MAHLE: This optional battery for X35 Systems is one of the most interesting accessories for X35+ propulsion. Its 208 w complement the 250 w of the main inner battery, reaching a total capacity of 458 w. These numbers can power the system for 4.5 hours with an average consumption of 100 wh, the system’s current average. Features: External Battery SP1 without any logo (Including holder, user manual, shipping box and two silicone bands). Transportation box included.