mattmiller
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Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 7:13 am

Following recent experiments with 4xAA Alkalines, viewtopic.php?f=63&t=160415

I thought to try the approach of seeing if a PiZero with WiFi will run off 3 instead of 4 thereby eliminating any potential over-voltage damage issues

As before - its flashing a LED and sending mqtt out to mosquitto.org topic pizero3aa every 30 mins

Volts now is 4.4

I'm using the RPI official white dongle since it did so well yesterday
[edit:
SUMMARY
3 x Alkaline AAs last about 3 hours

4 Alkaline AAs last more than twice as long at least 6 and average 8 hours

4 Alkaline AAs start off producing around 5.7 volts, which is way above the stated tolerance of a PiZero and any WiFi dongle attached but this soon (with 30 mins) drops below 5.25V which is safe.

My PiZero continued to work down to 3V (and mikerr confirms that this is nothing unusual) which is good but might cause issues if you were trying to use an add-on board that needs 5V to run properly

I'm going to carry on using a sets of alkalines on PiZero and see what the long term effects are
[/edit]
Last edited by mattmiller on Mon Sep 26, 2016 6:39 am, edited 1 time in total.

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Gavinmc42
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 7:59 am

Wondering which WiFi dongles use 3.3V chips?
Think 5V RF chips are dinosaurs these days.
Guessing most WiFi dongles have a low dropout reg in them.
Some perhaps even have 1.8V cores and the RF amps are the only 3.3V bit.
Voltage down to 2.9V, shorter RF range?

After 3 x AA, you want to try 3 x NiZn 4.8V (1.6V rechargeables).
Then one A size Li-Ion 3.7-4.2V.
Then A size LiFePO4 3.0-3.6V.
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johnb_summers
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:13 am

Have you tried fruit yet? understand they used fruit to produce electricity in Babylonian times.
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mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 11:03 am

Something went wrong (I think I knocked a wire loose) as I went away and no flashing led or mqtt posts

Anyway - restarting at 11:55 with new batteries volts = 4.3

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 11:07 am

After 3 x AA, you want to try 3 x NiZn 4.8V (1.6V rechargeables).
Then one A size Li-Ion 3.7-4.2V.
Then A size LiFePO4 3.0-3.6V.
I'll leave that to others - I just need to use cheap plain AA batteries for this project

interesting about the WiFi dongles possibly using LDOs to drop down.

And its interesting that everything still works even below 3.3V

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 1:20 pm

Ok - going fine after 2.5 hrs - volts down to 3.6
LEDs still flashing - MQTT updates still making it out

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DavidS
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 1:38 pm

Why not try using 6 AA batteries and a 5 volt switching regulator? That would likely keep the Pi Zero going a good deal longer, and would be safe as the regulator would keep the voltage into the RPi good.
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mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 2:24 pm

I've a need for just a plain battery pack - thats why I'm trying all this out :)

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 2:28 pm

Well 3 x AA have failed after just 3 hours so I think I'll have to go out and buy a pack of 8 new Duracells (these other ones have been lying around a while in a drawer) and repeat both the 3 xAA and 4 x AA

And I'll try sme test out with some PoundShop ones (but mix 2 sets of 4 packs up to try and even out any batch issues)

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Elescalador

Fri Sep 23, 2016 2:50 pm

I, for one, appreciate the data you're providing. Sometimes you need simple and cheap and disposable. That said, I've guessed best bang for the disposable buck might be a 4xaa pack with a 7805 regulator - would waste some energy as heat, but I'd guess it wouldn't even need a heat sink. Haven't tried it, though...it would ensure no overvoltage damage and its 3 leads could be soldered right to the pack.
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Re: Elescalador

Fri Sep 23, 2016 9:53 pm

ElEscalador wrote:I, for one, appreciate the data you're providing.
Me too. Never would have occurred to me that you could use standard 1.5v batteries in any way without some sort of regulator to power. Well...

