Li-ion cell temperature limits

[madstabber]

i have been letting my Miboxer C4-12 charge my cells at a rate which it determines based on resistance and temperature. Well it’s been charging my 18650’s from 3.3-3.4 to 4.2 in one hour and a few minutes. It doesn’t seem to be getting hot but I’ve been monitoring to see what temps. It reaches. It’s usually around 40-45 degrees centigrade but I’ve seen it hit 49 degree C on a warm day in an upstairs of a warm house. So my question is what temperature is dangerous and what temperature starts making a difference wearing down the cell and decreasing its life substantially? I’ve searched and haven’t found an answer to this so I’m hoping this thread will help me and others.

 

[GOMuniEsq]

Here ya go! How can we extend the life of our batteries? | E-Cigarette Forum

 

[madstabber]

Here ya go! How can we extend the life of our batteries? | E-Cigarette Forum

Thank you, I am terrible trying to find information that most would say is readily available.
Now I need to watch closer and see how long my batteries are at or above that 45 degree Celsius. The highest I’ve seen is 49 but that was only once and it was 85 F in the house so that may have contributed. It seems most of the time it’s in the high 30’s but now that I know 45 C is sorta the number you don’t want to hang out at or above I can get a better idea of how this charger treats my cells. I just realized most people don’t care about this and I’m the only person that will read this so I’ll stop talking to myself and wasting electricity and digital space, memory and whatever else I’m using up...oh yes oxygen.

 

[GOMuniEsq]

That post is canon from our famous battery guy Mooch. Check out his blog, he's meticulous but also quite conservative. He even made a table of recommended charging currents for the most popular cells. My takeaway is as follows:

Rule of thumb is that from a safety perspective you don't need to worry until the battery is uncomfortably hot to the touch.

From a perspective of maximizing battery life at the expense of convenience, warm to the touch is as much as you want.

 

[madstabber]

That post is canon from our famous battery guy Mooch. Check out his blog, he's meticulous but also quite conservative. He even made a table of recommended charging currents for the most popular cells. My takeaway is as follows:

Rule of thumb is that from a safety perspective you don't need to worry until the battery is uncomfortably hot to the touch.

From a perspective of maximizing battery life at the expense of convenience, warm to the touch is as much as you want.

Yea I’ve heard warm is ok and hot is a no-no. I was surprised that 49 C is 120 F because when I felt the cell the was reading 49 C it just felt kinda warm but no where near hot. It may have been a bad reading also because it’s the highest I’ve seen it after watching for a while and the next closest was 45-44 C somewhere in that neighborhood. Anyway thanks for your help @GOMuniEsq and I think I’ll just let my charger decide on what current to use and stay close by. If it wears them out really fast I’ll just buy some new ones and I’ll select the current. I enjoy having my cells fully charged in an hour so if I lose 10% life over my usual charge current of 0.8 amps that takes around three hours, if I remember correctly, then I can live with that for the convenience. By the way if anyone is looking for a great charger the Miboxer C4-12 is a good pick for you. It can do 3amp charge in all 4 bays but also gives you a ton of choices. It’s also nice and roomy to fit your bigger cells like 21700’s with room to spare. Finally it’s inexpensive at around $30 and it’s the best $30 I’ve spent in a long time.

 

[sonicbomb]

Any heating of the cell will cause some degradation, best to keep them as cool as possible. Charge them at as low an amp rate as possible, it may take longer but what's the rush?

 

[madstabber]

I’m not really in a rush I just don’t like to leave batteries charging unattended. So when it takes four hours, I have to be nearby for four hours. When it’s done in an hour, I can go about my day without restrictions. If these cells die out much faster then my cells have in the past I may reconsider.

 

[GOMuniEsq]

I’m not really in a rush I just don’t like to leave batteries charging unattended. So when it takes four hours, I have to be nearby for four hours. When it’s done in an hour, I can go about my day without restrictions. If these cells die out much faster then my cells have in the past I may reconsider.

Yeah that's why I prefer to charge at 2A and have it done in an hour. If I need to buy replacements at 18 months instead of 24 months then so be it.

 

[sonicbomb]

So my question is what temperature is dangerous

Over 100c

what temperature starts making a difference wearing down the cell and decreasing its life substantially

How long is a piece of string.

Factoring convenience against longevity is fine, as long as you are not significantly damaging the cells.