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I found a cheap powerbank (it costs about 6 $) that has power of 2400 mAh. I need it for my Switch-like Rpi console. But is this powerboank worth buying? If you need more details, check these informations out: Size: 94 x 22 x 21 mm Input voltage: 5 V DC 500 mA Output voltage: 5 V DC 1000 mA

So... what do you think?

  • I think this isn't a question about a Raspberry Pi. It's a question maybe better suited here: electronics.stackexchange.com – Quintin Balsdon Dec 14 '17 at 10:02
  • It will vary from a long time - (if you don't have any USB peripheral devices drawing power and have Bluetooth/WiFi switched off) – Andy Anderson Dec 14 '17 at 21:16
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TL;DR: 3-5 hours at moderate load.

They use the Ah rating for the li-ion batteries at nominal 3.7V. You can always stick semi-expensive panasonic 2800mAh 18650s in there if the vendor has lied about the capacity. I use some from a golfcart in my USB batteries. Gung-ho.

So you have 3.7V*2.4Ah=8.8Wh. Assuming a boost efficiency of 85%, you have 7.5Wh.

In my many tests, I’ve had Pi1 and 2 far below 2.5W, usually peaking at 1.5W (I don’t overclock). 7.5/1.5=5 hours. EXPECT less, maybe 3 hours.

Can’t recommend the USB ampmeters, use a DMM set to ‘A’, and measure current in series with a pair of clip-on probes.

For power longevity, you can do a few more or less invasive things, like cut off LEDs, use memory filesystems, and use google to find powersaving tricks for Pi. I’ve seen libraries for a greener Pi experience.

It is better, however, to use a car battery instead, with a quality step down converter to 5.1V. Stepping down voltage is always more efficient than boosting it. Use a LVCO of 11.6V, you’d need e.g. a TLV431 with vref 1.25 for this... https://electronics.stackexchange.com/a/318196/147045

BTW: The TLV431 can be used with Li-Ion batteries - like venerable 18650s - a recommended LVCO is 3.3V for a parallel bank, or 6.6V for a parallel-series bank.

A nice 90Wh S/LA battery is cheap and small. About the size of a baby’s head. A big battery of about 720Wh is the size of lady ada’s head (but not pink or purple), and would let you run at MAXIMUM POWER, SCOTTY! (12W I assume) for <=60 hours...

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I'm not so sure if this output current is actually enough to power the Pi. I can only speak for my RPi 3 B where a minimum of 2 A is required (as stated in the manual).

Check the manual if you still have it :)

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There are too many variables that effect how much power a device draws to try and answer this for you directly. So, I will try to give you a process:

  • Go get yourself a USB-based power-draw measuring device (a good one is the Charger Doctor, but any that show you how much amperage you are drawing will do).
  • Use the device to measure what your amperage draw is on average while your device is running and doing what it is meant to do. Remember that variable workloads will effect this drastically over time.
  • Use this quick (and very dirty) calculation to figure it out:

    Battery Size (in maH) / average-current-draw (mA) * efficiency
    
  • Typically an efficiency value of 0.7 is used for most small electronics.

Example:

  • Your battery is 2400 maH in size.
  • Your average power draw of the device is 200 mA (just an example - your measurement will vary!)
  • Equation: 2400 / 200 * 0.7 = 8.4 hours of battery life

This is a VERY subjective measure, and you should always do real-world tests to verify. But at least it should get you in the ballpark range of what a given size of battery will get you.

Good luck!

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  • Thanks a lot man :D . I wanted it to be standalone, Nes console, but due to lack of NesPis in my local shop, I'm considering making a Switch like Portable console, in case of no NesPis in stock till Christmas. But I will laso sak my sisters, if she had some powerbanks in stock. Anyway, thanks a lot man :D. Take care. – P0le Dec 13 '17 at 21:16
  • Excellent! If you could, please +1 this and mark this as the answer. It helps! Good luck with your gaming efforts! – MrChips Dec 13 '17 at 23:19
  • I had a USB ampmeter like that. It showed very different current readings when I compared it against an off-the-shelf multimeter’s milliamp measurements. Why don’t you try that, MrChips? – user2497 Dec 20 '17 at 18:09
  • @P0le MrChips’ answer is lacking in matter, but not brevity. – user2497 Dec 20 '17 at 18:16
  • @user2497 Your answer is very thorough and will definitely give a much more accurate result. Awesome! It also requires the person to put in a lot more time, effort and money into getting their answer. Sometimes people just want something that is easy, cheap, and will quickly get them "close enough" without having to become an electrical engineer. I tailored my answer to his level of question. Based on his positive response, it looks like I gave him what he needed. Also, please be positive, uplifting and stop negging everyone else's answers. It makes you look like a jerk. – MrChips Dec 20 '17 at 18:31
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Here is a calculator to save the math work:

https://spellfoundry.com/raspberry-pi-battery-runtime-calculator/

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