2004 Toyota Corolla Repair Question
You're smart to ask first instead of later, but I have an easier solution. Check if your cigarette lighter works with the ignition switch off. If it does, you can use a "memory saver" that plugs in and is powered by a 9 volt transistor battery. That will keep the memories alive in all of the car's computers and the radio. Don't use that in the lighter if you have to have the ignition switch on because that battery won't be strong enough to power all the other things that are on with the switch on. Even if it tried, it would blow the fuse because more current will be needed than what the cigarette lighter fuse is rated for.
I connect a small battery charger to the car's battery cables anytime I replace a battery. It prevents even having to reset the clock and it saves all the memories. The negative cable can go to any paint-free surface on the engine, body, or steel brake line. That just leaves the positive cable that you have to be careful of to not let it touch anything metal on the car, and that the charger's cable doesn't fall off. If you have a smaller red positive wire going from the battery to a stud on the under-hood fuse box, that's a better place to put the positive cable because it's away from where you're working and won't be likely to get bumped and fall off.
Be aware that when you disconnect and reconnect the battery that sparks will occur. Batteries give off hydrogen gas which is explosive so eye protection is recommended.
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