I have a Motorola V550 cell phone. When I use it as a modem, it drains
its battery quickly. So, I decided to make an auxiliary power supply
for it, to be used when I am away from AC power.

The phone's AC adaptor supplies 5.81 volts when the phone is not
plugged in, and 5.61v when the phone is charging. The phone starts
charging when supply voltage reaches about 4.8-4.9 volts.

I bought a battery pack that has about 6.7 volts when fully charged.

I would like to know if, in your opinion, it can be simply connected
to the cell phone directly. Or is 6.7 too much.

If, in your opinion, 6.7 volts is too much, an easy option to consider
is to just add a diode like N4007 for a 0.7 volt voltage drop.

Any thoughts will be appreciated etc.

i

Ignoramus15609 wrote:
I have a Motorola V550 cell phone. When I use it as a modem, it drains
its battery quickly. So, I decided to make an auxiliary power supply
for it, to be used when I am away from AC power.

The phone's AC adaptor supplies 5.81 volts when the phone is not
plugged in, and 5.61v when the phone is charging. The phone starts
charging when supply voltage reaches about 4.8-4.9 volts.

I bought a battery pack that has about 6.7 volts when fully charged.

I would like to know if, in your opinion, it can be simply connected
to the cell phone directly. Or is 6.7 too much.

If, in your opinion, 6.7 volts is too much, an easy option to consider
is to just add a diode like N4007 for a 0.7 volt voltage drop.

Any thoughts will be appreciated etc.


I'd put a diode in series just to be safe. It'll probably be fine either
way but you can't really tell without looking at the circuit design.

"Ignoramus15609" wrote in message
...
I have a Motorola V550 cell phone. When I use it as a modem, it drains
its battery quickly. So, I decided to make an auxiliary power supply
for it, to be used when I am away from AC power.

The phone's AC adaptor supplies 5.81 volts when the phone is not
plugged in, and 5.61v when the phone is charging. The phone starts
charging when supply voltage reaches about 4.8-4.9 volts.

I bought a battery pack that has about 6.7 volts when fully charged.

I would like to know if, in your opinion, it can be simply connected
to the cell phone directly. Or is 6.7 too much.

If, in your opinion, 6.7 volts is too much, an easy option to consider
is to just add a diode like N4007 for a 0.7 volt voltage drop.



I'm not sure if the .9 or so volts would be to much but you might not want
to risk it since theres no reason to. You can use a diode but make sure you
get one that can handle the current(look at the AC adapator and see how much
its rated for). Ofcourse if you use a diode you'll be wasting that power
but if you don't mind then its no big deal(not like its that much anyways).

Since your using it as a modem you might want to tap into your computers
supply. It should have a 5.x(not sure bout a laptop but I would imagine it
must have one) voltage that you can use. Should be ok as long as the cell
phone doesn't use to much current and would probably be worth the effort
instead of having to have to seperate supplies and waste the batteries.

On 9 Apr, 04:45, Ignoramus15609
wrote:

I have a Motorola V550 cell phone. When I use it as a modem, it drains
its battery quickly. So, I decided to make an auxiliary power supply
for it, to be used when I am away from AC power.

The phone's AC adaptor supplies 5.81 volts when the phone is not
plugged in, and 5.61v when the phone is charging. The phone starts
charging when supply voltage reaches about 4.8-4.9 volts.

then you want 4.something volts

I bought a battery pack that has about 6.7 volts when fully charged.

I would like to know if, in your opinion, it can be simply connected
to the cell phone directly. Or is 6.7 too much.

too much by about 2v

If, in your opinion, 6.7 volts is too much, an easy option to consider
is to just add a diode like N4007 for a 0.7 volt voltage drop.

Any thoughts will be appreciated etc.

i

Get the right battery, trying to drop it may damage the phone. Diode
drop depends on current, its not 0.7v IRL except at i~=0.


NT

On 8 Apr 2007 21:29:52 -0700, wrote:
On 9 Apr, 04:45, Ignoramus15609
wrote:

I have a Motorola V550 cell phone. When I use it as a modem, it drains
its battery quickly. So, I decided to make an auxiliary power supply
for it, to be used when I am away from AC power.

The phone's AC adaptor supplies 5.81 volts when the phone is not
plugged in, and 5.61v when the phone is charging. The phone starts
charging when supply voltage reaches about 4.8-4.9 volts.

then you want 4.something volts

I thought that the ideal voltage would be 5.61 volts.

I bought a battery pack that has about 6.7 volts when fully charged.

I would like to know if, in your opinion, it can be simply connected
to the cell phone directly. Or is 6.7 too much.

too much by about 2v

If, in your opinion, 6.7 volts is too much, an easy option to consider
is to just add a diode like N4007 for a 0.7 volt voltage drop.

Any thoughts will be appreciated etc.

i

Get the right battery, trying to drop it may damage the phone. Diode
drop depends on current, its not 0.7v IRL except at i~=0.


Thanks. Some people recommended some low dropout regulators that could
be helpful for me.

i