Hacker News Reader

Comment by eurg | Hacker News Reader

I've to admit I'm surprised that the battery management is not on a separate IC. While quite a few battery management decisions are better done by software, hard-limits on current/temp/discharge really are not.

Am I misinterpreting this?

View on HN

I don’t know what battery pinephones source, but I am under the impression that all smartphone batteries have a battery management IC that handles safety hard limits internally. Lithium ion inherently needs a lot of care in charging and discharging. You can get lithium ion batteries without smarts attached for RC planes and cars, but those are known to catch fire often since they’re driven so hard :).

These battery management ICs will permanently shut down the battery off above a dangerous temperature threshold. Better to kill a battery than to risk a fire.

> Lithium ion inherently needs a lot of care in charging and discharging.

For longevity this is true, but even the while overcharging the risk of a fire isn't that high nowadays (from what I've seen close to 0 with cylindrical cells). Some pouch cells are even fine when punctured.

Of course I want these issues to be fixed to keep Pinephones working and AFAIK the batteries in the Pinephone are of an older model, so maybe they're a bit more dangerous. The author definitely has a point.

That's usually the case in the battery packs. Looks like I'll be ripping apart my battery when I get around to taking out the Pinephone.

Those chips on the packs are last resort safety, not something to be relied upon daily as charge controllers.

Certainly not. That is what the PMIC is for. It’s up to the developers to responsibly configure the PMIC and that is a real hazard. However, the safety situation might not be as bad the author makes it out to be. I don’t know any better though, and it is always a good idea to know when it comes to safety. It’s an important topic to shine the light on.

The author also mentions LCD damage from SoC heat. Could it lead to a runaway from that side?

Last time I read about PinePhone, the topic was kill switches hardwired to chip enable pins that also make it impossible to sleep peripherals from main SoC. That was only “weird but okay”, but personally, with this discussions going, this phone and associated ROMs aren’t something I consider anymore.

For RC cars/aircraft etc those are usually incredibly high current LiPo chemistry and wired in series to deliver much higher voltage. The LiIon chemistry used in electronics on the other hand is quite pedestrian and packs are constructed with lower peak current and voltage output.

Despite similarity in name they are very different beasts. I'm not all that afraid of a LiIon pack unless it's been sorely mistreated or is a huge EV pack or something. On the other hand I treat LiPos with the utmost respect and get them far away from anything at the first sign of bloating or accidental shorting.

Yeah, getting your wire cutter arc-welded to the cable because you accidentally touched it to both ends of a LiPo is... fun.

I would love to see a write-up and pictures of that incident. I think a lot of people, probably myself included, don't always give them the respect they deserve, and that would be a really neat story/visual to drive the point home.

Obviously, no pressure, but figured I'd express the interest

It's much less interesting than it sounds, I was cutting the connector off to solder on a new one, and the first wire accidentally touched for a moment while I was cutting the second one. There was a huge spark and a big mark on the cutter.

> I don’t know what battery pinephones source

From the Pinephone wiki: "Battery: Lithium-ion, rated capacity 2800mAh (10.64Wh), typical capacity 3000mAh (11.40Wh) (nominally replaceable with any Samsung J7 form-factor battery)"

I guess they're sourcing unmarked Samsung compatible batteries which should be all protected, where should equals to 99.999%.

If that's the case, then there's no way malicious software or even firmware could damage it. The protection in those batteries is implemented hardware level; the chip contained in the cell will cut off its connection if it detects either an excessive discharge current (to avoid potential explosion), excessive voltage discharge (to avoid chemical degradation and subsequent charging attempts related dangers), excessive temperature (again to avoid explosion), excessive charging current (... explosion). They are all detected outside of system control, so no need for panic.

Define excessive discharge. In-battery circuit kicks in at 6-8A. Battery is specced for max 1.4A continuous charge/discharge current. With the safety margins in these things, it will probably take 2-3A continuously, too. But can it take 4A for 1 hour? Wanna try?

Also, there's no protection against excessive temperature in the battery protection circuit's specification, so not sure where you're taking your information from. It would be nice if people actually used the datasheets that are freely available, since Pinephone is mostly open HW, instead of proclaiming random generalities.

I for one, would like batteries without built-in IC as we can run the device with external power even after the battery has died, with the battery removed, older phones/tablets where capable of being used with external power with a trivial hack.

With current generation devices, once the battery is dead, it requires replacement even to use the device for an application which has constant power supply(e.g. external monitor), especially if it has become a spicy pillow and constant power supply means it can again become a spicy pillow[1].

[1]https://twitter.com/heavyinfo/status/1302310594423345152?s=2...

There is virtually no batteries without ICs, and, that has nothing to do with whether the device runs without a battery. That’s just a design choice.

>There is virtually no batteries without ICs

There are after market batteries w/o battery management ICs like TI Gas Gauge, its up to device on whether it will accept a battery without such IC.

>that has nothing to do with whether the device runs without a battery. That’s just a design choice

I agree that just having a battery without IC doesn't guarantee that the device would function directly with an external voltage regulated power supply, but a device which accepts only the battery with specific IC makes it difficult or even impossible to run the device that way.

These two things are not mutually exclusive. The decision to allow operating without a battery is a mainboard design decision and has very little to do with the protection circuitry on the battery pack. In a device like this, the decision to require the battery as the primary current source is usually due to the high current draw for activities like initial searching for a cell tower. Lithium batteries can source this current easily, but if you want to run without the battery, your charger needs to be able to source that max current as well. Sizing the charger to handle this brief load translates directly to additional product cost, so it is often not done that way.

The protection circuitry on the battery pack is designed to protect the cell from charging and discharging situations that may damage the battery. You definitely want those protections in there.

It is separate IC: AXP803

Reply on news.ycombinator.com