I have an Icharger 3010B that I am using to check capacity of different 18650’s. The way I am doing it is to start with a fully charged battery (4.2v) and set the discharge on my Icharger to 1A. I set the termination voltage at 3 volts. I know this is lower than you should take a lipo battery….but it is above the “protective” limit of 2.5 volts. Is this too low a threshold? Is 1A too high of a discharge current?
I am trying to compare the TrustFire 3.7V 3000mAh 18650 Protected battery against the 3100 mAh NCR18650A Panasonic by Orbtronic.
Any suggestions/modifications to the above parameters would be appreciated.
I'm no expert, but I usually see discharges to 3.0v so I believe that is fine. Not all cells can go down to 2.5v safely; many are 2.75v. 1A discharge is no sweat, you could go up to 3A (depending on the cells ability and safe max discharge, but 3A for an 18650 should be fine).
It depends on the internal resistance of the battery. While some low resistance chemistries like INR, IMR or LIFEPO4 won’t have problem even at higher amps, you’ll have to reduce current to measure ANY capacity with aged/fake recycled cells.
After some time, you’ll know what you are dealing with just by how much the voltage drop/rise when charging/discharging.
And for the discharge point - it really doesn’t matter much, especially with high discharge rates as the voltage will bounce back quickly. You can discharge with lower rates to get more accurate results or discharge with 1 amp to speed it up and than squeeze the rest of the juice with 0,2A.
Thanks……I forgot to cancel the 120 minute timer on my charger. It stopped the discharge at 120 minutes. The results were: Trustfire 18650 3000mAh
3.4v under load
2,011 mAh used
battery jumped back up to 3.56v once the load was removed. Not bad for a Trustfire. Might have been around 2500-2600 if the charger hadn’t terminated at 120 min.
Nice, not bad, now you can try to finish the discharge with 0,2A and 3.0V. I doubt it will have those 500-600 mAh, but around 300 could be there. Panny’s CGR would still have like 1/3 left.
Suprised me that you remembered that from one of my earlier posts!
No…this Trustfire is the one that I received reading “0” voltage. Evidently the battery was shipped to me so discharged that it tripped it’s lv protection. I was curious to see how it would behave. Next I will test the Panasonic from Orbtronics….they are supposed to be really nice (from what I have read).
In the OP, you said Li-Po which refers to Lithium-Polymer. Those should not go below 3.0V per cell. I stop around 3.2V just to be sure. Get too low and they gas up and bubble out like a balloon.
Li-Ion cells are all different for discharge cutoff, but 3V is safe for most if not all of them. most can go to 2.8V without issue.
I test mine at 1A discharge down to a 3.0V cutoff.
You are correct……I was thinking Lithium Polymer……I just realized that I am dealing with Lithium Ion with the 18650’s. The fact that they both max out at 4.2v made me think they were the same. So to get this right…lithium ion can be safely discharged to 3.0 volts.
