Don't forget to check the fuses inside.
There's a couple of things to consider before we assume you have a problem. The insane engineers have gifted us with a lot of unnecessary computers that do things we never needed computers for before. They all use a small amount of current to maintain their memories. Unless specified differently by the manufacturer, 35 milliamps is what's allowed, and at that rate a good, fully-charged battery will still crank the engine fast enough to start after sitting for only three weeks. You will likely get more than three weeks, but that's the standard.
To add to the misery, there are now some computers that take quite a while to go to "sleep mode" when the ignition switch is turned off. That can drain a partially-charged battery. Then, when the battery runs down, some computers will "wake up" again and draw high current. That can totally discharge the battery and could be related to why it was dead after only a week. You didn't say what kind of driving you did for those couple of days. If it was a lot of short trips with many engine restarts, the battery may have never fully recharged.
More importantly, you must be aware that to recharge a totally dead battery, it takes at least 15 minutes on a charger before the acid in it becomes conductive and it STARTS to take a charge. There is no way to get enough current through jumper cable clamps to run a starter motor. All you can do with jumper cables is to assist a weak battery. If you have a battery charger with an amp meter, you'll see with a dead battery, the meter stays on "0" amps, then by around 15 minutes, it slowly comes up to around 15 to 20 amps if you're using the low charge setting. After about an hour, the meter will show close to 5 amps when the battery is fully-charged.
Always use the lowest charge rate if you use a large wheel-type battery charger. The current pulses differently than the relatively smooth three-phase output of the vehicle's generator, and that pulsing vibrates the battery's plates. That vibration helps the lead to flake off and shortens the battery's life. That is much worse on older batteries.
It is common now for fuses to blow when reconnecting a battery or when connecting jumper cables. That's due to surges from the computers' memory circuits charging up. Charge the battery at a slow rate for an hour or two, turn the charger off, then after a minute, turn on the head lights for ten seconds, then measure the battery's voltage. You should find 12.6 volts. If it's closer to 12.2 volts, it's not fully-charged yet.
Next, with the engine running, measure the voltage again. You must find between 13.75 and 14.75 volts. That proves the generator is working.
Friday, July 25th, 2014 AT 9:26 PM