date(mdy) v
11/6/2022 4.1876
11/14/2022 4.1072
11/17/2022 4.0954
11/25/2022 4.0734
11/29/2022 4.0582
12/4/2022 4.0314
12/7/2022 4.0062
12/26/2022 3.8913
12/29/2022 3.8808
1/30/2023 3.7539
Here are my measurement data on one of my cells. I used YR1035+ for the measurements. I don’t think this is normal, but I noticed it too late to file a dispute or ask for a replacement.
On the other hand, batteryuniversity.com documents that fully charged li-ion batteries can lose 20% of its charge in a month. (See Table 4 in the first link) According to the website 70mV drop is is roughly 10% of a li-ion battery capacity, so 140mV drop in a month in my data can be considered normal in the batteryuniversity standards. However, I have not noticed these kinds of voltage drops in other batteries. Maybe recent li-ion batteries have significantly improved self-discharge rates.
Average self-discharge rates documented in batteryuniversity.com are about 1~2% capacity in a month for a half-full li-ion battery at optimal temperature. (See Table 3 and 4 in the first link) That is roughly 7~14mV per month. The monthly self-discharge rates on my cell on sub 4.0v voltage is above 100mV, so my cells have high self-discharge rate even according to the website’s numbers.
To summarize, self-discharge on my “fully” charged UH1835P is in the normal range, but the self-discharge rate is very high when the battery is half-full (below 4.0v).