Mobile charger from Car or Bike

[debasisswan]

Hi,
How safe is it to use a 7805 or LM 315 based circuit to charge Mobile phone from Car or Bike battery (12V Lead Acid) while on drive? I mean how safe will this be for the mobile battery? I am sure some of our senior members must have tried this before. Is there any suggestible circuit? I intend to put my Samsung Galaxy in charge from my Bike or Car on the move.

Though readymade China made chargers are available for this purpose, I am not very confident on their quality.
Thanks to all in advance-
Debasis

[admin]

Though readymade China made chargers are available for this purpose, I am not very confident on their quality.

These would be definitely better than a LM7805 circuit.

FYI, LM7805 is a voltage regulator and not a battery charger. Lithium Ion batteries used in mobile phones need a constant current/constant voltage charging technique and also charge complete detection schemes are more complex.

There are many single chip battery charger ICs avaiable from Texas Instruments, Microchip, Maxim etc. You can check their websites, but these are in surface mount package which are difficult to solder and requires great skills. You will also need a LM7805 because most of these charges work at 5V max. input.