You read it here first : )





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mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:04 pm

I've guessed best bang for the disposable buck might be a 4xaa pack with a 7805 regulator
Well as much as its good VFM -its really old school nowadays :)

Buck converters are the device of choice nowadays as much more efficient

But this is about using plain naked batteries - feel the wind in our faces #Freedom :)

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morphy_richards
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:08 pm

The bonkers thing is... All that time!
I'm almost tempted to get out my old original model B and give that a go.
(Almost)

mikerr
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:39 pm

Well I beat you by 3 whole years :)

Power a pi by a single aa battery in 2013

viewtopic.php?f=37&t=49987
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morphy_richards
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:40 pm

Pretty damn cool

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 10:42 pm

Well I beat you by 3 whole years
Don't see running a Pi direct from batteries in that thread :)

I'm claiming copyright on 3 x AA :)

Although your post in other thread made me think about it :)

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Gavinmc42
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Re: Powering PiZero from 3 AA Alkaline batteries

Fri Sep 23, 2016 11:55 pm

Think you might have to fight Dave for the rights.
He put one of the first Zero 1.3 into space on 3 x AA
http://www.daveakerman.com/

The original Pi B I don't think had low dropout regs, just the cheapest?
I did get some LD Vregs to try but life got in the way.
And now the Zero is a better target for battery powered Pi's anyway.

One day will try 3 x NiMH for solar because they can stand trickle charging better than li-Ion.
Solar powered Zero 1.3 with camera and WiFi, on my very long To Do list.
Can get WiFi to uart pcbs that run off 3.3V?
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ElEscalador
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 1:09 am

mattmiller wrote:
I've guessed best bang for the disposable buck might be a 4xaa pack with a 7805 regulator
Well as much as its good VFM -its really old school nowadays :)

Buck converters are the device of choice nowadays as much more efficient

But this is about using plain naked batteries - feel the wind in our faces #Freedom :)
Tru Dat. Just I think 7805s are almost free now, lol. Especially because I have a million of them lying around. Those things are like weeds in my parts boxes. But as a Red, White, and Blue, bleeding American, FREEEEEDOM!
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gregeric
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 8:20 am

Conversion efficiency of
1. linear regs eg 7805, even LDO ones: Vreg/Vsupply. Adding extra cells in series doesn't increase you run time, only your inefficiency.
2. buck/boost switching reg ~90% - and adding extra cells in series increases run time.
3. straight 3xAA's: no conversion, so 100% energy transfer.

If your set-up will run error-free for sufficient time off 3 (or 4) AA's, that's the best for efficiency & run time. If you need longer, then use higher capacity cells, or more AA's in series & a buck reg.

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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 8:25 am

Also see these 2x AA holders with USB buck-boost - which I still use:

Image
viewtopic.php?f=37&t=41054#p334942
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 9:37 am

I did power Pi Zero with LCD display from single LiPo cell (fully loaded it provides 4.2V):
https://twitter.com/HermannSW/status/767043572583497730
Image

Since you are looking for a battery solution, although this is not the Pi Zero, I did power an Arduino Uno from a single(!) AA battery which had only 1.22V left with a 0.52$ step up module that works as low as 0.9V!
https://twitter.com/HermannSW/status/735617300758470657
Image

Hermann.

P.S: The 600mA step up converter provides seems to be enough for many applications of Pi Zero, driving 4 Laser LEDs (they have built in serial resistor) takes 80mA in total only:
https://twitter.com/HermannSW/status/762740327434387459
Image
Last edited by HermannSW on Sat Sep 24, 2016 11:14 pm, edited 2 times in total.
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mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 9:58 am

He put one of the first Zero 1.3 into space on 3 x AA
AFAIR He used Lithiums not plain alkaline :)

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 3:19 pm

Tried again late last night with my Kirkland CostCo batteries and got 3.5 hours

I've bought 2 four packs of Energiser Max and mixed the batteries up and stuck 3 of them in - lets see what it does with them starting volts 4.35 [edit - fault meter so ignore Voltage]
Last edited by mattmiller on Sun Sep 25, 2016 7:12 pm, edited 1 time in total.

mattmiller
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Re: Powering PiZero from 3 AA Alkaline batteries

Sat Sep 24, 2016 5:22 pm

2 Hours in 3.45V [edit - fault meter so ignore Voltage]
Last edited by mattmiller on Sun Sep 25, 2016 7:13 pm, edited 1 time in total.

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