[QUOTE=ewmayer;513289]but fingers crossed that batteries don't start exploding after a few months. [/QUOTE]While they are unlikely to "explode", they will certainly gradually lose capacity over time. Why not just remove them entirely? In their current situation they are an unneeded liability.

[QUOTE=retina;513301]While they are unlikely to "explode", they will certainly gradually lose capacity over time. Why not just remove them entirely? In their current situation they are an unneeded liability.[/QUOTE]

As a mini UPS. I don't fancy having to restart 12 phones, 12 UserLAnd sessions and 12 Mlucas jobs every time there's a glitch in the power or a charging cable gets jiggled. Hooking the charging stations to an actual office-desk-style UPS solves the former issue, but not the latter. I don't really care if the batteries lose half their capacity or more over the next couple years, since these are destined to be cannibalized for parts, of which the battery is just one.

Is the main factor degrading LiIon batteries the number of charge *cycles*, constant-full-chargedness, or what? The former is not a problem since the batteries will be at 100% nearly all the time. The built-in periodic-partial-discharge cycling (which seems to happen roughly once a week, based on my limited testing) should address the latter issue, right? IOW, I though the main reason typical heavily-used cellphone batteries degrade quickly is that they undergo many cycles, roughly one a day. Am I misunderstanding the tech here?

[QUOTE=ewmayer;513302]As a mini UPS. I don't fancy having to restart 12 phones, 12 UserLAnd sessions and 12 Mlucas jobs every time there's a glitch in the power or a charging cable gets jiggled. Hooking the charging stations to an actual office-desk-style UPS solves the former issue, but not the latter. I don't really care if the batteries lose half their capacity or more over the next couple years, since these are destined to be cannibalized for parts, of which the battery is just one.[/QUOTE]Okay. I hadn't realised the jobs could not self start. But the setup seems very fragile to me.[QUOTE=ewmayer;513302]Is the main factor degrading LiIon batteries the number of charge *cycles*, constant-full-chargedness, or what?[/QUOTE]In your case the main factor is the passing of time. A secondary factor is that full charge degrades the battery faster than 40% charge.

The ideal situation, which is impractical, is to have the battery at 40% charge constantly. That will give the longest lifetime. But it will still degrade over time. So unless you have some fancy stasis booth to keep the battery in then your battery will degrade no matter how you treat it.

One thing I do with rechargeable batteries that I keep plugged in is to have a programmable timer cut the power off periodically to avoid overcharging which causes chemical loss. This way my rechargeable batteries last for years. iPhone reduces the charging current (trickle charging) after 80% charge to avoid overcharging.
One thing to be careful with lithium batteries is that they can catch fire and indeed people have perished as of resulting fires of such batteries.

[QUOTE=a1call;513306]iPhone reduces the charging current (trickle charging) after 80% charge to avoid overcharging.[/QUOTE]All phones have similar circuitry. But it is not at 80% (how would it know the charge state anyway) and it isn't trickle charge. They use a four state charge cycle.[list=1][*]Trickle, for when the battery voltage is very low (usually under 3.0V). This should never be needed in normal usage.[*]Full current for the main charge.[*]Ramp down in current at full voltage (usually 4.2V).[*]Standby when current reaches 1/10 of full output.[/list]This is usually referred to as CC/CV cycle.

At least that is the basic charge mode that the very cheap controller chips support. There are other methods and cycles, like pulse charging to reduce the ramp down time, and sometimes other voltages and current cut-offs are used to avoid premature failure, etc.

So in any modern phone (i.e. made after ~2005, and even before that) you won't need to manually alter the power delivery to "protect" the battery. The charge controller will do it all itself.

It is 80%
Please see the animation here:



[QUOTE]
Your Apple lithium-ion battery uses fast charging to quickly reach 80% of its capacity, then switches to slower trickle charging. The amount of time it takes to reach that first 80% will vary depending on your settings and which device you’re charging. Software may limit charging above 80% when the recommended battery temperatures are exceeded. This combined process not only lets you get out and about sooner, it also extends the lifespan of your battery.

