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Old Nov 09, 2012, 03:27 AM
aka JetMan Joe
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Battery Load Test Comparisons

This post is to share my results from testing a number of batteries under high amp load. I've questioned whether buying a high priced Thunder Power was worth it and if the GensAce 5500 25C really performs as well as a TP 45C. I wanted to know if 60 and 65C ratings were just hype. I discussed ideas with a great 3D flying buddy who has lots of technical savvy, Racerxky. We kicked around different ways to test batteries and what to look for and how to determine if a battery is really actually putting out "60C". I could find no definition for measuring "C" rating. Battery manufacturers never, ever, ever talk about it so there's probably a lot of hype going on.

We decided the only way to get some answers was to put a few batteries under a serious high load and see what squeezes out. Regardless of what the manufacturers imply with their high C ratings, even a gold plated battery pushing 200 amps through 10 gauge wires will melt the solder off the junctions. A case in point is the first test of Thunder Power's flagship 5000mah, 65C, 6S $250 Lipos showed that the 4mm bulleted split pack link connector melt off their wires at the equivalent of 32C.

To be fair TP's have the reputation of running strong long after the cheapies will turn to junk. However I take that on faith because I've never put 100 cycles on any one battery so I have no other way to tell. But what I do think is if I reeeeaallly load up a battery a few times it will start to show it's true colors. It will run hotter then the higher quality cells, get puffy when maxed out, etc.

Lipo break in is another issue. I've seen that the better batteries tend to get stronger as more cycles are run but have seen little change with the cheapies. I made sure all the batteries had a minimum of 6 light duty break in cycles on them before testing.

Voltage available under high load was another area of question. I've seen ESC's cut out when the throttle is opened past 75% because a crap battery couldn't keep up with a motors current demand so the ESC shuts down on low voltage. So what's a "respectable" percentage of voltage a battery will hold under load? Does one hold 5% voltage reserve at WOT conditions while another will hold 25%?

To get a start at some answers I built a box that puts a constant resistance across the batteries terminals. Using OHM's law and 6S as my standard I calculated what the nominal current should be and provided a number of different "taps" or resistances I could plug into. The resisters are large spiral types that act like a powerful heater so 1200 SCFM of air is blown over them during testing. While the batteries are under load the voltage, current and temperature are recorded. A common lipo tester is plugged into the balance taps so the actual percentage of voltage remaining is displayed.

There are the caveats: This is called "resistive" loading. When we run our motors we are putting them under an "inductive" load which is a different kind of load. A resistive load will tell you alot but there will be difference in the results. Also differences whether the load is pulsed or sustained, etc. Therefore the second half of this posting will be with an inductive load producing tester.

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INDEX OF HIGHLIGHTS FURTHER IN THE THREAD:

Page 6:
Data acquisition hardware (Report # 84)
FB Jets Velox w/ Schubeler DS94-HST 12S Test Rig (Report # 86)
http://www.rcgroups.com/forums/showt...1767093&page=6

Page 25:
Test Rig setup for the 12S testing series (Report #365)
Thrust Sensor Hysterisis & Dead Weight Validation Graphs (Report #370)
http://www.rcgroups.com/forums/showt...767093&page=25

Page 26:
12S Test Series Graphs (Report #376)
Product Review and Pricing Comparison (Report #378)
http://www.rcgroups.com/forums/showt...767093&page=26

Page 28:
Thunder Power new G8 Test Results (Report #417)
http://www.rcgroups.com/forums/showt...767093&page=28

Page 34:
JJ604- Why Measured IR is Useful (Report #507)
http://www.rcgroups.com/forums/showt...767093&page=34

Page 39:
Thunder Powers Revenge- What can happen when you really pull 40C (Report #585)
http://www.rcgroups.com/forums/showt...767093&page=39

Page 42:
Habu 6S Test Rig Setup (Report #620)
http://www.rcgroups.com/forums/showt...767093&page=42

Page 44:
6S Series Testing Results (Report #653)
http://www.rcgroups.com/forums/showt...767093&page=44

