Multiple AA USB charger (minty boost like) with 4+ battery

[tamere22]

Hi,

I'd like to charge my USB devices (especialy my lg phone) using AA nimh batteries.

I tried to order a "stupid" box on ebay that claimed to be a charger for my phone using 4 * AA, but it didn't work. I opened it and seen it's empty of any electronics, just a box that connects 4 AA battery together and link them to an usb port...


Anyway,

I'd like to make a circuit using 4 or 6 or 8 nimh AA battery that would output 5V at 700mA (or 1A)

I've been told that my previous item (the "stupid" box) didn't work because the phone was drawing too much power and killing battery.

So is there any way to create an electronic circuit that would limit the current power output to max 700mA (or better, 1A ?) at pure 5V ?

I don't care if I need 8 AA's battery to do this, I'll make the box. I just want to recycle all the unused AA I have and get a strong battery.


Also a good option for those stupid phones would be a detector of low level of battery inside the box that would cut the circuit and prevent idiot discharging. Because ATM, when the batteries are empty, the phone keeps thinking he's been recharged, and so eat its battery very fast.


Thanks

 

[Dragon Tamer]

Send the stupid box back, get a refund and charge the designer for any damage he caused to your phone. (6V on a 5V phone can damage it)

The stupid box most likely didn't work because a lot of devices that charge with USB need refference voltages which were not supplied by the stupid box. If you are building a charger using AA batteries then the good news is that the batteries should be able to charge the device at least once. I have a circuit that I built to charge my iPod off of AA batteries but I don't have it on me right now, if you can wait I'll get it to you as soon as possible. It has everything you need, a low voltage cut off, a regulator, and a circuit that should charge you phone.

 

[tamere22]

Hi,

Already got refund for it

I'd like to build using 4 or 8 AA battery (prefer 4) but that would not draw too much power at a time because it kills battery (I've been told so).

So, 700 mA would be a nice limit for power output.

Also I need the circuit to complety cut himself when battery are close to death so the phone stops running at maximum speed thinking he's plugged on wall power.

 

[KJ6EAD]

You can probably use the Minty Boost PCB attached to more batteries. It uses a versatile boost converter circuit based on Linear Technology's LT1302. You may need to change the inductor to a higher value. Consult the data sheet. I also think it would be better to develop the voltages for USB pins 2 & 3 with resistor voltage dividers from the 5V output instead of just a single resistor pullup to the variable input voltage.
https://www.electro-tech-online.com/custompdfs/2011/09/lt1302.pdf

 

[canadaelk]

I picked up an "Energizer" made USB charger for Can$7.00. Seems hardly worth the trouble for DIY. E

 

[Dragon Tamer]

He doesn't necesarily need a boost converter if he has all of those batteries at his disposal. If anything I would sugest a buck converter to cut the voltage but increase the current. He'll get more life out of 1 battery. I would like to know if he has any recargeable batteries lying around anywhere.

 

[KJ6EAD]

If he used a buck/boost converter with enough input voltage latitude he could wring every last electron out of his used "dead" batteries.

 

[Dragon Tamer]

I was thinking he could use an LDR to regulate a higher voltage but a converter would be even better. Especialy one similar to the one you post it. But he never said that the batteries were dead so a boost converter may not be necesary. If he used a buck converter it would drop the voltage but increase the current and the life of the batteries he's using. Even though the phone only needs 500mA to charge. If he uses a voltage monitor then he can watch the battery voltage and shut off the converter before it drops below it's effective opperating voltage.

 

[tamere22]

You can probably use the Minty Boost PCB attached to more batteries. It uses a versatile boost converter circuit based on Linear Technology's LT1302. You may need to change the inductor to a higher value. Consult the data sheet. I also think it would be better to develop the voltages for USB pins 2 & 3 with resistor voltage dividers from the 5V output instead of just a single resistor pullup to the variable input voltage.
https://www.electro-tech-online.com/custompdfs/2011/09/lt1302-1.pdf

View attachment 57014

Hi thanks all for your answers.

I'm not good at electronics because I didnt get a thing about what you said.

Basicly, the above schematics could work replacing 3V batteries with 4*1.2V using a different inductor ? Could you tell me which value then?

"I also think it would be better to develop the voltages for USB pins 2 & 3 with resistor voltage dividers from the 5V output instead of just a single resistor pullup to the variable input voltage."

There you lost me 100% !

 

[KJ6EAD]

First you said NiMH batteries, then "unused batteries". I took all this to mean you wanted to reuse "dead" alkaline batteries. Designing a buck or boost converter is not a beginner project. You can probably use one of the available USB chargers like the Energizer mentioned above or study some buck/boost IC datasheets to see what's involved.