I have 1998 D3C III Hystat LGP that is not charging the batteries?? I have replaced both batteries and alternate.. Serial # 5GS00269.. Hired CAT service truck and they told me to replace the batteries which I did. I have to recharge the batteries manually after 18 - 20 hrs of operational time... What am I missing as checking for faults?? Fuse, Relay?? need help on resolvng this concern so I dont destroy new batteries and or have to replace the battery cables..