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Thread: Was finally able to test the internal resistance of my LIPO's

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Old 06-27-2019, 03:36 PM   #1
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Default Was finally able to test the internal resistance of my LIPO's

Having had a problem with one of my lipo's, I decided to get a tester to see what the IR of each cell is.

Here's what I've got:
  1. 10ohms ; 4 ohms
  2. 6ohms; 2 ohms
  3. 6ohms; 3 ohms
  4. 4ohms; 9 ohms
  5. 16ohms; 142 ohms
  6. 2ohms; 16 ohms; 14 ohms

Are there any that look concerning? One of these batteries gets warm/hot when charging (and one of the cells always lags behind), and one came with a used truck (haven't even used it yet). All of these are at storage voltage.
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Old 06-27-2019, 04:13 PM   #2
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Default Re: Was finally able to test the internal resistance of my LIPO's

#5, 142 milliohms (IR is always measured in milliohms) is way too high. I'd retire that battery immediately.
The rest are in pretty good condition. Anything less than 10 milliohms is in excellent used condition. Personally, I won't use a lipo if any cell is over 20 milliohms.
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Old 06-27-2019, 04:27 PM   #3
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Default Re: Was finally able to test the internal resistance of my LIPO's

Quote:
Originally Posted by nightcrawler48 View Post
#5, 142 milliohms (IR is always measured in milliohms) is way too high. I'd retire that battery immediately.
This is from the used truck and I wasn't planning on keeping it. Thank you for stating that it's in milliohms. The reader gives an "o", so I assumed ohms.

But the 3 cell is having issues - heating and cell one always takes hours to catch up to the other two cells. Venom said it should go because of the heat and I'm in agreement. Even with a batsafe I don't trust this battery.
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Old 06-27-2019, 05:20 PM   #4
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Default Re: Was finally able to test the internal resistance of my LIPO's

I wonder does the size or capacity play a role in this? All of my small batteries (850 mah and less) have terribly high IR even a pair of brand new ones, they're up in the 80's to 100's.
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Old 06-27-2019, 05:53 PM   #5
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Default Re: Was finally able to test the internal resistance of my LIPO's

Quote:
Originally Posted by HumboldtEF View Post
I wonder does the size or capacity play a role in this? All of my small batteries (850 mah and less) have terribly high IR even a pair of brand new ones, they're up in the 80's to 100's.
Yes. A 1000mah cell will have twice the IR of a 2000mah cell if both are equal discharge rate, factory, chemistry, etc.. Teeny cells have high IR by the nature of things.
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Old 06-27-2019, 06:30 PM   #6
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Default Re: Was finally able to test the internal resistance of my LIPO's

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Originally Posted by HumboldtEF View Post
I wonder does the size or capacity play a role in this? All of my small batteries (850 mah and less) have terribly high IR even a pair of brand new ones, they're up in the 80's to 100's.
All the lipo packs I have on that list are 5000mah and used in 1/10 trucks. I haven't tested any of my smaller packs, but it's good to know there will be a difference in what I should expect.
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Old 06-27-2019, 06:39 PM   #7
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Default Re: Was finally able to test the internal resistance of my LIPO's

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Originally Posted by JohnRobHolmes View Post
Yes. A 1000mah cell will have twice the IR of a 2000mah cell if both are equal discharge rate, factory, chemistry, etc.. Teeny cells have high IR by the nature of things.

Awesome, thank you
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