Hi! On Mon 2016-04-18 10:59:23, David Laight wrote: > From: Pavel Machek > > Sent: 18 April 2016 11:40 > ... > > > >> > 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. > > > > But cellphone user knows what he connected his charger to, and that's > > why it is useful to be able to lower the current. Even when you said > > "less is just stupid" I demonstrated it is not, at least in case when > > your power source is a battery. > > It reality you may want the phone/tablet to be configurable to take power > from USB, but disable the li-ion charging circuit. > That will maximise the time you get when running from an external battery. > I connect my tablet to the 1A output (which discharges the internal battery > slowly) rather than the 2A one (which will charge it with some > cables). Yes, being able to power device from external without charging the battery is useful, too. But I'd still like to control individual currents, too. If I have power bank and two devices, I may want to select which one charges faster. Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
