The battery that came with my Focus Pro is a Samsung INR18650-32E. I'm pretty sure that it has a lower CDR than the Sony VTC5A batteries that I just bought for my iStick Pico. I read that the Pico requires a battery with a CDR of 25A or better. I was able to operate the Pico with the Samsung INR18650-32E, but I never tried operating the Focus Pro with the Sony VTC5A batteries. I don't know if it makes a difference, but @SirFall might want to look for the Samsung INR18650-32E specifically.Try any shop carrying e-cigarette/e-shisha gear. The 18650 is very common in that trade.