One way to keep the car electrical system energized while the battery is disconnected is to use a charging cable into the OBDII connector. I have trickle charged the battery this way with a NOCO cable as well as changed batteries without losing your mind... But the Redarc gizmo described below solves this problem and several others.
Many modern vehicles do not start charging the battery for a good long while after you start them up. This means starting the car to charge the battery without waiting out the delay period (several miles/20 minutes???) will further discharge the battery. This is one reason why having some kind of starting battery backup with you at all times becomes almost a requirement these days. Having a cheap DC voltmeter/multimeter (Hazard Fraught, I mean Harbor Freight) to check your state of charge and charging status can be helpful to tell what is going on. 12.8 Volts is fully charged for a lead acid battery, usually, and the battery terminals should read at least 14+ V if the car battery is actually receiving charging current at the moment. It's not hard to memorize the correct voltages for your specific system when you check them often.
Buy most batteries by weight; the heavier it is the more plate material, typically. Heavier means more plate, more power and longer battery life.
Having a second battery for camping which does not involve discharging the car system is probably the safest option. One excellent way to do this is use a Redarc BCDC1225D DC to DC battery charger which also acts as an automatic battery isolator and solar charge controller all in one tiny package.The DC to DC design means your camping battery can be fully charged no matter what weird charging setups you are using, and you can plug in your solar charging components and the solar inputs are prioritized for charging when available. This may be overkill for your purposes, but the device is so elegant you need to know about it.
Speaking of solar, Hazard Fraught sells a very cheap 100 Watt solar power photovoltaic kit and some accessories that allow you to get solar charging going easily and cheaply. If you use the Redarc you can plug these panels directly into it. You can use as many of these panels as you like to satisfy your electrical loads and weather conditions and leave the rest at home.
Just a note about name-brand equipment; these days almost everything is cheap junk from China, even name brands you wouldn't think of this way. My experience is you have to research very carefully to figure out if a specific product is any good, or just buy it cheap and try it. Referrals are great. Price and brand usually have little to do with utility and longevity.