Great benefits, but only 30% brightness 4.3 inch nüvi

The unit is comfortably light and compact, even has an on / off switch and a small indicator light. On my first test with Sanyo Eneloop (2000 mAh) batteries then the disappointment: when I set in my nüvi 660T (4.3 inch screen) brightness to more than 30%, the screen still just as bright as at 30%! I then worked for the firm. Called. "We recommend batteries with at least 2500mAh" it said. Thereupon I ordered Sanyo 2500 mAh NiMh - like the eneloop also very well rated batteries. The result is unfortunately the same: 30% brighter than the screen will not (of course the batteries before fully charged).
On the not sufficient current for full brightness in some Navis the manufacturer would have to point, I mean (even if it's not the product itself but to the batteries), ultimately the product as for the nüvi 660T is described suitable.
Due to the high benefits for me (while hiking / cycling in the forest / at dusk rich 30%) but overall still 3 stars.