/diy/ - Do It Yourself

Please help, I'm retarded. I found an old pair of wireless headphones but the lipo battery was dead and way below the undervoltage threshold. I did want to risk starting a fire by slow charging it with a bench power supply, especially since I have other batteries laying around. The markings on the dead battery lead me nowhere so I can't find a data sheet or any specs, pic related.
I replaced the dead battery with two 3.7v 70mah batteries in parallel, and everything works well.
After sealing the headphones back up I noticed a small pcb connected to the dead battery terminals with a singular component. I did not install that board across replacement batteries I used in parallel.
My question is am I going to start a fire?