9v usb ipod charger help

[Cameron589]

Hello,

Im kinda new to electronics and im trying to make a portable 9v usb ipod charger.

My goal is to make it so i can plug a 9 volt battery into the circuit and have a female usb connector output 5 volts so i can charge my ipod.

Ive got all these parts, but im not sure how to correctly wire them together.

Could someone tell me how to wire it correctly?

**broken link removed**

Thanks,
Cameron

 

[Hero999]

Why do you want to do that?

That little 9V battery won't be able to charge your mp3 player without being drained flat.

 

[SimonW]

Circuit configuration

Cameron,

here is the basic configuration:

**broken link removed**

Once the ipod has been charged, will the ipod disconnect the 'charger' or will it continue to charge?

An alkaline 9v battery can only deliver approx 0.6A for an hour before it dies

Regards,

 

[audioguru]

The 7805 needs to have a minimum input voltage of about 7.5V. The little 9V battery's voltage will quickly drop to less than 7.5V before the ipod's battery is charged. The little 9V alkaline battery is too weak for this job.

 

[Hero999]

The dropoutvoltage varies with the current, for light loads, it's 2V and for heave loads it's 3V.

Interestingly I have an NiMH 9V battery that's 9.1V when fully charged and it doesn't drop much below that value until it's flat.

 

[Sceadwian]

As was so recently explained to me in another thread here the voltage curve on an alkaline cell goes down pretty steadily as the battery drains.

 

[Nigel Goodwin]

As was so recently explained to me in another thread here the voltage curve on an alkaline cell goes down pretty steadily as the battery drains.

Alkaline cells discharge very much like NiCd cells, dropping fairly slowly throughout their life, then suddenly dropping off drastically at the end.

 

[audioguru]

Most "9V" Ni-MH batteries have six AAAA cells inside. The nominal voltage for six cells is only 7.2V to 7.5V.
I just measured a charged (a while ago) "9v' Ni-Cad that has a 20ma load. it is 7.34V. Its voltage was 8.4V without a load directly from the charger.

 

[audioguru]

The little "9V" Ni-MH battery seems to be allergic to current. A 9V alkaline battery is about the same at high currents.

 

[bananasiong]

Interestingly I have an NiMH 9V battery that's 9.1V when fully charged and it doesn't drop much below that value until it's flat.

What brand of 9 V battery are you using?
I have a 9 V Energizer which drops to 7.5 V after I use it for 200 mA load for a while. It is rated only 150 mAh, so it is reasonable.

 

[Hero999]

FiF.

It says 150mAh 9V.

I use it to power a multimeter and it normally measures about 9.1V.

I don't know how many cells it contains and I don't want to find out by disassembling it.

 

[audioguru]

I use a 9V alkaline battery in my LCD Fluke multimeter and it lasts for years. The meter powers itself down when I forget to turn it off.

A "9V" Ni-Cad or Ni-MH battery self discharges itself in 1 or 2 months so I would never use one in my multimeter.