I think a liquid cooled L5 would be the way to go…after all Porsche had to eventually…lol.
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Like a water cooled Laptop where you just plugin in the external magnetic liquid cooler (just to the side of L5)? 
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https://pubs.acs.org/cms/10.1021/acsenergylett.9b00663/asset/images/medium/nz-2019-006632_0002.gif
Would indicate Safe Lithium Ion internal battery temperature up to 60-70degC occasionally, as it reduces battery life. So 40degC appears indeed somewhat unrealistic assuming Ambient Temperature = Internal battery charging temperature which is a conservative assumption since charging increases battery internal temperature.
e.g. even at 45degC based on the chart the internal charging temperature based on current use is probably higher and indicates that this would be the best for max life (battery temp might be at 50decC during this case).
For the L5 why not set it at 55-58degC for internal battery temperature? This seems a good compromise. Ideally though at temperatures above 40degC the charging current could just be reduced to 1A, or max charging Amps until temperature is exceeded, this could depend on battery charge e.g. 0-50% battery use max amps, 50-100% use 1A for high temperature scenarios. Or a settings toggle where the user can decide between what is most important to them: switching battery max life to max performance.
The chart also indicates that at -10degC it might actually be better to increase charging current, or heat the battery by say utilizing the CPU artificially to keep it operating at an internal temperature of at least 0-5degC.
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Thanks for that @Captain_Morgan.
I really don’t know what the setting should be, I just know that today, again, I got the blinky light while trying to charge on my car dash… in Washington State, in March. I mean yeah, it’s warm in the sun, but not that warm. 
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You should confirm that by monitoring the thermals when you are experiencing this problem.
Incidentally, the text you quoted in the OP was written by me based on: It's a burning phone so you may want to review that topic too.
Based on that I guess it is also pertinent to ask what else the Librem 5 was doing at the time.
Cycle Life may not be the only consideration but putting aside the question of whether you want the potential of sacrificing your Librem 5, is it even possible to adjust that threshold? Maybe there is some i2c incantation but you may need to read the datasheet to find it as @dos may be reluctant to encourage you in this direction. 
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I believe it’s possible, but if you do it you’re the only one responsible for your burned down house if something goes wrong
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C’mon, it’s only the OP’s car, not his whole house.
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The battery can be safely operated and stored at temperatures above 40-45°C (although it will reduce its life as your graph shows). What can’t be done at high temperatures is charging. I believe 50°C is the absolute maximum specified for our battery pack (and only at reduced current and voltage, so you can’t charge it to 100% at this temperature).
Absolutely not, the opposite is true.
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Just on a side note i took my iphone into a Finnish sauna once while i was in Canada and read the news. Surprisingly it lasted quite a while before it shut down due to overheating ~30min-1hr dont remember exactly. That was at 80degC. I kept the phone inside the sauna for another hour without any issues as far as i can tell aftrerwards. (i have had my black iphone shut off while just laying in the sun too with phone screen exposed to the sun before - probably =>80degC).
Maybe a feature to shut off the phone if the battery gets too hot to balance the charging at high temperature need.
Your right lower charging amps at lower temperature may be needed not to reduce battery life. So thats probably also a feature that could ve useful for folks with phone exposed to 0degC frequently.
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Got it, thanks for the explanation, so discharging temperature of 65degC should be fine but charging temperature above 40degC gets complicated, due to having to lower voltage and charging as to not blow up the battery, and with 50degC being the absolute highest possible internal battery charging temperature if voltage and current were to be properly regulated.
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Here’s a screenshot… the L5 was on my dash, admittedly in the sun. The car says it’s 9°C outside, 22°C on the climate control. I was listening to Kasts over bluetooth, chatty was running in the background.
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A few thoughts:
- refine the above 40degC charging feature of the phone to allow for use and simultaneous charging in cases of high battery temperature up to say 48-49deg.
- critical temperature should be defined in the battery spec for discharge and should probably be about -10degC, or 70-80degC? below or above which the phone turns off
- critical charging temperature should be also defined in the battery spec for charge and should be about 50degC? above which charging turns off
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So I would guess that you could eke a bit more charging out of it by having the phone not running Kasts.
But you would probably get much more result by moving the phone out of the sun and into the path of the climate control. Given that you are seemingly using Bluetooth for audio out, I wonder why you would put the phone in the sun (but obviously you have a much better understanding of your in-car requirements).
Possibly part of the problem is the (current) lack of Bluetooth HSP support in the Librem 5.
I’ve had an iPhone shut down due to overheating just from use outside in the sun. I don’t know how you managed to get it to 80°C.
That already happens. So if you are able to work out how to change “40” to “49” then instead of charging ceasing at 40.something degrees, charging will cease at 49.something degrees.
The (hypothetical) question: Can the Librem 5 tell whether it is being charged supervised or unsupervised? It’s one thing to push “40” up to “49” if you are right there watching e.g. in car, quite another for, say, unsupervised overnight charging.
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If you have the Sparklan card HSP works. Although the echo cancellation needs work.
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Contact suport@puri.sm about the modem firmware.
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It’s not that experimental anymore. It’s pretty stable and I have it on by default nowdays.
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HSP? Yes! Sounds like it’s time to unbox the SparkLAN and crack open the L5.
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Somewhat related: My phone started the red blinker any time I charge it now. However it does this when basically on idle, inside with the AC on. A quick check of the temps and the GPU, VPU, and CPU when I turn the screen on - they climb from about 40 up to over 50 in pretty short order; The max170 battery is at 32 and climbs to 35; and the bq25890 actually states 0.
I would suspect that the temperatures are info from the chips themselves, right? Not a separate temperature measurement from the phone? So maybe my TI chip is gone completely? Anyone know of any query commands I can send to check on it?
Replacements are a few bucks on digikey, but they’re surface mount components that I don’t think I’ll be soldering onto a board myself… Anyone know if those things are on the main board, or could they hopefully be on a cheaper daughter/component board or something?
For now, I leave it plugged and it stays charged fairly well. Then I’ve been removing the battery and charging it directly with a variable voltage power supply. Kind of jenky, but it works and has kept me going so far. But not a permanent solution. Anyone know about that chip?
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What happens if you charge with the phone shut down?
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Good question. I tried that (which means shutting it down while plugged, otherwise it starts itself up) and get the same blinky red light.
Someone suggested that maybe the thermister was actually on the battery itself as opposed to that chip, which I have no idea if it’s true? I guess that’s where I’d still like to figure a way to query that TI chip.
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