title_body: Is voltage sag safe if the voltage isn't too low?
upvoted_answer: Yes, voltage sag is perfectly normal and safe for the battery, so long as it remains above the recommended minimum voltage levels.
  
  The C rating is important as the construction of a cell affects how quickly it can provide current. The internal surface area of the positive and negative terminals is related to the current it can provide - a larger surface area lowers the internal resistance and this causes less heating when discharging. This is why higher C packs are bulkier.