cell phone charger

Posted by: zuulmusic

cell phone charger - 06/13/07 12:34 PM

Left my cell charger at home this week. This lab power supply really seems to do the trick, though!
Yesterday I fully charged my phone in less than 15 minutes. The battery probably hates me. I'll charge it slower today.

Posted by: SlickGTP

Re: cell phone charger - 06/13/07 12:37 PM

Nice... Now if you could find it in a more portable casing...
Posted by: Richard Candelario

Re: cell phone charger - 06/13/07 01:16 PM

Hey, Zuul, is that the LG VX5200? If so, I have the same phone. What voltage/amperage did you force into that battery to get to charge so fast? nm, I'm retarded. 4 vdc at 3/4A. Funny, the labs in this bldg have the same pwr sply.
Posted by: zuulmusic

Re: cell phone charger - 06/13/07 01:34 PM

Theres a slight trick if you do this...
The best way to charge li-ion batteries properly is to give is a constant-current charge till it gets to your threshold voltage. Then there is a period of constant-voltage top-off.
Ideally the constant current should be 50% of what the battery is rated (so 0.5C). Mine is 1000mAh, so ideally I should charge it at 0.5A until it hits my target of usually 4.05v. This requires monitoring the ammeter on the power supply, and raising the voltage every 30-60s at first (you need to keep raising it because the current will slowly decrease). You'll barely nudge the voltage knob each time (a tiny increase in voltage leads to a bigger increase in current here).
When I finally reach 4.05v with the 0.5A current, I leave it there, and the current dwindles down.

For a faster charge, I used 0.75C, 75% of rated current for the constant-current portion (which is why the pic shows ~0.75A).

*edit: another nice thing about this particular power supply is that you can connect the wires to the battery, with the voltage turned all the way down, and the voltage display will tell you the voltage of your battery, amps will read 0, and you can slowly crank up the voltage till current starts flowing.
also, for a REALLY fast charge, charge it at the rated current (1C). I'll try that next. Try this at your own risk, haha!

btw, I have the older vx3200 LG model.
Posted by: Richard Candelario

Re: cell phone charger - 06/13/07 02:21 PM

always an EE lesson with ya. thanks alot for the lesson. let us know how spectacular an explosion Li-ion batts make when "super-recharged" (ya, a play on the GTP, guys). that 1.0A should be cool to watch. Can you hook a thermometer to the batt and monitor that too? I'd be interested in how hot the thing gets if it doesnt blow.

EDIT: Incidentally, you have the same batt as our VX5200.