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Old Jun 11, 2006, 07:51 PM
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Enerland 3300 20C, CBA & 10X Curent Amplifier Graph

This is a relatively high amperage discharge graph using a CBA and West Mountain Radio 10X prototype amp. combo:
http://www.rcgroups.com/forums/showthread.php?t=528314

Pending a prospective software patch, the deicimal point must be moved one place to the right on the Amperage and AmpHours readings.
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Old Jun 12, 2006, 12:16 AM
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The cell's graph doesn't look so bad...

I must admit RD, this graphing setup is a bit neater .
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Old Jun 12, 2006, 04:12 AM
phillyphly
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Nice graphs...

The cells look like an honest 15C cell. High temperature and volt drop below 3.3V at ~50% capacity is too great to be called 20C cell.

Everyone has their own subjective criteria for judging a cell though... despite objective data!
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Old Jun 12, 2006, 05:51 AM
sloping addict
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Thanks RD, glad more people will know be able to test the bigger cells.
Keep us tuned of the max amps/power this unit will be able to deal with.

Do you know in which packs / brands these cells are being used ?
Are there any cells in that area of capacity & weight that sustain a higher voltage than this particular cell (aka better Ri) or is that (likely) the best 3300/80g cell to date ?

There are some 4900 mAh that have been graphed by Gerd (Elektomodellflug) that seem stupendous, do you plan to have these graphed as well anytime soon ?

Also since many users (LMR glider, 3D planes, F3A, Helis...) don't use such cells for continuous high rate discharges, but rather at high peaks but low avearge, is there a possibility to do burst tests: say 5seconds @30C - rest 10 or 15 seconds - repeat until no load voltage is too low (say 3.3 volts or 3.0 ?) ?
FYI, unlike many, since I'm flying high perf sailplanes, I'm only looking for best power/weight ratio for short full power bursts with typically zero overheating issue - I have in mind to use 4900 cells at up to 180Amps (not paralleled) for 3000+W geared power plants

thanks !
...Proto
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Old Jun 12, 2006, 05:58 AM
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e-guru

If the criterion for C-rating were to sustain an average voltage of 3.5 during the discharge, then 20C cells up to now seem to be about 11C, e.g:
Post #3: http://www.wattflyer.com/forums/show...2952#post72952
Post #3: http://www.wattflyer.com/forums/showthread.php?t=6802

- RD
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Old Jun 12, 2006, 07:32 AM
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Protocooler,

The best info I know of re pack brands containing Enerland cells:
http://www.rcgroups.com/forums/showt...ghlight=brands
Re their merit relative to other cells in their class, see my last post.

I do plan to test more of the larger 20C cells. But variable duty cycle ("burst") discharging would have to be repeated quite a few times for an indication of LiPo lifetime. That's too time-consuming to be done manually and automatic cyclers cost upwards of twenty thousand dollars. So, I will do ten 20C continuous discharges of this Enerland cell, and others, manually. It's a tough test and should provide some grounds for inference re comparative lifespans. In any event, it's the best I can do with equipment I can afford.

- RD
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Old Jun 12, 2006, 09:35 AM
sloping addict
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Thanks RD, great info nonetheless - and certainly relevant for comparisons between cells.
BTW, it would be interesting also if you could calculate the IR of the cells - say, halfway through the discharge. People could use that to enter/correct (more easily) the default cell resistance values of the various calc programs, that are usually very pessimistic for the better cells => it occurs quite often now to find people end up with +50% amps than predicted and they wonder why - sometimes bashing the calc program itself

PS: I guess Gerd has developped is own SW to create the variable duty cycles.
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Old Jun 12, 2006, 02:03 PM
phillyphly
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Like I said, the great thing about providing objective data is that everyone can tailor their own rating system based on their needs/ how they fly...

I like 3.3V/ cell under given discharge for at least 80% of cell capacity just because that's what I set my LVC to. Of course, WOT the entire flight is a rarity but I figure if it can do it then less aggressive use will increase lifespan.

Thanks again for the objective testing!
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Old Jun 19, 2006, 10:40 AM
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I just noticed this morning that my results using the CBA 10X Amplifiier do not agree with Rod's (RC_Tester's) using the CamLight.
http://www.wattflyer.com/forums/showthread.php?t=3676

Possibly the cells were different, I don't know, but I believe Enerland shipped Rod's and my cells to us about the same time.

Rod's test showed the cell going below 3 volts @ 18C, while mine showed it successfully completing a 20C discharge at an average of about 3.3 volts.

I'll do another 20C discharge (66 amps) and check the amperage with my clamp-on ammeter. Meanwhile, I've emailed Rod.

- RD
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Old Jun 19, 2006, 12:49 PM
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The second 20C graph was consistent with the first, see attachment.

The voltage was monitored during discharge and appeared consistent with the graph; it lagged a little high compared with the CBA's voltage readout. The current (Sears Clamp-on, "Professional" model) measured 65.4 amps near the start of the discharge and drifted downwardly to 64.6 near the finish.

The fact that the amperage changed indicates the CBA/amplifier combination is not perfectly linear (a stable, low amperage reading could be ammeter inaccuracy), but the overall anomaly is not nearly enough to account for the difference in results between Rod's results and mine.

Gerd Giese apparently graphed this cell under the Polyquest brand, but not above 15C:
http://www.elektromodellflug.de/akku-test/polyquest.htm

- RD
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Old Jun 19, 2006, 02:03 PM
Brit in NZ
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Just to clear the confusion - the cell data you reference is from batches manufactured late last summer, not the same as the newer cells we both have.
Enerland have stated that since December they have improced the performance of the XP cells - I think this is what we are seeing. We'll know for sure when I finish all my packing and start testing the newer batch of Enerland cells.

HTH

Rod

Quote:
Originally Posted by RD Blakeslee
I just noticed this morning that my results using the CBA 10X Amplifiier do not agree with Rod's (RC_Tester's) using the CamLight.
http://www.wattflyer.com/forums/showthread.php?t=3676

Possibly the cells were different, I don't know, but I believe Enerland shipped Rod's and my cells to us about the same time.

Rod's test showed the cell going below 3 volts @ 18C, while mine showed it successfully completing a 20C discharge at an average of about 3.3 volts.

I'll do another 20C discharge (66 amps) and check the amperage with my clamp-on ammeter. Meanwhile, I've emailed Rod.

- RD
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