Xiaomi YI battery replacement

I fly fpv and I hate when my recording camera just dies. Or i didnot remember to charge the battery. This is mod to replaice xiaomi yi's battery whit step down regulator like this http://www.ebay.com/itm/5pcs-Mini-3A-DC-DC-Adjustable-Step-down-Converter-Standard-Power-module-LM2596-/121383523820?hash=item1c430595ec:g:pu4AAOSwd4tTv~aF