DIAGNOSIS This tool is a power hog, but what you're describing is beyond normal. The three main suspects are a dull/dirty blade, extreme binding, or using the wrong type of battery.
FIX 1) Blade: This is culprit #1. A dirty, gummed-up blade or a blade meant for a miter saw (with a negative hook angle) creates massive drag. Use a sharp, clean 24-tooth or 40-tooth carbide blade designed for table saws. Clean your blade with a dedicated blade cleaner or simple oven cleaner. 2) Technique: Are you forcing the stock through? Let the blade do the work. Pushing too hard strains the motor and kills the battery. 3) Battery: You MUST use High Output (HO) M18 batteries. The standard compact batteries can't deliver the sustained amps and will sag and die quickly, even if they show a full charge.
IF THAT DIDN'T WORK Try a different HO battery. If a different battery performs normally, your first battery might be worn out and unable to hold voltage under heavy load anymore.
HEADS UP Ripping thick, wet, or hard lumber (like maple or oak) will naturally consume battery much faster than cross-cutting pine. For big ripping jobs, have multiple HO batteries on the charger. Think of this saw like a corded 15-amp saw—it needs a robust power supply.