Okay, looks like I found a way to do it with "File>Script>Image Processor" (I don't run photoshop in its english version so it may not be the exact terms. Sorry for that.)
But i still would like to know why is the batch process not working ?
Have script loop your 1500 files...?
Since the script didn't play, the tabs weren't closed. So it looped as much as it could, but in the end I had a message saying that i had too many tabs opened to continue. Then I created a folder with only 10 images and used the batch on it to test. It looped the 10 images, but didn't play the script.
Here is the script process :
> Define selection
> Crop
> Exportation (Save for Web)
> Close
For the Batch process, i did : (sorry for the trad...)
> File>Automate>Batch
> here i selected my script
> Origin : Folder (selected my folder)
> Priority on script Instructions "open" :checked and uncheck (tested both)
> include all sub-folders : unchecked
> close open-file-option-windows : checked and uncheck (tested both)
> close color-warning-windows : checked and uncheck (tested both)
> Destination : folder (selected my folder)
> Priority on script instruction "save as" : checked and uncheck (tested both)
> File name : MyFile.extension
> Error : stop in case of error
> Ok.
Then it began opening the tabs.