Chrysler says a good, fully-charged battery will be charged enough to start the engine after sitting for three weeks. That assumes a maximum of 35 milliamps, (.035 amps) drain from the multiple computer memory circuits. That 35 milliamps has become an industry-standard unless specified otherwise by the manufacturer.
In actual practice, most cars' computers don't draw that full 35 milliamps. I have two vehicles with lots of computers, both driven vary seldom, and they've sat as much as six weeks and still started. It sounds like you have nothing to worry about, but be aware that some computers draw very high current for as much as 20 minutes after you stop the engine, then they go to "sleep" mode. If the battery runs down enough, or if you simply open a door, those computers can wake up and draw that high current again. That will run the battery down even faster.
If you ever do get in a situation where the battery needs a jump-start or charge, if it was really drawn down, it can take a good ten or 15 minutes before the acid becomes conductive enough for the battery to start recharging. That means it isn't recharging very much during the first few minutes when you start driving again. Also, even if the engine does start, after three weeks of sitting, it might take as much as an hour or more for the battery to fully recharge.
If you think you might run into a problem, look into a solar-powered battery maintainer. You can find them at Harbor Freight Tools, Walmart, any auto parts store and at most hardware stores. They have to see the sun during the day, then they put a very small charge into the battery to make up for what the computers used. Most of these plug into the cigarette lighter socket, so they'll only work if that socket stays turned on when the ignition switch is off. Those lighter sockets go dead with the ignition switch off on a lot of import models. There are some models of battery maintainers that clip right to the battery's terminals. Those are a little more cumbersome and should be disconnected when you drive the car.
Thursday, October 22nd, 2020 AT 7:41 PM