Hi all,
I'm new into this community and also start having an interest in diy gadgets.
I'm interested in making a compact charger that I can use 2-3 Sanyo Eneloop battery to charge up via microUSB (pc), and then when outside, charge my phone via USB too.
As I am new to how things work, I was hoping to get some advice.
What I know so far
4x Sanyo Eneloop batteries, 2000mah, 1.2v, that means I'll need 4 at about 4.8v to make the charging happen
4x AA battery holder : http://sg.element14.com/keystone/2478/battery-sizes-accepted-aa/dp/1650685
1x USB type A - http://sg.element14.com/wurth-elektronik/61400416021/receptacle-usb-type-a-tht-r-a/dp/1642033http://sg.element14.com/multicomp/mc32595/connector-type-usb-a/dp/1696536
1x microUSB type A - http://sg.element14.com/fci/10104110-0001lf/micro-usb-b-receptacle-smt-ra-5way/dp/2293753?in_merch=New%20Products
What I do not know
How do set up the current to be constant in case of surges, stop the charging when the batteries are full, and also, once you charge your phone until your AAs are empty, how to prevent the batteries from trying to draw the charge back from my phone.
I did see something like this in DX @ http://dx.com/p/aa-aaa-batteries-usb-charger-67, but I'm trying to do one of my own into a black metal casing, that way, I can also vent the heat generated much easier.
Appreciate if someone could guide me on this, as I've searched through almost most places but they only taught AA to USB devices without the part on charging from USB(pc) itself
Max