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  • Pi model: 4 B, 4GB RAM
  • Batteries: two INR18650-30Q
  • Battery holder: UM-18650x2

I thought of buying a new battery holder but can't find one with a USB-C end, so I need to power my Raspberry Pi with these components.

My current plan is to buy an open end USB-C cable and connect its red and black wires to the battery holder, but a friend told me it wouldn't be good for the Raspberry Pi since it needs 5V 2A to run and the batteries' voltage and amperage differs. What can I do or use to correct this? Does a small circuit exist to control/adjust voltage and amperage?

Note: I can't use the pins to power it since I'll be using both the 5V ones for a display.

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4 Answers 4

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Without knowing your background and resources for a few dollars purchase a new Raspberry Pi adapter. Be sure it is capable of supplying at least 2 amps, more would be OK as the Pi is not greedy and will take only what it needs. The more it does the more it uses so the load will vary. That is probably the safest and easiest solution.

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I can't use the pins to power it since I'll be using both the 5V

Are you using a display on a shield, or wiring your own connector? You can certainly wire your own 5V input in parallel.

since it needs 5V 2A to run and the batteries' voltage and amperage differs.

OK, you or your friend are suffering from a very common misconception about power supplies (and two-terminal components in general). A power supply (whether it's a battery or a wall wart) cannot dictate the voltage and current through a load simultaneously. Just one, or the other, or some current as a function of voltage.

See this thread, and where it talks about a power supply, think "my battery".

Two Lithium-whatever cells in series is going to be too much voltage for a Raspberry Pi. So you need something that's regulated at 5V, and that has the capacity to drive enough current (note the difference between "regulated at" and "has the capacity").

I'm assuming you want battery power. If not, just get a USB charger (or a Pi kit that includes one). If you want battery power, and you have the money, the easiest way to arrive at that is to get one of those USB charger packs, and make sure it has enough rated current to power your Pi, your display, and whatever else you're going to stick on there. Then just plug it in and go.

The next easiest thing to do is to use your 18650 cells and power the Pi through a switching converter (since you're going down in voltage, you want a "buck converter").

I'd like to say that you want to get one rated at 5V and 3A -- unfortunately, there are a lot of really enticing-looking, really badly built switching converters on the market, that don't deliver power to their ratings. If you buy stuff off of mass-market sites, then go way over on the ratings. If you buy name-brand devices from reputable distributors (in the USA: DigiKey, Mouser, Newark, Avnet), then you can worry less.

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Your friend is right you can't just run a battery voltage into raspberry pi. Two lipo cells will be more than 7 volts when charged and will damage the raspberry pi as it's only rated for 5 volts.

You need some kind of voltage regulator use ABC to DC converter with a BMS make sure the DC to DC converter can support a 5 volt output and at least two amps

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Instead of buying a battery holder, why not to buy a powerbank (used to charge mobile phones)? They are very easy to find, and most of them now have at least one USB-C port (and otherwise, USB-A to USB-C cables are easy to find).

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