Thread: New Product ESR / IR Meter fo Lipos
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Old Nov 17, 2013, 06:02 AM
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Melbourne, Australia
Joined Jul 2005
8,250 Posts
Not at all!

It's just that the more I learn about the performance of LiPos the more I see how complex it is. And I worry about some folks taking IR as a "simple minded" fundamental predictor of performance. The variation of composition of electrolytes and cathode/anode materials plus the physical construction including plate thickness all appear to have a significant affect on performance. IR is a measure of those affects - not the cause of them. And like most things it is not a simple linear gain. What you win in some areas you trade off in others. Nor is it something amenable to causal-effect prediction by the armchair theorists. LiPos are very complicated little beasts.

I remain impressed by how the LiPo rule that Mark and Wayne created continues to be such a reliable and straightforward predictor of a reasonable maximum current under almost all conditions. I use my ESR meters daily and rely on the LiPo Tool for practical guidance. But when you start pushing packs beyond that LiPo Tool recommendation to their limits things get a bit unpredictable.

Just one cautionary tale.
One of my three Turnigy A-Spec Packs, referred to in my earlier post a couple of days ago, has been the best performer of my 3S 2200 size packs under increasing current and had significantly lower temperature rise than any other similar pack. It had consistently lower IR across the whole temperature range 0-50degC than any other similar sized pack I own. It had also performed well at 78 Amps which is about 40C based on true capacity, which is a rate higher than most packs can deliver and stay in good shape. This pack is rated by HobbyKing at 65C continuous 130C burst on the label. So I tested it at 124Amps which is 65C for this pack based on actual capacity or about 56C based on label capacity.

It could just keep 10.1-10.2V (3.4V/cell) which is well above the 3V/cell used by some manufacturers, although it showed a marked voltage dip, produced significant amounts of fumes and smoke and had a surface temperature of 105degC and rising when I finished the test and dumped it in a pail of sand. I have no idea how hot it eventually got internally but I'm guessing 120-130deg C minimum. It is puffed like a pregnant pig and, although it will recharge, for all practical purposes is as dead as a dodo. It went in the trash tonight.

John

Quote:
Originally Posted by xStatiCa View Post
I hope you didn't take what I said as a complaint or anything negative.
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