Post by thread:[EE] Very simple portable iPhone charger and lowvo

RussellMc wrote: > So at 4.8V battery voltage you get about 4.4V available for LiIon > charging (enough) but you hit 4.2V for LiIon at about 4.6V battery = > 1.15 cell, which the eneloop graph says is well up the discharge curve > - perhsp 80% - 90% of total capacity, which is highly commendable. I think the characteristics of LiIon have nothing to do with this problem, since there very likely is a switching power supply and charge controller between the raw USB power input and the internal batteries of the phone. So as long as you can produce a voltage within the normal USB range, the phone should take care of the rest. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000

> > I think the characteristics of LiIon have nothing to do with this problem, > since there very likely is a switching power supply and charge controller > between the raw USB power input and the internal batteries of the phone. > So > as long as you can produce a voltage within the normal USB range, the phone > should take care of the rest. > As far as I understood solarwind does not want to put a dc-dc in his application, and that's where all the problems occur. In other words he cannot guarantee stable USB voltage level, otherwise it was too easy with a similar way as MintyBoost. Tamas > > > ******************************************************************** > Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products > (978) 742-9014. Gold level PIC consultants since 2000. >

Yes, but Olin is talking about _inside_ the phone. In other words, he suspects that the phone does not attempt to directly charge the battery from the 5V USB power but rather has a switcher in-between which may be able to handle 4.4V or some similar lower limit. Sean On Mon, Dec 6, 2010 at 11:13 AM, Tamas Rudnai <spam_OUTtamas.rudnaiTakeThisOuTgmail.com> wrote: {Quote hidden}>> >> I think the characteristics of LiIon have nothing to do with this problem, >> since there very likely is a switching power supply and charge controller >> between the raw USB power input and the internal batteries of the phone. >> So >> as long as you can produce a voltage within the normal USB range, the phone >> should take care of the rest. >> > > As far as I understood solarwind does not want to put a dc-dc in his > application, and that's where all the problems occur. In other words he > cannot guarantee stable USB voltage level, otherwise it was too easy with a > similar way as MintyBoost. > > Tamas > > > > >> >> >> ******************************************************************** >> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products >> (978) 742-9014. Gold level PIC consultants since 2000. >> -

>> So at 4.8V battery voltage you get about 4.4V available for LiIon >> charging (enough) but you hit 4.2V for LiIon at about 4.6V battery = >> 1.15 cell, which the eneloop graph says is well up the discharge curve >> - perhsp 80% - 90% of total capacity, which is highly commendable. > I think the characteristics of LiIon have nothing to do with this problem, > since there very likely is a switching power supply and charge controller > between the raw USB power input and the internal batteries of the phone. So > as long as you can produce a voltage within the normal USB range, the phone > should take care of the rest. You may be correct. Logical design says you are likely to be. Occam and my experiences to date suggest maybe not. My comments have been based on the assumption that Apple has followed the herd and used a linear (or buck) regulator from the USB charging input to a sigle LiIon cell. I may be wrong. The large majority of equipment that I have seen that charges a single LiIon cell from from USB uses linear regulation and no (boost) smps. There are various / numerous ICs to do this. One company a while ago made a feature of getting x% more than the herd by using a 'patented' current amplification technique, aka a buck converter. Apple "tend" to do things reasonably well technically, but seem to be averse to technical gold plating when they can make a 10 cent solution work. Gargoyle dig dig, gaggle dig, gargle dig dig ... Linear charge apparently. If claims below are correct, as they appear to be, then my comments on 4 cells apply. This is an image (allegedly) of an iPhone3G PCB http://farm4.static.flickr.com/3143/2670622531_eedee6381f.jpg wit red marked IC being an LTC4066 LiIon controller IC. http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1037,C1774,P12292,D26042 "Making a charger" article, with explanation of how voltage dividers control charge current. http://tzywen.com/modules.php?name=News&file=article&sid=696 LTC4066: The LTC®4066/LTC4066-1 are USB power managers and Li-Ion battery chargers designed to work in portable battery-powered applications. The parts control the total current used by the USB peripheral for operation and battery charging. The total input current can be limited to 100mA, 500mA or “unlimited” (i.e., above 2A). Battery charge current is automatically reduced such that the sum of the load current and the charge current does not exceed the programmed input current limit. The LTC4066/LTC4066-1 include a standalone constantcurrent/ constant-voltage linear charger for single cell Li-ion batteries. The fl oat voltage applied to the battery is held to a tight 0.8% tolerance, and charge current is programmable using an external resistor to ground. A programmable end-of-charge status output (CHRG) indicates full charge. BAT pin charge and discharge currents can be monitored via an analog output (ISTAT). Total charge time is programmable by an external capacitor to ground. When the battery drops 100mV below the fl oat voltage, automatic recharging of the battery occurs. Also featured is an NTC thermistor input used to monitor battery temperature while charging.

RussellMc wrote: > If you look at the prior thread (often not a terrible idea) you'll > see that the xxx's battery seems to die rathjer quickly if not charged > with brand xxx charger. Indications are that the unit MAY not be > suitable for "real" USB connection. If so, probably purposefully > rather than incompetently. Yes, but isn't charging from a real USB port also a approved method? If not, then they provided a USB compatible plug but you're never supposed to actually plug it into a USB port. That doesn't make any sense. Isn't the USB port also there for a data link to a PC? If so, then plugging it into a USB port is part of normal operation. No matter how evil, they can't let that destroy the battery. Something doesn't add up here. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000