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I would build a small present for my friend's child who has a 3D pen like this: 3D pen link

By now it only works with an AC-DC adaptor, so it always requires a wall plug. My idea is to build a battery pack to allow the use even when there's no AC plug.

Reading the "3D pen tech. details" I sketched some project requirements:

  • voltage: 12V
  • current: 2A (max I suppose)
  • Li-Ion battery like 18650
  • At least 3000mAh capacity
  • Integrated IC for battery recharge and battery over-discharge protection
  • Others IC to protect output and avoid overheating etc (if required)
  • 3D printed custom case, so I'm not too dimension limited (smaller is better obviously).

My first idea was to use 4 18650 cells, to reach a voltage between 16.8V (full charged) and 13.6V. Then using a step-down board to level voltage to 12V.

Another solution will be using only 3 cells (12.6V - 10.2V) without any regulator, and using only a over-discharge IC. This solution is the simpler, but I have no idea if the pen would tolerate under/over voltage.

What do you suggest? There's any other solution to achieve that?

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  • \$\begingroup\$ Over discharge IC are called under voltage lock out uvlo ICs. \$\endgroup\$ – Passerby Jan 8 '18 at 9:05
  • \$\begingroup\$ If you use protected 18650 cells, the 3-cell version requires just a battery holder. And probably you'd need to include a Li-Ion charger with the present, I think they aren't commonplace. \$\endgroup\$ – anrieff Aug 26 '18 at 8:06
  • \$\begingroup\$ Have a look and see if some portable power tool battery could be fit for your purpose. They have simple chargers available and come in all sorts of sizes. If you think the pen requires regulated power then you may have to get a suitable switched mode regulator for a few bucks. \$\endgroup\$ – KalleMP Sep 26 '18 at 10:56
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Buy a mini-UPS from eBay. They are cheap and some of them provide a 12VDC output as well as a 5VDC USB socket for emergency phone charging. They have internal Li-ion batteries.

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Measure the actual current requirement of the pen, if you can, as the design may be simplified depending on it.

For a similar scenario (powering a WiFi router outside, far from any wall sockets), which also had the same power requirements on label (12V, 2A), I've used a powerbank + a step-up regulator board (which you can buy cheaply from Amazon/ebay, I used this one). However this relied on the case that the router didn't actually need 2A to operate, it needed much less - but this may be the case with the pen, too.

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