Connecting directly to either the battery or the starter cable connection will charge the battery, but the ammeter will not function if there's still one in the circuit. Depending on the capacity of the alternator, a 12 ga. fuse link might not be heavy enough. A high-capacity alternator like a 75-100 amp model can produce enough surge current immediately after starting to overload a fuse link that size. The link only needs to be a couple of inches long. Make sure it's very well crimped, or soldered into the charge lead. Any resistance in the connection will cause it to heat up and burn in two, which is what it's designed to do in case of a bad short.
Jerry
