ShahbazAli
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You have to limit the current into the VCHG pin, which an LM317 will not. Look carefully at the battery charger requirement for those devices.ShahbazAli said:VCHG is 5V coming from an LM317T...
The Lithium Ion chemistry is very sensitive to charge current and voltage. If not properly controlled you will effect the life of the battery. You'll need to design your circuit to isolate the other circuitry from the VBAT pin when the SIM300 is charging the battery. Otherwise the SIM300 will 'think' that it is supplying more current to the battery than it actually is.ShahbazAli said:How will SIM300 gauge the charge on the battery when VBAT is coming from power supply?
If your other circuitry can handle a lower voltage you could use a Schottky diode to seperate the VBAT fro the 12V line. A relay would also do.ShahbazAli said:So what would you suggest for VBAT separation while charging? A miniature relay or some semiconductor?
We're still working on the eCommerce part of that web site. Send me a PM with your contact info and I'll arrange for you to get a copy.ShahbazAli said:P.S. I want to buy GSM Book from GSMMadeEasy but can't. You have any idea how to contact them?
Is this a current-limited charger, or just a 300mA transformer with filter/regulator. If it's a transformer, its output voltage may drop when the battery voltage is low and it draws a lot of current.susano said:i'm charging a Li=ion battery via VCHG pin(of sim300cz), connected to an ordinary 300mA cell phone charger.
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