PeriUSBoost: A DIY USB Battery Pack

If you travel often, use your mobile devices a lot, or run questionable ROMs on your phone, you likely have an external USB battery pack. These handy devices let you give a phone, tablet, or USB powered air humidifier (yes, those exist) some extra juice.

[Pedro]’s PeriUSBoost is a DIY phone charging solution. It’s a switching regulator that can boost battery voltages up to the 5 volt USB standard. This is accomplished using the LTC3426, a DC/DC converter with a built in switching element. The IC is a tiny SOT-23 package, and requires a few external passives work.

One interesting detail of USB charging is the resistor configuration on the USB data lines. These tell the device how much current can be drawn from the charger. For this device, the resistors are chosen to set the charge current to 0.5 A.

While a 0.5 A charge current isn’t exactly fast, it does allow for charging off AA batteries. [Pedro]’s testing resulted in a fully charged phone off of two AA batteries, but they did get a bit toasty while powering the device. It might not be the best device to stick in your pocket, but it gets the job done.

34 thoughts on “PeriUSBoost: A DIY USB Battery Pack

    1. I don’t know; the link contained no circuit that I could find, and I don’t know what a mintyboost is anyway, but little USB step-up modules are available from eBay starting at just $1, so I’ve been using them.

      As to the speed of 0.5A, that’s all relative, of course. Suprised that apparently they don’t know this. I tie mine to my belt, that was the style at one time. Now, to take the ferry cost a nickel, and in those days, nickels had pictures of bumblebees on ’em. “Give me five bees for a quarter,” you’d say.

      Now, where were we? Oh, yeah: there’s an interesting story behind this nickel. In 1957, I remember it was, I got up in the morning and made myself a piece of toast. I set the toaster to three: medium brown, I put the toast in my pocket …

    1. This isn’t a question of initial capacity, but rather a question of currently available capacity… a dead phone battery could have 100 Ah of capacity, but if it’s not charged, it’s no good… but a newly purchased pair of AAs could have as much as 5Ah…

      1. Initial capacity is ncesaary in order to know how much capacity the battery will obtain oncve it recahes full capacity. If it can only take 100 Ah than when reaching its full capacity it can be much more useful than a AA 5 Ah. :) Your welcome

  1. Those boost converters are becoming ubiquitous, you can find them in virtually any emergency battery pack, flashlights with USB output or get online for $0.5-$1 each. Many will have proper resistors wired for data pins (although different devices require different levels) and more expensive models (for $1-2) will have a 1A sustained output.

    1. Not exactly. This has pads for a resistor network on D+/D- for forcing some devices into high current charging mode. It’s also a cleaner PCB. I dig the gratuitous ground plane stitching.

  2. Nice build. But it seems to me that 0.5A limit is a bit conservative, few more resistors and mini switch for 0.5A/1A selection would be a great feature. My camera flash likes to draw about 6 amps from AA batteries, and it doesn’t seem to hurt them.

    1. Highly unlikely that you can draw 6A from AA battery.

      From Energizer AA Alkaline battery datasheet:
      Internal Resistance for new battery: 0.150R to 0.300R
      Based on those numbers, the internal resistance is so high that you won’t be able to draw that kin dof current unless you have a dead short and only for the good batch of battery.

      Battery capacity dropped from close to 2800mAHr to 1500mAHr when you are drawing only 500mA. The battery drain is going to be close to 1A for a 0.5A output at 5V. At 1A drain, you’ll be lucky to get 1AHr if at all.

      1. Yes battery chemistry and sizes (which affects surface area between the electrodes) affects how much current you can draw out of them.

        NiMH AA cells are a lot better as they have much lower internal resistance (ironically not specified on datasheet). Energizer actually spec their NiMH battery at 1C for 2300mAHr.

  3. I use a 4 AA holder with a USB jack soldered to it with no regulator. I use NiMh cells. Fresh off the charger it’s about 5.7V unloaded but drops after even a few minutes. I know USB standard doesn’t allow form more than 5.25V but it’s never bothered my mp3 player or phone.

  4. The full schematic is in The device can easily give 1A, but when conventional alkaline and rechargeable batteries are used, they get really hot when are reaching the full discharge level. This is due to the fact that the converter increases the battery current to get the constant 5V out, and this current goes through the internal battery resistor. This was just a project for fun and when I did that I didn´t check “others” suppliers, obviously is pretty hard to compete with massive production.

    1. This sounds a bit dangerous, drawing more and more current from rechargeable batteries as they die. The circuit should have either an input current limit or a low-voltage input cutoff point, or both. In anything being powered by multiple cells in series, unless the cells have exactly the same capacity, once the weakest cell has been exhausted, the other cell(s) will charge that cell BACKWARDS (look at the current direction during charge and discharge cycles if you don’t believe this), which both increases the heating (reverse charging has higher series resistance, I’m guessing) and causes permanent damage to the cell (as stated in multiple nickel battery data sheets and app notes I’ve seen). The additional energy you get by draining batteries all the way to totally dead is minimal when compared with the potential damage. I’ve seen alkaline batteries leak their nasty potassium hydroxide guts out just from being overloaded, so even non-rechargeable batteries shouldn’t be treated this way.

      1. If you use rather than the default (and why would you not), then you willl need to add a couple of lines to that script..

        >>> Below
        // @include*
        // @include*
        >>> Add the following
        // @include*
        // @include*

        .. other than that, the script is perfect for all of the HAD greenophiles, and tones down the shoutey fonts quite nicely.

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