Can I change the capacity in a camera flash light so it can support 14500 batteries?
I've found the schematic of the board from a Russian website:

NOTE: Designators may not match the ones on the actual circuit.
The input voltage is applied to IC6 (an LDO) and IC1 (a step-up DC/DC controller). Abs. max input voltage for the LDO is 18V which is quite acceptable. But abs. max input voltage for the Step-up DC/DC controller is 10V. Most likely the IC is damaged.
You should never apply more than 10VDC. But technically, the whole circuit is designed for 6-7VDC input voltage.