Absolutely, especially with a Cadillac. As far back as the 1990s, Chrysler said the "ignition-off-draw", (IOD) current could be as high as 35 milliamps, (0.035 amp), to keep the memories alive in the multiple computers. At that rate, a good, fully-charged battery would still be strong enough to crank the engine fast enough to start after sitting for three weeks. That became the industry standard unless specified differently by the manufacturer. Cadillac was one of those manufacturers. Their maximum allowable IOD current is 50 milliamps. A '97 Cadillac could have up to 47 computer modules. Most of them draw a little current to keep their memories alive. I don't know if they ever said what that would translate into for weeks, but it depends on the electrical size of the battery, and which of those computers your car has. When 50 milliamps is listed, that is the maximum that's allowed. It takes a complicated procedure to measure that current, but you're almost certain to find it is less than that maximum. For other car brands, 20 milliamps is typical.
All cars are shipped to the dealer with something disabled to eliminate that IOD current when the vehicle is sitting in a storage lot waiting to be sold to a dealer. On my '93 Dodge Dynasty and '95 Caravan, that is a large bullet connector in a fat cable right behind the battery. You can still drive the vehicle with that disconnected, but some features don't work, and others only work while the engine is running, (power mirrors, for example). Everything needed to drive the vehicle onto the hauler will work
In later years, once the vehicle was dropped off at the dealership, part of the "new vehicle prep" included finding one fuse taped inside the fuse box cover, and installing that to turn on the computers. Still later it was common to find two fuses for the Air Bag system that needed to be installed. Those will always be in bright yellow holders so emergency workers can identify them quickly. Typically that holder is in a "pulled up" orientation during transport or storage, and it simply gets pushed down into its installed orientation to turn the computers on.
If you plan on putting the car in storage again, I can try to figure out which fuse to remove or which wire to disconnect, but it might be faster to just visit the dealer. Any mechanic will be familiar with this.
At this point you'll need to recharge the battery with a small portable charger. This is less important with a new battery, but especially with an older one, always charge at the slowest rate the charger allows, typically for two to four hours. The lead flakes off the plates over time. The rate increases as the battery gets older. When it builds up high enough in the bottom of the case, it will short one of the cells, then the battery must be replaced. Battery chargers vibrate the plates and make that flaking occur faster. That is worse at higher charge rates.
Most newer vehicles use a new type of battery called "absorbed glass mat", (AGM). Those require a longer time to charge, as in days, and at slower rates to prevent excessive gassing. After charging those for just a few hours, it should start the engine, but to fully charge, the car needs to be driven for substantial distances. A lot of short-trip city driving won't do it. I found with my truck, a weekly 35-mile drive to a friend's shop is enough to keep the battery charged.
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Thursday, May 4th, 2023 AT 6:26 PM
