Volvo Forums - Volvo Enthusiasts Forum - electrical problem, I think

I love my 1994 850 Volvo and would like to get it fixed but, so far, nobody can figure out what is wrong. Here's the story:

First of all, it was running great, no noises, very smooth, etc. My ABS light would randomly come on. This started on a Sunday. On Tuesday, I took it to the mechanic. On the way, I also noticed a little puff of smoke or steam coming from the left front corner of the hood when I would stop at a light. I told the mechanic. He "cleaned some sensors" to resolve the errors the ABS light was indicating. He didn't know what was causing the smoke. On the way home, my ABS light came back on and when I stopped in my driveway, I saw the little puff of smoke and smelled a horrible acidic smell - it was coming from the battery. I took it back to the mechanic the next day. He replaced the battery and the altenator. Less than a week later, I went to lunch. The car wouldn't start. All the lights come on, the ABS light goes out and you hear a click under the hood which also can be felt in the brake pedal. The car will not attempt to start. Electric windows work, electric locks work, radio works, etc. Any ideas as to what it could be would be appreciated.