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Update

  • AASaver 2.0 is now available. Buy it from Rayshobby Shop.
  • For details about AASaver 2.0, assembly and usage instruction, please check this blog post.

Order

You can order the AASaver from my hobby shop. The kit comes with one assembled and tested circuit board, one AA battery holder, a pair of bright white LEDs (for use as flashlights), two breadboard headers (for use as breadboard power supply), and two screws and nuts.

Overview

When your electronic devices report that the batteries are ‘dead’ and need to be replaced, do you ever feel frustrated that there is often still a lot of juice in them? Don’t throw away the batteries yet! You can use the remaining energy to do a lot of things, such as powering LED flashlights. This is possible by using a boost converter, which can bump the low battery voltage to a higher voltage, enough to light up LEDs or even power breadboard circuits.

Based on an efficient boost regulator IC, the AASaver is a small and multi-purpose boost converter that can help you harvest the remaining energy in AA batteries. It has a few nice features:

  • Takes up to two AA or AAA batteries. Start-up voltage as low as 0.9V.
  • Outputs regulated 5V, up to 500mA maximum output current (actual current output depends on the battery condition).
  • Has built-in USB port, LiPo charger, bright flashlight LEDs, and breadboard pin headers. Use it to charge USB devices (e.g. mobile phones), Lithium-Polymer (LiPo) batteries, as LED flashlight, and breadboard power supply, all from two AA batteries!

As in the original AASaver, the 2.0 version works perfectly as a small flashlight. The boost converter generates enough sustained current to power bright LEDs. Even running on low-voltage batteries (starting 0.9V), it can still power the LEDs for a long time. Now I never have to worry about keeping fresh new batteries for my flashlights — I have so many old AA batteries that are pronounced ‘dead’ by various electronic gadgets, remotes, clocks. I can use them all! This makes me feel a little greener :)

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I also enjoy it a lot as a compact breadboard power supply. It does not require any external power adapter, which is quite convenient. With a pair of fresh AA batteries, it can provide up to 500mA output current, enough for many breadboard circuit experiments or even powering a motor!

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23 Responses to “AASaver”

  1. Deedee says:

    I also had the same idea a while back to use low current
    leds to get the last juice out of used batteries for a free
    flashlight effect.

    It worked but some of the batteries oozed out chemicals after
    doing this and ruining my contacts , so i stopped doing it.

    • ray says:

      This depends on the quality of batteries. Even with no boost converter, if you leave them in the circuit for long enough, some will ooze and leak chemicals. So I don’t think boost converter is the direct cause of this.

      • Deedee says:

        Yes my point exactly ,dont bother doing this with cheap , nobrand batteries.
        I guess mine were cheap as well. :)

  2. [...] AASaver @ Rayshobby. I was on Show and Tell two weeks ago and I demonstrated my project called AASaver. Thanks a lot for providing this great opportunity for DIYers to talk about projects. Here are some details about my project, in case you find it interesting to post on Adafruit blog. [...]

  3. foz says:

    Awesome project! The breadboard connection is a great idea as well. Building your own long-run flashlight is easy with this – thanks for sharing this!

  4. Dave C says:

    I just built two of these kits (Nov ’11 version). This would be an excellent kit for those learning to solder.

    I have more zombie-AAAs than AAs, so I decided to buy one of these kits:

    http://www.amazon.com/Bluecell-Converter-Adapter-Battery-Storage/dp/B0069YEOPS/ref=pd_cp_e_0

    They are a more upscale (1%? LOL) way to fit AAAs where only AAs are supposed to go.

    • ray says:

      Hi Dave, this is a great idea. Someone suggested that I add another set of PCB holes for AAA batteries so the same board can be used for both AA and AAA. Using a converter like you mentioned is obviously a solution too.

  5. Richard says:

    Hi Ray, I like the AAsaver idea. I am interested in sucking the power out of 1.5 V batteries and using it to charge an HTC phone and Ipod Touch. I was thinking of using rechargeable batteries, perhaps fully charged to serve as a way to charge my phone using when grid power is down. I don’t exactly know how much current my HTC phone sucks down while just sitting idle and charging may be really slow. Do you think this idea is practical? What if I use a plastic 3 or 4-battery holder soldered to the appropriate input pins of the AAsaver?

    Thanks

    • ray says:

      Hi Richard, the maximum output current is 350mA. This is probably not enough for iPod Touch, which requires 500mA, but I think it should be ok for HTC phones, which I think require only 100-200mA. I don’t know for sure, but I have a couple of low-current USB chargers that always work with HTC phones but not iPhone. The output current will not increase even if you use more batteries. You can only increase the output current by connecting two AASavers in parallel, or by using a different chip. You should check out Adafruit’s MintyBoost. It uses a stronger switching regulator that can output 500mA, but the downside is that the start-up voltage is also quite high, which means it won’t work with low-voltage batteries.

