portable cell phone problem

[miaomiaooh]

i use 6 NiMH rechargeable battery to charge a cell phone,juz place a diode & resistor to connect cell phone, make the output current is 500mA and output voltage is 6v, but the current flow to phone is nearly 0A,so cannot charge. Then i use it to connect a load, like LED, small radio, it have response.
But at lab, i use DC power supply set the output as 6v and 300mA, successful charge.
y use the rechargeable battery cannot charge a cell phone???
is it wan to design a charger circuit to make rechargeable battery to charge other rechargeable battery ???

 

[audioguru]

6 Ni-MH cells are 7.2V. Then a series diode drops it to 6.5V. Did you measure it? Maybe 1 or 2 cells are dead. Maybe the diode is backwards.

What is the fully-charged voltage of the cell phone?
How did you calculate a 500mA current-limiting resistor? How many ohms?

 

[miaomiaooh]

6 Ni-MH cells are 7.2V. Then a series diode drops it to 6.5V. Did you measure it? Maybe 1 or 2 cells are dead. Maybe the diode is backwards.

What is the fully-charged voltage of the cell phone?
How did you calculate a 500mA current-limiting resistor? How many ohms?

thx ur help again
I measure the voltage of Ni-MH cell oledi, when place it at battery holder,output is over 6v
The fully charged voltage of the cell phone is minimun 5.5v,i use the DC power supply try to charge the cell phone,izzit correct???i juz a newbie
i use the 10ohms/3w resistor , so the current is around 500mA++.

 

[audioguru]

I measure the voltage of Ni-MH cell oledi, when place it at battery holder,output is over 6v
The fully charged voltage of the cell phone is minimun 5.5v.
i use the 10ohms/3w resistor , so the current is around 500mA++.

If the cell phones battery is 1.2V then the charging current is 6.2V-1.2/10 ohms= 500mA.
If the cell phones battery is 5.5V then the charging current is 6.2V-5.5V/10 ohms= 70mA.
If the cell phones battery is 6.2V then the charging current is ZERO!.

 

[miaomiaooh]

If the cell phones battery is 1.2V then the charging current is 6.2V-1.2/10 ohms= 500mA.
If the cell phones battery is 5.5V then the charging current is 6.2V-5.5V/10 ohms= 70mA.
If the cell phones battery is 6.2V then the charging current is ZERO!.

The nokia battery label is show 3.7v, so 6.2-3.7/10=0.25A?
or must calculate the charging current with the cell phone operating power( not the phone battery)???
if i use 0.57ohm/3w, izzit more better?

 

[audioguru]

Before you said the cell phone's battery measures minimum 5.5V. Now you say its label says 3.7V.
I think it is a Lithium battery that will catch fire if you overcharge it.
Maybe the charger is in the battery.
Maybe the charger is in the cell phone.
Maybe the charger is in the mains charger.
Use the charger that is made for it.

 

[miaomiaooh]

Before you said the cell phone's battery measures minimum 5.5V. Now you say its label says 3.7V.
I think it is a Lithium battery that will catch fire if you overcharge it.
Maybe the charger is in the battery.
Maybe the charger is in the cell phone.
Maybe the charger is in the mains charger.
Use the charger that is made for it.

soli,bro, my explanation not veli clear..
bcos of i set the output voltage (by using DC power supply) at 5.5v and 0.3A,
it will start to charge my phone,if lower than 5.5v, not charging
3.7v is the cell phone battery
juz now i charge the Mi-NH cell,same diode & resistor, then i measure output voltage (6xAA) increase to 7.2v, it can charge my phone.
but, after i plug out the charger cable, then plug in again,not charging, then i measure the voltage is around 6v, so i think if use rechargeable battery to charge cell phone, must maintain the voltage over 7v, it is correct??y like this?

 

[miaomiaooh]

have any components or circuit design can maintain the Mi-NH cell's voltage,dun let the voltage drop down after charging the cell phone??

 

[audioguru]

Is the battery in your cell phone Li-Ion or Li-Po?
If you charge the cell phone's battery then remove it from the phone does its voltage drop below 3.6V without a load?
If you put the charged battery back in the phone but don't use the phone (stand-by), does its voltage drop down below 3.6V?

 

[miaomiaooh]

if i have a solar panel which output is 10v & 0.3A,can can it charge 6xAA NiMH cells and 6xAA NiCD cells??which type reachargeable battery(NiMH,NiCD...) u prefer to use in solar cell phone charger project??

 

[sam2]

soli,bro, my explanation not veli clear..
bcos of i set the output voltage (by using DC power supply) at 5.5v and 0.3A,
it will start to charge my phone,if lower than 5.5v, not charging
3.7v is the cell phone battery
juz now i charge the Mi-NH cell,same diode & resistor, then i measure output voltage (6xAA) increase to 7.2v, it can charge my phone.
but, after i plug out the charger cable, then plug in again,not charging, then i measure the voltage is around 6v, so i think if use rechargeable battery to charge cell phone, must maintain the voltage over 7v, it is correct??y like this?

Most modern cell phones have single cell lipoly batteries ( 3.7 volts nominal and 4.2 fully charged).

My cell phones have unregulated chargers , so that tells me the charging circuit must be in the phone, because lipoly batts require a cc/cv charger.That is, they are charged at a constant current ( usually 1C) and then at a constant voltage till done(4.2 volts). If you charge them at a higher rate or worse, at a higher voltage, they can ignite and burn hot!

The lipoly chargers that I have built, use voltage regulators that require an input at least 3 volts higher than the output needed.
Sam2

 

[audioguru]

Try your 10V/300mA solar panel for charging 6 AA cells. Ni-Cads were low capacity and aren't made anymore. New Ni-MH cells are 2500mA/hrs.

Your solar panel will produce 10V and 300mA for maybe only 1 hour each day. AA cells will probably take many days to fully charge from being dead. The cell phone's battery and its charger might take more power from the AA cells than they are charged with then you will end up with no charging.