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Old Jan 29, 2008, 11:25 AM
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ajreynolds's Avatar
USA, CA, San Diego
Joined Mar 2005
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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?

Thanks,

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

http://www.rcgroups.com/forums/showt...ipo+resistance

Glen
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Old Jan 29, 2008, 12:59 PM
Jesper Frickmann
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Raleigh, North Carolina, USA
Joined Aug 2005
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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.
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Old Jan 29, 2008, 04:53 PM
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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
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Old Jan 29, 2008, 05:13 PM
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ajreynolds's Avatar
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Joined Mar 2005
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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.

Andy
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