2009 SL550 42000 miles.

My daughter went to a shopping center, came out 15 minutes later, pushed the start button and heard just a click.
Normally to diagnose if the problem is the battery or the starter you would turn the headlights on and then try to start and look for the headlights going dim etc. None of that works on this car because the starter has its own separate battery. I connected a good battery with jumper cables - no change. I disconnected the ground cable and jumpered it directly to the spare battery - still no change. I took the starter battery to Autozone. The battery tester showed:

BAD BATTERY
12.83 volts 100%
REPLACE BATTERY

Does that make any sense? Is it a dead battery, or does it have 100% charge?

While the Autozone guy was pushing the buttons on the battery tester, he wouldn't let me see the screen. I don't know if he has a way of making the tester show the result he wants. 12.83 volts sounds good enough to me.

I took the battery home, and connected a charger to it. Normally on a dead battery the charger would show 6 amps in the beginning and then gradually drop to something lake 2 amps a few hours later. When I first connected the battery, the needle moved about 1mm. So something is the matter with this battery.

I want to believe an original battery (VARTA - Made in Germany) should last more then 5 years. I've had Interstate battery last 10 years. But more than anything else I want to believe an original Bosch starter will last more than 42000 miles.

So, what do you guys think?


Thanks

It was the battery. I left it on the charger for about 4 hours. It picked up enough juice to start the engine. Glad it wasn't the starter. Replacing it is hell on earth.

Hot climates cause batteries to fail earlier. Anything over three years is good.

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Prost!