As per the instructions I charged the batteries fully before the first use. This took 14 hours which is much longer than the suggested three hour charge time. After the charging was complete I paired the socks with the included remote control. Pairing each battery was actually pretty easy, once of the nicest things about these socks. The socks fit my feet well. You can easily feel where the wires are but it only took a couple of minutes before you forgot they were there. Once the sock were on I connected the batteries and tucked them away in their respective pouches. The using the remote I turned the socks on High. After an hour I pulled each battery out of the pouch to check the indicator light, sure enough the light showed that each battery was on high but I couldn't feel any warmth on my feet. And this was on High. I kept the socks on for four hours, at about the third hour I started to feel a hint of heat. The reason these socks didn't meet my expectations and received a two star rating is because of the exceptionally long charge time as well as it taking three hours before I felt any hint of heat. Even at hour four there was very little heat on the High setting. I didn't test Medium or Low.