0

I'm charging a 3.7V li-ion with a TP4056. The load (approximately 20mA) is connected in parallel with the li-ion. If I disconnect the battery while the TP4056 is receiving 5V on its input, I hear a buzzing sound. Once I reconnect the battery it dissappears.

Any idea what this could be?

enter image description here

MP2315 is stepping down a 12V battery to 5V. I also tried disconnecting R1 from 5V and injecting 5V from my RD6006. Same buzzing. Output with no battery: 40mVAC (an buzzes a lot), 1 battery: 60mVAC (still some buzzing), 2 batteries: 2.5mVAC (next to no buzz). Load is always 20mA (MCU + other things). Seems the TP4056 is more happy with more load. Scope of BAT+ at various battery loads is attached. Strangely enough, the 2 batteries have some bad spikes here and there, but less audible noisy. (The frequencies measured on the scope varies greatly from shot to shot.)

No battery:

No battery

1 battery:

1 battery

2 batteries:

2 batteries

okwestern
  • 39
  • 2
  • What is your 5V supply? What exactly is the load you have connected? Can you provide an oscilloscope trace of input and output, or provide the actual DC and AC voltages at those points? – PStechPaul Mar 13 '23 at 01:32
  • @PStechPaul. I updated the description with measurements and scope images. – okwestern Mar 13 '23 at 11:52
  • Do I understand you correctly that in addition to the battery you have a load connected to the battery line, and sometimes you do not have the battery connected? – Math Keeps Me Busy Mar 13 '23 at 13:05
  • Yes.But I will redesign and not draw directly from the battery line:

    https://electronics.stackexchange.com/questions/411283/tp4056-and-li-ion-battery-charging-that-never-ends

    The battery will never be removed. Sleep, charge enable, etc will be software controlled. But I'm trying to simulate what happens when the battery life is completely worn out, ie. won't accept charge. In that case, the battery will be equivalent to a very tiny load (and that's when the buzzing starts). The audible buzzing doesn't worry me, but I am concerned it's not good in the long run (battery or ic).

     – okwestern Mar 13 '23 at 18:46
  • Can you change the sensitivity and timebase on the scope, to see the size, shape, and frequency of the waveform? And approximately what frequency is the buzzing? And how does the Vcc supply look? – PStechPaul Mar 13 '23 at 22:17

0 Answers0