1

After having burned a small hole in my finger, I'm trying to figure out why exactly the Micro-Lipo charger heated up instantly.

I am using the Adafruit Micro-Lipo charger

which has the following specs:

3.7V/4.2V LiPoly/LiIon 100mA charge rate default Short jumper for 500mA

I had connected a 3.7V 1200mAh battery to the terminals where the entire board heated up instantly. The battery is an uxcell 603450.

Was this because the mAh rating on the battery was way too high? There was no power source connected to the MicroUSB port on the charger.

If it is the size of the battery, how do I calculate what size charger I need in order to charge 3 of the 3.7V 1200mAh batteries wired in a series?

VBwhatnow
  • 602
  • 5
  • 15
Brian
  • 13
  • 5
  • Do you have a datasheet or part number for the cells you were using? Did the charger overheat and let the smoke out? or did it just heat up? – VBwhatnow Feb 25 '19 at 17:54
  • @VBwhatnow Added in a link to the battery I'm using. the charger went from regular room temperature to too hot to touch in a split second; I was mistakenly holding it. It hadn't started smoking yet, but there was a burning smell. The battery was on there for about 20 seconds before I found some pliers to disconnect it. – Brian Feb 25 '19 at 18:00
  • Are you certain that the red and black wires were the right way round? – Finbarr Feb 25 '19 at 18:22
  • @Finbarr Yes, as given the male and female receivers, there's only one way. – Brian Feb 25 '19 at 18:37
  • 1
    "If you are soldering on a JST cable or using a non-Adafruit battery check the polarity of the wires going into the battery port. A backwards battery can destroy the charger!" As you're using a non-Adafruit battery, did you actually check or just assume it must be right? – Finbarr Feb 25 '19 at 19:11
  • Don't buy ebay crap that doesn't even have reverse polarity protection. Anyway, a cheap multimeter would have saved your thumb. – Lundin Feb 26 '19 at 10:30
  • 1
    You should probably re-think the whole project - you **cannot** use these to charge series connected cells as you state as your goal. Nor can you use three of them, unless their power sources are fully isolated (and even that would be a very bad idea) – Chris Stratton Feb 26 '19 at 16:20
  • @Lundin Is there a way to know if there is reverse polarity protection on it? – Brian Feb 27 '19 at 15:16
  • @ChrisStratton What would be a better way to charge a series of connected cells? The reason I had chosen this is I need a total of about 12V to power an LED strip, while getting the longest amount of life possible from them. – Brian Feb 27 '19 at 15:18
  • @Brian Most commonly there's a P channel MOSFET with a diode built-in, battery voltage to drain and battery ground to the gate, optionally through a big resistor. Check this: https://electronics.stackexchange.com/questions/82692/reverse-polarity-protection-pmos-vs-schottkey-diode. Cheap ebay crap won't even have the simple schottky solution. – Lundin Feb 27 '19 at 15:45
  • Oh and Chris is right, this MPC7381T is a single cell charger IC. To charge 3 cells you need a BMS capable circuit. – Lundin Feb 27 '19 at 15:55
  • @Lundin Thank you, I'll have to do some reading up on this, at this point all of this might as well be in Latin for me... – Brian Feb 27 '19 at 18:15

1 Answers1

2

Given the Keying of the connector on the battery and the keying of the connector of the Adafruit Micro-Lipo charge; Finbar is probably right, you appear to have connected the battery with the wrong polarity.

enter image description here

enter image description here

VBwhatnow
  • 602
  • 5
  • 15