Power RPi zero W with 3.7v lithuim battery

[OutoftheBOTS]

OK I have normally been powering my RPi Zero W from a battery with a buck converter to convert the voltage to 5v then power it off the 5v pin.

Now here's my question if I have a very small project where space it at a premium can I power the RPi Zero W directly from a 1S lithuim battery to the 5v pin. I understand it is a lower voltage but I assume that the RPi doesn't use the 5v rail except for powering USB ports that I won't be using and then the RPi has a voltage regualtor to drop the voltage to 3.3v for the rest of the RPi to use. I would asume that as long as the 5v rail is getting more than 3.3v then the RPi will still run execpt the USB ports will be under powered????

[mattmiller]

Certainly worth a try - I experimented using 3 x AA NiCd a while ago and IIRC the PiZero I was testing on kept going (even the WiFi dongle was still working) down to 3.4V

Certainly won't do any harm (as long as you don't short out the battery - Lithiums don't like that very much!!!)

[OutoftheBOTS]

I am hoping to hear the opinion of an engineer but am likely to try it as RPi zero r cheap.

You can get batteries likes these http://www.ebay.com.au/itm/5pcs-1200mAh ... SwzgBY07vA

They r smaller than a RPi zero with 1200,mha and capable of up to 30amps discharge as r designed for RC helicopters so being discharged at the rate that RPi zero draws they will last long time before going flat.

[PiGraham]

Pi models with switchmode regulators will work at lower voltage but they won't work down to the minimum voltage of a LiPo. That means you won't get the full capacity of the battery. The Pi will stop working before the battery is exhausted.
This blog suggests 3.4v is viable. Don't try battry direct to 3.3V rail. LiPo can produce 4.2v fully charged which could be lethal to 3.3V logic.

Sparkfun data suggests 3.4v will get you 80% of the charge, wasting 20%.

[OutoftheBOTS]

Ok thanks for that.

Looking at the Battery discharge chart looks like that I will get over 85% capacity before it drop too low for the RPi Zero.

lipo.JPG (46.58 KiB) Viewed 24354 times

It is looking like a great option for my little projects and should get at least a couple of hours out of these little batteries

I also wanted to run a little 2.4" SPI screen on this project but I might pull the power for the screen directly from the battery not the RPi and put a little 2.8v voltage regulator on it as the specs for the screen says it is suppose to run on 2.8v not 3.3v anyway

[alphanumeric]

Would something like this work, https://shop.pimoroni.com/products/lipo-shim
Removing the battery connector and soldering the battery directly would slim it down some. And snug it down on the GPIO, solder it in place, and clip the excess GPIO pin off. Or just use wires from the Pi GPIO pads to the shim. Just a thought.

[PiGraham]

It is important not to over discharge LiPo batteries (they can catch fire when recharged if they have been over discharged). The LiPo Shim looks like a good option

Automatic shutdown at 3.0V to protect your battery

The Adafruit product mentioned by Pimoroni would be a good all-in-one
https://shop.pimoroni.com/products/powe ... t-1a-1000c

[alphanumeric]

I have a powerboost 1000c in one of my projects. No complaints. I'm using a 6600 MAH battery that I haven't even come close to discharging.

[OutoftheBOTS]

I do already own boost converters like this http://www.ebay.com.au/itm/MT3608-Micro ... SwHsBZm8fn

but I am super tight for space and want to be able to remove them.

The RPi will shut down before the battery can be over discharged so over discharge won't be a problem.

I have a CNC mill that I built (RPi powered btw) and will cnc mill out my own custom PCB for the project.

I have got prototype working see bottom pic and will use the back of the custom PCB to mount all needed components. You can see from the first pic I have a surface mount header to connect to the RPi and will make a battery connection on the custom PCB to power it from there and will add a voltage regualter for the power supply for the screen. I have used a 2046 touch ADC to read the touch screen (see bottom pic) and will also mount that on the PCB. There r a few more parts like 0.1uf decopupling cap for the 2046 chip and a 10k resistor for the peniq pull up and a transistor to switch the backlight LED off the battery and a curretn limting resistor so not o iver the back light LED. I will probably also mount a charging plug for the battery too but will make my own charger with a TP4056

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20170926_213610.jpg (109.04 KiB) Viewed 24282 times

[PiGraham]

The RPi will shut down before the battery can be over discharged so over discharge won't be a problem.

You need to do more than shutdown the Pi. You need to disconnect the battery. A Pi in shutdown draws current and will over-discharge the battery. If you connect a battery to a Pi Zero's 5V pins on the header that will be a problem.
Check you have negligible current (<10 micro amps) from the battery in the off state. Measure it.

[OutoftheBOTS]

I will mount a small on/off switch on the battery that the user can manually switch off when the RPi shuts down.

I think that I might use a Li-ion battery as can get slightly better size/capacity ratio and they should be able to handle the current that I need.

