IDK if this one is any good, and it's only 4 cells. I'd like to get one more powerful and have it do other voltages.

https://www.amazon.com/Docooler-Soshine-Portable-External-Dual-USB/dp/B01M7170PB/ref=pd_sim_107_2?_encoding=UTF8&pd_rd_i=B01M7170PB&pd_rd_r=159652fc-9be1-11e8-af6e-0720243a5fcc&pd_rd_w=95je9&pd_rd_wg=gAYkI&pf_rd_i=desktop-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=2610440344683357453&pf_rd_r=36TYK5S9AXR524B67P6C&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=36TYK5S9AXR524B67P6C