> Isn't lithium ion 3.6 volts?

Rolling together parts of my prior answers to this and another question.

- LiIon and LiPo =3D  Lithium Polymer (as opposed to LiFePO4 which is
different) typically need 4.2V at the battery for full charging.

- I guesstimate that you'll be liable to drop 0.2V in the iPhone and
0.2V in the charger when you are at limiting low battery condition at
full power.

- If so, you will need a minimum NimH battery voltage of 4.2 + 0.2 +
0.2 =3D 4.6V to fully charge the LiIon battery.

-   4.6 / 4 =3D  1.15 Volt.
So IF you can achieve only 0.2V drop in charger and 0.2V drop in
iPhone you *may* 'get away with" batteries as low as 1.15V to provide
a full charge.

- YMMV.
I'd expect that it probably would.
0.2V is easily "eaten up"

A quick flick through the LTC4066 data sheet doesn't seem to provide a
Vin-Vbat saturation figure (or I missed it) but based on other
figures, something in the 50 mV - 150 mV range seems likely. At say
100 mV that alone is half your allowed 0.2V for my above assumptions
to hold.

A way to check the iPhone charger drop is.
- Open iPhone (Gargoyle knows) and attach a wire or wires to battery
AFAIK iP3  has soldered in battery (non replaceable, sealed for death,
200 charge cycles lifetime :-( )(be evil).
- Charge from approved or whatever USB charger
- Measure voltage drop on each charger lead between charger and battery.

This will give you some indication of capabilities. If you use a
variable bench supply as charger (as has been suggested)( and which
has a MUCH more controlled voltage than a USB port does) you can
measure voltage and current at various battery voltages.
This allows you to determine minimum voltage drop at peak desired
current (1 A in your case AFAIR).


 Russell
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