rommel

Hi, my military 98 defender ffr wolf is a 24 v electrical system but the voltage output on both alterrnaters is 35/36 v. I want to install two leisure batteries to power a 24 volt inverter, but wth this output i know it will fry the batteries, can anyone tell me how i can get the normal output from a 24 v alternater, is there a step up box or a reason other than that why this is happening ?