Increasing Overdischarge Protection Voltage on a DW01A-G IC

Projects
1

Hi

I am working on a academic project which requires DW01A-G. Looking at the datasheet here:
http://www.ic-fortune.com/upload/Download/DW01x-DS-17_EN_53550.pdf

How do i increase the Overdischarge Protection Voltage (VODP) to 3.2V. The datasheet mentions it is typically 2.4V.
Can this be done by increasing the resistor value R2. (shown in the typical application circuit)

Please guide.

Thanks
S

2

Use a IC rated for your cell voltages. (R2 does not influence the under discharge protection voltage. At least not according to the note below the schematic you reference)

An example of chips that have a larger range of possible voltages: http://www.ti.com/lit/ds/slusbu9d/slusbu9d.pdf

Also 3.2V is quite high for under discharge voltage. What cell chemistry are you using in your application?

3

I am using a 1S LiPo 500mAh and i would ideally like to keep it at 3.2v since most of the LiPos which i get here are cheap clones.

4

This does not really tell you/me what the cell chemistry is. (The cell chemistry determines what the cell is capable of doing.)

Why do you think keeping it at a higher minimum voltage is necessary for cheap clones?

5

The project is basically a UWB tag which is used for 2D trilateration / localization. I am trying to put the charging circuit directly into the tag. My circuit draws less than 200mA. I am combining this circuit with a TP4056 (W. battery protect DW01A) to have the circuit shutdown when the battery voltage is less than 3.2V.

I have drained the batteries below 3.2v before (2.8V) and it seems that the ones which i currently have does not seem to recuperate back even after charging. This is the reason i want to keep the cut-off voltage at 3.2V.

I am not sure if this answers your question on cell chemistry.

6

Your source of cells must give you the following information about the cells:

  • nominal capacity
  • end of discharge voltage
    (This is the voltage where your protector should turn off)
  • end of charge voltage
    (This is the other voltage where your protector should turn off)
  • temperature range for charge and discharge
    (Ideally your protecting circuit has the means to turn off when outside this range)

If they don’t list the above data, get your cells someplace else! (These are safety critical informations. Operating lithium cells without this information can be dangerous.)

I would suggest you check your cells if they are any good when you get them. They should have nearly the nominal capacity when new. (If they have lower than 80% of the nominal capacity throw them away.)

Also measure the internal resistance over the full charging/discharging range. It should never exceed a few milli ohm.
(When full it should be close to the internal resistance given in the datasheet of your cells. This might not be given in there.)

Make sure you operate within the allowed temperature range. (Remember the charging temperature range is smaller than the discharging range.)

A good paper about cell ageing: http://www.sciencedirect.com/science/article/pii/S0378775305000832

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