On 12/11/2010 13:20, V G wrote: > On Fri, Nov 12, 2010 at 7:53 AM, Olin Lathrop = wrote: >> Not necessarily. USB voltage at the device can be from around 4.3 to 5.= 5 >> volts worst case if I remember right. Probably the phone contains a >> switcher to charge its battery and you don't need to be right on 5 volts= in. >> Give it a try with a variable power supply to test it. > Yes, I'm going to experiment with voltage on my $700 phone. > I understand the concern, but USB voltage can vary a lot - at least from=20 around 4.4 to 5.25 (and probably to the figures Olin gives above in=20 extreme cases) and a $700 phone almost certainly has a dedicated chip to=20 handle the charging, which may handle voltages of quite a margin from=20 nominal. Any USB chargable phone has to handle these variations. If this=20 is only a one off then it would be worth finding out before proceeding=20 (phone manual?), so you know what specs you are designing towards. It=20 may work fine with 4 AAs (with some basic protection), personally I=20 would be temped at least to see how low the voltage can drop before=20 charging cuts out... In my experience mobiles are quite robust - I have messed about quite a=20 bit over the years with "non standard" charging solutions (when chargers=20 break etc) for different phones and never managed to break one yet. One small thing you may or may not be aware of - some phones (my Omnia=20 for instance) need to actually talk (Activesync or whatever) to the PC=20 before commencing charging over USB, for instance if I use a standard=20 USB cable into a portable charger it won't work. With mine I have to use=20 a "special" (I think 5 pin on the phone end or something to tell the=20 phone it's in charging mode) cable to charge without doing this, so it's=20 worth checking how yours works in this respect. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .