30Q cell voltage in storage

On November 22, 2019 I charged four 30Q cells until each reached 3.80 volts. Then I tagged the box and placed them on a shelf in the workshop where the temperature seasonally varies from someplace in the 50’s (F) to hitting summer highs in the 90’s. Not ideal temperatures for storage perhaps but probably typical of where many people store cells; at east typical of where I keep cells and batteries so they are handy.

Today (day 266) I did a voltage check using the same meter as before.

All four cells read 3.79 volts. :slight_smile:

So maybe 1mV per month for self discharge—that’s really good to know.

Phenomenal. I’m surprised.

That’s normal from healthy, authentic batteries.

I have six or maybe seven year olds that came in in their original voltages and never bothered recharging them, up to now.

Good experiment MtnDon. Li-ion batteries are pretty amazing.

So, today I opened the box these 4 Samsung 30Q’s have been sitting in and measured the voltage. Each cell read 3.77 volts.

These were not stored under and special conditions. They have been in a cabinet in the old workshop and now sit in another cabinet in the new shop. In summer it can get hot (upper 80’s F) and in winter the temperature can drop to the low 50’s.

To summarize; on November 22, 2019 the cells were charged to 3.80 volts.
On August 13, 2020 all four cells read 3.79 volts.
Today is day 944 from the start.

Very cool. If you ever end this experiment you should test their capacity.

I have marked this coming Nov 22 on my calendar. That would be three years and then I will run a capacity test. At least that is my plan.

Were these brand new when you started this? Did you cycle them at all?

They were about a year old and had seen a little use in a Q8.