      • Cal says:

        I like Richard’s idea. Would it be possible for you to use a stronger switching regulator in your design and add more batteries to the circuit? Being able to charge an iPhone using nearly dead batteries would be very popular.

        • ray says:

          The problem is not with the switching regulator. The one used in AASaver 2.0 can deliver up to 1A, which is more than enough to charge the iPhone. The issue is that dead batteries simply cannot deliver that much current, and iPhone will refuse to charge if the charging current is below 100mA. Adopting a stronger switching regulator does not help.

      • Cal says:

        Check out this video about using “dead” batteries to charge cell phones: http://www.youtube.com/watch?v=2uwznkk_uAc&hd=1
        I’m thinking a scaled down version for personal use would be great. Your AASaver comes close but it needs to provide more power…

        • ray says:

          Well, that video shows a wall of AA batteries! If you have more than several AA batteries, you can simply connect them in series and charge your phone (as long as the total voltage is above 4 volt or something). But this is an inefficient solution, mainly because the battery conditions vary, and when you connect them in series, some batteries will end up charging other batteries (i.e. you will find that some batteries in the series will start to have reverse polarity).

          In any case, that’s not the point of AASaver — AASaver is designed as a voltage booster, so it can be used to extend the life of one or two batteries, which is a more efficient solution. It can do more than USB charging.

  6. Richard says:

    Thanks for your thoughts. I was considering using more batteries to supply more usable power to the charged device, and maintain higher output currents rather than operating at the lower limit of the device, where current output is less. I agree that this may not put out enough power. Having a charger that can charge a phone quickly is a big bonus, especially if it operates on batteries that other devices reject as spent because of poor design, when we know there is more usable power in them. Great idea, and your kits appear to be the highest quality! Cheers to you!

  7. Martin says:

    Ray.
    The AASaver seems a great idea. Is the output clean? Do you have any specification for the output noise level?
    Martin

    • cae2100 says:

      the output is a clean dc signal, I had +/- 2-3mV at most variation when I hooked it up with my stress tests. I used it with microcontrollers and such that are very sensitive to ripples in voltage and it works perfectly fine.

  8. cae2100 says:

    will the 1.0/1.1 versions still be available for purchase? I like using them for projects and breadboard power supplies, and the new 2.0 is waay overkill for most uses.

    • ray says:

      At this moment, there is no plan to make 1.0/1.1 version again. 2.0 has more features because some 1.x users wanted USB charging and LiPo charging support. I understand that not all users need these, but I think it’s better to design the product to have multiple functions, than having separate products. Frankly, if price is a concern, I should point out that the price of 2.0 is pretty reasonable: you can compare it with Adafruit’s MintyBoost and similar products at SparkFun – AASaver 2.0 is noticeably cheaper, and can do a lot more.

  9. Mark says:

    Hi Ray
    I have the AA Saver v1.0
    Using it with the two LEDs is pretty neat but I have been trying to power other stuff
    I soldered a USB Type A (f) port to the unit and tried to charge an iPhone 4S (No joy)
    I wired in a small electric motor (No joy)

    I am nowhere near an expert in electronics or electricity, in fact I am as lame as they get

    When a load is presented to the AA Saver a) it doesn’t work, b) the small RED LED goes out on the AA Saver
    I can only assume that the ‘draw’ is too much for the AA Saver?

    I see that v.2.0 is able to use the on-board USB port to charge devices

    My Q’s are:
    1) Is it possible for me to modify or make work – the ability to charge a USB device? (i.e. iPhone 4S or battery operated pencil sharpener)
    2) Other than illuminating x2 LED’s and powering a breadboard, what else can the AA Saver v1.0 do?
    3) Is there a case available?

    Thanks for you product
    I look forward to your reply
    Regards
    Mark (UK)

    • Mark says:

      … or I could have v1.1

    • ray says:

      First of all, AASaver 1.x was never intended to charge USB devices (that’s what AASaver 2.0 is designed for). The reason is that at the maximum 1.x can only output about 300mA of current, and devices like iPhone 4s requires 500mA of charging current.

      Second, all AASaver 1.x have been tested with 300mA of output current. The actual current output obviously has to do with the battery condition — with a fresh pair of batteries, it should be able to deliver 300mA. The more used the batteries are, the less current you can draw from them. If the batteries are almost dead, they probably can’t deliver more than 30 to 40mA, which is enough to light up LEDs but not enough to drive a motor.

      So to answer your questions:
      1) yes, it’s possible, but keep in mind the board cannot deliver more than 300mA even if you use a fresh pair of batteries. if you have to charge iPhone 4s, consider getting AASaver 2.0.
      2) other than lighting up LEDs, it can also be used for circuit board experiments, and you can use it to drive any device that draws less than 300mA.
      3) we don’t provide a case. but it’s possible to fit the board in a mint tin or similar boxes. if you do so, make sure you use tape to insulate the box before putting the circuit board in.

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