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Charging LiPo On Feather Huzzah
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Please be positive and constructive with your questions and comments.

Charging LiPo On Feather Huzzah

by doylep on Mon Oct 10, 2016 3:44 pm

Hi all,

I have built a LiPo battery-powered Feather Huzzah into a couple of our escape room props, and am looking for an easier way to charge them (rather then disassembling the prop and plugging in the micro USB). Thinking I was clever, I connected a 5V power supply to the GND and USB pins on the Huzzah, only to realize (with a pop and smoke accompanied by my horror) that I had burned our our favorite prop.

Luckily, it's only Monday and I've ordered a replacement next-day shipping, but I still haven't solved my original problem: How should I charge the battery? The power to the Feather is switched, so in a perfect world I would I would just charge the battery without needing to turn on (or run power through) the Feather. That said, I'm not very familiar with battery charging circuits, and I don't want to add "burned out battery" to my list of accomplishments for today.

Any help is appreciated. I can always just unscrew the prop and plug in the USB.
Patton

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Mon Oct 10, 2016 4:59 pm

Thinking I was clever, I connected a 5V power supply to the GND and USB pins on the Huzzah, only to realize (with a pop and smoke accompanied by my horror) that I had burned our our favorite prop.

Was it a regulated 5v supply? Did you verify the polarity before connecting? The GND and USB pins are directly connected to the USB GND and 5v. But there is no reverse polarity protection.

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Re: Charging LiPo On Feather Huzzah

by doylep on Mon Oct 10, 2016 5:04 pm

Yeah, I used the Adafruit 10A supply (https://www.adafruit.com/products/658) and tested output at 5.2 Volts. I will reexamine my setup before heading home and see if I missed something.

Anyway, this setup should work? Maybe I got solder on the board or there was a short somewhere.

Thanks for your quick reply,
Patton

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Re: Charging LiPo On Feather Huzzah

by doylep on Mon Oct 10, 2016 5:09 pm

No, everything seems to be in order. I tested briefly with a second prop (same setup) and the board turns on but then the processor quickly becomes hot to the touch. Removing the voltage immediately seemed to prevent any lasting damage.

Let me know if you can get it to work - it's possible (nay, likely) that I made the same mistake twice.
Patton

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Re: Charging LiPo On Feather Huzzah

by micglin on Mon Oct 10, 2016 8:05 pm

doylep wrote:Yeah, I used the Adafruit 10A supply (https://www.adafruit.com/products/658) and tested output at 5.2 Volts.
Patton


I'm curious why you're using a 10A power supply to run a Feather. Does the rest of your prop require the additional current?

Given that the USB socket is wired to the USB and GROUND pins on the board, and USB power supplies often put out 5.2V too (to prevent against voltage drop), that shouldn't cause an issue. You did confirm that you don't have the polarity backwards as was asked, right?

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Mon Oct 10, 2016 8:15 pm

As the schematic shows, the USB pin is the same as the USB 5v pin. Both feed into a 3.3v regulator, so it is hard to understand how a correctly connected 5v - or even 5.2v source would cause overheating of the processor when a USB connection would not.
https://cdn-learn.adafruit.com/assets/a ... 1458433763

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Re: Charging LiPo On Feather Huzzah

by doylep on Tue Oct 11, 2016 11:08 am

Okay, thanks for your help. I will reexamine my setup this morning and send a picture if I can't figure out the error.

Patton

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Re: Charging LiPo On Feather Huzzah

by doylep on Fri Oct 14, 2016 10:57 am

For anyone checking on this thread in the future:

After quite a bit of testing with an ohmmeter, I determined that the voltage from my power supply (~5.2V) is just barely too high for the Feather on-board regulator. A small resistor (1-5 ohms) is enough to bring the voltage down and keep the board from frying. But putting a resistor in series with the voltage source seemed risky to me (as the voltage would not be a constant for the board), so I opted to directly expose the battery leads to the outside of the prop.

Here's how my setup works now:
Switch on: LiPo battery => Feather
Switch off: External leads => LiPo battery

This setup isn't dummy proof: if someone on staff plugs in a 5V source to the prop (rather than a LiPo charger: https://www.adafruit.com/products/1304), we might get a huge conflagration. Unfortunately, our 5V sources have the same plug, which is asking for trouble. But with big signs on the plug and the device to warn staff, at least we no longer have to worry about burning up the Feather.

Thanks again to Bill for his help!
Patton

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Fri Oct 14, 2016 11:07 am

I determined that the voltage from my power supply (~5.2V) is just barely too high for the Feather on-board regulator.

Interesting. What other circuitry (if any) do you have connected to the Feather? They are designed to run on up to a 5v source. I would not expect 5.2v to be an issue for a 'bare' Feather. But any additional 3.3v circuitry would increase the load on the regulator.

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Re: Charging LiPo On Feather Huzzah

by doylep on Fri Oct 14, 2016 2:14 pm

On one prop, we have a small neopixel ring powered from the BAT pin of the Feather. On the other prop, the only attached device is a button that ties pin 12 to ground. Both devices overheated when attached to the 5.2V source.

Interestingly, an ammeter provided sufficient resistance when in series with the 5.2V supply. In other words,
5.2V => Ammeter => USB Pin of Feather
worked just fine. I chalked it up to the small internal resistance of the ammeter (and confirmed with small resistors that a small resistance would work), but maybe something else is going on with the ammeter.

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Fri Oct 14, 2016 2:27 pm

Thanks for the info. I'll have to check out the current draw of the Huzzah. Sounds like it may be running closer to the limit than some of the other Feathers.

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Re: Charging LiPo On Feather Huzzah

by mrSidX on Tue Dec 06, 2016 4:33 pm

I'd like to take a moment to report on my situation, as I've looked all over and this is the closest thread that I believe would relate to:

I'm just trying to determine what happened with my own Huzzah after connecting 3.7 lipo battery.
I got a Huzzah Feather, with neopixels connected, and would run fine from a usb output from computer, regulator normal luke warm temp.

When things went awry is when I connected a 3.7 lipo-battery to the mix, the board would power on normally ,but then noticed a slight puff of smoke coming from within the unit.
All wiring was good, nothing external like USB was plugged in at the time.

I haven't read anywhere needing to resist the power of a 3.7 battery, as the regulator can handle upward of 5v when powered via USB? Why the burning sensations?! lol

Just trying to figure that out before I attempt again burn it all out.

Thanks for any feedback to the related post.

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Tue Dec 06, 2016 5:47 pm

That is unusual. Are there any visible signs of something having burnt? Does the battery charge and operate normally otherwise?

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Re: Charging LiPo On Feather Huzzah

by mrSidX on Tue Dec 06, 2016 6:28 pm

Well this particular config with the Huzzah feather and the neopixel feather board, they are hard soldered together with the pins, not using the female jumper pins, to minimize form factor height, all soldering points look clean and proper,

so long story short: I can't see without desoldering and looking on top of the Huzzah.
:(

but:

After looking at the insides with an otoscope, I can see a small IC: KDvv4?? Can't really read it. Obvious signs of burn.

I managed to grab a decent photo of the burn marks on that IC.

Thanks for your speedy reply, Hope this img helps ...

:(
Attachments
IMG_1640.JPG
IMG_1640.JPG (728.23 KiB) Viewed 1965 times

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Re: Charging LiPo On Feather Huzzah

by adafruit_support_bill on Tue Dec 06, 2016 9:18 pm

That looks like the MCP73831 charge controller. Looks like it got pretty well toasted. If you contact support@adafruit.com with a link to this thread we can replace the Feather.

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Please be positive and constructive with your questions and comments.