Trinket M0 with Adafruit LiIon/LiPoly Backpack

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mrseemoo
 
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Joined: Thu Sep 21, 2017 3:10 am

Trinket M0 with Adafruit LiIon/LiPoly Backpack

Post by mrseemoo »

Hi,

I'm trying to get an Adafruit LiIon/LiPoly backpack to a Trinket M0 connection working, but getting some unexpected behavior.

I connected the following ports:

LiPo Backpack: BAT - Trinket M0 BAT
LiPo Backpack: G - Trinket M0 Gnd
LiPo Backpack: 5V - Trinket M0 USB

I also have a small 3.7V 100mAh LiPo Battery connected to the Backpack. (The backpack does not have a switch attached and is still set to 100mA charging not 500mA)

I let my project run overnight to make sure the battery was empty in the morning. When I plug it in to charge it, (via USB cable to the Trinket M0), both red and green LEDs on LiPo Backpack lite up. This is strange, the documentation for the LiPoBack pack mentions that only the red one should be on while charging. Also, the battery never seems to fully charge or at least I am never getting a solo green light indicating the battery is full. The 100mAh battery should be full after ~2.5h of charging. When I unplug the USB cable, the battery is still dead. When I test it with a multimeter, it reads as 0V.

However, if I connect the battery, (by unplugging it from the backback) to another charger for a few seconds or so, it seems to "remember" that it's actually charged. When testing it with a multimeter again, the correct charged voltage of ~4.2V comes back, which indicates the charge with the backpack actually worked, but the battery didn't "realize" it. I tried this with several different 3.7V batteries and am getting the same behavior.

What am I doing wrong? Did I connect the backpack correctly to the M0? Or is this backpack not compatible with the Trinket M0? What does red AND green lit LEDs mean on the backpack? Or are the batteries not compatible?

Any thoughts would be appreciated, Thanks

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dastels
 
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Re: Trinket M0 with Adafruit LiIon/LiPoly Backpack

Post by dastels »

Examining the schematic https://learn.adafruit.com/assets/19692 you wold think only one of the LEDs could be on, which is the intent. The charger might be faulty with the STAT output oscillating between high & low (effectiively PWMing both LEDs) or it might be floating in between providing enough of a drop across both LEDs to light both. Alternatively one or both of the LED resistors could have an exceptionally low value providing a path between 5v and ground, lighting both LEDs.

Regardless it sounds like a problem somewhere and you don't want to mess around with LiPos and their charging.

Please email [email protected] with a link to this thread, your order number, and request the replacement of one LiPoly/LiIon Backpack.

Dave

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mrseemoo
 
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Re: Trinket M0 with Adafruit LiIon/LiPoly Backpack

Post by mrseemoo »

Thanks dastels for your quick reply.

Unfortunately I'm not advanced enough yet to understand the schematic, but thanks for the explanation.

Following your advice, I set up the same setup with a 2nd Trinket M0 and a 2nd Backpack. And I'm getting the expected (just red led lighting up while charging and green one turning on when done) with the same battery attached. It does seem like the 1st backpack is busted... This never occurred to me, since so far ALL Adafruit products have always been working out of the box... :)

One follow up question:
With the battery attached to the backpack and it attached to the Trinket M0, I should be able to let the battery run out, plug it in to charge (via the Trinket M0), charge it, unplug and it should work again, right? (It also works while charging of course). If everything is working as expected, there is no need to unplug the battery...

Thanks again for your help and happy 4th.

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dastels
 
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Re: Trinket M0 with Adafruit LiIon/LiPoly Backpack

Post by dastels »

Your expectation is correct.

And you're right, Adafruit products usually just work. But now & then something goes wrong during manufacturing, or there's simply a bad part. There's testing, but at times something will slip through.

Dave

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mrseemoo
 
Posts: 25
Joined: Thu Sep 21, 2017 3:10 am

Re: Trinket M0 with Adafruit LiIon/LiPoly Backpack

Post by mrseemoo »

Thanks again Dave.

Oh, I totally understand... Nothing is 100%... But Adafruit is darn close to it... ;)

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