You can adjust the length of the excerpt in Divi blog kits in th jQuery.
Once you have added the jQuery to your site, find the following section of code (values in the image below may look different depending on which blog kit you are using)
Change the two number values (115 in the image above) to the number of characters you want displayed. Whatever values you set here will be reflected in the blog module and across all archive pages.
For sliders using the Divi slider module, you can set the excerpt length in the module settings. For sliders using Slick.js, the values you set in the jQuery above will also apply to the slider.