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Hallowing Battery Holder Powered
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Hallowing Battery Holder Powered

by sv98229 on Mon Oct 15, 2018 8:37 pm

I am not a fan of LiPo batteries (to many LiPo sentences end with 'will explode').

Instead of 3.7V LiPo batteries I would prefer to use AA or AAA battery holders.

With Adabox 009 can I power the Hallowing with a 4.5V battery holder like:

3 x AAA Battery Holder with On/Off Switch and 2-Pin JST
PRODUCT ID: 727

or

3 x AA Battery Holder with On/Off Switch, JST, and Belt Clip
PRODUCT ID: 3287

Three AA or AAA provide 4.5V. Would a battery holder for two AA or AAA (3V) be a better choice?

Thanks.

sv98229
 
Posts: 37
Joined: Thu Jul 03, 2014 11:42 pm

Re: Hallowing Battery Holder Powered

by adafruit_support_mike on Tue Oct 16, 2018 3:52 am

LiPos have a good record for being safe and reliable as long as you use them correctly. The commercial products that blow up generally have cutting-edge battery designs that try to pack more energy into a smaller volume, and even those are 99.99% good. It's just that 0.01% is enough to be exciting when you have millions of devices on the market.

Among hobbyists, LiPo failures almost always follow a statement equivalent to "hold my beer and watch this." People go beyond the safe operating range because they either don't know about the limits or think nothing bad will happen to them.

LiPos have a narrower safety zone than other battery technologies, and the consequences of getting things wrong do tend to be flashy.. both figuratively and literally. Billions of people hold LiPos against their head every day though, so it's possible to use them safely.


That said, you're free to use any kind of battery you want as long as it's in the Feather's safe operating range.. about 3.7V to 5.5V.


To connect a 3-AA pack to the FONA, make the connections to the USB and GND pins, and run the connection to USB through a diode. That will keep Bad Things from happening to your computer that one time you forget to unplug the battery pack before plugging in the USB cable.

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Re: Hallowing Battery Holder Powered

by sv98229 on Tue Oct 16, 2018 8:22 pm

Thanks for the reply.

The operative phrase with LiPo batteries is 'as long as you use them correctly'. To hot, to cold, overcharge, undercharge, accidentally pinch, crush or pierce them and you can have problems. I find it easier to use easy to get AA or AAA batteries. I lose the compact, high energy density of the LiPos but I gain not having to be concerned with are they being treated correctly.

I was not sure I could use a 2xAA (3V) or 3xAA (4.5V) battery holder with Adafruit's Feathers and Hallowing. All the guides have the Feathers and Hallowing USB 5V powered which is fine when setting up a project. What I got lost on was what was a safe voltage that could be connected to a battery connector - for the various Adafruit boards is input battery voltage limited to 3.7V or not? Adafruit guides usually discuss 5V USB and 3.7V LiPo power sources but rarely mention/recommend possible alternative power sources for Adafruit products such as AA/AAA battery holders. A simple statement in a guide saying in addition to USB and 3.7V LiPos a 2xAA (3V) and/or 3xAAA (4.5V) battery holder can be connected to the input battery connection to safely power an Adafruit Feather M4 or Circuit Playground Express or <name your product here> would help (at least for me).

Adafruit has the very nice AA/AAA battery holders with JST connectors that make them obvious drop-in replacements for LiPo batteries.

The projects I work on typically do not have a limited space requirement so AA/AAA battery holders aren't a problem. Another advantage AA/AAA batteries give me is some of the projects (seismometers, seismic arrays) are designed to work outside (sunny locations, shady locations), be buried, possibly be stepped on, accidentally being hit with a hammer/rock/tree limb and being thrown in a car trunk. Able to withstand abuse is good. Also it is a lot easier to replace AA/AAA batteries in the field instead of trying to charge a LiPo battery in the field.

One project I am working toward is incorporating Adafruit and possibly Pololu buck/boost converters with AA/AAA battery holders to build 3.7V-4.2V and 5.2V power packs for use in projects. A steady, standard design power source will be a big help.

Thanks again for the help.

sv98229
 
Posts: 37
Joined: Thu Jul 03, 2014 11:42 pm

Re: Hallowing Battery Holder Powered

by adafruit_support_mike on Wed Oct 17, 2018 3:27 am

sv98229 wrote:for the various Adafruit boards is input battery voltage limited to 3.7V or not?

The BAT pin is connected to the LiPo charger, so connecting anything but a 3.7V-nominal/4.2V-full-charge LiPo to that pin will cause problems.

The USB pin is connected to the USB jack's 5V pin, and BAT connects to them through a low-Vf Schottky diode. Then that trace connects to the input power for the LiPo charger and the 3.3V regulator.

