I'm very happy with this portable water flosser. I have a plugged in model as well and I feel like this portable one feels just as strong or if not stronger. It's been our new favorite since we don't have to deal with cords and take it anywhere. The flosser offers 3 settings, normal, soft, and pulse. We found that the soft setting was the perfect setting for us. It was still very strong and more then enough to get our teeth clean. Which means if we ever needed a bit of a boost normal is always available.
The runtime with the smaller water container is only about 40 seconds on soft mode. While 1 min and 45 seconds on soft mode if you opt in to use the larger container. I measured the small container only to hold 150 ml of water and 350 ml for the large. I did time the runtime running on normal with the small container and got 35 seconds till it ran empty. So even if you run on normal you don't loose too much runtime, and even if you do. It's really easy to fill it back up with water. There's a little flap on the bottom and opens and closes without any hassle.
As far as battery runtime, I have yet to recharge it. I did make sure I charged it completely before using it. After using it about 10 times and also doing all my testings. It shows no sign of weakening or asking for a recharge. It charges via a USB cord. The cord it comes with plugs into a standard usb port, but the end that connects to the flosser is proprietary. So make sure you don't loose the cable. I really wished they used a micro usb or a type c. I'm not one to loose cables, but I can see it being a problem for some. Especially if there are multiple users.
I definitely recommend this water flosser as it works well. I do recommend doing it in addition to regular flossing. At least that's what my dentist recommends. Keeping your teeth clean and adding tools like this to your arsenal is still far cheaper then going to the dentist with problems. So give it a try, you'd be surprised how great this flosser works and how clean your teeth will be.