Internal Resistance - Zippy 3 cell 2200 mah lipo - WattFlyer RC Electric Flight Forums - Discuss radio control eflight

Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

Internal Resistance - Zippy 3 cell 2200 mah lipo

Old 03-19-2015, 11:07 PM
  #1  
craigrs84
Member
Thread Starter
 
Join Date: Nov 2011
Posts: 26
Default Internal Resistance - Zippy 3 cell 2200 mah lipo

I was wondering if someone could tell me what the internal resistance of a Zippy 3 cell 2200 mah lipo battery should measure when the battery is in good condition?

When I first bought the batteries I didn't own a charger capable of measuring the IR or capable of setting the batteries in storage capacity. So the result is I've let the batteries (two of them) sit in my refrigerator for the last 2 years almost fully charged.

I have a new charger now and I measured the IR:
Battery #1: 8, 8, 11
Battery #2: 11 10 10

Good or bad?
craigrs84 is offline  
Old 03-20-2015, 04:04 PM
  #2  
Larry3215
Look out for that tree!!!
 
Larry3215's Avatar
 
Join Date: Mar 2006
Location: Gig Harbor, Wa USA
Posts: 7,061
Default

It can be difficult to compare battery Ir. For one thing, different chargers come up with very different numbers. Things like room temp can also change the numbers slightly.

Its more important to compare a pack to itself over time. You can watch the Ir go up as the pack ages - or gets abused

If those numbers had been measured on my Hyperion charger, Id say they were pretty good. If they had been measured on my CellPro, Id say they were fantastic for a 2 years old 2200 pack
Larry3215 is offline  
Old 03-20-2015, 06:05 PM
  #3  
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,395
Default

I have a couple of storage charged same packs and numbers are very similar. That's using my Imax mini 6

Nigel
solentlife is offline  
Old 03-20-2015, 06:25 PM
  #4  
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 6,120
Default

Yeah they are usable, not great by a long stretch, but should be fine for moderate demand applications.
JetPlaneFlyer is offline  
Old 03-20-2015, 06:48 PM
  #5  
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 4,786
Default

Storage voltage is more important than temperature for LiPo longevity.
fhhuber is offline  
Old 03-20-2015, 08:08 PM
  #6  
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,395
Default

TBH I honest I have packs with much higher figures, but because the models using them are moderate demand, ie Sunday sport models - they perform fine.

I may be wrong but Ir figures give me indication of what model they will perform in. I have some with figures in the 00's ... but in my powered glider are fine. They only have to provide short bursts. My EDF's though demand far more and then I look for best Ir figs packs.

Nigel
solentlife is offline  
Old 03-21-2015, 04:28 PM
  #7  
dereckbc
Super Contributor
 
Join Date: Jun 2013
Posts: 1,221
Default

You did not say what C-Rate they have but those numbers are OK, not great, but acceptable. I have a few Hyperion CX G3 3S 2100 ma 25C batteries and when new measured 7-7-7 a year ago and now 10-10-10.
dereckbc is offline  
Old 03-22-2015, 04:51 AM
  #8  
craigrs84
Member
Thread Starter
 
Join Date: Nov 2011
Posts: 26
Default

Originally Posted by dereckbc View Post
You did not say what C-Rate they have but those numbers are OK, not great, but acceptable. I have a few Hyperion CX G3 3S 2100 ma 25C batteries and when new measured 7-7-7 a year ago and now 10-10-10.
Sorry they're 20C. Does higher internal resistance just shorten flight time?
craigrs84 is offline  
Old 03-22-2015, 05:25 AM
  #9  
Larry3215
Look out for that tree!!!
 
Larry3215's Avatar
 
Join Date: Mar 2006
Location: Gig Harbor, Wa USA
Posts: 7,061
Default

Higher Ir does several things.

The higher resistance causes the pack to reach LVC sooner because of the larger voltage drop. That shortens the flight time because it lowers the effective/usable capacity of the pack.

It also causes the packs to run hotter - again due to the larger voltage drop across the packs.

It also lowers your power output because the motor sees a lower voltage and turns at a lower rpm.

Higher Ir is never good
Larry3215 is offline  
Old 03-22-2015, 06:01 AM
  #10  
kyleservicetech
Super Contributor
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,952
Default Double Checking Ri on your batteries

Originally Posted by craigrs84 View Post
I was wondering if someone could tell me what the internal resistance of a Zippy 3 cell 2200 mah lipo battery should measure when the battery is in good condition?

When I first bought the batteries I didn't own a charger capable of measuring the IR or capable of setting the batteries in storage capacity. So the result is I've let the batteries (two of them) sit in my refrigerator for the last 2 years almost fully charged.

I have a new charger now and I measured the IR:
Battery #1: 8, 8, 11
Battery #2: 11 10 10

Good or bad?
It isn't to hard to calculate the exact internal resistance of your battery pack. All it takes is a wattmeter, motor, prop and the battery in question.

Power up the motor, and increase power to around 20% or so. Record Volts and Amps on the wattmeter.

Then run the motor to full power, and again record Volts and Amps on the wattmeter.

The formula for battery resistance is as below:

Ri = ([email protected]% minus [email protected]%)/([email protected]% minus [email protected]%)

So, if you measure 11.1 Volts and 12 Amps at 20% then 10.3 Volts and 45 Amps at 100% you get:

Ri = (11.1-10.3)/(45-12) which calculates out to 0.024 Ohms for the total of three cells in your battery pack.

You can use that calculated test derived from your setup to compare with the indicated battery resistance shown by your charger. My Cellpro PL8's show individual cell resistance, so you'd have to add them up to get the total cell resistance.

And, yes, you can calculate individual cell resistance by measuring the voltage on each cell during the load test. Gets to be a bit of a problem with the propeller blasting everything though.
kyleservicetech is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
CHELLIE
Hi-Performance and Sailplanes
2014
02-25-2018 11:51 AM
sticks
Batteries & Chargers
8
06-28-2014 05:08 AM
SimonXi
Batteries & Chargers
0
08-12-2011 05:08 PM
Henry111
Batteries & Chargers
118
03-18-2011 06:27 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Quick Reply: Internal Resistance - Zippy 3 cell 2200 mah lipo


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.11528 seconds with 14 queries