According to some radio manufacturers the dynamo effect does exist but is only a potential problem under certain circumstances and the device you linked to at Emcotec is not the right one. Multiplex says it can only be a problem with certain high power servos when the battery is blocked from absorbing voltage spikes by diode battery backers

http://www.multiplex-rc.de/en/produc...5c757e9973c3bf

http://shop.rc-electronic.com/e-vend...&t=6&c=67&p=67