Hi, Pavel Machek <pavel@xxxxxx> writes: >> > Very often, you want to charge using 1.8A from an old desktop PC. >> >> if that old desktop's port is not a charging port, you shouldn't be >> allowed to do that. Not ever. > > Yes, Felipe just decided that I should not be able to charge my N900 > in useful way. you can do whatever you want with *your* kernel binary, but we're not gonna ship something potentially dangerous. If that PC port is telling you it can only allow 100mA, you should *not* be allowed to overcome that limitation from the device side, sorry. >> >> a) you are connected to a dedicated charger >> >> >> >> In this case, you can get up to 2000mA depending on the charger. >> >> >> >> If $this charger can give you or not 2000mA is not detectable, >> >> so what do charging ICs do ? They slowly increase the attached >> >> load accross VBUS/GND and measure VBUS value. When IC notices >> >> VBUS dropping bit, step back to previous load. >> >> >> >> This means you will always charger with maximum rating of DCP. >> >> >> >> Why would user change this ? More is unsafe, less is just >> >> stupid. >> > >> > Actually, less is not stupid. Charging li-ion battery from li-ion battery might >> > be stupid. Imagine I'm on train, with device like N900 (50% battery) and power bank >> > (3Ah). I'm actively using the device. If I let it charge at full current, I'll waste >> > energy. If I limit current to approximately the power consumption, it will run the >> > powerbank empty, first, then empty the internal battery, maximizing total time I >> > can use the device. >> >> why would you waste energy ? What the charger chip would do is charge >> battery to maximum then just to maintenance charge from that point >> on. Where is energy being wasted other than normal heat dissipation ? > > Physics 101, of course wasted energy goes to heat. Lets not waste > energy by charging li-ion from li-ion when it is not required. your cellphone has no means to know that it's connected to a Li-Ion battery. We don't have visibility on what we're connected to, just how much it can source. -- balbi
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