This Instructable is written on how to choose and build an Efficient *AA* Charger for charging power hungry Smartphones, Mp3 players, Bluetooth headsets, Fitness trackers, Digital cameras and to power other 5V devices too.
Why AA's ?
AA Batteries are widely available throughout the world including small remote countries. They are affordable, safe when compared to Lithium ion cells. In Emergency situations, where there is no power, AA's are available faster and can be used with the boosters to keep people's devices powered on.
Booster Module Efficiency
I chose the booster modules with minimum input voltage less than 2 x AAs (1.2v x 2 = 2.4V). The efficiency increases when supply voltage is maintained between 2.4V and 3.7V with Voltage output maintained at 5V @ 500mA to power most devices. Timed the booster to make sure its charging at a decent pace. I look for approx 1% percent charge per minute when charging my iPhone 5s. Other small devices should charge at a much faster pace provided their battery is smaller than iPhone.
How much Juice ?
2 x 2000 mAh AA Eneloop Batteries can give you approx 50% charge on your iPhone 5s in approx 60 mins. This was tested using both Adafruit and Pololu booster modules. Your mileage may vary depending on type of phone, age etc. 2 x 2500 mAhs can provide you 60% +.
- 1 x AA Battery Pack
- 2 x AA Alkaline or NiMH Batteries
- 1 x Adafruit Power booster for 500mA output
- OR 1 x Pololu booster 5V @ 600 mA @ 90% efficiency
- OR 1 x Adafruit power booster for 1Amp output
- 2 x 49.9K 1% Tolerance Resistors
- 2 x 75K 1% Tolerance Resistors
The good thing about these Booster modules is they work efficiently with AA and Li-Ion Batteries too. If you are Interested, you can use power it with Li-Ion battery too.
Disclaimer: I do not work for Adafruit or Pololu. I am recommending these projects as I enjoyed using them and thought would be a help to the community. Please be cautious when working with any electronic projects. Use safety gloves, glasses, be careful not to smell solder fumes. I cannot be held responsible for your mistakes caused during assembling of this project or failures. Please take precautions. Thank You.
Step 1: Power Booster Using 2 X AA Batteries
This is an Excellent power module for the money. For $10, Its a great device (Made in USA). You can power it using 2xAAs or Lithium Ion battery. It comes with onboard resistors to charge iPhone. It does not heat up like older boosters did like minty boost.
Shown here is 2x AAs (2000 mAh) connected to Battery/Gnd terminals as Voltage IN. This charged my iPhone approx 50% from dead.
Step 2: Power Boost Module Demo Using Lithium Ion
This option is shown to educate that this module supports lithium ion battery too, but it does not charge lithium ion battery. You have to charge it separately.
Step 3: Power Booster Using Pololu Module
The Pololu module is tiny and can be used where space is at Premium. The module has 4 pins with Shutdown pin not connected. Vin is AA Battery Input and Vout will goto USB via Resistor Network as shown in the next step.
Step 4: Pololu Connection to Resistor Network and USB for IPhone Charging
Here is the circuit which gets connected between Vout of Pololu module and USB out. This resistor network is required for charging iPhone. Other devices may or may not need them, please test it out.
Step 5: Some More Tips.
Use Pololu booster shield example to experiment with other Voltage booster module and compare the efficiencies of various other power boosters. (Note: iPhone needs resistors for charging)
- 3D Print your Enclosure
- Add a Solar Cell to your project and charge the NiMH Batteries while you are on the go (this cannot be used for Lithium ion batteries)
- Carry charge holding batteries like Eneloop
- Add a Switch so you can load the batteries and carry it with you
Above all Enjoy. Have fun building and Inspire others.