Page 53:
Wayne Giles' revealing calculation on 10AWG power lead heat build up (Report #789)
http://www.rcgroups.com/forums/showt...767093&page=53

Page 56:
7S Series Testing Results (Report #836)
http://www.rcgroups.com/forums/showt...767093&page=56

Page 61:
40C Stress test comparison between Revolectrix's new HV 70C Silver series, Diamond 60C and Dinogy in a 12S configuration.
http://www.rcgroups.com/forums/showt...767093&page=61 (Report #909)

Page 63:
Wayne Giles explains why cell voltage matching is important to lipo health and performance
http://www.rcgroups.com/forums/showt...t=wayn&page=63 (Report #941)

Page 65:
30C comparison between Revolectrix's new HV 70C Silver, Diamond 60C, Dinogy and Nano ASpec in a 12S configuration. http://www.rcgroups.com/forums/showt...767093&page=65 (Report #962)

Page 66
Comparison between Revo SilverHV's charged to 4.27v and 4.20v
http://www.rcgroups.com/forums/showt...767093&page=66 (Report #981)

Page 72
Results of China Hobby 5000/50C packs tested at 40C
http://www.rcgroups.com/forums/showt...767093&page=72 (Report #1079)

Page 73
Results of China Hobby 5000/50C packs tested at 30C
http://www.rcgroups.com/forums/showt...767093&page=73 (Report 1087)
(Report 1092 shows Dynamic EDF based test rig)

Page 74
Brand Evaluation Synopsis
http://www.rcgroups.com/forums/showt...767093&page=74 (Report 1103)

Page 75
20C Comparisons
http://www.rcgroups.com/forums/showt...767093&page=75 (Report 1123)

Page 78
40C Comparison Table for Revo "HV", Revo 60C, Dinogy, ASpec, ASpec "G2", Magnum 250A, ChinaHobbyLine and Hyperion
http://www.rcgroups.com/forums/showt...767093&page=78 (Report 1164)

Page 79
30C Comparison Table Revo "HV", Revo 60C, Dinogy, ASpec, ASpec "G2", Magnum 250A, ChinaHobbyLine and Hyperion
http://www.rcgroups.com/forums/showt...767093&page=79 (Report 1172)

Page 84
Dynamic (EDF) Thrust & Efflux Comparisons Revo "HV", Revo 60C, Dinogy, ASpec, ASpec "G2", Magnum 250A, ChinaHobbyLine and Hyperion
http://www.rcgroups.com/forums/showt...767093&page=84 (Report 1258)

Page 78 & 85
REVOJohn shares excellent insider info regarding Chinese manufacturing process realities effecting our Lipo quality
http://www.rcgroups.com/forums/showt...767093&page=78 (Report 1156)
http://www.rcgroups.com/forums/showt...767093&page=85 (Report 1261)

Page 109
Life Cycle Test System overview and descriptions
http://www.rcgroups.com/forums/showt...67093&page=109 (Report 1626)
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Old Nov 09, 2012, 02:38 PM
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Interesting the comparison between C ratings - The 25C rated packs are right up there with the 60C rated packs.

What is "reserve voltage? How is it calculated?
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Old Nov 09, 2012, 03:02 PM
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nice setup! on the gens ace 25c vs 60c...If I remember correctly I think everydayflyer's test echoed the same thing.

it's also interesting to see how well the nanos held up though.

I recently bought a couple of Haiyins and they do hold up fairly well....
it looks like the Haiyins are right up there and even a tad ahead of the comparable 25C gens ace.
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Old Nov 09, 2012, 03:46 PM
aka JetMan Joe
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Quote:
Originally Posted by hoppy View Post
Interesting the comparison between C ratings - The 25C rated packs are right up there with the 60C rated packs.

What is "reserve voltage? How is it calculated?
The lipo voltage checker shows the value as a percentage of full charge. I believe an average of 4.20 volts per cell would be 100% and 3.20 volts per cell would be 0%
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Old Nov 09, 2012, 03:50 PM
aka JetMan Joe
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Quote:
Originally Posted by rcalldaylong View Post
nice setup! on the gens ace 25c vs 60c...If I remember correctly I think everydayflyer's test echoed the same thing.

it's also interesting to see how well the nanos held up though.

