Measuring lipo internal resistance - RC Groups
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Jan 29, 2008, 11:25 AM
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ajreynolds's Avatar

Measuring lipo internal resistance

I was wondering what the proper way is to measure lipo internal resistance. I was thinking of hooking up a taillight bulb as the load on a pack and measuring voltage and current then calculating the resistance. Do I need to then subtract out the resistance of the bulb itself to get the total internal resistance of my pack?


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Jan 29, 2008, 12:58 PM
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ggcrandall1's Avatar
Check here:

Jan 29, 2008, 12:59 PM
Jesper Frickmann
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I think the bulb resistance is a little hard to get as it varies with the temperature of the glow wire. If you measure current and volts under load as well as resting, then you can estimate the inner resistance. But that will tend to overestimate the inner resistance, as there is also some diffusion resistance in the electrolyte which causes a voltage drop as well.
Jan 29, 2008, 04:53 PM
Permanently Banned
LIPO Z ( impedance) changes differently as a load when charged and as a source when it drains

if U R concerned about hi-resistance interface , check your COLD solder joints by re-doing it or look at those spot welds on the aluminum TABs with the nickel TABs and RE
-TIN them with Harris aluminum soldering flux
Jan 29, 2008, 05:13 PM
I need a bigger garage...
ajreynolds's Avatar
Thanks for the responses, everyone. That link that Glen posted is just what I was looking for, as it's the reason I asked. I wanted to figure out IR on some of my packs that the manufacturer doesn't provide specs on, so I can put them in Motocalc.


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