Quick 18650 observation in cold

[markr6]

I was always under the impression that Li-Ion suffers in the cold. So when I go backpacking, I sleep with my cell phone and headlamp, if I take the 18650 version. IIRC, when I don't sleep with my phone the cold really kills the battery overnight. I noticed the same thing with my laptop in a car overnight.

Yesterday I had an extra 18650 sitting on the shelf, so I put it in my refrigerator for about 10 hours. It happened to be at 3.96v. I tested it when I took it out and it was still 3.96v. I ran it in my PD32UE for a few minutes and retested it at 3.96v. So, it appears I am worried for nothing? Maybe my cell phone has a different type of Li-Ion, but I cannot explain the laptops poor performace sitting in a cold car overnight.

 

[RetroTechie]

Refrigerator = cold, but not that cold (above 0 degree Celsius). Maybe not such a bad case for Li-ion.
Voltage reading = unloaded. Read: at ~0 Celsius, it might not be able to deliver large currents, but still put out unloaded the same voltage.
You ran these on high in your PD32UE? If so, the discharge current may have warmed the cells just enough to perform like on higher temps.

In short: thx for the info, but your post contains too few data points. :ooo:

 

[markr6]

In short: thx for the info, but your post contains too few data points. :ooo:

Exactly why I didn't use the word "test" in the description. This was a simple "observation".

Going back thru my post, you'll see I did not mention running the light in the fridge (sorry, I may have led you there). I simply put the battery in then checked the volatge. Because like I said about sleeping with the battery while backpacking, left out in the cold (10hrs sleeping/low temps) my cell phone really takes a hit. But the 18650 did not in this case. I feel the temperature in the fridge is pretty common for many backpackers.

The reason I ran the PD32UE for awhile is to check for a quick drop. Similar to when I turn my phone on in the morning at 70%, then it drops to 50% right away.

 

[TEEJ]

I think for the computer, there are mechanical things that need to move, like the hard drive platter, etc. The resistance may be from the moving parts having stiffer lubrication initially, etc, rather from the cells being weakened per se, etc.

That's in the fridge.

I think I read that at - 20º C, most batteries stop functioning, with NIMH stopped at -40º C.

I did see this too:

[h=2]Abstract[/h] Low temperature electrical performance characteristics of A&T, Moli, and Panasonic 18650 Li-ion cells are described. Ragone plots of energy and power data of the cells for different temperatures from 25 °C to −40 °C are compared. Although the electrical performance of these cells at and around room temperature is respectable, at temperatures below 0 °C the performance is poor. For example, the delivered power and energy densities of the Panasonic cells at 25 °C are ∼800 W l−1​ and ∼100 Wh l−1​, respectively, and those at −40 °C are <10 W l−1​ and ∼5 Wh l−1​. To identify the source for this poor performance at subambient temperatures, both two- and three-electrode impedance studies were made on these cells. The two-electrode impedance data suggests that the cell ohmic resistance remains nearly constant from 25 to −20 °C but increases modestly at −40 °C while the overall cell impedance increases by an order of magnitude over the same temperature range. The three-electrode impedance data of the A&T cells show that the increase in cell resistance comes mostly from the cathode electrolyte interface and very little either from the anode electrolyte interface or from the ohmic resistance of the cell. This suggests that the poor performance of the cells comes mainly from the high cathode–electrolyte interfacial impedance.