I want to know if there is a way of increasing a voltage drop by a given battery at a time.
So, I have this hp 50g graphic calculator here which uses 4 AAA batteries and they last like 4 hours of constant use. I've used a battery bank on the calculator usb port but it doesn't last long either because if there is a usb connected to the battery bank, even if the other end of the usb cable is disconnected, a small irritating green led stays on, and the bank lasts like 3 days disconnected from everything.
A solution that I've come up, is to buy a Tp4056 lithium battery charger and use a 3.7v nk18650 battery, then install it at the bowels of the calculator to make it rechargeable by the usb port.
So I need to make 3.7v go to at least 5v, (because the low bat warning starts at 5v), or to simply come up with two or three of the batteries and make the voltage go up 4.2v, because that voltage is the max chargeable voltage of the tp4056.
Best Answer
Use boost converter to step up 3.7 V to 5 V. There are various range of input/output voltage of boost converter chip.
You can also simply buy boost converter module, it is quiet cheap on the market.
Below is an example of boost converter: