1998 Plymouth Breeze kills batteries

Have a 98 breeze that I have had to change batteriesi n 4 times in last six months keeps killing cells in batteries or batteries lose thier cold crank. Fine for 2 or 3 weeks but then have to use jumpers or charger to get running in morning then fine all day. Had alternator checked and is fine under load test and all really starting to puzzle me any help welcome thank you.