[/QUOTE]
[CODE]
Stage 2: Trickle Charge
Eases the electrical current to extend battery lifespan.
[/CODE]


[url]https://www.apple.com/ca/batteries/why-lithium-ion/[/url]

[QUOTE=a1call;513308]It is 80%
Please see the animation here:




[CODE]
Stage 2: Trickle Charge
Eases the electrical current to extend battery lifespan.
[/CODE]


[url]https://www.apple.com/ca/batteries/why-lithium-ion/[/url][/QUOTE]Yeah, I know what they [i]say[/i]. It is standard marketing bollocks. They do it like everyone else does it.

So I was playing with my one S7 that has a slightly warped backplate to see if I could hack the cooling - my plan was to use my Dremel moto-tool with a cutting wheel to cut a little rectangular window in the backplate to allow me stick a mini-heatsink on the metal plate over the CPU, but that is easier said than down - the backplate is not metal, it's some kind of weird metallized plastic sandwich with a graphite-based cooling sheet glued to the inside, very hard to cut through without cracking the back. So I decided to do a bit of reading-up on the details of the S7 cooling system, [url=https://pocketnow.com/galaxy-s7-cooling-system-explained]which is quite impressive[/url] - that copper pipe running down the chipset on the opposite (front) side of the phone is in fact a sophisticated liquid-evaporator-condenser system whose inside is a copper micro-mesh. The copper heatpipe is more important to cooling than anything else, and anything which damages it even slightly can really hurt performance of the CPU. I found this out with one of the last several of the batch of 10 S7 Active phones I set up. All the phones are running DCs at 2816K, for the most part timings with the modest airflow supplied by the USB fans range from 64-70 ms/iter. The warped-backplate S7 suffers more throttling and runs 75-80 ms/iter. But the one S7 Active in question wwas inexplicably running at a whopping 120 ms/iter, even though its backplate was intact. This phone has damage to the glass in the bottom-right portion of the face, it looks as if some set it on the ground and stomped on it there. That portion of the case also happens to be where the bottom (recondensation) end of the heatpipe is, and there is a set of 10 pinholes in a 5x2 array in the bottom of the case (these are clearly visible in the photo I added to the Mlucas readme page in the new CCC section, reproduced below) - Since there's no micro-fan inside the case there I don't think they are vent holes, but they definitely appear to be important to the heat spreader system. In the stomped-on phone the holes had been partially blocked by whatever event damaged the case. I used a pin to open them and restore them to their original shape, and moved the phone from the center of the 5-port charging station (by the center of the USB fan, where airflow is weakest) to the leftmost port, and the timings have now dropped to a still-anomalously-high but much better 85 ms/iter.

I think those 5x2 holes are for the microphone.

[QUOTE=retina;513575]I think those 5x2 holes are for the microphone.[/QUOTE]

Ha! the coincidental proximity to the end of the Cu heat pipe fooled me. No *wonder* there's no hot air coming out of this thing, it's all coming out of the person talking into it! :)

So my bit of hole-opening needlework didn't make a difference on the slow phone, it was all due to getting better air from outer part of the USB fan. The only possible use of the holes I could think of in re. heat dissipation was some kind of ambient-air sensor, but even that made little sense.

Oh, someone asked how an S7 stacks up vs a Raspberry Pi3 - Based on Mlucas SIMD-build benchmarks, my Odroid C2 equals 1.5 Raspberry Pi3s, and the Snapdragon CPU of the S7 gives a bit more than 2x the throughput of the Odroid C2, so each of my broke-o-phones gives me around 3.5x the compute throughput of a Pi3.

[QUOTE=ewmayer;513576]Oh, someone asked how an S7 stacks up vs a Raspberry Pi3 - Based on Mlucas SIMD-build benchmarks, my Odroid C2 equals 1.5 Raspberry Pi3s, and the Snapdragon CPU of the S7 gives a bit more than 2x the throughput of the Odroid C2, so each of my broke-o-phones gives me around 3.5x the compute throughput of a Pi3.[/QUOTE]

Cool!