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Thread: How to use an Adafruit LiPoly/LiIon Backpack Charger with a Teensy

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    How to use an Adafruit LiPoly/LiIon Backpack Charger with a Teensy

    Hi!

    I used an Adafruit LiPoly/LiIon Backpack Charger with a Teensy 3.1, and made a little How-To as I though it could be useful for someone.

    Let me know if you have any comments or questions!


    How to use an Adafruit LiPoly/LiIon Backpack Charger with a Teensy

  2. #2
    Senior Member onehorse's Avatar
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    Adafruit makes excellent products (I use many myself) and I would encourage anyone who needs the specific attributes of this LiPo backpack charger to use it. musinou's how-to should make it easier. Did I miss the picture of your set-up?

    Thanks for the link to my Teensy-specific LiPo battery charger on Tindie. Since the topic is LiPo chargers, I hope it is not off-base to mention that this improved LiPo charger will soon also be made available. This one offers up to a 800 mA charge rate, which some applications need.

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    Great onehorse! Let us know when it is ready! I will put a link to it.

    You are right about pictures, I will put some up soon.
    Last edited by musinou; 08-14-2015 at 03:50 PM.

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    Senior Member onehorse's Avatar
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    OK, I put one of the new LiPo battery chargers together tonight and I am happy to report it works as expected.

    I did make a trace error so the green "VIN is on" led is on all the time, which is wrong. It should be on only when the switch is supplying battery power to VIN. Doesn't affect the charging function though.

    I am having more (corrected) boards made so they won't be at Tindie for another two weeks. If anyone needs one sooner and doesn't mind a non-functional Teensy power on led, I will be happy to make to order these.

    The charger seems to charge very fast at 500 mA current, which is the default. This is five times the current supplied by the old (and still available) LiPo charger using the MAX1555. I will perform some timing tests tomorrow on a standard 350 mAH one cell LiPo battery and report how long it takes to charge at various rates. 300, 500, and 800 mA are available on the board at the cost of closing or opening a solder jumper.

    I chose a red led for charging, a green led for VIN has power or Teensy is powered, as usual, but I have a choice of either yellow or blue for USB power present or power good. Any general preference?

    This is a rather silly indicator for many applications since when the user plugs the USB into the Teensy, she knows the power is on. But the chip also makes sure the power is "good", meaning if it is out of the expected range, noisy, or just not there, the light will not be on. Maybe blue would be best since yellow connotes caution, whereas the opposite is intended with the light on.

    Pictures and timing results tomorrow...

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    Nice!

    I agree, not yellow, blue, purple or white, but blue is probably better. But maybe faint? I have a blue LED indicating standby mode on some devices and they are lighter than the moon at night.

    If the power is not "good", as a user I would expect the LED to do something when plug-in, maybe flashing quickly, but not only not turning on, as that would mean, for me, that their is no power at all.

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    Senior Member onehorse's Avatar
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    I still don't have pictures but I have some timing results.

    I first drained the 350 mAH one cell LiPo by connecting it to a power hungry clock/display apparatus I built. The new STBC08 LiPo charger set at the default 500 mA current completed the charge cycle in exactly 75 minutes, or about 4.7 mA per minute.

    I repeated the experiment with the original LiPo charger that uses the MAX1555 and after 375 minutes, it is still charging. The MAX1555 charges at a rate of 100 mA current from the USB so I am expecting it will complete soon, but the advantages of the new LiPo charger should be obvious.

    Having worked with the STBC08 charger a little I am beginning to like the yellow power good light, since it makes a pleasant orange glow when charging, as the red and yellow lights are fairly close. I might just leave it, but use a 2K2 resistor on the red, which is very bright.

  7. #7
    Onehorse,
    I've bought your MAX1555 powered board and like the product.
    But I've got a power hungry GPS project with a 1800mAH battery.
    Charging this takes forever
    When can I order the new STBC08 design?

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    Senior Member onehorse's Avatar
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    Pretty soon now, just waiting for the corrected boards from OSH Park. I expect to have the new chargers available for sale ($12.95) at Tindie this weekend. I can sell you one I could assemble now but the power-on green led is always on due to a trace error I had to correct. I tested the charging rate at the 800 mA maximum and was able to fully charge a depleted 350 mAH LiPo battery in 48 minutes. Based on this, your battery would take about 4 hours to charge.

  9. #9
    Great!
    I don't mind to receive 1 "broken" unit for my test unit, but I need 3 correct working ones. (promised some units )

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    Senior Member onehorse's Avatar
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    Expected delivery of the boards is Saturday, which means I will have them on the Tindie site by Sunday.

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    Senior Member mortonkopf's Avatar
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    looking forward to playing with these. Great stuff onehorse.

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  13. #13
    Senior Member onehorse's Avatar
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    yes you may order now if you would like to. (ten words!)

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    Thanks One Horse, I see it's on its way here by Thursday. I'm looking forward to the goodies.

    Kb

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    Senior Member onehorse's Avatar
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    My pleasure; I'm down to just two left until I get the next board increment from OSH Park.

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    Quote Originally Posted by onehorse View Post
    Adafruit makes excellent products (I use many myself) and I would encourage anyone who needs the specific attributes of this LiPo backpack charger to use it. musinou's how-to should make it easier. Did I miss the picture of your set-up?

    Thanks for the link to my Teensy-specific LiPo battery charger on Tindie. Since the topic is LiPo chargers, I hope it is not off-base to mention that this improved LiPo charger will soon also be made available. This one offers up to a 800 mA charge rate, which some applications need.

    404 on that OSH Park link.

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