How do you KNOW it charges to 4.22V? Are you using a CALIBRATED meter with over 4.5 digits of display? Most cheap DMMs are doing good to get within 2-3% of reality.
OK, you got me. It’s a Fluke 8050A 4.5 digit bench DMM, but Lord knows when it was last calibrated. On the other hand, it agrees within .01V of two lesser DMMs, and my other two chargers measure 4.19-4.20V.
I’ve been meaning to buy one of those 5.000V precision voltage sources, but haven’t gotten around to it.
The ones from voltagestandard.com are rather nice for the money. You should consider getting one with a voltage that won’t shift the meter up a range (like a 3V one to test a meter with a 4V range). He does sell a ref that puts out 5 different voltages.
I have 2 Fluke meters exactly alike, same model and they don’t read exactly the same. I wouldn’t worry about it and .2 is nothing to worry about in the first place.
The plus can calibrate more ranges and the resistors for ohm calibration is slightly better.
The PentaRef is also very useful for DMM voltage calibration, because you can order one with a 4.2 volt value (Then you now your DMM is correct for LiIon), or for more general purpose, select as needed from: 1.9 (2000 count DMM), 2.9 (3000 count DMM), 3.9 (4000 count DMM), 4.9 (5000 count DMM), 5.9 (6000 count DMM).
Checking my batteries after they are on the i4, I'm also usually seeing 4.21-4.22 not 4.2 exactly. I don't think it's really a big enough of an issue, since it does stop charging at that point.
What batteries are you guys using to get these results? If they are newer higher cap batteries it could (Accurately) detect that it could push more voltage into them and do such. I had my i4 give out at 4.17 on my older sanyo 2200’s batteries and about 4.19 on my newer 2600’s.
Then again my meter is junk, but it still is reasonably consistent. I still trust my accucel 6 more than the i4, which on the same cells and meter stops at 4.15v and 4.17v respectively.
No. The differences in termination voltage are either
A) Random variation. The Analog Voltage measurement circuitry has precision error from one cycle to another, especially if the room temperature changes.
or
B) Caused by the time between actual charge termination and your measurement. Once the charge terminates, there will be a little fall-back in voltage. If you wait longer after termination, the fall back will be more.
or
C) Your meter has precision error from one measurement to another
or
D) The Charger follow correct CC/CV Charging protocol, and every battery will take current a little differently once near the end of the CV portion of the charge
or
E) a combination of the above.
They are not, however, due to the charger “Sensing” the higher voltage tolerance of the cell and charging it higher.
PPtk
edit: To add Option D - Brain malfunction and I forgot to type that one out…
my nitecore i2 charges the sanyo 2800 up tu 4,24v when measured right after charging and it drops to 4,23v an hour after…
the panasonic 2900 are terminated at 4,22v…