I am using the DW01 in one of those tp4056 & DW01 lithium-ion charging and protection boards. I was trying to figure how much current I can pull until the protection trips/ One small problem the values make no sense.

the first 4 entries in the table make sense but what does the over current voltage mean. can I calculate the actual current I can pull until it trips? If not can I increase the current to power bigger things?


closed as unclear what you're asking by Marcus Müller, RoyC, Sparky256, Voltage Spike, PeterJ Jan 24 '18 at 14:08

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    \$\begingroup\$ Welcome to EE.SE. Please put enough of extract of the link into your question that it can make sense when the link dies so that it remains useful in the future. You're missing some punctuation and capitalisation all of which help with legibility and credibility. \$\endgroup\$ – Transistor Jan 21 '18 at 18:17
  • \$\begingroup\$ What @Transistor said already happened: I can't access your screenshot. so. Your question is not understandable, because it's missing the core image. VTC as unclear. \$\endgroup\$ – Marcus Müller Jan 21 '18 at 19:07

It's not a straight forward value. the voltage across the dw01 CS sense resistor R2, typically 1k ohm determines when the over current triggers. The voltage at CS rises based on the current draw through the battery internal resistance and the control mosfet chosen. Basically the ground voltage at CS will rise as the current increases. See the datasheet for these two sections:

Overcurrent Protection
In normal mode, the DW01-P continuously monitors the discharge current by sensing the voltage of CS pin. If the voltage of CS pin exceeds the overcurrent protection voltage (VOIP) beyond the overcurrent delay time (TOI1) period, the overcurrent protection circuit operates and discharging is inhibited by turning off the discharge control MOSFET. The overcurrent condition returns to the normal mode when the load is released or the impedance between BATT+ and BATT- is larger than 500kΩ. The DW01-P provides two overcurrent detection levels (0.15V and 1.35V) with two overcurrent delay time (TOI1 and TOI2) corresponding to each overcurrent detection level.


Selection of External Control MOSFET

Because the overcurrent protection voltage is preset, the threshold current for overcurrent detection is determined by the turn-on resistance of the charge and discharge control MOSFETs. The turn-on resistance of the external control MOSFETs can be determined by the equation: RON=VOIP/ (2 x IT) (IT is the overcurrent threshold current). For example, if the overcurrent threshold current IT is designed to be 3A, the turn-on resistance of the external control MOSFET must be 25mΩ. Be aware that turn-on resistance of the MOSFET changes with temperature variation due to heat dissipation. It changes with the voltage between gate and source as well. (Turn-on resistance of MOSFET increases as the voltage between gate and source decreases). As the turn-on resistance of the external MOSFET changes, the design of the overcurrent threshold current changes accordingly.

So it depends entirely on the mosfet chosen and the target current of the boards designer. You could test by measure the mosfets RON or by testing the board with various current loads. Or if your so lucky as to have the mosfet part numbers, look up it's datasheet.

  • \$\begingroup\$ even then it shuts down when providing about 8 w of power (3.7ish v boosted to 12v drawing 400ma) \$\endgroup\$ – 9291Sam Jan 21 '18 at 18:28
  • \$\begingroup\$ So would a current shunt at .1 ohm be reasonable? \$\endgroup\$ – 9291Sam Jan 21 '18 at 18:31
  • \$\begingroup\$ The sense resistor is used for a comparator. I'm going to delete this answer while I fix it. \$\endgroup\$ – Passerby Jan 21 '18 at 18:35
  • \$\begingroup\$ @9291sam fixed it. \$\endgroup\$ – Passerby Jan 21 '18 at 18:47
  • \$\begingroup\$ So How could I increase the over current to something closer to 5a instead of 1.5 \$\endgroup\$ – 9291Sam Jan 21 '18 at 20:01

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