10 hours to charge one new 18650 3400 and 6.5 hours to charge the other on the D4?

Hi - I'm still fairly new to all of this, but I have been reading many threads here and learning.

I have two new KeepPower 18650 3400mAh batteries that I have not charged before or used for more than a few seconds to test. I put them both in my new Nitecore D4. I didn't change any settings on the D4, so it started charging at the 750ma rate. At the beginning of charging, the first bar was flashing for each battery; I don't recall the voltage. One battery finished in a little over 6.5 hours. The other one finished at just under 10 hours (9.52 reading - I assume it reads like a clock).

From reading threads here, it seems the 6.5 hour time is about normal. What about the 10-ish hour battery? Should I be concerned? I have some understanding of how charging Li-ion is different from NiMH (CC, CV), and the battery was in CV mode with amount reading anywhere from 6ma to 30ma or so as I was watching it in the last hour or so of charging.

To me that seems too long. I always charge at 1A which isn't that far off and my cells are always done in under 3h. My cells top out around 3000mah so will be a little faster but less than an hour difference

Have you checked the fake D4 thread to see if you have a fake D4?

I bought from the Nitecore store, and so far the visual check seems OK (printing on box, power cord, power cord outlet on the device). I haven't scratched off the code on the box and gone through the registration process yet.

Around 6hrs is ok for at 750ma, But 10hrs, maybe the battery had a bad connection or high impedance and the charger decided to charge it slower.

EDIT: Have you used the battery's before charging them, as the cells should have had 50% charge in them, some reject a new cell if the voltage is below 3.0 volts when you receive them.

John.

After receiving the cells and before charging them, I used them for maybe < 1 minute in my flashlight just to see that everything worked.

I didn't mark which cell was slower. I wonder if I should drain them some and then charge and see if they finish around the same time.

Did you actually check the read out timer on the D4 to see that the charge time was 10 hours? Or are you assuming that the cell was charging for 10 hours because it was 10 hours later that you happened to notice it was still charging each hour for 10 hours?

I'm not sure why, but sometimes my D4 will complete a charge cycle for a cell. If the cell sits there, it is possible the D4 actually loses contact with the cell, doesn't recognize there is a cell in a slot. Just as mysteriously, later, the D4 may again notice there is a cell in a slot... and it starts a new charge cycle as if it had just been inserted. This could be dirty contacts, but I have noticed my D4 has trouble sometimes immediately recognizing some cells, some usual suspect cells, meaning, there's a handful of cells I have in various states that it takes a few tries or inserting before the charger recognizes them.

What I am suggesting is your 18650 may have not been actually charging for 10 hours. Maybe it charged in 4. Then mysteriously, lost connection to the cell, then just as mysteriously, regained contact to the cell... perhaps it initiated several new charge cycles and completed each of them while you weren't watching every minute.

Obviously, if you confirmed on the charger readout that the charge cycle did take 10 hours, this is not what happened.


edit:
duh! I see that you already specified you did see the charge time on the D4 readout. Leaving my silly post here for lulz. ><

No I did not monitor the charger enough through the 10 hours to be able to say that it did not fully charge earlier and then start charging again. Thanks for the feedback on your experiences. Right now I am running down two other 2600mAh batteries and will pop them in the charger to see what happens. Then I will try the same with the 3400mAh batteries in question.

Do you have another charger you can try charging the batteries on?