RetroRevive
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Joined: Sat Nov 09, 2019 10:40 am

Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 11:16 am

Hello everyone,

I'm working on a project using Raspberry Pi 3b+ and one of the requirements is that it need to work on UPS for 15 hour during daytime while street lights are off.

Unfortunately, I don't have any other mean to power RasPi but UPS. And I'm restricted by enclosure case for all the components.

I have at my disposal CyberPower UT2200 -> 2200VA / 1320W

Do you have any suggestions how to increment autonomy?

Using simple math, I figured to get more than 15 hours of battery time, but I get max 9.

HDMI is off
USB hub is off
WiFi is off

I need only GPIO and audio.

Is it possible that internal fan is consuming a lot of battery time?

Do you think that connecting bigger powerbank in series is a good idea?

Thanks.

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neilgl
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Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 2:26 pm

That UPS should power a 3B+ easily for 15 hours - as 3B+ uses 400mA current idling, and a maximum of 2.5A
What other items (besides the pi PSU) are you powering from the UPS?

RetroRevive
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Joined: Sat Nov 09, 2019 10:40 am

Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 2:54 pm

Actually nothing except RasPi,

I suspect that UPS fan is drawing enough power to "steal" those extra hours.

Can anyone confirm that?

I powered all off via console, maybe there is some other way to shutdown the features I don't need.

It was interesting to see that I wasn't able to tinker with CPU overclock inside raspi-config.


I also have a classic B+, maybe that should do the trick?
It suits my needs for this project.


RetroRevive
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Joined: Sat Nov 09, 2019 10:40 am

Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 5:10 pm

I think I saw that one, however even if I followed the steps described in that thread, I've managed to max out from 8 to 9 hours.

If someone did something similar, please let me know.

Is someone using their powerbank as UPS?

W. H. Heydt
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Location: Vallejo, CA (US)

Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 7:51 pm

You also have to account for the losses in converting AC line current (the UPS output) to 5v DC to feed the Pi.

dustnbone
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Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 9:19 pm

The problem here isn't the actual capacity of the UPS, it stores orders of magnitude more power than you actually need to run the Pi for that amount of time. The problem here is massive overkill.

The UPS itself is using almost all of the power, between it's control systems, battery monitoring, communication, as well as the absolutely abysmal efficiency you will get from a sine wave inverter being run with such a small load. Most of the power from the batteries is simply going out as heat before it gets to the AC outlet.

The answer is a far simpler and more efficient UPS system tailored to your needs. Luckily this problem has been mostly solved for you already.

https://www.buyapi.ca/product/raspberry-pi-ups-hat/

That's pretty much exactly what you need, it handles interfacing a Lithium Ion battery to the Pi. It will take power from the Pi when the Pi is powered through USB, and give power to the Pi when there's no power coming from it. It handles converting the voltage to and from the 5V the Pi supplies and requires, to and from the battery voltage that varies from 3.0 to 4.2V depending on it's state of charge. It also controls the charging of the battery to keep it from being overcharged, and can provide some status information to the Pi through GPIO.

The next thing is sizing the battery correctly. Let's say the Pi is pulling 1A at 5V, that's 5W. Multiply that by 15 hours and you need 75Wh. The conversion to 5V from the battery is at least 85% efficient (more like 90), so 90Wh or so should be enough battery. Lithium Ion batteries are capacity rated at a nominal 3.6-3.7V, so 90Wh/3.65V=24.65Ah.

To get this capacity I'd go with 3 10Ah tablet batteries connected in parallel. That's going to give some reserve and plenty of time before the cells degrade to the point they can't provide enough capacity anymore. You should be fine for a couple thousand cycles at least. 3 of those cells should set you back less than $50 if you shop around. Example ebay listing below, but these are something you should be able to source locally without much trouble.

https://www.ebay.ca/itm/3-7V-10000mAh-L ... 3987810100

It's a much more efficient way to handle the whole process than what you're using now. The Pi doesn't need high voltage AC power, it just needs an Amp or 2 of 5VDC. You're actually spending a fair amount on electricity running things through a giant UPS that drains itself daily, your overall efficiency is probably in the single digit %, not to mention the poor batteries will not tolerate being cycled daily for long if they're the lead acid type used in most UPSs. Lithium tablet batteries are designed specifically for that task.

I've used the Pi UPS board in a couple of projects, one as a short term (2Ah) UPS to provide a graceful shutdown when power is lost and another for a portable media player with a similar size (20Ah) battery to what you'd need. It seems to be built with reliable power handling components, there are other similar HATs out there.

Also saw this thread, might be of interest if you decide to go with the Pi UPS setup. It's really not relevant to your current setup because the Pi isn't currently the main consumer of power

https://www.raspberrypi.org/forums/view ... 3&t=208110

LTolledo
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Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Sat Nov 09, 2019 11:23 pm

hack the UPS... get 5.1v from the internal batteries....

the "internal fans" need to turn ON only during the UPS charging phase....
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

RetroRevive
Posts: 10
Joined: Sat Nov 09, 2019 10:40 am

Re: Using Raspberry Pi 3B+ with UPS - need 15 hour autonomy

Thu Nov 14, 2019 7:27 am

£15.98 8%OFF | Raspberry Pi 4B/3B+/3B 18650 UPS HAT & Safe Power Management Expansion Board, X750 Shields for Raspberry Pi 4 Model B/3B+/3B/2B
https://s.click.aliexpress.com/e/pWVdx8xI


Is this any good?

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