Adjustable Lipo Charger PRT-14380 Charging current

Components & Accessories Power
1

Hi,

I’ve recently acquired one Adjustable Lipo Charger PRT-14380 from one of your retailers.

After trying to charge a 800 mAh lipo (just in case, the lipo health was good) at 300 mAh which took more than 12h (disconnect before charge ends, and only 0.2-0.3 V raised), i’ve devided to make some tests.

Stuff used :

  • - A 5V / 2A usb power supply
  • - A Voltcraft DMM
  • - Some wires and alligator clips
    • This stuff works well.

    I tried with different li-ion battery :

  • - 50 mAh lipo discharged
  • - LIR2450 coin cell (200 mAh)
  • - 800 mAh lipo 60% charged (~3.75V)
  • - 900 mAh lipo 90% charged (~4.1V)
  • - 1200 mAh 18650 cell discharged
  • - 3200 mAh 18650 cell half charged (~3.50V)
  • - 3500 mAh lipo battery without protection circuit, half charged (~3.55V)

    • All listed batteries - but the 50 mAh Lipo & the coin cell - can handle at least 500 mAh charging current (tested with another charger).

    For each battery, I’ve tested all the presets switches (except for the smallest ones).

    With the 100 mAh switch, charging current was about 16 mAh, according to the DMM.

    With the 200, 300, 400 and 500 mAh switches, it was about 7 mAh.

    With a 68k Ohms resistor and the PTH switch, I got about 14 mAh, which is - according to the ~15 mAh theorical minimal current - fairly good, but I think it’s much more a coincidence.

    First, I thought it was the termination current, but most of the batteries were only half charged, or empty, so I’m pretty sure it wasn’t.

    Second, I thought it was preconditioning, but after 15 minutes of charge and same current, it wasn’t.

    One important thing is that I let the LIR2450 coin cell charging totally (PTH switch, 68k resistor). It took time, but it was ok.

    Same for the 50 mAh lipo.

    So, for sure it can charge a battery, but current is wrong.

    I’ve also tried :

  • - Using a 50 kOhms resistor, charging current is ~15 mAh (vs. 20 mAh theory)
  • - Using a 20 kOhms, ~14 mAh (vs. 50 mAh theory)

    • Also, I’ve noticed that :

  • - If PTH resistor is between 10k and 67 kOmh, charging current can be any value between 13 and 17 mAh, but it's not linear to the resistor value.
  • - Any PTH resistor smaller than 10k Ohms lead to a 6 to 8 mAh charging current, alike with regular 200-300-400-500 DIP switches.

    • I can’t figure out what’s wrong.

    I’m pretty sure I didn’t short-circuited or damaged anything.

    I’m charging only one battery at a time, and only one switch is ON.

    No strange smell while using it, and resistors didn’t heat. Nothing looks strange when looking at the circuit board.

    Supply voltage is good, charger output voltage seems to be acceptable too (~4.31V with no load), and when I’ve plugged a battery, the blue led turned ON and the battery started charging.

    Of course when a full (4.2V) battery was plugged, the blue led stayed OFF.

    So, the behaviour seems to be normal.

    Could it be a circuit fault ? Or anything else I’ve missed ?

    I’ve mailed the retailers but no answer.

    I’m not hardly looking for a guarantee, but I wanna know if it’s more a bad use or a factory default.

    Best regards,

    Christophe

    2

    Hi Christophe, it sounds like a defective board, just let the retailer you purchased know it’s defective and we are authorizing a replacement and they will get you a new one. :slight_smile:

    You can use this forum post as proof if needed.

    3

    Hi

    Thanks you, I’ll mail the retailer with this thread link.

    Have a good day,

    Christophe