The difference of approximately 4V would be too much normally. But in this case it seems both voltages are supported, as the La 1703 was sold with 10.8V and 14.8V batteries - at least according to
http://www.amilo-forum.de/topic,15892,- ... -1703.html (German). In this thread one user mentions that he asked Fujitu and they said both work. (But you could ask them yourself to be sure.)
A higher capacity is no problem.
It seems that the batteries for the La 1703, Esprimo Mobile V5515, V5535, and V5555 really are the same. My reason for this assumption: the page
http://www.akku.org/original-siemens-ak ... html?rf=pr mentions these models as compatible under "Passende Modelle" (the page is also German).
Regards
Aaron