Now that I can my scanguage I always like to look at my voltage. Usually my truck reads 13.8-14.2 On the meter. Today I was getting 12.8-13.1 No chages done during readings. If i turned the truck off it would jump back up to 13.9 after restaring but would go back down to 12.8 Does this mean my battery is about to take a dive? It never really flucates that much before so It got me wondering if it was normal? Why does it do it today and not at all last month?