We have a 2009 BMW X5 with an AGM battery that leaked and damaged the negative cable. We don’t know what caused this, and we’re concerned it might be due to a problem with the battery sensor, voltage regulator, alternator, or electronic system/software. The dealer says there’s no way to tell, and that “batteries just leak.” However, we pointed out that BMW’s online marketing info states that “The acid cannot leak and damage the battery housing.” Based on this express warranty, the BMW dealer refunded us the cost of the new battery, cable, and labor. However, since we’ve read that battery failure is rarely due to the battery itself, but rather a symptom of some other problem, we’re concerned. Do you have an opinion as to what would cause this, or what we should do?
Was the leak around the negative battery post?
If so, whoever installed the battery may have put just a little too much force on the clamp nut, cracking the casing around the negative post.
Once you replace the battery and cable it should be straightforward to determine if the charging system is working correctly. I bet it is.