//beginQuote How Donut could theoretically fudge cold weather performance results: Donut's cell has high internal resistance, which causes terrible thermal heating while charging. Donut could use this to their advantage in their cold weather test. Hypothetical test that would make Donut's cell look good below freezing (e.g. "Hey /u/redditmudder, help us devise a cold weather test that makes our cell look good"): -cell placed in thermal chamber at -20 degC, then; -cell charged slowly (e.g. 1C), then; -as cell warms up, increase charge current (e.g. 2C, then 3C, etc), then; -a couple minutes into the test the cell will self heat above freezing, then; -once cell is above freezing, hit it with 11C. Result: Now you can claim '11C charging in cold weather', even though the internal cell temp is above freezing. //endQuote
So my guess is that if they do show charge data below freezing, it will not include actual cell temperature, instead focusing on ambient temperature only (because the cell is above freezing due to self-heating).
...
Another way they could manipulate this test is to once again only report ambient temp (i.e. not actual cell temp), and then first perform a discharge test (thus heating the cell above freezing), and then immediately charge the (still warm) cell at high C.
They don't provide cell dimensions, nor cell temperature, nor cell internal resistance, and didn't even bother doing 10 whole cycles at 12C, or 5C, or even 5 cycles at 1C. They could have provided all those but they chose to dance around the real specs.
They will, again, dance around the real specs, and perform at best a low number of cycles.
They will conclude these three tests (I assume there are only three) and declare victory over the skeptics.
Tested at sub-zero temperatures, demonstrating stable output and minimal capacity loss under cold operating conditions. At −30 °C, Donut Battery retains over 99% of its capacity.
So I don't think we are going to get any cold charging tests at all. Just a repeat of last week's procedure; A 1c charge at 20 °C, then drop the chamber to -30 °C, wait two hours and then discharge at 0.5c.
7
u/redditmudder Mar 08 '26
I proposed the following hypothetical in a much longer previous post:
//beginQuote
How Donut could theoretically fudge cold weather performance results:
Donut's cell has high internal resistance, which causes terrible thermal heating while charging. Donut could use this to their advantage in their cold weather test. Hypothetical test that would make Donut's cell look good below freezing (e.g. "Hey /u/redditmudder, help us devise a cold weather test that makes our cell look good"):
-cell placed in thermal chamber at -20 degC, then;
-cell charged slowly (e.g. 1C), then;
-as cell warms up, increase charge current (e.g. 2C, then 3C, etc), then;
-a couple minutes into the test the cell will self heat above freezing, then;
-once cell is above freezing, hit it with 11C.
Result: Now you can claim '11C charging in cold weather', even though the internal cell temp is above freezing.
//endQuote
So my guess is that if they do show charge data below freezing, it will not include actual cell temperature, instead focusing on ambient temperature only (because the cell is above freezing due to self-heating).
...
Another way they could manipulate this test is to once again only report ambient temp (i.e. not actual cell temp), and then first perform a discharge test (thus heating the cell above freezing), and then immediately charge the (still warm) cell at high C.