Instructables

i want to know how i could wire a rechargeable battery?


i want to know how to wire a rechargable battery that recharges using a usb cable. im thinking of buying something like this http://www.allelectronics.com/make-a-store/item/LBAT-55/3.7V-2650-MAH-LI-ION-BATTERY/1.html if anyone has a better suggestion for a rechargeable battery that is better please tell me.

im trying to put it into this so i wont have the hassle in spending money on batteries http://www.instructables.com/id/How-to-make-a-fast-blinking-LED-bike-light/step7/The-Electronic/

iceng3 years ago
You are pushing your technology. Step 7 ( you refer ) is a 555 timer. A quick look at the 555 spec supply voltage is max of 18V down to a minimum of 4.5V. The battery you want to use is only 3.7V fully charged. Your blinker would be 0.8V below operating supply ( Sorry it will Never Run on one battery ).

To make this work would be beyond hobby crafting. If you understood the involved electronics you would advise against trying.
diabloboy (author)  iceng3 years ago
im aware that its 3.7. thats why i would buy three more so i could get like 11.1 volts
iceng diabloboy3 years ago

OK, Li-Ion batteries are tricky to charge, if you stay with the USB as a power
source you can not charge the cells in series (only 4.4V is USB guaranteed).

Not that series charging is recommended because Li-Ion cells may not share and one will end-up being under charged or one may get hot. That is why they come with an internal Negative Temperature Coefficient (NTC) thermistor sensors, so you can monitor the battery temperature.

Li_Ion battery charging starts with a current limited source watching voltage up to a fixed voltage point, then a constant voltage watching current down to a minimum value.

As soon as one cell starts heating up or reaches 4.2V +/-50 mV you need to
reduce the charge current. A better method is to charge each cell individually
but a simple series resistor won't do because nobody can watch three or four charging batteries without damaging one in the process.

Here's a pointer to National Li-Ion charger IC's.
http://www.national.com/appinfo/power/files/f7.pdf

Maybe some one, like Apple, makes a smart USB Li-Ion charger that has built in step-up electronics.
I would look to buy an AC line smart Li-Ion charger on ebay.

The following may be useful information;

USB 2.0 can deliver 500 ma at 4.4V - 5.25V
USB 3.0 can deliver 900 ma at 4.4V - 5.25V

A Dedicated USB Charging Port can supply a max of 1800 ma at 5.25V

Sleep-and-charge USB ports can be used
to charge electronic devices even
when the computer is switched off

Battery Li-Polymer rechargeable cell. 3.7V 2650mAh
72 x 40.3 x 8mm overall.
Built-in charge control board with 10K NTC.
Three 38mm leads with female connector
(Molex 51021-0300 or equiv).

Hope this helps answer your question.
Re-design3 years ago
That battery should only be charged using a charger especially designed for li-ion batteries.

Because.
you could just use 3 - 1.5 volt nicad or nimh. That would let you use the 555 also.
diabloboy (author)  Re-design3 years ago
would you know of any. and if i could convert it to a usb