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Old 01-29-2009, 07:50 AM   #121
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Originally Posted by Joel Lagace View Post
Perhaps we could just get a show of hands of who would be intrested in such a shootout in print in xtreme rc....

We can argue the results and testing methodes after the shootout gets published.

Instead arguing how to do the test, maybe we could all agree we would like to see some sort or test aka shootout....



So would you like to see a LIPO shoot out in XTREME RC?
(ROAR catagory and non RoaR)
I would. I like Danny's test and results. Done this way in the same lab would give an apples to apples comparison. In the end batteries may need to be grouped like motor winds depending on available current output regardless of what sticker is on the outside. It would at least let me know as a consumer that I'm potentially buying a dud or diamond. I'd rather pay 100 once than 30 four times over the same period of time. On the other hand I'd rather pay 30 once than 100 if the life of the battery is the same. That makes all 3 tests relevant.

Thanks for the graphs Danny.
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Old 01-29-2009, 09:29 AM   #122
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A battery race shootout article would be a nice read (until the next battery comes out or one is changed). A battery graph vault would be more usefull inmop. The nice thing about a graph vault is that multiple users can contribute with the very fair comparisons , and graphs can be done old or new, can overlay a brand new pack with a graph that was done a year prior under same conditions.

Yes, they can be manipulated.
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Old 01-29-2009, 09:35 AM   #123
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A battery race shootout article would be a nice read (until the next battery comes out or one is changed). A battery graph vault would be more usefull inmop. The nice thing about a graph vault is that multiple users can contribute with the very fair comparisons , and graphs can be done old or new, can overlay a brand new pack with a graph that was done a year prior under same conditions.

Yes, they can be manipulated.
I like the add it to the heap theory. Seems more objective with cumulative information over time.
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Old 01-29-2009, 09:39 AM   #124
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Many contributed to the battery graph vault , but it has died out.

This is kinda different since the rules are tightly established. It would not be hard to compare many of the roar packs since we can use the exact same standard for all packs . The packs are all similar in spec and it seems most are interested in a standard 30 or 35 amp continuous.
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Old 01-29-2009, 08:29 PM   #125
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*raises hand*

shootout plz.
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Old 01-29-2009, 08:32 PM   #126
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*raises hand*

shootout plz.

+1
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Old 01-30-2009, 01:29 AM   #127
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+2
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Old 01-30-2009, 02:12 AM   #128
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give us our shootout!
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Old 03-02-2009, 02:17 PM   #129
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bump, someone was asking wich lipo is the best.......

I could not answer the question because at this time all we have are fan boys and no facts.... would be nice to see a shoot out...

SMC is the only one that prints out the data from there packs...
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Old 03-02-2009, 04:05 PM   #130
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Just finally looking at jumping into lipo so I'd like to see this test.

I need to see one asap

so somebody get on it
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Old 03-03-2009, 03:48 PM   #131
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Default How I See the Test Process

Here are my thoughts to clarify the basic test procedures. I built a low-wattage current regulator (10W heat sink) and use a DVM sensitive to 1mV to measure the internal resitance of 7.2V NiMH pack at modest load. The same concepts apply to testing at greater regulated discharge current.

A. Pulse Testing with a Current Regulator:
Vs - open circuit source voltage (no current draw)
Ic - step level of pulse current (current regulator)
Vt - terminal voltage with pulse current applied
Vc - cutoff test voltage
Ra - armature resistance (visit motocalc online database for examples)
tF - final time in seconds

Rs = (Vs-Vt)/Ic internal source resistance. To create a set of curves just automate the pulse testing over a discharge cycle downto cutoff test voltage.

Pd = Ic*Ic*Rs power dissipation (loss) inside the battery

Measurement error of Rs depends on the current regulator precision and Voltmeter sensitivity.

Plot Vs, Vt, Rs at designated Ic and compare batteries.

Peak mechanical power output of a PMDC or Brushless motor occurs for the battery with greater Vs and lower Rs at every point on the curve.

B. Discharge Testing with a Current Regulator:
Vt - terminal voltage with continuous current applied
Ic - reguated current

C = Ic*tF*3.6 mAh

C. Maximum "Punch" Current (Start/Stall) :

Imax = Vsmax/(Rs + Ra) peak current occurs when shaft speed = 0

Last edited by SystemTheory; 03-03-2009 at 03:54 PM. Reason: correction, define Ra
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Old 03-03-2009, 06:33 PM   #132
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so when do you start running tests? We're all waiting


Quote:
Originally Posted by SystemTheory View Post
Here are my thoughts to clarify the basic test procedures. I built a low-wattage current regulator (10W heat sink) and use a DVM sensitive to 1mV to measure the internal resitance of 7.2V NiMH pack at modest load. The same concepts apply to testing at greater regulated discharge current.

