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I have a hardware that is powered by a standard polymer battery (http://www.ebay.com/itm/3-7V-Polymer-Rechargeable-Battery-2000mAh-PCM-103450-for-GPS-ipod-Tablet-PC-MP3-/262605237924).

The hardware draws a lot of current, more than 3A, perhaps up to 5A. This triggers the overcurrent protection of this battery. The protection circuitry includes two SOT23-6L (http://www.phaselink.com/QA/SOT23-6L.pdf) ICs:

enter image description here

As replied on this question (Over current protection for a 1-cell battery), the overcurrent protection is probably set up for 3A (25mohm ron of mosfets).

I would like to "decrease" the overcurrent protection up to 5A without losing the overdischarge protection. My options are:

  • either replacing the dual mosfets. But I can't find any SOT23-6L with Ron=10mohm. 25mohm seems to be the minimum.

  • or shorten M1 to disable the overcurrent protection. But I think it will disable the overdischarge detection voltage.

How can I fix my problem?

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  • \$\begingroup\$ it is possible to reduce RdsOn but also possible to create a new problem with T['C] rise in the battery due to increased Pd=I^2ESR in the battery ( * Rth thermal resistance), where ESR rises with age, %DoD and inverse with Ah capacity \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 3 '16 at 20:46
  • \$\begingroup\$ diodes.com/_files/datasheets/DMN1019USN.pdf \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 3 '16 at 21:01
  • \$\begingroup\$ +1 for excellent documentation and clear problem formulation. \$\endgroup\$ – Ale..chenski Dec 3 '16 at 21:02
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    \$\begingroup\$ Are you sure it is safe to draw 5A from that battery? Is it just a short-term burst? \$\endgroup\$ – mkeith Dec 3 '16 at 21:10
  • \$\begingroup\$ @mkeith 100ms burst from time to time. \$\endgroup\$ – gregoiregentil Dec 3 '16 at 21:12
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The circuit looks for voltage drop across two power mosfets. It looks like the sensing circuit is between CS pin and GND pin.

Instead of looking for MOSFETs with lower Rdon, you can make a divider, splitting the R2 in two resistors, and connect the CS pin to the middle of the divider. The voltage between CS and GND will drop, IC will think that the current is small, and will trigger the overcurrent threshold at higher drop-through voltage.

Just try to connect another 1k resistor between CS and GND, and see if the cell will deliver more current before cut-off.

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  • \$\begingroup\$ I am studying the DW01-P so I come to this post. This is an old post but I still want to comment to help other people if they come to here like me in the future. I believe changing R2 cannot change the overcurrent threshold, because the datasheet said it is used for: "latch-up protection when charger is connected under overdischarge condition and overstress protection at reverse connecting of a charger." Also the R2 is connected in series to the negative input of a comparator in the block diagram, changing its value will not change the sensed voltage at the comparator. \$\endgroup\$ – eepty Sep 18 '18 at 18:25
  • \$\begingroup\$ @eepty, you misunderstood. I am not suggesting to "change R2", I am suggesting to make a voltage divider on CS pin, since "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 ...". According to block diagram, all thresholds are relative to GND pin. Therefore a voltage divider on CS pin will shift all thresholds, including overcurrent threshold into desired direction. \$\endgroup\$ – Ale..chenski Sep 18 '18 at 21:26
  • \$\begingroup\$ i tried connecting 1k resistor between CS and GND pin making a voltage divider as you suggested. and now i am able to draw more current but it has also disturb other feature which are controlled by CS pin like short circuit and also charger detector. \$\endgroup\$ – abdulsamad Jan 13 at 16:26

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