Battery Replacement

[xchen]

1. The owner (a family friend) of the X5 took the vehicle to a local AutoZone store, asking to replace the battery (which the store would do for many other cars). The store clerk said that they could not install a new battery for BMW vehicles. So they brought the replacement battery (from AutoZone) home and asked me for help (since I replaced WP/thermostat and breaks on the vehicle before). I then asked for advice on this Forum about precautions of replacing the battery, and was told that battery registration can be done afterwards, within a week or so. So I went ahead and replaced the battery, and later got the surprises of Yellow warnings.

2. The new replacement battery has a 09/17 time stamp on it. I did not check the charge capacity of the battery as I don't have equipment to do that. I had no problem start the engine after battery replacement, just the Yellow warnings. What do Check Engine and Break warning lights have to do with Power Management issues affected due to a yet-to-register replacement battery?

3. I have a regular/standard battery charger by Sears Craftsman. Would this charger work with an AGM battery?