Yes, unfortunately your math is wrong. You are running this battery ~20% over max. temperature limit set by manufacturer.
There is a reason LG set Operating Temperature (Cell Surface Temperature) or The temperature range over which the battery can be discharged to maximum 70C (I call it safety limit for very good reason).
They could rate their own product as 25 amp battery, but Operating Temperature (Cell Surface Temperature) is very high (battery gets damaged internally).
I would never write my feedback on your tests, but once I noticed
Aspire 18650 rewrap as one of the best
batteries you recommend... - something has to be done (at least here on ECF where not many members know about battery safety).
BTW there is a reason LG set maximum operating temperature 70 C for LG HD , and 75 C for LG HG.
5 Degrees Celsius is obviously important to LG, and should be to us too.
Ahhh...thanks! Yes, my math was wrong.
There are reasons why LG uses a particular temperature. But it's not a hard safety limit where damage occurs above it and the cell is fine below it. These cells experience damage every second they exist after being manufactured. Their capacity drops and their internal resistance increases. As the temperature rises the pace of this damage accelerates. But unil you get up to around 125°C there aren't any real physical changes to the battery caused by the high temperatures. Below that you just get an accumulation of this temp-related performance damage. The 70°C spec was chosen by LG either in response to customer requests or as a result of their tests determining that it's the temperature you can run the cell at and still get a decent number of cycles (number of charges/discharges) before the capacity drops, or internal resistance rises, above a certain number. It's not the point at which safety is suddnly compromised.
If a customer is willing to accept a drop in cycle life down to, let's say, 100 cycles before the capacity drops a certain percentage then they can operate the battery at a higher temperature. This is done in a lot of severe environment applications where the ambient temperature is very high.
My ratings are to be used to directly compare the performance of different batteries without worrying about the different criteria that each manufacturer uses to rate them. If one battery runs cooler than another for me then it can get a higher current rating to allow direct comparison of their performance. For example, if your setup draws 15A and you can choose a 20A or 25A battery you could choose the 25A one knowing that in my tests it would run cooler than a 20A one.
My ratings, or any rating for that matter, aren't recommended operating conditions. They're just ratings to be used to compare performance. For the HD2C, no one is going to get near its ratings in use. Even at 70°C the battery is too hot to hold and the user of that mod will stop.
You have gotten me to take another look at my data though and I now realize I gave the HD2C an unfair advantage. I think I was too focused on the HD2's 25A rating and used the upper limit for an acceptable CDR temperature instead of the average temperature, as I would for a rewrap. In my tests the HD2C's reached 74°C at 20A. This is hotter than LG's test results considering their 20A rating but that's completely acceptable considering the difference the setups and, possibly, the ambient temperature. If I rate the HD2C with the same critical eye I would use for a rewrap I would rate it at 22A. This results in a 79°C temperature, the average for cells at their CDR in my tests. But, lower than what I normally see from LG's run at their published ratings, which is typically 82°C-83°C in my tests.
My 22A rating would result in a 79°C temp in my tests. With the 4°C diference in our setups that would mean that the HD2C would reach 75°C in LG's tests. This is very close to their test results and would never be seen when vaping except perhaps by vaping competition participants.
I'll update my test report to reflect the new rating. It's only a small change but even that is still important to me. Thank you for your time regarding this!
What were your concerns regarding my Aspire test report?