mostafaRaspberry
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Raspberry pi zero: power saving and battery life

Wed Apr 21, 2021 8:07 am

I have two question about Raspberry pi zero, I want to limit the power consumption, so I think to:

- Switch OFF USB/
- Turn OFF HDMI
- Throttle CPU
- Disable Bluetooth
- Disable on-board LEDs

1) What will be the power consumption (watts) ?

2) And If I use a 10000mAh battery it will power this device for how long time ?

Thanks

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neilgl
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Re: Raspberry pi zero: power saving and battery life

Wed Apr 21, 2021 11:27 am

Some benchmarks show that as around 80mA when nothing else is connected (or any sensors on GPIO using power).
80mA at 5V is 0.4 W
So if you could use all the battery power (you can’t) it would run for a maximum of 125 hours (5 days)

drgeoff
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Re: Raspberry pi zero: power saving and battery life

Wed Apr 21, 2021 11:44 am

neilgl wrote:
Wed Apr 21, 2021 11:27 am
Some benchmarks show that as around 80mA when nothing else is connected (or any sensors on GPIO using power).
80mA at 5V is 0.4 W
So if you could use all the battery power (you can’t) it would run for a maximum of 125 hours (5 days)
That theoretical calculation assumes that the 10,000 mAh battery outputs 5 volts. However there is currently no cell chemistry that can produce a 5 volt battery. The vast majority of 5 volt "batteries" contain a cell or cells which have a varying voltage as they are discharged but 3.7 volts is commonly taken as the average for runtime calculations. Moreover, mainly for marketing reasons, the quoted capacity is invariably that of the cell. After conversion to 5 volts the theoretical mAh figure is reduced to 3.7/5 of the advertised figure.

For that and other reasons a rule of thumb is to divide the advertised mAh figure by 2 before estimating run time.
Quis custodiet ipsos custodes?

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neilgl
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Re: Raspberry pi zero: power saving and battery life

Wed Apr 21, 2021 2:41 pm

Yes as I said you can’t use all the available battery power...

W. H. Heydt
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Re: Raspberry pi zero: power saving and battery life

Wed Apr 21, 2021 3:14 pm

neilgl wrote:
Wed Apr 21, 2021 2:41 pm
Yes as I said you can’t use all the available battery power...
As drgeoff pointed out, it not just that. A 10Ah battery is NOT 50Wh. Rather it is 37Wh. *Then* you have to take into account conversion losses and the inability (or, at least, inadvisability) to fully drain the battery.

As a practical matter, I get 12 hour run time from a 4Ah "powerbank" driving a Pi0W and 2.5" LCD display.

What we need from the OP is some information about how long he wants the system to run, what he is actually doing with it (as there may be solutions that require less power than a Pi0), and what his expectations are. (A Pi0 with as much shut down as possible is just an exercise in power savings. It won't actually *do* anything.)

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