If the units are such that the accelerometer values are varying by +/- 0.1 m/s^2, then you are getting 1% accuracy. That is actually pretty damned good, and you can't hope to do much better with an inexpensive accelerometer.
If the units are such that the accelerometer values are varying by +/- 0.1 m/s^2, then you are getting 1% accuracy. That is actually pretty damned good, and you can't hope to do much better with an inexpensive accelerometer.