onboard charging?

[rosshimself13]

are there any easy solutions? would like my first self made mod to have a mini usb port to charge the battery and i am not an electronic engineer... read something about using chips from PT's, but dont have one on hand to understand what this would entail.. it will be a 3.7v 18650 mod so this should be easy right?

any help would be great

 

[misterD]

i dont like having the charger in the box. i usually have just a mini usb port on the box and add the charger to my cable if i want to and if i dont i can just get rid of the charger and batt and use the box as a PT with no inline batt. but you can use one of this or maybe an ego/riva fast charger would do it...

 

[rosshimself13]

i dont like having the charger in the box. i usually have just a mini usb port on the box and add the charger to my cable if i want to and if i dont i can just get rid of the charger and batt and use the box as a PT with no inline batt. but you can use one of this or maybe an ego/riva fast charger would do it...

please tell me you have a picture or how to this sounds much easier

 

[CapeCAD]

Reference designs are available from many companies like Linear Technology, National, Maxim: I am using this LT1512 Linear Technology chip to charge (2) cells up to 8.4V off USB with added thermal protection to activate Sync/Shutdown if batteries overheat:
http://cds.linear.com/docs/Reference%20Design/dc099.pdf

Demo boards are available from these companies as well.

 

[misterD]

please tell me you have a picture or how to this sounds much easier

you just add a mini usb and wire the batt + and - to it. than you can get that ebay charger and add a male usb to the output and you're on game.
10Pcs Mini USB 5Pin Female SMT Socket Connector Short - eBay (item 170520530600 end time Oct-27-10 08:56:54 PDT)

 

[rosshimself13]

ok thank you for the explanation.. this should work right? seems like it would

 

[misterD]

yeah it does. output charger on it is 180mAh i believe. i had one similar on one of my boxes.
this one has an output of 420ma so it charges faster.

 

[warbdan]

As long as your batteries are protected, I don't see why it wouldn't work. They need to be protected so they will stop taking charge when full.

 

[WillyB]

As long as your batteries are protected, I don't see why it wouldn't work. They need to be protected so they will stop taking charge when full.

That's not correct. A charger (not be be confused with so many things folks call a charger, like a cell phone 'charger) has it's own circuit to determine when to cut the voltage. A real charger can charge un-protected batteries. And if were relying on a batts protection circuit to terminate the charge you would always be overcharging past the 4.2V ideal.

 

[capecodjim]

ok, so this discussion is about lipo's.....what about charging 4 AAA NiMH batteries in my Puck? What kind of a circuit do I need for that? Can I do it via a standard USB somehow?

My 4 AAA's read about 5.9V unloaded when fully charged. It quickly drops to around 5.2V and stays there most of the time and drops off when it dies. It drops between .6V and .9V under load with a 901 atty.