That explains a lot actually.
Most batteries sold for this vehicle have about 650 cold cranking amp. Every time the vehicle is started, some of the battery charge (amp) is used up and will be replenished by the alternator as the vehicle is running. Let's simplify your mother's daily routine (work, grocery, home). That is a minimum of 5 start ups every day, for five days a week (that is 25 average). Since your mother can finish everything that she needs to do in 3 mile radius, the alternator does not have enough time to replenish the charge back into the battery.
Without going into anything technical, I'll explain with an analogy. Imagine you have $650 in your pocket. For the sake of example, there will be a $5 charge every time you start the vehicle. To get more money, obviously you have to back to the bank (the alternator), which is located say 20 miles away.
In this example, you will spend a minimum of $25 per day, $125 per week. Since you can do everything that you need to do within 3 mile radius, you see no need to go the bank located 20 miles away. Now, you keep saying you don't have the need to drive 20 miles to the bank for more money, you will run out of money after 5.2 weeks.
Your battery works in similar way. Your mother keeps taking the charge to start the vehicle, but never give the alternator the opportunity to "recharge" (replenish is the better term, my opinion) the charge back into the battery. That is the main reason for the dead battery every six months, or so.
This is what I suggest. If the vehicle is mechanically safe and sound, (no oil leaking, no overheating, no rod knocking, or the sort) take the car for a road trip (about 1 hour). Not only will it replenish the charge, it will also give the engine to "breathe", getting to the optimum running temperature once in a while.
Another thing that I suggest is for YOU to purchase/procure/whatever a small battery charger. Once a month, you need to manually charge the battery, to give back what the alternator does not have time to replenish.
Monday, February 23rd, 2009 AT 7:50 PM