RE: Power Connection problem

Recommend you first draw or sketch a schematic and check each component for 3.7v capability. You may need to include 5v circuits as well as 3v circuits. 

I usually build my own breadboard using convenient connectors for power distribution , usually pcb to screw terminals. Ill include screw terminals for an external fuse and on/off switch. 

The battery could have a max voltage higher than its nominal 3.7V , maybe as high as 4.2 V. Pico has a regulator that outputs 3.3V and expects interface signals to be 3.3V compatible. Do you have a specific question about the peripherals you mentioned? Are you looking for a schematic?

In the future I was considering starting a project that will use a chargeable battery.  I was thinking of having a SEPIC converter between the battery and my downstream 3.3V devices.  The thought process being that it could handle the higher than expected voltages like the 4.2V that you cite and also keep ticking as the battery voltage gets depleted.  Do you know if this is a common approach?

Systems that require multiple supply voltages are very common and it is much simpler now to use efficient switching converters to meet these requirements than it used to be. It is very common to generate high voltages with step-up converters. 

If you must have 3.3V you will have a hard choice. To get the most out of a nominal 3.7V Lithium Ion battery you would like to run it down to 3V or even 2.7V. 

Fully charged it will deliver 4V. 

For low power stuff you could use an LTC3532 regulator which will do the business:

I think this is a quite common approach - and there will be other (and cheaper) chips than the LTC3532  but I've used it and know it works. It is also supported by a good model in LTSpice.

The max input voltage for the chip is only 5.5V so don't forget to have some kind of transient clamp on the input.

MK

Thanks michaelkellett this is what I want to achieve.

Thanks dougw 

Thanks I will draw it.

Hi, Sorry for being a noob. I want to start with the charging unit, I am using FP6277 as charger / booster, I want to connect the 3.7v 4000mA battery to the FP6277 and raspberry pi pico 0 : RP2040, in such a way that it it can charge the battery while connected to usb port and run and boost the voltage as necessary even without connected to USB. It would be helpful if you can send me a schematics so that I would have an idea. I need to see the connection how it is connected also to pico ports. Thanks.

The FP6277 is a boost converter - not a battery charger.

You don't need a booster to charge a Lithium Ion battery from USB - just a charger control chip.

https://www.adafruit.com/product/259

https://www.amazon.co.uk/Lithium-Battery-Charging-Protection-Functions/dp/B08DQXPNR1/ref=asc_df_B08DQXPNR1

You could then connect the Pico directly to the battery.

https://randomnerdtutorials.com/power-raspberry-pi-pico-6-different-ways/#batteries

I haven't tried or tested any of the above.

I suggest that you do a good bit more web research before spending money.

MK