The pass thru senders I had previously used replaceable batteries. I replaced them once. You have to order fresh "O" rings and remove 4 little screws to gain access to the battery compartment. Those screws make the ones they use in eyeglasses look BIG. They are tapped into plastic and stripping or cross threading them is a real risk. If you do so or the "O" ring doesn't seat properly you can cause a leak. Good by sender in the first wet weather you drive in! If the Tire Patrol folks make any improvements in the sending software that compatible software is automatically incorporated into the factory sealed replaced units. If you are full timing and on the road all year round then owner battery replacement may be the way to go. On the other hand, if you RV seasonally, factory low battery, total unit replacement could be more attractive. I'm in the latter category. As mention in a prior email the fact that the system is USA made is also a positive factor for me.