I don't know how the Excaliber goes together since I dont't have one "YET" but i had a Garrett seahunter. Iknow on the rechargeable batteries the way I got the best results was to charge the battery and go hunting. when I got done I would leave the detector on untlil the batts were almost dead, then slap it in charger. Never had a problem doing this.
Also where you have any connections you should be using Dielectric grease, you can pick it up at radio shack and most marine stores. This will just about cease any kind of corrosion and also helps with expanding and contracting contacts. When it gets cold metal contracts and you lose connection the grease helps to conduct the connection. I work in the marine industry and people just don't understand that salt air is just as bad as salt water. Also the heat (especially here in Miami) is terrible on batteries, the heat just sucks the juice right out of a battery. You don't believe me stick a flashlight with new batts in your attic and see how long it lasts. I did alot of attic crawling installing alarms for ten years and heat is a battery killer.
Also you may want to look into a different battery pack. I know they make a waterproof rechargeable for underwater lights, it is 12V and is a great pack. I'll check at my local shop,the owner is a real inverntor nut and knows a lot about the batteries they use.
Hope some of this helps.
