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Thread: weird behaviour with the LiPo battery charger add-on

  1. #1

    weird behaviour with the LiPo battery charger add-on

    Hello,

    I recently bought the LiPo battery charger add-on from Pesky products but I am not 100% satisfied and I would like your opinion/advice.
    Everything is fine when the microswitch is on: The battery charges if the board is connected to USB and its powers the board if the USB cable is unplugged.
    But when I try to switch the board off while connected to USB I am getting a strange error message "USB Accessories Disabled; Unplug the accessory using too much power to re-enable USB devices" (macbook), as if there was a short circuit... Can it damage my Teensy somehow ? What's the worse that can happen ?

    I have to say also that I haven't been able to fully charge the battery (supposedly the green led turns red). After a couple of hours the tension indeed reach a plateau around 4.1V (which is what is expected for a battery rated at 3.7V nominal). I stopped because I didn't want to damage the battery but it is a bit annoying if I always have to use a multimeter and cannot rely on the the led to tell me it's done... Not to mention potential damage to the battery, fire, explosions, zombi apocalypse...

    Cheers !

    PS: I am using a 3.7V 104 mAh LiPoly and a Teensy3.2

  2. #2
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    Quote Originally Posted by MattH View Post
    Hello,

    I recently bought the LiPo battery charger add-on from Pesky products but I am not 100% satisfied and I would like your opinion/advice.
    Everything is fine when the microswitch is on: The battery charges if the board is connected to USB and its powers the board if the USB cable is unplugged.
    But when I try to switch the board off while connected to USB I am getting a strange error message "USB Accessories Disabled; Unplug the accessory using too much power to re-enable USB devices" (macbook), as if there was a short circuit... Can it damage my Teensy somehow ? What's the worse that can happen ?

    I have to say also that I haven't been able to fully charge the battery (supposedly the green led turns red). After a couple of hours the tension indeed reach a plateau around 4.1V (which is what is expected for a battery rated at 3.7V nominal). I stopped because I didn't want to damage the battery but it is a bit annoying if I always have to use a multimeter and cannot rely on the the led to tell me it's done... Not to mention potential damage to the battery, fire, explosions, zombi apocalypse...

    Cheers !

    PS: I am using a 3.7V 104 mAh LiPoly and a Teensy3.2
    did you cut the trace on the teensy?

  3. #3
    Yes I did.

    By the way there are three rectangular pads (a big one close to the centre and two small ones between the big one and Vin through hole). Do you separate all three pads (cutting 2 strips) or do you just cut the outermost pad off ?

    I did not use any extra diode. Is that a requirement even if I am using the charger add-on ?

    Cheers.

  4. #4
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    Quote Originally Posted by MattH View Post
    Yes I did.

    By the way there are three rectangular pads (a big one close to the centre and two small ones between the big one and Vin through hole). Do you separate all three pads (cutting 2 strips) or do you just cut the outermost pad off ?

    I did not use any extra diode. Is that a requirement even if I am using the charger add-on ?

    Cheers.
    only one cut (between the two smaller pins close to Vin), diode not necessary.
    The bigger one are USB pins
    I could not find a schematic of Onehorse (Persky) Lipo charger, so you should drop him an e-mail.

  5. #5
    There it is:

    Click image for larger version. 

Name:	2014-08-21T01-54-49.161Z-LiPoSchema.jpg 
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    The green led does not turn red. there are two different diodes however I should have seen the red one during charging.
    I fully charged a LiPoly then looked at the discharge with a multimeter (that's how I know the add on charges the battery with USB power then powers the board when USB is disconnected).

    Why do I get this strange message on my computer then when I switch the board off ?

  6. #6
    Am I reading the schematics wrong ? If you turn the switch in position P$3 doesn't it create a short circuit ? Because it's connected to the GND and JP2 to +3.3V

    I think there is another mistake with the JST connector the + is connected to GND and the - is connected to the BAT pin of MAX1555

  7. #7
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    Quote Originally Posted by MattH View Post
    Am I reading the schematics wrong ? If you turn the switch in position P$3 doesn't it create a short circuit ? Because it's connected to the GND and JP2 to +3.3V

    I think there is another mistake with the JST connector the + is connected to GND and the - is connected to the BAT pin of MAX1555
    I saw the 'short' in the circuit. As I do not have the HW, I gave up to think about it.

  8. #8
    FYI this is the answer I got from "horsey":
    onehorse
    The switch connect VIN to either VBAT or GND IIRC.
    The foorprint for the JST connector has a + mark that doesn;t represent polarity. Not sure why this was put there.
    So it is a short... but why would one do that ?

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