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Need a circuit for Mobile Power bank

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Need a circuit for Mobile Power bank

Postby MEERA » Sat Feb 01, 2014 10:17 am

im at hallf of designing a portable charger for mobile phone!
i bought 6v 1300mAh Ni-MH battery
useed LM7805 for constant output of 5v, but after 10min my phone gets heated !
can u provide me a circuit for this !
MEERA
 
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Re: Need a circuit for Mobile Power bank

Postby pebe » Sun Feb 02, 2014 8:45 pm

The LM7805 has a 2V minimum drop between input and output. It needs at least 7V in so it won't work on 6V.
But as.your phone is getting hot it looks like it's getting more than 5V.

If the 7805 goes unstable it is not possible to predict what its output would be. To keep it stable, the makers recommend a 0.33µF cap on the input pin and a 0.1µF cap on the output. Have you fitted them?
pebe
 
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Re: Need a circuit for Mobile Power bank

Postby MEERA » Mon Feb 03, 2014 4:16 am

yes im using the capacitors !
but can u tell me will 7805 supply constant 5v from my 6v battery for some time !
what is the max. time will it provide me charging !
MEERA
 
Posts: 2
Joined: Sat Feb 01, 2014 10:06 am

Re: Need a circuit for Mobile Power bank

Postby pebe » Tue Feb 04, 2014 2:08 pm

As I said before, an LM7805 will NOT work on a 6V input - according to the datasheet it needs 7V minimum. I don't know how it is managing to heat up your phone.

How is the phone normally charged? Is it from a 5V supply?
pebe
 
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Location: Ellon, Scotland


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