Scott, if you were to contact Customer Service (CS) regarding your post, they will probably need to know the following questions before diagnosing the issue with your string trimmer.
Which model string trimmer are you using?
How old is your string trimmer?
Which battery size did you use with your string trimmer?
Was your battery fully charged before using your string trimmer?
I bought my EGO 15" trimmer early 2016 and have had "great success" thus far. Therefore, I would recommend you review the Troubleshooting section below and see if any of these suggestions will work for you. If not, then I would recommend you contact CS to help you resolve this issue - good luck!