[gridspy]

There are good reasons for this

- When the battery has just started charging, the voltage will not be high enough for the phone to actually work, because the draw from the battery exceeds the plug pack input

- Sometimes when transmitting, the phone uses more power for a fraction of a second than the power pack can deliver. This surge of energy could come from the battery, but the battery is empty so it won't work correctly

- Having some amount of battery means the phone can soft-off correctly when the plug is removed suddenly. The alternative is an un-expected hard off which is usually bad. The user might experience data loss.

There are a bunch of grey areas around low voltage, such as flash writes failing marginally or radio not working correctly or partial saves. Much easier for the engineers and perhaps more reliable for the users to make them wait just a little.

[mkesper]

Sounds logical, but then why on earth do many phones turn the screen on right after plugging in?

[jjoonathan]

> There are good reasons for this

They all seem pretty bad to me.

> When the battery has just started charging, the voltage will not be high enough for the phone to actually work, because the draw from the battery exceeds the plug pack input

What type of battery has an innate "draw"? They need a certain voltage and have a certain internal resistance, but it's easy to efficiently increase the effective internal resistance by boosting voltage with switched capacitor circuits (or whatever). If there's a "smart battery manager" you can bet the hardware to do this is already there.

"Draw" would be an excuse if you were hooking things up manually to a car battery. It's not an excuse in the highly integrated environment of a cellphone where corrective circuitry is dirt cheap (and free relative to what's already probably there).

> Sometimes when transmitting, the phone uses more power for a fraction of a second than the power pack can deliver.

That's what capacitors are for. They're almost certainly more efficient, too. Efficiency slumps away from the optimal I,V much faster for batteries than for capacitors.

> Having some amount of battery means the phone can soft-off correctly when the plug is removed suddenly. The alternative is an un-expected hard off which is usually bad. The user might experience data loss.

I'm pretty sure this is the actual reason why it's done. It's an awful reason.

First of all, you claim that "an un-expected hard off is usually bad". WTF? Does your ext4 linux partition usually die when you hard-off it? I've probably hard-offed ext4+linux 1000 times, never had any problems. I would go to great pains to avoid hard-offing a production server but you must acknowledge that in the age of solid journaled filesystems, hard-offs almost never lead to actual bad consequences, especially for light usage patterns. I'm sure it's worse on some hardware configurations but I've never met a system where it got all the way to "usually bad" territory.

On the other hand, having a power manager lock me out of my phone for 15 minutes after I determine I need to use it has led to loss of data. Significant loss of data. And worse. Pictures that were never taken, phone calls that were delayed at significant inconvenience, the inability to look up contacts for others... these are real world negative consequences that are 1000x more important than a .1% chance of filesystem corruption times, say, a 20% chance of actual power failure. It seems hopelessly myopic to suggest that the cost/benefit trivially favors the prevention of uncommon filesystem errors over addressing the immediate and possibly time-sensitive needs of the user.

I think that whichever organizations choose to implement the lockout feature are doing a massive disservice to their customers, foisting significant hassle upon them in order to save a few pennies/customer of repair costs, if that. Your arguments haven't convinced me otherwise.