TP4056 question

Sort of off topic, but I can't think of a better forum to ask this question.

I've been using the more recent TP4056 based circuit boardswith power out terminals as a smallUPS for my WiFi-router.





That kind.

The problem is that it will not give away any power on the load terminalswhen connecting a battery until it get a small current on the input terminals. So if I just connect a battery and a load nothing will happen. My guess is a MOSFET switch. Is there some way I can hack the circuit so it will pick up this small current from the battery and then disconnect? Or is there some alternative to the circuit I use that indeed will work out of the box the way I want it to?

If you're sitting on a bunch of these circuits, it would be really cool if you can see if they act as mine does or not. If they do work as I wish mine did,could you please let me know where you bought them?

:heart:

(BTW, I use a DC/DC buck set to 3.9V to feed the TP4056 to keep the cell charged at 3.8V so I don't kill it.)

You probably could use an NPN, you probably wouldn't need a MOSFET. I'm not sure of the circuit design, but connecting the NPN with a resistor and what not, you could use the power from the battery to trigger the switch, and once there's power on the load side, it disconnects the switch. Maybe would need 2 NPN's to keep it balanced right.

But that's my un-electricaly-educated guess


On a side note, I did order a bunch of these units. I will have to test them out when they get in to see how the exhibit this type of behavior.

If you cannot draw power from the OUT terminals with a battery connected there is something wrong. Either the wires aren't making contact or the circuit is defective.
The board is designed to be an embedded charger and also power the device via the battery, regardless of whether or not you are charging.

BAT+ and OUT+ are always connected
BAT- and OUT- are connected when a battery is present.
You should always have battery voltage at the OUT terminals, otherwise the board is useless.

These are the ones I have, and they will power a load without nothing connected to the input terminals.

http://www.banggood.com/10Pcs-USB-L...le-With-Charging-And-Protection-p-943765.html

APD said:

If you cannot draw power from the OUT terminals with a battery connected there is something wrong. Either the wires aren't making contact or the circuit is defective.
The board is designed to be an embedded charger and also power the device via the battery, regardless of whether or not you are charging.

BAT+ and OUT+ are always connected
BAT- and OUT- are connected when a battery is present.
You should always have battery voltage at the OUT terminals, otherwise the board is useless.

These are the ones I have, and they will power a load without nothing connected to the input terminals.

http://www.banggood.com/10Pcs-USB-L...le-With-Charging-And-Protection-p-943765.html

Click to expand...

I think you might misunderstand. I can draw current on the output with only battery connected, but not if I never sent a current on the input.

if I pick up a circuit that's not connected to anything on any terminal andconnect it to a battery, then I get no currenton the output terminals. I need to send an input current in order for the circuit to enter a state where there is current on the output. After that I can disconnect the input current and still get the output current. This is why I think one of the ICs on the circuit has a MOSFET switch that needs a current from input in order to get it running.

Once the circuit is in the correct state it will stay in that as long as you don't disconnect thebattery. So I don't know if this renders them useless. Well, useless insituations where you use the circuit as a overdischarge controller inanbatteryonly solution, perhaps outdoors. I realise that this is not what the circuit was intended for.But I'm still interested in knowing if it's the way they all workorif it's just the two batchesI'veordered.

Are you sure that you can drawcurrent from your circuitif you only connect a battery and never sent current to the input? Did you test?

Batteriapan said:

Once the circuit is in the correct state it will stay in that as long as you don't disconnect thebattery.

Are you sure that you can drawcurrent from your circuitif you only connect a battery and never sent current to the input? Did you test?

Click to expand...

I first tested your idea on boards that have been used, but sitting unused/unpowered for weeks. OUT terminals always have battery voltage.

Then, I had ONE TP4056 still in the wrapper, never used. OUT terminals always have battery voltage.

There is a capacitor that connects OUT- to BAT-. When that bleeds off, OUT- and BAT- will no longer show continuity. As long as there is a good battery connected the OUT terminals have battery voltage.

Mine do not behave the way yours do.

APD

Thanks a whole bunchfor testing and getting back to me on that!
I just ordered a bunch of those that you use. The third batch from CZisa charm...