really wonky now, please help!
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The C5 needs a battery with the correct RESERVE CAPACITY. It is ALWAYS powering the modules even when the vehicle is OFF. The BCM draws 20-25 milliamps in the sleep security mode. If you get a battery with a low reserve cap, the car just sitting can cause the battery to deplete.
I prefer the autozone AGM batteries but the AZ premium lead acid battery will do you fine. Just get something that has at least 100-110 amp hours reserve capacity and the correct 550 amp -600 amp current. That RC will allow most C5s to sit at least 30 days and still be ok to crank and run.
Bill
I prefer the autozone AGM batteries but the AZ premium lead acid battery will do you fine. Just get something that has at least 100-110 amp hours reserve capacity and the correct 550 amp -600 amp current. That RC will allow most C5s to sit at least 30 days and still be ok to crank and run.
Bill
Thread Starter
Instructor
Joined: May 2018
Posts: 122
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Just wanted to add that the reason it might have seemed OK initially is because you had a battery at the ragged edge. So it had just enough power to cycle up the computer(s), run the DIC display, turn on the interior lights, etc. but as you screwed around in there the battery drained down, the voltage dropped and everything started freaking out. The buzzing you heard was indicative of a relay opening and closing very rapidly due to insufficient current. (and unless you're an 800 lbs gorilla, there's little to no chance that you managed to short something out with the little thumb screw that holds on the fusebox cover)
