Last January I got 6 Panasonic NCR18650A (PROTECTED) 3100 from FT. All got 4.19 resting voltage from my Pila after charging.
Two days ago I received 4 of the same brand and type of cell, this time UNPROTECTEDS. All 4 had a resting voltage from the same charger at ‘only’ 4.15V. Does the PCB had anything to do with the results? Are this batch of UNPROTECTEDS not as fresh as the PROTECTEDS? What do you guys think is the reason?
I have recorded the discharge capacities of all these cells and surprisingly not much difference in their capacities (2890mah lowest-3050mah highest).
Could just be cell differences, On a set of 4 bought at the same time albeit 3400s if I balance charge them 2 of the four have a .03 difference in resting voltage 30 mins after charge. (The same cells each time). Not overly concerned only a few hundreds of a volt after all.
Do the protected and unprotected cells take the same amount of time charging after you do a discharge test? If the protected cells take longer might indicate that the protection circuit might be having an effect.
My DMM is a one-year-old Japanese-made Sanwa CD-771. I’m fairly confident it’s accurate and I used the same tester on the same cells, so I can safely say it’s not my tester for I also tested the resting voltages of the NCR protecteds that has been in storage-mode and the 4 cells had decreased by .01V, all of them after 4 months.
I’m just a little concerned since in my experience with laptop pulls, any cell that does not go over 4.15V after charging are almost certainly ‘tired’ cells (low discharge capacity remaining) but these new cells have only 4.15V but still has high discharge capacities, a contradiction of sorts.
May be worth an experiment to see if the charging times are any different.
I have had some cells that after a few charge/discharge cycles, they kept a slightly higher voltage after a charge.
If they have a tested capacity within spec I would give greater lean towards that being a good indicator of a good cell, rather than a few hundredths of a volt, but I could be very wrong.
It sounds like you only charged them one time and got 4.15 volts? Cycle ’em 10 times or so and then see what you get. Also try another charger. Even a cheepie two-bay trustfire or something if you want to perhaps bring em up to 4.2 volts faster without the cycling.
I don’t know what the deal is with panasonics, but I find you need to cycle ’em 10 times or so when new (well, not new but the first charge from the shipping voltage of 3.60-3.80.) SOMETIMES to get ’em up to the full 4.20 volts. Other times, same batteries, same mah and they go to 4.20 the first charge. But after the 10 cycles, the lagging cells usually pop up to 4.2 and do fine.
I pulled 6 2900mah gray panasonics from one of three identical NEW power packs, when those ebay panasonic battery deals were circulating a few weeks ago. The other pack cells immediately went to 4.2 volts, but the I4 charger would say these were done at 4.16-4.17 volts. Tried 3 different I4s. They all did the same.
In fact, the cells were getting charged to 4.2 volts, but slid back to 4.16-4.17 after 15 minutes or so. After 6-7 charging cycles, they were fine. It also takes 10 or so cycles so that they hold the charge reliably. before the 10 cycles or so, they slide. And by cycles, I mean, running ’em in a light down to 3.7-3.8 and then charging them up to 4.2 again. Wait 12 hours or so, and do it again and again and again.
At Ubehebe’s li-ion battery farm (now approaching 300 batteries — giveaway coming up I promise), I have encountered this initial low charge with quite a few panasonics, so it is NOT an isolated deal. Had some Samsungs 2200 mahs that acted similarly recently, but it’s usually the panasonics for whatever the reason.
As has already been stated, you may need to cycle the cells a few times before the cell voltage remains high. Had the same experience as Ubehebe with the 2900mah Panasonics from older (brand new unused) laptop pulls. It took a few cycles to get the resting voltage to hold around 4.18v. If the cell holds close to the same voltage over about a week from the day of charging then the cell is fine. The capacity test is a sure way to test cell performance which you did. All seems normal to me. The capacity difference between 4.20v and 4.15v is very minimal.
The cells could have been stored for awhile and need a few cycles (woke up) to achieve best performance.
I have a laptop with nearly dead cells, 10 minutes of battery life, and they charge to 4.2V, they drain to empty to the same dead voltage as a brand new cell
sanyo 2200mAh if i remember correctly (maybe it was 2400)
>>>>>> have a laptop with nearly dead cells, 10 minutes of battery life,
>>>>>>>and they charge to 4.2V, they just don’t last long till they are down to 3.6V
Yes, many pulled cells that I have rejected (because of not holding a charge for long) DO charge merrily right up to 4.2 volts but only last maybe 10 minutes — as you report — until they drop to 3.6 or whatever. I don’t know what chemical change is responsible for them still being able to reach 4.2 volts but unable to hold a charge for very long. But I have seen that behavior many many times.
But sometimes it takes a few cycles to get new cells up to what we consider OUR optimum voltagefor flashlights — 4.2 volts. I could be completely wrong about this, but I don’t think laptops charge their packs that high. The highest cells I have pulled were from a just-charged pack, and they were only at 4.07 volts.
As you know, 4.2 volts isn’t even an optimum voltage for li-ion cells. It is theoretically the highest charge a li-ion cell will take before damage begins to occur to the cell chemistry.
6 Brand-new Panasonic NCR18650A 3100mah, Protected from FT
Charger used: Pila IBC
Resting voltages: 4.19V resting (all of them, 4.2V hot off the charger)
Discharge capacities: between 3030-3060mah (iCharger 106B+ hobby charger used)
Discharge rate used: 1.3A
Voltage reading of cell at ‘start’ of discharge: 4.01 to 4.03V
4 Brand-new Panasonic NCR18650A 3100mah, UnProtected from FT
Charger used: Pila IBC
Resting voltages: 3 cells at 4.14V, 1 cell at 4.17V (4.15V hot off the charger)
Discharges capacities: Between 2959 to 2780mah
Discharge rate used: 1.3A
Voltage reading at “Start” of discharge: goes down to around 3.52V (unusually low I should say, but surprisingly the discharge capacity at the end of the run is not too far down)
My question is: 1. Does the PCB of the ‘protecteds’ has anything to do with the higher resting voltages?
2. Did I happen to get a bad batch of unprotecteds?
I don’t really mind the resting voltages nor the discharge capacity differences. I am just wondering why!
a laptop can charge as high or low as the manufacturer designs it to.
i like the idea that some may not charge that high, you may get less battery life, but more battery longevity, mine does certainty charge to 4.20V
Which output tabs on the battery pack do you touch with your DMM probes to get the 4.2 volt reading? If you could tell us that, it sure would be a GREAT help. It would allow many members to test packs before buying them or pulling them apart to only find bad batteries.
I have tried touching every combo of those laptop battery contacts —- from MANY different manufacturers — and can’t get any kind of reading, but I guess I must have missed a combination. Please let us know.