2004 Sport Trac. I don't know how old my battery is, but the guy I bought the truck from last May said it was relatively new. But, here is the problem. I have the little red battery light glowing on my dash and the charging meter reads close to, but less than 50% charging. Shouldn't this meter be near 100% if the alternator is charging as it should? Does this tell which is not performing up to standard? Do I need a new battery or a new alternator?