Powering a Pi Zero from Li-ion batteries

Has anybody tried running a Pi Zero from a single LiPO cell such as you'd
use in a RC model aircraft or a drone? The voltage varies with charge
from 4.2 v down to about 3.7 v
I think it should work since the Pi has a regulator that drops the 5v
supply voltage to 3.3 for internal use, but I don't know what minimum
voltage the internal regulator needs to work correctly.
FWIW, I'd prefer to avoid using a standard off-the-shelf 5v output power
pack because:
- They're are rather bulkier than a bare LiPO and, if possible, I'd like
to get a Pi zero plus the battery into the space behind a Pimoroni
HyperPixel - 4.0, which is 86mm x 56.5mm
- Almost all power packs only have a single mini USB connection for both
charging and power output, so it would need a additional wiring and at
least an external socket plus plug to avoid the need to unplug it from
the Pi to charge it - adding more bulk and fiddling.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Loading thread data ...
Sadly it appears not
formatting link

I would suggest a 2 cell pack and a model type SBEC.These are very small and low RFI. e.g. if in the UK
formatting link
--
"The most difficult subjects can be explained to the most slow witted  
man if he has not formed any idea of them already; but the simplest  
 Click to see the full signature
Reply to
The Natural Philosopher
On a sunny day (Mon, 9 Mar 2020 14:15:17 -0000 (UTC)) it happened Martin Gregorie wrote in :
No Pi zero here, but ebay is full of things like this:
formatting link
It has a separate charging connector. Has a small switcher on board... 9 USD.
Was seventh hit searching ebay for 'raspberry pi battery supply'.
Single cell, not bad, a Pi zero should run a long time on 3800 mAh.
I have some bigger ebay buck and buck-boost switcher stuff from ebay. Hard to beat their prices.
Reply to
Jan Panteltje
On Mon, 9 Mar 2020 14:15:17 -0000 (UTC), Martin Gregorie declaimed the following:
USB devices expect 5V... So if you don't have at least 5V provided to the board, don't expect to use anything connected to a USB host port.
Also, any boards connecting to the pin header that makes use of the 5V pins will be unusable.
And if using the USB client port for providing the power, I suspect you will need to be within USB specs before the regulator even activates.
--
	Wulfraed                 Dennis Lee Bieber         AF6VN 
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/
Reply to
Dennis Lee Bieber
Good question ... I haven't tried, but I have a project in mind for which that would be a good solution.
But ... are you aware of the various buck/boost converters available?
Adafruit do quite a nice one, which is tiny and only around a tenner, and there's the Pi-specific "wide input shim" from Pimoroni that does a similar job.
Adafruit also have some similar little boards that manage charging the battery as well as regulating the output power, under the "powerboost" label. I have one of these, but beyond satisfying myself that it works I haven't done much with it. In particular, I'm not sure how well it behaves when the battery becomes exhausted ...
All available from the usual suspects ...
--
Cheers, 
 Daniel.
Reply to
Daniel James
You don't want to power it directly from the lithium cell - you need a cutoff circuit to prevent overcharge and overdischarge. The cutoff is often integrated into a 5V stepup chip, so there's no point using the bare cell even if it would work.
However you can buy the power board from a power bank without the batteries. If you search ebay or better Aliexpress for 'power bank pcb' there's lots of them of varying form factors. For example, a selection:
formatting link

(shipping from China might take a while at the moment)
Theo
Reply to
Theo
There are bits inside te Pi still need that 5v supply - RAM, HDMI, USB ...
I use the little Adafruit 1000C units with LiPo's. I power a Pi Zero that's running ~80 multiplexed LEDs plus wi-fi from a 2700mAh cell for about 7 hours.
See e.g.
formatting link

