# change cell protection value for 18650 from DW01? [closed]

From what I read, the tp4056 with protected circuit can still damage the cell. According to data sheet, VOCP at 4.3v, VODP at 2.4v.

Is there an "easier" way to lower VOCP, 4.1v, AND increase VODP, 3.0v?

TP4056 data sheet

Thx

edit
For your info, i'm not a expert, just a DIY guy.

I think i dont explain correctly.
I need to protect my cell, 18650, from over use, (Overcharge or Overdischarge)

I bought several TP4056+DW01 from Aliexpress. Frankly, no schematic is needed, data sheet is enough?
I read several forum about TP4056 and DW01. Those chip are not perfect.

TP4056, is a OK a charger.

My concern is DW01 and restrict of space for my usage.
DW01 should protect the cell not to Overcharge and Overdischarge.

All I want is to change the cutoff circuit from DW01.

Overcharge detection voltage [VOCP] (V) : 4.250±0.050
Overdischarge detection voltage [VODP] (V) : 2.40±0.100

Here the perfect chip, FS312F-G
Overcharge detection voltage: 4.25±0.025 V
Over discharge detection voltage[VODP]: 2.90±0.08 V

I found a perfect chip for my need, but why should I buy if i could trick the DW01. Could I?

I check the CN305, it seem good, but not easy to find here :(

Till now, i could not find someone that could change the cutoff, probably because it it not possible with DW01 ??? :)

What do you think of this option,
1. Use TP4056 + DW01 + voltage divider for EACH cell
a. TP4056 charge to max 4.263V, good for not to Overcharge
b. DW01 + Voltage divider, i can adjust to cutoff around 3v, good for not to Overdischarge, but my cell stuck with TP4056 permanently.

2. Use TP4056 + FS312F-G (replace DW01)
a. TP4056, as a charger
b. FS312F-G, Cell protection

*thx for good comment or suggestion :)
merci!

## closed as off-topic by Voltage Spike, Enric Blanco, Wesley Lee, Olin Lathrop, winnyMay 31 '17 at 13:52

• This question does not appear to be about electronics design within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

• BTW, i was thinking to add voltage divider, it will work to increase VODP, not "LOWER" VOCP. – CSK May 25 '17 at 6:00
• Draw a schematic or show a picture, ask a specific question and spend some time writing a clear question. – Voltage Spike May 25 '17 at 7:11
• I'm voting to close this question as off-topic because no effort went into writing this question. – Voltage Spike May 25 '17 at 7:12
• @laptop2d I suggest some language revision on your part with emphasis on technical aspects relevant to SE EE. | The question is clear and the requirement concisely and fully stated. Methinks. – Russell McMahon May 25 '17 at 7:51
• CSK - data sheet links are ALWAYS a good idea. Post in plain text if unable to embed properly due to rep and someone will add correct;y. – Russell McMahon May 25 '17 at 8:01

Update: The DW01 can have it's low voltage turnoff voltage increased by use of a divider that presents Vbat x K (K <=1) to the IC.

The divider will increase the overvoltage protection voltage by the same ratio but, as long as the charger is competent the overvoltage protector is less needed.

Operation of the OV protector could be obtained by disabling the divider by shunting the input resistor with a MOSFET which is turned on for Vbat > V_lowvoltage and well prior to Vbat = Vbatmax.

If I wanted flexibility I'd try to use another IC unless there was a compelling reason to use the TP4056.
Is there?

The TP4056 is intended to NOT damage batteries.
Where did you find suggestions that it does? - links useful.

TP4056 datasheet here

V_chg_max is said to be 4.2V +/- 1.5% or 4.137 / 4.2 / 4.263 V min/typ/max.
That disagrees with your 4.3V figure.

I assume that your Vodp = Vtrikl in the above cited datasheet.
This is well above your cited 2.4V.

It sounds like your datasheet is suspect as the ones in the sheet I've referenced sound reasonably standard.
Can you provide a link to the 4056 ds you are quoting?

• Hi, thx for info but my concern is about the dw01 :( – CSK May 27 '17 at 17:46

I don't think there is an easy way. The IC is pretty complicated (3 feedbacks) and adding a resistor divider probably will fail.

If OCP (over current protection) is not critical, you can look at CN305 - you can easily setup the OVP and UVP thresholds.

You could try adding diodes in series in both directions, like this:

simulate this circuit – Schematic created using CircuitLab

This way, when the battery is being charged, TP4056 will see the voltage equal to $V_{BAT}+V_{D1}$ and stop charging when that sum reaches 4.3V So you want a diode which has a forward voltage drop of 0.2V at 100 mA (look for a Shottky or Ge diode)

In a similar way, when the battery is being discharged, TP4056 will see a voltage of $V_{BAT}-V_{D2}$, so the over-discharge protection will kick in when that value drops to 2.4V. This calls for a regular Si diode with about 0.6V of voltage drop (at your load's typical current).

Of course this is a hacky approach that may work for one-off indoors-only prototypes where you can actually measure the voltage drop of the diodes you're going to use, and keep those diodes at the same temperature all the time. Also note that your load will see the voltage of $V_{BAT}-V_{D2}$ as well. If you need something efficient and production-friendly, get a charger IC with programmable thresholds.