But it maybe a good idea for me to also include a DW01a on the back of the PCB to protect the 1S li-ion battery

[Imperf3kt]

Note that if you drain beyond 50% capacity, a Li-Ion battery will have a shorter lifespan than one that was kept above 50%

[OutoftheBOTS]

I have found these for a few bucks each so won't be too worried about life span and user can always charge more often than waiting till it shuts down by self
http://www.ebay.com/itm/103450-3-7V-180 ... SwT5xZOLtA

I am more concerned about size.

[PiGraham]

I am more concerned about size.

The concern with Li-Ion and Li-Po batteries is the fire risk. Over discharge can lead to crystal growth in the call that causes overheating during charging and can result in fire. You may know that Samsung had problems with Galaxy Note7 LiPo batteries catching fire and similar stories have made the news now and then.

A manual switch can be forgotten.

I don't now what risk the particular cells your want to use may pose. You may have a cast-iron protocol for charging cells in fire-proof containers with thermally regulated chargers. Be aware of the issue.

Battery protection circuits that are small and cheap are readily available and should prevent the common problems of over discharge, over charge and short circuit. Some packs, even 1S, will have such circuits built-in, but many won't.

[OutoftheBOTS]

As I said on earlier post I will put a tiny DW01a on the power supply it has a mosfet the switches off the power if it gets too low see http://cxem.net/master/files/97_DW01A-DS-11_EN.pdf

But the previous post was about dropping below 50% for longer life. I am happy to go below 50% and shorten life the DW01a is a pretty standard 1s Li-ion protection IC, it protects from over charge, over discharge and over current for both charge and discharge

[PiGraham]

As I said on earlier post I will put a tiny DW01a on the power supply it has a transistor the switches off the power if it gets too low see http://cxem.net/master/files/97_DW01A-DS-11_EN.pdf

Cool

[bullen]

What do you think about this: http://alchemy-power.com/piz-uptime/

[PiGraham]

I found this relevant info yesterday. You can run a Pi Zero from a single cell with the limitations that you noted - maybe 80% capacity useable and possible problems with USB peripherals.

http://www.raspberry-projects.com/pi/pi ... ifications.

As others have mentioned you can't rely on the Pi to shut off drain on the battery and you need a power switching solution. It should be automatic to protect against users forgetting. You should always use LiPo cells with protection circuits. An abused cell is a fire hazard
Over discharge protection will remove power from the Pi eventually but you might find that low voltage leads to erratic behaviour of the Pi, possibly cycling over multiple partial boot cycles, which could be bad news for the SD card. A more definite switch off is a good idea.

[ScheissSchiesser]

Hi all.

I realize this post is over a year old, but I am having trouble powering a Pi Zero v1.3 with a LiPo battery directly connected to the 5V GPIO. I am trying to avoid using a boost converter for a small integrated project.

With the battery directly connected to the 5V GPIO, the Pi appears to go into a boot loop. The LED blinks on like a normal startup, and then quickly oscillates on/off, and the pi reboots. Is there some undervolt protection that I need to disable in order to get this to work?

Any help would be greatly appreciated.

Thanks!

Edit: *minutes later* well, it looks like I probably had too long of wires or a poor connection or something, because it seems to be working now. I will leave this up for posterity.

[HermannSW]

The reboots I saw with my Pi3B(+) were caused by not enough current providing mains adapters (the official works great).
I assume that your reboots were caused by undercurrent and not undervoltage.
The smallest Lipos I have are 150mAh 25C type. They can deliver 25*0.15=3.75A permanently.

You did not tell which type of lipos you use, a Pi ZeroW has recommended 1.2A:
https://www.raspberrypi.org/documentation/faqs/

P.S:
Boost to 5V converters are cheap and small, this 1$ one delivers 1-1.5A and its size is "<18mm × <26mm" from comparing with similar items with size specification:
https://www.aliexpress.com/item/DC-DC-B ... 45286.html

[hippy]

With the battery directly connected to the 5V GPIO, the Pi appears to go into a boot loop.

You could connect your Pi to a bench PSU set to the battery voltage which will help determine if it's an issue with the battery, the voltage or something else.

[Imperf3kt]

The smallest Lipos I have are 150mAh 25C type. They can deliver 25*0.15=3.75A permanently.

Not permanently. 6 minutes under ideal conditions. You will likely get less than 2 minutes before the battery is below a useable voltage.

[HermannSW]

You are right, for those cases I do have 10 of these 150mAh 25C lipos to change (with reboot), I used them when I did attach a Pi Zero with camera to a cheap RC airplane for powering the Pi Zero, camera and the airplane. Each 25C 150mAh lipo lasted more than 4 minutes of flight:
viewtopic.php?t=190407

Or I use bigger 25C 1000mAh, that can deliver 3.75A much longer.