A. Pulse Testing with a Current Regulator:
Vs - open circuit source voltage (no current draw)
Ic - step level of pulse current (current regulator)
Vt - terminal voltage with pulse current applied
Vc - cutoff test voltage
Ra - armature resistance (visit motocalc online database for examples)
tF - final time in seconds

Rs = (Vs-Vt)/Ic internal source resistance. To create a set of curves just automate the pulse testing over a discharge cycle downto cutoff test voltage.

Pd = Ic*Ic*Rs power dissipation (loss) inside the battery

Measurement error of Rs depends on the current regulator precision and Voltmeter sensitivity.

Plot Vs, Vt, Rs at designated Ic and compare batteries.

Peak mechanical power output of a PMDC or Brushless motor occurs for the battery with greater Vs and lower Rs at every point on the curve.

B. Discharge Testing with a Current Regulator:
Vt - terminal voltage with continuous current applied
Ic - reguated current

C = Ic*tF*3.6 mAh

C. Maximum "Punch" Current (Start/Stall) :

Imax = Vsmax/(Rs + Ra) peak current occurs when shaft speed = 0
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Old 06-10-2009, 12:45 PM   #133
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Xtreme RC Cars July 2009 has an article on C-rating and impact of internal resistance on acceleration curves in a standardized system. Only thing I would like to see is more system data about the car used for acceleration curve testing, and some battery measurements.

It's not a battery shootout, but a good effort to communicate the insights discussed on this thread, so I'm giving this a bump.
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Old 06-11-2009, 09:04 AM   #134
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Just for information in Germany there is a guy testing Lipos, chargers, balancers and other things in this direction. He is highly regarded in the elctric flight area and is known for true testing. If someone here wants true information you always will be directed on his website, there is just no better information public available. Itīs just bad he does just Lipos for electric flight until now, donīt know if he had request for others as well.
In the past he used his own equipment, meanwhile he has a professional equipment lent by a manufacturer for electronic testing equipment whoīs founder is model pilot as well http://www.hoecherl-hackl.com/index.php
This testing device is fully programmable via computer and could do up to 450 amps and 4200W load overall.
The hompage is http://translate.google.com.hk/trans...hl=de&ie=UTF-8
Actually this is a German website, translating is done via Google. If someone could read German language this is the original website http://www.elektromodellflug.de/news.htm
Some information on his testing is found here http://209.85.129.132/translate_c?hl...LLbX-pFJ4EQYOQ
Database for testing results and some technical informations (mostly model flight related) is found here http://209.85.129.132/translate_c?hl...sGmPDAsJ8eT7cw
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Old 06-11-2009, 02:58 PM   #135
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Quote:
Originally Posted by V12 View Post
Just for information in Germany there is a guy testing Lipos, chargers, balancers and other things in this direction. He is highly regarded in the elctric flight area and is known for true testing. If someone here wants true information you always will be directed on his website, there is just no better information public available. Itīs just bad he does just Lipos for electric flight until now, donīt know if he had request for others as well.
In the past he used his own equipment, meanwhile he has a professional equipment lent by a manufacturer for electronic testing equipment whoīs founder is model pilot as well http://www.hoecherl-hackl.com/index.php
This testing device is fully programmable via computer and could do up to 450 amps and 4200W load overall.
The hompage is http://translate.google.com.hk/trans...hl=de&ie=UTF-8
Actually this is a German website, translating is done via Google. If someone could read German language this is the original website http://www.elektromodellflug.de/news.htm
Some information on his testing is found here http://209.85.129.132/translate_c?hl...LLbX-pFJ4EQYOQ
Database for testing results and some technical informations (mostly model flight related) is found here http://209.85.129.132/translate_c?hl...sGmPDAsJ8eT7cw
THAT'S the guy we need to talk to! Since I live in Germany now, everyone send me a bunch of LiPo's and I'll pass them along to this guy to test. I'll let you know when I'm done with them but it might be a few years....

Seriously though, is there any way to get this guy to test *our* batteries? V12, do you know this guy or know how to get in contact with him?
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