Oddly, the manual I saw said to actually disconnect the cable from the battery terminal (not from the cable from the body like everybody does LOL). It seems to never say to disconnect the positive cable...even though it has those convenient connector clips that might tempt me... So I guess all those sparks disconnecting the negative are...OK?
People have been disconnecting cables from battery terminals since forever, because cars forever ago usually didn't have a nice plug-in connector you could just unplug. And everybody learned the safety reason to disconnect at the − post first and reconnect there last (in any negative-ground car) because if your wrench bonks between the − post and the body metal nothing serious happens, and once the − post is disconnected you can do the same at the + post and wrench bonks there won't cause any trouble either. But if you go wrenching on the + post and the − post is still cabled to the body, and you bonk the wrench, you end up branding your hand with the wrench logo. Happily, when there's a nice fully-sheathed plastic plug-in connector at one of the posts (doesn't matter which one), you can just squeeze that and unplug it and you're done. If all you want is to power down the car. If you're going to proceed to take the battery out, then yes, you still have to undo the clamps on the posts, and yes, it still matters to undo − first and reconnect it last.
it just depends on the health of the battery, the ambient temperature and the draw the car has when off. it's a gamble, not always worth taking.
A battery maintainer is your best bet. But make sure it's the type that will stay on after a power failure. I use the NOCO Genius 5. I don't recommends trickle chargers. I used one for the winter, and by spring the battery was completely destroyed.