The LiPo charger won't do anything until its input voltage is at least 150mV higher than the battery voltage, and thanks to the Schottky diode it will be about 250mV lower when the Feather gets its power from the LiPo.

The voltage regulator can handle up to about 14V IIRC, but the LiPo charger's maximum input voltage is 5.5V, and that sets the limit for the maximum voltage on the USB pin.

sv98229 wrote:Adafruit has the very nice AA/AAA battery holders with JST connectors that make them obvious drop-in replacements for LiPo batteries.

They won't work with a Feather. The LiPo charger will freak out if it sees a voltage/current pattern that doesn't look like a LiPo, and any voltage higher than 5.5V will kill it.

The Feather line has several design goals, and flexibility of input power didn't make the cut. Connecting a 3-AA or 3-AAA pack to the USB pin through a diode is about the only other option that works, and the battery efficiency is fairly low.

Alkaline cells start at about 1.7V when they're new and drop to 0.9V by the time they're 95% depleted. A 3-AA pack will start at about 5.1V and drop to 2.7V before the cells are dead. The Feather's 3.3V regulator needs a couple hundred millivolts of headroom to maintain regulation, so running the power through a silicon diode will make the regulator start acting flaky by the time the pack voltage drops to 3.9V (1.3V per cell).

A low-Vf Schottky will give you about another 400mV of headroom, but that still puts the limit around 1.15V per cell. The cell will be about 80% discharged at that point, but the Feather can't get the remaining 15% that takes the cell voltage down to 0.9V.

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Re: Hallowing Battery Holder Powered

by sv98229 on Wed Oct 17, 2018 6:55 am

Thank you for the detailed information.

Considering how to power my projects all I can say is 'rats'.

In place of a AA/AAA battery holder can a Feather be powered by connecting a USB Battery Pack like #1566, #1959, or #1565 to the Feather's USB connector?

If powering the Feathers is restricted to foil packaged LiPo batteries than I am going to have to switch from Feathers to other microcontrollers (pyboard?, raspberry pi zero?, teensy?). I'd like to be able to continue developing the code using circuitpython, micropython or just python so that will influence microcontroller choice.

I appreciate the 'you are about to make a mistake' information. Not being able to use Feathers means I will have to make design changes. Design changes at this stage are can be easily done. Rethinking the overall design could result in a better project. You never know.

Thanks again.

sv98229
 
Posts: 37
Joined: Thu Jul 03, 2014 11:42 pm

Re: Hallowing Battery Holder Powered

by adafruit_support_mike on Fri Oct 19, 2018 2:55 am

The best way to handle problems is to prevent them if possible. ;-)

Yes, you can use a 5V power brick to power a Feather. You can also connect a 3-AA pack to the Feather's USB jack if you send it through a micro-B plug. Nothing on the board enforces a requirement of 5V at that point, and the major problem of connecting some other voltage to the USB pin is the conflict when you plug in a USB cable. You can't have that problem if you have to unplug the battery pack to make room for a USB cable.

You also have the option to use a JST-PH2 plug on a jumper like this one:

https://www.adafruit.com/product/3814

soldered to USB and GND on the Feather. Putting a diode in the positive line is still a good idea in that case.

There are a bunch of other connector options.. the physical wiring details are a lot more flexible than the electrical requirements.

sv98229 wrote:If powering the Feathers is restricted to foil packaged LiPo batteries

There's no requirement limiting you to foil-pouch LiPos. Metal-can 18650 cells will also work. The electrical requirement is a LiPo with 3.7V nominal voltage and 4.2V full-charge voltage. Physical packaging isn't a concern.

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Re: Hallowing Battery Holder Powered

by sv98229 on Fri Oct 19, 2018 9:02 am

Oh thank you. You made my day.

I can stick with Feathers and just power the equipment with USB power bricks or AA/AAA battery packs through the USB connections. Design changes will be minor and the cost/unit kept reasonable. I like your idea of incorporating a diode. When I build a 'universal' 5.2V power package (

Being able to use circuitpython and low cost are important features of the project. Once I get everything together and working I plan on showing the project to a geophysics professor I have been talking to at the local university. Setting up a class where students can build their own seismic sensor, learn to program it and analyze data is the goal.

Thanks again.

sv98229
 
Posts: 37
Joined: Thu Jul 03, 2014 11:42 pm

Re: Hallowing Battery Holder Powered

by adafruit_support_mike on Sat Oct 20, 2018 12:48 am

Sounds like an interesting project. Feel free to post back if you have other questions!

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Please be positive and constructive with your questions and comments.