3 cells LiPo Battery charging

I have a battery pack made of 3 LiPo cells (3.7V each. total 11.1V). I want to design a circuit which can charge this battery with an ac-dc adapter of 15V. When adapter is connected, adapter should charge the battery as well as drive another system (load). When the adapter is not connected, the battery should power the load.

I researched about it and came across many components like battery protection ICs, gas gauge ICs, battery charging ICs, host controlled/standalone... I learned that LiPo batteries need proper monitoring and protection and cell balancing. But, I am not sure if I need all these components or not.

Which components do I need to make a complete battery pack with charger and battery protection? My Battery pack comes with a protection control module. Do I need another protection circuit? The battery pack is external, so it is not interfaced with internal processor. Do I need the gas-gauge?

Can I just use battery charging IC like **broken link removed** or https://www.ti.com/lit/ds/symlink/bq24610.pdf only?

MAX1757
https://www.maximintegrated.com/datasheet/index.mvp/id/2287

I have to use 15V adapter. I couldn't find 13 or 14V adapter. Also, do I need to use gauge IC and protection circuitry?

Try to decrease voltage somehow, try to use two diode in serie, what to say.

yes you must use protection circuit to protect battery from bad using in charge and discharge, and to save the life battery.