My LG G3 D855 is suffering the same condition, now it can only survived connected to a wall charger or an external battery, otherwise it will keep rebooting. What is it? The battery? or the mainboard?
If i replace the battery would it work normally? I am in Venezuela and do not have any other G3 users at hand to try with another battery, my G3 warranty expired (very few days ago). VERY early batch. It is a SEA version from Hong Kong. Contacted LG HK today, waiting for reply. My phone also has the cracks, and i only can survive attached to a power source.
Best bet would be to order an Anker batt from Amazon?