Thread: New Product ESR / IR Meter fo Lipos
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Old Feb 06, 2011, 03:01 PM
Wayne Giles is offline
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Quote:
Originally Posted by jaccies View Post
Thanks Wayne for the result.
How did you measure every 50mah the IR while charging/discharging ? , can you do it with the ESR/IR meter while charging/discharging ?


" the IR of the pack is essential independant of state of charge" what we can see in your graph.

Software of Hyperion stores every second all measured values in a database during charge/discharge.
So you can see afterwards the charge/discharge results in a graph.
Attached graph is during a 3S 3Amp 35C lipo charge, charged with 3A
TCS = terminal capacity state in % ( 100%= fully charged)
the Lipo was discharged to 34% level before charge.
And Ri dropped from 27 to 13mOhm.

Charging with (1C) 3Amp will the lipo being heated up inside ( i dont feel the pack is getting warm at all) that much so the Ri drops from 27 to 13mOhm ?

Yes I will measure with IR meter my lipo's and compare with my report, and i will report it.
Jac,

Yes, you can read the IR at any time during the charge or discharge cycle. All you need to do is connect the IR meter in parallel with the charger/discharger and just press the button any time you want to measure the IR; so I connected a Medusa wattmeter in series with the pack and took a reading every 50mAh. The meter takes a reading in 15mS so that it does not interfere with charging or discharging and does not heat the pack.
Thanks for the attached plot from the Hyperion charger. Almost certainly the IR is falling because of internal heating from the charge current through the IR. The dissipation is about 0.25W in your pack which does not sound much, but in my charging of the 3S1000 pack you can see how reducing the charge from 1.2A to 0.7A stopped the IR falling and allowed it to start rising slightly.
In that case the dissipation was only 0.065W, but it was obviously heating the inside of the pack.
The IR of lipos is very sensitive to temperature; if you take a reading with the meter of a cell on the outside of a pack, place your hand on the cell and take another reading only 10 seconds later you will see that the IR has fallen.

It seems very likely that the reason that the Hyperion charger produces such results is twofold; firstly the charging current is heating the pack and secondly, the measuring system is reading the IR at low charging currents, whereas we are interested in the IR at high discharging currents which is not necessarily the same thing.

I assume the pack you are referring to is 16A in your table. Presumably the Av, Min and Max Ri figures refer to cells within a pack?
When you have a set of figures from the IR meter taken at the same temperature, you will really be able to compare your stock of lipos.

Wayne
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