I am working on an autonomous robot which is controlled by my RPi 3. I was concerned about how to power up the Pi, so I dissected an old laptop battery and got 6 Samsung ICR16850 LiPo cells from it.

Each cell gives 3.7V with 2200 mAh. If I use two of these cells connected in series, and pass them through an L7805 IC for voltage regulation will it be enough to run the Pi?

Please note that there is an Arduino connected to the Pi as well, so the USB ports might draw more power. Also, how should I check the amperage?

Here's a technical description about the battery- http://lygte-info.dk/review/batteries2012/Samsung%20ICR18650-26F%202600mAh%20(Pink)%20UK.html Please note that this is the pink one(2600 mAh), I have the green one(2200 mAh).

So is using two of these batteries together is fine? And how do I get the amperage to be 2 amps?

  • What's the question?
    – Ghanima
    Apr 22, 2016 at 18:08
  • That's Is it okay to use 2 of those batteries together? Also 1 battery's discharge current is 5200mA, which means I get about 10.4 Amps when 2 batteries are connected... Can the Pi protect itself from that or do I have to bring down the amps?
    – YaddyVirus
    Apr 22, 2016 at 18:11
  • highly related raspberrypi.stackexchange.com/questions/39255/…
    – Ghanima
    Apr 22, 2016 at 18:19

1 Answer 1


May I suggest you use 2 (or 6) cells in series and use a UBEC to generate the 5V.

This is pretty much what UBECs are designed to do.

A L7805 will just be wasting energy as heat.

Example UBEC.

  • Sounds interesting but there's a problem. Most of the UBECs I came across online aren't shipped to India. I chose the L7805 because of its easy availability, and I haven't found any UBECs yet in my city's local markets... Any other alternatives?
    – YaddyVirus
    Apr 24, 2016 at 8:19
  • @YaddyVirus That's a pity. If you can find a radio control vendor they should stock UBECs. A 7805 will work. It'll just get very hot (will need a heatsink) and be wasteful. Have a look on eBay etc. for a DC buck converter.
    – joan
    Apr 24, 2016 at 8:25
  • Yeah I know about the heating issue with L7805, I used thermal paste(the one I use for my processor), plus a heatsink to bring down the temperature and until now I havent seen any problems related to heat, anyways I'll continue my hunt for a UBEC
    – YaddyVirus
    Apr 24, 2016 at 17:43
  • P.S I have an old mini RC helicopter, I haven't opened it yet but do you think it might have an UBEC good enough for the job?
    – YaddyVirus
    Apr 24, 2016 at 17:45
  • Impossible to say. It's worth having a look if you can do so without damage.
    – joan
    Apr 24, 2016 at 17:47

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