Safe and economic recharging requires a charger specified for these cells. A related technology is flow batteries, in which the fuel can be regenerated by recharging. The "Schnorchel" reduced the need to spend dangerous periods on the surface recharging batteries. The environmental effects involved in recharging the batteries can of course be reduced. Twiggy sees prison as a holiday and describes it as "recharging the old batteries". The place for the refueling has also been used for the recharging connection. Terra includes Wi-Fi capabilities and a docking station for recharging. The phone can be connected to a computer for data transfer and recharging. Urban runoff and storm water capture also provide benefits in treating, restoring and recharging groundwater. There are three Tesla recharging stations near Posts. Greater water retention is also important for recharging local watersheds. The Roomba 530 included two virtual walls and a recharging dock. Bioswales can also be beneficial in recharging groundwater. Health is only restored through automatic recharging when the player is not taking fire. They sometimes help in recharging aquifers as well.