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Old 07-30-2014, 12:47 AM   #1
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Default Lipo condition

What is a good internal resistance for a Lipo in good condition?

Ive got three packs with varying resistance but not sure if they are getting old or faulty.

Pack 1 Orion 7.4v 5000 90c 9.8 m ohms
Pack 2 Orion 7.4v 5000 90c 11.1 m ohms
Pack 3 LRP 7.4v 7200 100c 3.7 m ohms

All these reading are taking form the LRP touch charger.

Also i'm wanting to get new lipo packs, instead of looking at the "c" rating are you better comparing the wattage of the packs?

Cheers Mike

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Old 07-30-2014, 12:55 AM   #2
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Anything lower than 3 ohms per cell is really good in my book.
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Old 07-30-2014, 02:12 AM   #3
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Do you know if the LRP Touch reads the IR as a pack or per cell e.g. Is my Orion pack 9.8m ohms overall or per cell.
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Old 07-30-2014, 02:46 AM   #4
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There are only a few charges that give accurate results for IR, that charger isn't one of them
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Old 07-30-2014, 03:04 AM   #5
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Which chargers or stand alone devices give accurate IR readings?
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Old 07-30-2014, 09:53 AM   #6
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iCharger
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Old 07-30-2014, 10:03 AM   #7
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iCharger
Which model???
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Old 07-30-2014, 01:13 PM   #8
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Which model???
The 4010, 406, and 308 will all give IR while charging or whenever you want to check by pushing a button. My orcas stay at about 1.0-1.3 per cell and I charge on an icharger at 20+ Amps everytime.
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Old 07-30-2014, 07:17 PM   #9
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There are only a few charges that give accurate results for IR, that charger isn't one of them
On what basis or reasoning did you find the iCharger to be the best at measuring resistance? I.e. - if I bought the iCharger and compared it to my other chargers, how do I know which one is correct?
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Old 07-31-2014, 03:22 AM   #10
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On what basis or reasoning did you find the iCharger to be the best at measuring resistance? I.e. - if I bought the iCharger and compared it to my other chargers, how do I know which one is correct?
I've never used an iCharger (I wasn't the person who said they were good at it )

I don't think any charger can be accurate if trying to measure internal resistance while charging, if it stops to take the measurements that's different.
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Old 07-31-2014, 06:08 AM   #11
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I can check the IR of my battery without it being charged. I hold down a button and it takes 5-6 seconds to show my IR.

I am not an IR guru or anything. I just know the lower the number the better. However, I'm not sure what all affects the reading. Would longer/shorter cables give you a different reading? Would thicker charging cables give you a better reading? I need to play around it with it more to find this stuff out.
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Old 07-31-2014, 07:11 AM   #12
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I used the Nosram Stealth (same as LRP but in red) and I found it always read high for IR but as long as you keep a record of the IR numbers from new until just now you still have a point of reference to compare the quality of your cells on your charger.

As far as charger IR results go, Danny from SMC put up results from a few chargers on there Facebook page a few months back:

Quote:
Internal Resistance measurements on chargers can be misleading. On the most part they give you a good idea on your packs performance but they can't be trusted 100% like you can trust the ESR IR meter which is accurate.

Here is a test I did to show how IR readings on chargers can be misleading. I have 3 chargers that will give IR readings. One of them is the Revolectrix Powerlab the other is the iCharger 4010 Duo and the third is the Competition Electronics Turbo 35 GFX that gives IR under discharge. The other chargers give IR under charge.

I'm not sure how the Revolectrix measures the IR as it seems to be off compared to the iCharger and ESR meter. On some packs it seems to be closer to the iCharger and ESR meter but on others it's way off.

To show what I mean I did a test using a cheap 6200-30C-3S pack using the big long style cells that a company sent me for testing awhile ago. I'm also testing one of our 4300-40C-3S pack that fits in our 2S hardcase. This test also shows why you can't trust C rates.

Here are the IR numbers for each cell in the pack.

6200-30C-3S

Revolectrix IR: 3.1 - 2.9 - 2.9

iCharger IR: 7.5 - 9.3 - 6.5

ESR meter IR: 7.37 - 8.37 - 6.51

GFX discharge data: 5722mAh - 11.06 Avg.V - 15.2 IR

4300-30C-3S

Revolectrix IR: 2.7 - 2.5 - 3.2

iCharger IR: 3.5 - 3.7 - 3.6

ESR meter IR: 3.83 - 3.95 - 4.09

GFA discharge data: 4326mAh - 11.17 Avg.V - 9.0 IR

As you can see the Revolectrix gives better IR on the big 6200 pack but the iCharger , ESR meter and GFX all give better IR on the 4300 smaller pack. Based on this racers/customers need to be cautious when using the IR provided by chargers. I trust the ESR meter and the GFX and the Duo is not perfect but seems to be closer to the ESR meter than the Revolectrix. On some packs the Revolectrix does give a more reliable IR.

Another thing to note if you want to find which of your packs has the best IR you need to test them at the same temperature and charge rate. Temperature has a big impact on IR and the charge rate as well as it can get the cells hotter depending of the rate you're using.
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Old 07-31-2014, 08:40 AM   #13
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Quote:
Originally Posted by Conrad View Post
I used the Nosram Stealth (same as LRP but in red) and I found it always read high for IR but as long as you keep a record of the IR numbers from new until just now you still have a point of reference to compare the quality of your cells on your charger.

As far as charger IR results go, Danny from SMC put up results from a few chargers on there Facebook page a few months back:
Interesting
If my GFX showed I.R. numbers that high, I would toss that lipo pack

Also, the LRP touch has shown very consistent numbers in my experience, albeit on avg 2 pts higher than other hardware
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Old 07-31-2014, 08:48 AM   #14
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Quote:
Originally Posted by Mikkel_R View Post
Which chargers or stand alone devices give accurate IR readings?
SMC has a stand alone IR device

http://www.smc-racing.net/index.php?...product_id=103
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Old 07-31-2014, 01:05 PM   #15
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Quote:
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That's the ESR meter mentioned in some of the above posts.
It's also what I use
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