# How to find the standard error of a sample of measurements each with their own uncertainity

I have a scale that has a resolution of +-0.01 grams. I have assumed that it has a standard error of +-0.005 grams. I would like to measure the mass of an Samsung INR18650-30Q battery. I would like to estimate the average battery's weight because I am building a battery pack with a couple of thousand of these battery cells. I have measured three of them and their measurements are as follows...
1) 46.08 +-0.005 grams
2) 45.99 +-0.005 grams
3) 45.96 +-0.005 grams

How would I find the mean and standard error of the population given that each measurements has an uncertainty of +-0.005 grams?

------- What I've done so far --------
I have found the standard deviation which is 0.06245 (4 sf) and calculated the standard error using

SE=(standard deviation)/SQRT(Number of samples) which gives an SE of 0.0361 (4 sf).

I've also found the error propagation of averaging three measured values.
SE_P=SQRT(3*(0.005)^2)/3 which is 0.002887 (4 sf).

How can I combine the uncertainty that exists in the manufacture of each battery and the uncertainty of my scale?

I found this post but I'm not sure if it answers my question, as it finds the standard error when another measurement is made.