It’s amazing – 894 days (and counting) have elapsed since the start of my long-term experiment, documenting the real-world self-discharge behavior of the Kentli 1.5V Li-ion AA battery… and it’s still ongoing! How have things fared so far?
Kentli PH5 Voltage (Jun 18, 2015 – November 28, 2017)
Kentli PH5 State of Charge (Jun 18, 2015 – November 28, 2017)
Surprisingly, even after spending nearly 30 months on the shelf, there is still 12% capacity left. The voltage has dropped from 4.216 to 3.692 volts according to my bq27621 Li-ion fuel gauge; the State of Charge (SoC) has dropped 50% since my last update.
The linear end date prediction is holding pretty steady, having changed slightly to an estimated 0% charge date somewhere in February 2018.
On that note, I’m impressed by how much attention this little battery has received, even years after my initial review. Every day I see a handful of views checking out the teardown and performance metrics, and there seems to be hardly any sign that this will change anytime soon. To everyone who stops by to check out my blog posts: thank you! 🙂
It’s been almost a year since I started my discharge test of the Kentli PH5 Li-ion AA battery, and the battery has lost almost 40% of its capacity due to self-discharge.
Kentli PH5 Voltage (Jun 18 2015 – May 29, 2016)
Kentli PH5 State of Charge (Jun 18 2015 – May 29 2016)
The discharge curve has gotten a lot less… linear since the last time I posted a self-discharge update. The battery is down to 62% state-of-charge, and its voltage has dropped down to 3.89 volts. Still, there’s a lot of time left until this battery reaches empty… but when?
I’m no statistician, but doing a linear extrapolation in Excel gives an approximate end date of January 2018, and the SLOPE() function in Excel gives me an average drop of 0.111%/day. Of course, this can easily change over the course of this test, but only time will tell…
Aw what, it’s October already? So much for having another blog post in September…
But anyway, “more months, more data!™”
Kentli PH5 Voltage (Jun 18 2015 – Oct 1 2015)
Kentli PH5 State of Charge (Jun 18 2015 – Oct 1 2015)
The voltage of the PH5 has dropped down to 4.093 volts as of today (October 1st, 2015), and its State of Charge is now 93%. There’s just enough data to guess the discharge rate of the PH5: with the currently logged data, the PH5 self discharges at approximately 0.103%/day. At this rate, the cell should last years before finally reaching zero. Looks like this will be a very, very long term test…
(At least that would give me more time to procrastinate write blog posts.)
After my first self-discharge analysis of the Kentli PH5 Li-ion AA battery, I have collected another month’s worth of data.
Kentli PH5 Voltage (Jun 18 – Aug 27 2015)
Kentli PH5 State of Charge (Jun 18 – Aug 27 2015)
The battery’s voltage drop has been surprisingly linear. Although I didn’t get the exact day when the bq27621-G1’s State of Charge readout dropped to 99%, it is quite clear that the state of charge is dropping with a fairly steep curve now. That said, because the battery’s voltage is still far away from the ‘flat region’ of the discharge curve, it is difficult to determine when the battery will discharge itself completely at this time.
I started this test on June 18th, 2015 and will keep taking occasional measurements until the protection IC in the PH5 shuts down.
Since the 18th, the voltage dropped from 4.216 volts down to 4.192 volts as of July 6, 2015; the bq27621’s State of Charge reading remains at 100% for the time being. The voltage drop has been fairly linear so far, but I expect it to taper off as the battery discharges to the Li-ion cell’s “flat region”, and only after that do I expect the cell’s voltage to decline more rapidly.