Galaxy S2 discharges during navigation

In itself, this device works as intended. It brings 700mA, as the included with the Galaxy S2 in the original landline charger also. However, these 700mA not enough to charge the phone while navigating via Google Maps. Since this is a genuine accessory I find this particularly weak, because you should assume that Samsung may provide a charger that make it possible to use the phone with the supplied programs as intended.

Despite turning off Wi-Fi and Bluetooth while navigating lose my i9100 about 10% battery life per hour. That does not sound like much, but if you navigated eg with half-charged cell phone two hours to go somewhere and there then the phone also uses a little, then you can no longer navigate back -. Despite charger. And always remember to have that cell phone to charge fully before being navigated go somewhere not exactly ideal - apart from the fact that a long holiday trip with Navi and this charger are impossible because of the fun is after 10 hours ago.

EDIT: To have a tip for a better charger which can charge during the navigation, I would be very grateful.