I've made a portable project using 3v3 Pro Mini. I designed it to be powered by a li-ion battery salvaged from an old mobile phone. To do this, I'm using a TP4056 module like this one:
The Pro Mini (and all other periperals) are connected on Output + and Output - of this module, while the Li-Ion battery on B+ and B-, with a power toggle switch on the positive side of the battery.
The problem with this module is that it outputs no power when I connect the battery, only when I 'wake' the device by plugging in USB I get power on the output. Once the module is woken up, I can disconnect the USB and it would run just fine on the battery. When I turn the switch off and on again, I would need to wake up the device again by plugging the usb.
I want to have my project being powered by toggling a switch without having to wake it up with USB every time. Does anyone have any experience with this using this module?
Just a thought... This Thing is designed to be a battery charger, if you put a Switch on the battery, the module believes the battery has gone undervoltage and activates the battery protection. Wouldn't it work better if you put the Switch on the Out+ instead?
I bought the Banggood version of your module, and used it to convert my DSO150 oscilloscope to battery power. I didn't have any problem with it. In my circuit, the battery powers a boost converter.
The protection IC (DW01) and MOSFET package would be in control if USB is not powered. The B+ and OUT+ terminals are actually shorted together on the board. All the control is effected between B- and
OUT-.
Have you checked to be sure it's your charger module that's causing the problem? Your battery may also have a protection circuit of some kind. Do you get a good voltage reading on the battery, but not on Out+ and Out-? Otherwise, I don't know what to suggest. I think there are several Youtube videos on this module that may be useful, but these modules are widely used, and I don't think this is a typical issue.
One thing you need to be careful about is not trying to run your pro mini circuit while the battery is charging. The charger won't know what to do if it is also supplying all the circuit current, and may not shut off, which could lead to smoke. If you need to do both at the same time, you'll need a path for USB to also supply current to the circuit when it's plugged in. That would involve a MOSFET, a Shottky diode and a resistor. If you're interested, I'll see if I can find a schematic for that.
Sorry I don't have a solution for your problem. Others may be able to help.
JaBa:
Wouldn't it work better if you put the Switch on the Out+ instead?
Yes that seems to work on first glance, thanks! Now the battery is always connected to the TP4056 module, I'll be investigating what consequences this will have on battery life. On open load, it seems to be drawing 2.3 uA, so it looks promising.
ShermanP:
One thing you need to be careful about is not trying to run your pro mini circuit while the battery is charging. The charger won't know what to do if it is also supplying all the circuit current, and may not shut off, which could lead to smoke. If you need to do both at the same time, you'll need a path for USB to also supply current to the circuit when it's plugged in. That would involve a MOSFET, a Shottky diode and a resistor. If you're interested, I'll see if I can find a schematic for that.
That's an excellent point, I'd appreciate the schematic, it'd be nice to be able to use my device while plugged into USB. For now, I'll make sure to disconnect the load before charging.
The best explanation I've seen of the V+ bypass is at this link:
The picture "Charge circuit with load sharing" has the schematic. The charger is different from yours, but the principle is the same. And he explains in detail how it works.
For other ideas about parts selection, here's another example (but note that this one has the MOSFET oriented the wrong way):
And finally, the Microchip app note on this subject shows the same method:
Anyway, the idea is that USB V+ powers both the charger and the load independently so that charging can proceed to normal completion and shutdown even though the load is still drawing current. The MOSFET is OFF while this is going on, and its body diode blocks the 5V from coming back to the battery.
