If you melted the negative side of the battery, you have a short some where. Check for continuity between + on the battery and ground. Clean and inspect the cable that goes between your negative terminal and the engine. Check the main cable between your + battery terminal and the starter and the cable between the starter and the alternator. Make sure that the cable from battery to starter is fused. Make sure the cable from starter to alternator hasn't melted against the block and is shorting out.