Understanding internal resistance

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basher27

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So on my new charger there is a feature called internal resistance. If I understood it correctly from the guy working at my local hobby shop it had something to do with as a battery ages the internal resistance goes up. If that is correct could someone give me a idea on what number would be considered a battery that is nearing its end? Just so I have some thing to base it off of. Thank you

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There some brilliant members that will hopefully chime in , until they do sometimes the web is a good place to search.
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passionatelycurioussci.weebly.com
  • Internal resistance refers to the opposition to the flow of current offered by the cells and batteries themselves resulting in the generation of heat. Internal resistance is measured in Ohms. The relationship between internal resistance (r) and emf (e) of cell s given by.
  • with use over time a battery will degrade
 
Depending on who you talk to once those numbers get to around 16-20 it's time to consider disposing of them.

Also to get the most accurate reading. You should discharge the battery to 3.4v per cell, let it set for about 30-60 minutes to let it cool to room temperature, fully charge the battery to 4.2v, then again let the battery set for 30-60 minutes and then check the ir.

The way it sits now the cells appear to be pretty mismatched.
 
The best thing to do is get the IR when the battery is brand new, and take note of that. As the battery gets worn out the IR will increase. More resistance=more heat. I’m not an expert but as far as I know when you start getting up to 15-19 milliohms per cell the battery is considered near/at the end of it’s life. Someone may chime in to correct those numbers. IR is a number speed runners tend to focus on, as it let’s you know if the batteries are ready to party. For instance, my speed run batteries are 1-2 milliohms per cell, meaning they are capable of dumping lots of power very fast. There’s a lot more to it but I hope that gives you an idea of how important IR is to lipo batteries.
 
Depending on who you talk to once those numbers get to around 16-20 it's time to consider disposing of them.

Also to get the most accurate reading. You should discharge the battery to 3.4v per cell, let it set for about 30-60 minutes to let it cool to room temperature, fully charge the battery to 4.2v, then again let the battery set for 30-60 minutes and then check the ir.

The way it sits now the cells appear to be pretty mismatched.
Yeah I agree this picture was taken several seconds after starting the Charge cycle.
 
The best thing to do is get the IR when the battery is brand new, and take note of that. As the battery gets worn out the IR will increase. More resistance=more heat. I’m not an expert but as far as I know when you start getting up to 15-19 milliohms per cell the battery is considered near/at the end of it’s life. Someone may chime in to correct those numbers. IR is a number speed runners tend to focus on, as it let’s you know if the batteries are ready to party. For instance, my speed run batteries are 1-2 milliohms per cell, meaning they are capable of dumping lots of power very fast. There’s a lot more to it but I hope that gives you an idea of how important IR is to lipo batteries.

To add to this - record the temp also @basher27
Possible scenario to explain why.
On a cool day you record 7 ohms and then on a warm summer day in the garage it is 95 degrees... you might only record 3.5 ohms on the same cell.
 
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