You may need a larger capacity alternator possibly. If you keep going through batteries. If one battery has gone bad it could be the battery was defective. If it keeps happening it could be your charging system possibly thge alternator. You charging system may not be ableto keep up with all the accesseries that you are using.
Police cars have extra high output alternators to handle allthe radio equioment ,lights sirens and such and you may need the same.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T