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11-30-2010, 06:19 PM | #21 (permalink) |
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actaully how about V=IR so
(v1-v2)/I=R Schoolboy physics is a bit rusty |
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12-03-2010, 01:38 AM | #22 (permalink) | |
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Quote:
Or, if you want to use the abbreviations from your previous post: IR = (OCV-LV)/LC Succes with it.
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12-05-2010, 04:49 PM | #23 (permalink) |
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Thanks RedBird.
I am going to make an IR tester rather than buying a new charger. I hope Radioshack has some inexpensive voltmeters I can solder in line and some sort of current measuring device. I would like to rig up something that uses a load such as a small bulb. I'll post if I get this working. |
12-05-2010, 09:45 PM | #24 (permalink) |
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There's a guy in rcgroups that made and is selling IR testers. Supposedly, they are pretty accurate, more so than chargers.
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12-05-2010, 11:37 PM | #25 (permalink) |
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alexf ..I'll try to find it thanks.
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12-06-2010, 01:31 AM | #26 (permalink) |
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The voltage differences will be rather small, so you'll need a voltmeter with good accuracy and plenty of resolution, like at least a 3 3/4 LCD type display, not sure if a cheap one will give you satisfying results.
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01-03-2011, 05:05 PM | #28 (permalink) |
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Using a meter alone will not get you accurate measurements. You have to take measurements under load. I have not looked into all the specifics. You can probably get more detail info on rcgroups.com
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01-06-2011, 03:10 AM | #29 (permalink) |
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It's all explained in the very first post of this thread:
"To determine the internal resistance, first it is necessary to measure the open circuit voltage of the cell. Then a load should be connected across the cell causing a current to flow. This will reduce the cell voltage due to the IR voltage drop across the cell which corresponds to the cell's internal resistance. The cell voltage should then be measured again when the current is flowing. The resistance is calculated by ohms law from the voltage difference between the two measurements and the current which is flowing through the cell." Read more about it here: http://www.mpoweruk.com/testing.htm
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01-30-2011, 10:49 AM | #30 (permalink) |
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Excelent thread. I have noticed a dramatic drop in flight time. Yesturday I told myself I was going to test my Lipo's "3S"s". but was unsure if I was approaching the issue correctly. It seems I was on the right track and it's great to have the conformation.
Now if I could just get my DMM probes to fit in those tiny JST conectors. LOL FYI I have a Radio Shack DMM # 22-178, been using it for about 17 or 18 years so they are good meters, or at leaste they were. It has the same capabilities as a high dolor Fluke, but about 1/3 the cost. I think I paid 70 bucks for it. |
04-09-2011, 07:04 PM | #31 (permalink) |
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hey guys with my Hyperion DUo chargers i saw that my 6s lipos VOltz have 10-16IR...
Thats a good number... TOday i charged the same lipos on 2C on the field and i saw that the Ir was 5-7.... ANy ideas why??!
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04-09-2011, 09:09 PM | #32 (permalink) |
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Packs were likely warmer. IR is dependent on temp.
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06-17-2011, 07:33 AM | #33 (permalink) | |
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Quote:
I just got my new Icharger 208b and finally have a chance to try out the IR of my lipos. I found 2 x 6S that have to be disposed Curious thing a have 3x 6S Flightpower and the IR of all 6 S is 35.....guess they are garbage but wondering if those high numbers make sense. Thanks Chris
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11-14-2011, 06:44 AM | #34 (permalink) |
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Is it best to check internal resistance when the pack is fully charged or after it is down to about 20%? When I measure the IR before charging, I get 6 ohms on each cell. After charging it drops to 4 ohms per cell. Which figure should I be concerned with?
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11-14-2011, 12:29 PM | #35 (permalink) |
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There are many factors that change cell IR, temp, charge state, age, condition, etc. The only way to get useful results is to keep as many things constant as possible.
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11-20-2011, 08:55 AM | #36 (permalink) |
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very good info C.D. i use a plastic fork to puncture them
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12-02-2011, 12:49 AM | #37 (permalink) | ||
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Here's a video with great I.R. explanations and real world examples with simple math. I only halfway understood IR for a couple year and not enough to have a working knowledge of it. It wasn't until watching this vid a couple times that it began to click.
Oh and you can ignore the fancy gadget being demonstrated and still get something out of it.
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07-20-2012, 06:42 PM | #38 (permalink) |
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Logview v2.7.3 question
This program is really hard for me to figure out. Does anybody have a link to a quick user guide or have some advice. I have 6 3 cell batts all different c rating but same mah and 6 1 cell mcpx batts. I would like to have a profile or something like that to just click on when I charge a batt to monitor its health. How do I do this?
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07-26-2012, 11:59 PM | #39 (permalink) | |
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Quote:
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07-27-2012, 12:33 AM | #40 (permalink) | |
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Quote:
If you were to only pull 2A or so from your 2200s they would be fine to an IR of 50, less so if you want 20A from them (or more).
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