing more damage .
Refering back to the tool I played around a bit with a range of differing IR readings where for the pack rated at 5000Ma 50C the cell resistance would have to be in the region of 0.5 Ohme . Not rocket science to see that is virtually impossible so in the future I will be passing on any packs rated 50C and perhaps work on max of 30c .
Am reliably informed there is a new player in the lipo market by the name of Haiyin where a few of the electric flying lads have been getting excellent results.
There is a UK stockist ,Electriflyer, currently with a small range of soft pack but expanding the range with hard pack so perhaps will be giving those a try

Jim
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