Power Stacker: Stackable Battery System

Power Stacker is a portable, modular, and configurable USB rechargeable lithium-ion battery pack system.

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Power Stacker does what other USB rechargeable batteries have failed to do, and that's the ability to combine together for increased battery capacity or separate in to many small batteries for smaller projects. You can literally use the same Power Stacker battery pack cells for many years across many different applications!

Did you purchase a battery that was too big and takes too long to recharge? Power Stacker connectors allow you to disconnect excess cells from the pack and use the removed cells for another purpose.

Another unique feature of Power Stacker is that each battery receives its own charge controller, which guarantees true cell balancing and makes sure that each battery is charged to the right voltage in real-time even while charging and/or discharging.

Power Stacker Specs:  

* Time to Fully Charge: @5 Watts 3350mAh: 3 hours | @8 Watts 13400mAh: 7 hours

* Capacity: 3350mAh, 6700mAh, or 13400mAh / 3.6V

* Type: Panasonic NCR18650B Lithium-Ion

* Input - Current: 450 to 2600mA | Voltage: 5 Volts

* Number of USB Ports: Depending on the number of 5V adapter modules

* Output - Current: Up to 2000mA | Voltage: 3.6 Volts direct or 5 Volts with DC-DC converter module

* Battery Life Under Typical Use: 5-10years 

* Replaceable Batteries


One of the most difficult design decisions is choosing the right connector that is compact yet sturdy enough to last hundreds of insertions and provide enough current. Maybe this style of mini power connecter can be used when going in to production:


Connecting battery cells in parallel seems like the easiest way to increase capacity because series increases voltage but not capacity while parallel keeps the voltage the same and increases capacity. The only issue is that there is energy loss through the 5V step up regulator and the diode that is required on each cell pack connected in parallel to the bus bar in order to prevent back current. This diode voltage drop on each cell pack between .3 - 1V is equivalent to a significant reduction in runtime.

However, it may be better to connect cells in series in order to increase the voltage and then use a high quality switching regulator like the following:

with a large input voltage range (for up to 10X3.6V cells) to step down to the USB 5V voltage. Higher voltage means lower current through most of the PCB assembly allowing for a more compact design. Even though there is loss in the regulator and cut-off voltage, it may be more efficient than cell packs connected in parallel through a diode then stepping up the voltage to USB 5V. 


For all my battery projects, I tend to use the Panasonic NCR18650B batteries because they are the highest quality with the largest capacity for its size. In my 5 years of working with these cells, I've only seen one fail permanently due to over-discharge for about a year. Even though it doesn't have the highest current output, it makes up for it with capacity and reliability. Stacking cells together also reduces the need for high current from a each cell since the total output current is divided amongst all cells.

However, I am thinking about using the smaller version of this battery called the Panasonic NCR18500A, which does have a lower capacity due to its reduction in height, but if I'm making a stackable battery system with circuity built in to each cell, then a lower profile can help reduce the size of each stackable cell assembly. Especially if I choose to go with a series stackable design, I would need at least two cells anyways for the step down regulator to function properly.

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Power Stacker Lock.stl


Standard Tesselated Geometry - 60.14 kB - 04/26/2019 at 16:06


Power Stacker Case Lid.stl


Standard Tesselated Geometry - 170.59 kB - 04/26/2019 at 16:06


Power Stacker Case.stl


Standard Tesselated Geometry - 506.72 kB - 04/26/2019 at 16:06


Adobe Portable Document Format - 87.55 kB - 04/25/2019 at 16:42


Early concept for Version 2 of power stacker, which uses an isolated ground and a charge controller on each lithium ion cell for connecting in series without an external cell-balancer.

Zip Archive - 690.01 kB - 04/24/2019 at 16:54


View all 9 files

  • 1 × Lithium-Ion Charge Controller Circuit (Schematic, Gerber Files, etc. can be downloaded)
  • 1 × NCR18650B 3350mAh Unprotected Panasonic Lithium Ion Battery (If lower cost is necessary, try the Panasonic NCR18650
  • 2 × Hirose 2-pin connector DF3-2S-2C
  • 2 × Hirose Socket 24-28 AWG Crimp Pin DF3-2428SCC
  • 1 × 1" Wide Kapton Tape Roll

View all 14 components

View all 5 project logs

  • 1
    For a single cell setup

    Simply connect the charge controller board, battery, and 5 Volt DC-DC converter.

  • 2
    For a multi-cell setup

    Simply connect the charge controller boards and batteries in to the case, and then connect the 5 Volt DC-DC converter.

  • 3
    Charge your devices!

    Plug in your tablet, DIY project, or smart phone and start charging!

View all 4 instructions

Enjoy this project?



Blo0dygeek wrote 05/07/2019 at 07:19 point looks quite useful for my gadgets

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