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

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

@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.

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.

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.

I place a GTL 14.02 G IN BOTH BATTERIES in series in my last part, however my front door toward diode is rated out of the chamber after the fact, has 2.86v (front most battery) 3.62 backmost battery. Rear battery 3.88V same brand, only used together. Any feedback would be greatly appreciated. Thank you for your patience.

In case you didn't notice --this thread has been dead for 2 years

Batteries connected in series will drain at approximately) the same rate.
Manufacturing differences between the individual cells may cause some to drain a little faster than others

So, regardless of both batteries being of the same brand type,chem, amp rating, weight at point A, somehow the - terminal leading battery is -0.44 V defeciencient from the same battery behind it!? Any ideas please? Too high turnage on current flow potentiometer value. Doesn't explain the decency towards the rear voltages...please provide me with a time relevant response. As to how the rear battery could possibly rear in voltage.

Who knows? could be many reasons--maybe different internal resistance, each one? Poor construction, different lots. different age and/or actual manufacturers ?

GTL batteries are notoriously poor quality bad batteries with crazy high Amp hour ratings that are completely fraudulent ratings, incocsistent voltage output, poor quality control and high prices just like several other China made batteries.. Very often they are just repackaged used batteries from disposed/discarded old laptop battery packs with and new plastic sleve added. See example video below.

Try getting some good quality batteries.

Encap said:

In case you didn't notice --this thread has been dead for 2 years

Batteries connected in series will drain at approximately) the same rate.
Manufacturing differences between the individual cells may cause some to drain a little faster than others

Click to expand...

here comes hak's yeabutt.
MYB it should have been stickied. It is something that most here do not fully understand and good to know.
I saw it and thought that I need to read it again- its important justlike adding a load to get the right DMM reading--
I bet very few are putt ing a load on something you are metering like a wallwart.

WE are lucky to have an 'active' forum.. so we need those rules/suggestions.
I saw a forum the other day---SO INACTIVE== (how so?)
Necro posting was encouraged and same with doubles- triples and more.

sad... very sad
hk