im trying to bypass my modem battery im thinking about giving the battery terminal with 4 volt (just like when the battery is fully charged)

and i also have battery charger module laying arround (its tp4056) it can provide 4.3v with 1A current from a 5v supply

so should i just give the battery terminal 5v from a charger or should i use battery charger(tp4056) or should i use something else


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  • \$\begingroup\$ 4.3 V battery charger module will almost certainly be ok. You could add a series diode to drop 0.6V and a cap to ground after diode but probably not needed. \$\endgroup\$ – Russell McMahon Jul 22 at 7:11
  • \$\begingroup\$ 99% it will work fine, as already commented a diode drop could help \$\endgroup\$ – Lorenzo Marcantonio Jul 22 at 7:27

Since the TP4056 is a Lithium cell charger and protection module, there may be issues.

  1. It might not provide a steady DC output, because some smart chargers alternately charge and then sense the battery voltage.
  2. It is designed to stop charging when the cell reaches a given voltage, so may shut down if the current draw is incorrect.
  3. It is not a "stiff", i.e., voltage-regulated supply: voltage starts at perhaps a volt or two for a discharged cell and gradually rises. Likely your modem would not like voltage fluctuations.

Though you can try using that charger module, likely without harm to the device to be powered, it would be safer to use an ordinary voltage regulator, such as one of these low-dropout regulators from Mouser. You could make an adjustable voltage regulator using the LM338 analog IC which could handle up to five amps, too.


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