Can I use a charger with an output of 3V to charge a Sub C 3000mA glow plug igniter battery. Will it damage my battery or is it fine

Most Glow Igniters use NiCD batteries so you're charger will need to support that type. I use my Hitec or Venom charger set to NiCD at 1 amp. It will charge my igniters to 1.5 volts.

If you can afford 28 bucks, get this lipo battery and charger for your glow plug.
I bought one, and holy cow, what a difference on how bright your glow
plug lights up.
Horizon Hobby.

Features
•LiPo powered, providing higher power output versus NiMH glow drivers
•Switching power transfer (low heat dissapation)
•LED indicator light allows users to detect if the glow plug is good or not
•Includes a 1S 1200mAh Li-Po battery and charger
•Fits all glow plugs
•High-technology regulator, output voltage is 1.5V
•2.5mm DC Jack, Center pin positive charge hole