Over on our sister website we have published a new guide to replacing the battery inside the Waterpik WP-450 water flosser and other similar Waterpik models. You can read the full Waterpik WP-450 battery replacement guide online now.
We are also stocking the new batteries here in our secure online shop so buy your replacement Waterpik flosser battery now!
My battery and charging problems were solved by spraying the plug and pins with contact spray. Corrosion completely prevents the waterpik from charging I highly recommend to try this first!