Recently purchased a new Charge 2. Tested it out thoroughly for a couple of days but found that despite trying every different position, strap tightness and every other trouble-shooting suggestion, the HR accurate is appalling. At rest it is 5-10 BPM off my chest monitor and the old manual beat count to a stopwatch. And under any exertion it's completely useless. Repeated workouts of different kinds showed for example max HR of 147 BPM on chest monitor and 88 BPM on Charge 2. Averages totally off by a similar amount. Spent 1 hour with support trying everything, but to no avail.
Waiting on a replacement now and will update this if the problem proves to be a dodgy device.