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I'm not sure if this is standard behaviour or whether I'm doing something wrong.

I wanted to have a pizerow operating remotely on my roof without the need to bring electricity there. The plan was to use a solar panel (https://www.waveshare.com/solar-panel-6v-5w.htm) , a solar panel controller (https://www.waveshare.com/solar-power-manager.htm) and a battery to power up the pi. My hope was that the battery recharged by the sun during the day would have been enough to overcome the hours without light.

The pizerow is under some medium-heavy load: I have a DVB dongle connected which is used to upload ADS-B data to Flightaware and a camera connected which is sometimes used to take pictures. Wifi is always connected. CPU stays always at about 60% usage.

I tried to set up the solar controller with a 1600 mAh 3.7V AA rechargeable battery (it's mounted directly on the solar controller as you can see in the image) and, after loading with the micro usb, tried to disconnect and let the pizerow run with the battery.

enter image description here

Unfortunately after just 2 minutes the battery slowly dies. I understand the pizerow is under load but is it really normal to have the battery die so early? My understanding is that, even under load, the consumption should be about 400-500 mA which does not really justify such a short life span. Or maybe is the battery just dead?

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  • Could you edit your question to explain how the 3.7 volt battery is powering the 5 volt Pi and peripherals. Also could you quantify a few minutes.
    – joan
    Sep 1, 2021 at 19:41
  • Hey, you can see the battery in the image, it's part of the solar controller which outputs 5V 1A regardless of the source (battery, solar, input usb...).
    – Droid
    Sep 1, 2021 at 19:43
  • You need to add explanations to your question.
    – joan
    Sep 1, 2021 at 19:45
  • This question is NOT about the Pi. Rather than speculation you should use a 10Ω 5W resistor to test the battery/charger.
    – Milliways
    Sep 1, 2021 at 22:34
  • How much power does your DVB dongle and camera use?
    – CoderMike
    Sep 2, 2021 at 6:26

1 Answer 1

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Normally, for the step-up in voltage between 3.7V for the battery and 5V for the Pi, you would use a factor 1.5 in the current. (if your converter has 100% efficiency, you can use 1.35) That means you'll use about 550 mA. With the 1600mAh, that would mean about 3 hours.

These are figures are rounded extremely and give only a very rough approximation.

About 3 hours is clearly more than your 2 minutes. This means that "something is wrong", which may very well be a dead battery.

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  • Yeah that's what I thought. I unfortunately don't have a multimeter to measure the consumption from the usb cable, so that's why for now I only have speculations. But still, even in an ideal scenario ( 3hrs) , I think it would be really hard for me to use the solar + rechargeable battery to supply the pi under heavy load without power loss during the entire day. So I guess I would just go back to the old solution of bringing a cable up there.
    – Droid
    Sep 2, 2021 at 6:31
  • instructables.com/Solar-Powered-Raspberry-Pi gives a feasible solution based on a 12V battery. Sep 3, 2021 at 8:08

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