Replicating the resistance that gets converted to temperature is another way to do it, without touching the battery. For the power, well, you need a suitable power supply. Modern phones (everything since the iPhone) are essentially little computers, and the can and will draw a surprising amount of current.
Most of them will not accept it. There might be exceptions. If you want to power a cellphone from a power supply you will likely need the value of the thermistor that is used in battery pack for this phone. You probably see 3 or 4 connection points where the battery goes. One of those is for monitoring the battery temperature.
Say half an hour, then 24 V 24+ A supply. Replacing a battery from a battery-operated equipment with a power supply can be tricky. Especially when the equipment uses an electric motor. The problem is that an electric motor can draw very large startup current - it can be as 10-20 times the nominal for a couple of seconds.
Should you replace your phone's battery?
But consider springing for a new battery instead. As long as the phone is in good shape—no cracked screen, for instance—replacing the battery can make the device work like brand-new—and save you money. It's more environmentally sustainable, too. If you're curious about the health of your battery, here's how to do a spot-check.
How to choose a rechargeable battery for a mobile device?
A mobile device draws energy from the main power supply or one or more battery packs. The rechargeable battery needs to be small and light, but at the same time provide a lot of energy. Since these two requirements are contradictory, high energy density is at the top of the battery wish list. .
What is the difference between a battery and a power supply?
A battery is able to supply that current, while a typical power supply with overcurrent protecton may latch or enter hiccup mode, from which it cant escape. First of all you need to determine the nominal motor current and the maximum current. The maximum current flows when the motor is mechanically overloaded.
The battery monitoring system (BMS) will very likely be on the phone's motherboard, so a power supply would have to emulate a battery very convincingly for such a setup to work. In what scenario would you get hold of a phone with no battery significantly more cheaply than a phone with a battery?