I have a diesel Blazer that I need to keep running at my apartment complex to keep it. But I rarely drive it.. so I am wondering what I will need to do to keep the batteries in top condition. Also.. I think I may have an alternator issue because I had new batteries previously and they seemed to discharge even though I would take the vehicle on long drives frequently to keep the batteries charged. I do have a battery charger though.. would it be best to disconnect the batteries and just use them to start my vehicle once in awhile and then use the battery charger to keep them charged up? How frequently would I need to put the charger on them?