This is more than acceptable from the rechargeable Lithium-Ion battery, but the industry average does tend to be around 3-4 weeks. So the 4100 perhaps falls marginally behind here. The benefit is the slimmer and lighter handle. USB charging is more convenient for some. It takes up to 24 hours to charge the 4100. USB charging has some advantages

In addition, the electric toothbrush features pressure sensor technology to notify you if you are brushing too hard. At the same time, the brush head replacement light will flash, although this is nigh on impossible to actually see.

and 4000 Series are the broader product range names. Under each of these families might well be a few different models with subtle differences between each. You might not desire more power and a deeper cleaning, but based on Sonicares data this does make somewhat of a meaningful difference to your oral health. An industry average 2 year warranty against defects and workmanship is provided. Unfortunately, no parts on the brush are designed to be user serviceable thus, should it fail, in most cases, they will send you a new brush.

Where you get a large visible light on many Oral-B brushes, you don’t on the 4100. Technically the BrushSync replacement reminder LED also flashes amber. Given its position and size, it is not the easiest to see. Of course, few will ever use side by side. And in reality, the cleaning offered by the 1, 2 and 3000 Series is more than sufficient.

Triple tone of high-med-low means the Brush head replacement reminder feature has been deactivated. The battery level light indicator will also blink amber 1 time to confirm deactivation. Each can use the standard head, but you in turn lose the benefits of the brush head replacement reminder. Get 55% off Philips Sonicare 4100 - Philips Sonicare Electric Toothbrush for Adults with 1 x Philips W2 Optimal White Sonic Brush Head in White, Slim Travel Case and USB Charger (Model HX3683/33)