It can charge and run at the same time and there is a digital output you can hook into the Pi to give you a low battery indicator.
-Gordon
Reply to
Gordon Henderson
Good idea - thanks for suggesting use of an SBEC, since they're fairly small.
I've already discovered that there are 1000 mAh 2S batteries that should fit in my preferred volume behind the HyperPixel display.
BTW, I won't be using any add-ons apart from the screen: its a touch sensitive TFT and the Pi Zero W's wifi provides all the connectivity I'll need.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Interesting, but annoyingly, no dimensions are given.
I'll not be settling on the exact battery pack until I've got yhjre Pi zero running with the HyperPixel and can measure how much power it needs, which may be quite a lot since it will be used outdoors and may be on for much of a summer day.
The one number I'd really like to see is the current used by the display, but that's apparently not published. So who knows - I may be forced to use a bigger battery and end up sizing the encclosure to suit the battery rather than the display.
If the display determines the enclosure dimensions, the overall size could be something like 90 x 60 x 20 mm or even slightly thinner.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Nothing will be attached except the display, which connects via the double row of header pins.
Good point: SBEC and 2S battery it is, them.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Haven't looked yet, but from other feedback so far, its probably going to run off a 2S pack, so battery voltage will always be above 5V.
If it turns out to need a 2S battery, I'll charge that off a proper LiPo charger/cycler to keep both cells at the same charge state. Not doing that causes problems with LiPo batteries.
I strongly suspect that ripping a Li-ion phone charger pack apart will reveal a 5V regulator and a proper balancing charger in ine of the berrte ones. Not so much in the cheap'n cheerful variety.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
The three shared in our house all have a micro USB input and one or two USB A outputs. (But I think they are all the Anker brand.)
--
XML is like violence: if it doesn't solve the problem, 
try using more of it.
Reply to
Adam Funk
Sure - using a BEC commonly used on electric models sorts that out. I'm aware of that problem, and intend to deal with it, but ATM am more concerned to find out of I should use a 1S or a 2S battery pack - 1S is a lot easier to chanrge since no cell-balancing is required.
That's a GOOD thought - thanks.
Indeed.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Fantastic: many thanks for that idea.
That board does everything I need off a 1S battery. Now all I need to do is to get some power consumption measurements off the Zero + screen to size the battery.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
That goes for the ones I've seen. But as far as I know there are not many that can simultaneously be charged and discharged, so not fit for use as a buffer against mains failures.
--




/ \  Mail | -- No unannounced, large, binary attachments, please! --
Reply to
Axel Berger
Simultaneous recharging while running isn't needed here, but anything with a single connection for both purposes wound b annoying if it meant opening the enclosure the unplug the Pi and plug in the charger.
Fortunately, the Adafruit board doesn't need that and its ability to charge while running the Zero would certainly be a nice-to-have feature.
--
Martin    | martin at 
Gregorie  | gregorie dot org
Reply to
Martin Gregorie
Some people actually make step UP buck converters for single cell LIPO but they may be more expensive
formatting link

But TBH running with two cell LIPO packs is pretty good - they are cheap, available and reliable. And they don't stress even an analogue regulator on a heatsink too hard.
--
?Ideas are inherently conservative. They yield not to the attack of  
other ideas but to the massive onslaught of circumstance" 
 Click to see the full signature
Reply to
The Natural Philosopher
I never bothered with that - I've used an AstroFlight charger for YEARS that simply autodetects cell count and adds charge, and never had a 'single cell' issue. I've had cheap no name packs die altogether, but I am still using the first lithium packs I made up in around 2008
--
?Progress is precisely that which rules and regulations did not foresee,? 

  ? Ludwig von Mises
Reply to
The Natural Philosopher
I don't know why you'd want to use 2S if all you're powering is 5V stuff - it's easy to charge 1S (4.2V) from USB, and then a boost converter to generate 5V is easy.
Do BECs actually provide cutoffs? The one linked to in this thread doesn't seem to. Many battery packs already come with their own BMS which handles the cutoff - you don't get that if you're using bare cells.
A colleague also suggested looking at Poundland power banks - if you take them apart the board in the 2 pound ones seems to do the right thing.
There are some 'disposable' 1 pound one-time-use power banks that don't have a charging port, but it turns out they're actually fully equipped with a charging chip but they just save the cost of the connector - e-waste, sigh :(. If you solder on some wires they're a decent small pouch-cell 500mAh-ish power bank.
formatting link

As always, Poundland is pot luck as to what stock you'll find today.
Theo
Reply to
Theo
formatting link

is the teardown for those.
Theo
Reply to
Theo

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.