Electric tear off systems are a pain in the arse and are prone to frequent failure/problems. The only ones that I have seen work, were custom made of billet aluminum and had hand wound electric motors.
Only use
http://www.racingoptics.com/ tear offs which come in packs of seven laminated together.
Most off road guys do not know how to use tear offs properly. Here are a few tricks I have learned over the years.
1. When installing the tear offs on your shield, make sure the posts are adjusted so that you have to stretch the tear offs to get them on. If you do this, nothing will get between the shield and the first tear off.
2. If you pull with your right hand, always put at least one tear off on backwards (pull tab on the left), so that if you ever mistakenly pull all your tear offs off at once, you still have at least one more left.
3. When installing tear offs, you must fold the pull tab over and place it over the post and underneath the next one. This way it is almost impossible to pull all of them off at once, and the next pull tab springs forward making it easier to pull off.
Hope this helps.