Battery Drain Too Quickly

I bought a used Late 2013 15 DG model macbook pro. I installed coconut battery and it’s telling me the manufacturer is Simplo, and there is 20 charge cycles and the capacity is at 95%. The battery, based on coconut battery seems good, but the battery life does not. Any suggestions? What is the average battery life for this model?? There are times when the battery is better than other times. Right now I’ve lost 20% in 40 minutes. Other times a full battery charge would last me about 3 hours.