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How healthy are your batteries? (How to measure internal resistance)

Cyparagon

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Can you be more specific? What are you having a problem with?
 

paul1598419

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@Hakzaw1

I analyze my batteries too; especially the internal resistance of them over time. The cheap xxxxfire batteries have ESRs of several hundreds on mohms. My new Panasonic 3400 mAh protected cells typically have ESRs of 30 to 50 mohms. I also use my Opus to measure the effective charge capacity. The xxxfires also fail miserably here as the "5000 mAh" cells are lucky to have a capacity of 1000 mAh and usually much less. If you don't have any battery analyzing equipment, you can set up simple ways to get to the same results with some low value high power resistors, a DMM and a reasonably good charger.
 

Nordhavn

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Remember folks there are only a handful of mfrs of cells. Sanyo/Panasonic, Sony, LG Chem, and Samsung. Any other brand names are just rewraps, often with inflated capacities and current capabilities. Such exaggeration of these specs is not just wrong, it can (and often is!) dangerous!

If you get cells from a trusted supplier, use the correct specification for your application and don't abuse them, you will see long cycle times and good results.
Even worse than a rewrap is a counterfeit of the real thing. Nothing worse than getting what you think is a 30A capable cell and it's a poor spec 10 or 15A cell.
 

paul1598419

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Got my batteries in from liionwholesales today. I now need to test them to see how they perform compared to what they are claimed to be. I hope to get it done today, but it may take me more time as I have other things going on too. If they hold up to scutiny I will owe you a great thanks for bringing them to my attention.


Edit: When they said they send these out mostly discharged, they weren't kidding. One measured 3.15 volts and the other 3.17 volts unloaded. It took my Opus over three hours to charge them both with a charge value of close to 3 Ah for one and 2700 mAh for the other. Both have an internal resistance of ~0.1 ohms. I think that is a little high for new cells, but I can't complain too much at $7.00 for Panasonic, 3400 mAh, 5 amp, protected Li-ion batteries.
 
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