I recently bought a couple of Haiyins and they do hold up fairly well....
it looks like the Haiyins are right up there and even a tad ahead of the comparable 25C gens ace.
I was surprised by the nano also, especially where the output actually increased at the 20 second read when the battery warmed up to optimum temperature. However the starting "punch" was lacking. For the first 10 seconds, where you really need the kick if you were climbing out it fell behind the leaders by a full 14A which is significant. It even fell behind a couple of the 25C's. I believe this battery is one of those that would really benefit from preheating (all batteries started at just under 70 degree shop temperature).

I was surprised enough at the Haiyins to buy a couple of the 40C's to test. I also picked up the Glacier that I've heard some about.

One thing I've seen in general is if your running 60-80 amps just about all batteries do the same. It then becomes a matter of how many cycles a battery will last rather then actual performance.
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Old Nov 09, 2012, 09:27 PM
Space Coast USA
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Quote:
Originally Posted by MCSGUY View Post
The lipo voltage checker shows the value as a percentage of full charge. I believe an average of 4.20 volts per cell would be 100% and 3.20 volts per cell would be 0%
So that was the voltage of the pack under load? 5% reserve would mean the underload voltage was about 3.6V. Did you record the voltage under load or just the % from the cell checker?

BTW, thanks for posting this data, it's very informative.
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Old Nov 09, 2012, 09:31 PM
aka JetMan Joe
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Yes, that's about right. I just captured the %, not the actual voltage
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Old Nov 10, 2012, 11:10 AM
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very interesting
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Old Nov 11, 2012, 04:21 AM
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AaahhhhhhhHHH... now THIS is what we want to see manufacturers SHOW us... Not some hyped thumb sucked figure !!!!
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Old Nov 11, 2012, 07:00 AM
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For under $50 you can build a constant current discharger: http://www.rcgroups.com/forums/showthread.php?t=1107072
Then you can directly compare your results with other peoples' results.
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Old Nov 11, 2012, 01:22 PM
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It is a very correct aproach
The big load comparsion is giving the real imfo about the battery. not the stickers on it!
I have posted before the discharged curves at big loads.



It is 4000 80C made 2011 weight 127 gr/cell full discharged 200 Amps



It is 5000 65C made 2012 weight 133 gr/cell full discharged 275 Amps
You can see the difference betwin the original and the copy



It is 6600 65C made Oct 2012 weight 133 gr/cell.
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Old Nov 11, 2012, 03:43 PM
aka JetMan Joe
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Thank you Ivaylo, you have provided very good information, I appreciate it.
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Old Dec 26, 2012, 08:19 PM
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Awesome thread, looking forward to the brushless or pulsed inductive load testing, just to learn what sort of differences there might be.

Did you use the same resistance for all of the tests, or did you pick different taps for each battery?
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Old Dec 26, 2012, 09:12 PM
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Yeah, I'm in!

Thanks!
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Old Dec 27, 2012, 12:28 AM
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Quote:
Originally Posted by LoneWolfRC View Post
Awesome thread, looking forward to the brushless or pulsed inductive load testing, just to learn what sort of differences there might be.

Did you use the same resistance for all of the tests, or did you pick different taps for each battery?
No the load is not the same. It can not be the same if the IR of the Cell are not equal. But if it is programed, could be the same.
The tests are with purpously designated devices Load tester with heat extraction and calculas


The devices allow to test the battery performance with algoritm and/or governor controlling the battery figures and change the resistance as per load function programmed.

One example for such a test. (It is a racing battery for Boat 6800 30C, developed over 6600 65C)




On some of battery the loads aplied are bigger then the C-rate to test the strenght of the tabs, or analyse the electrodes after the test.
I have posted the curves for 5000 25C discharged with 150 amps (30C)
http://www.rcgroups.com/forums/showthread.php?t=1786416
One more good project 8000 25C (but in weight limits)
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