Camping out of my car for 3 months.

In my experience the gear will expand to more than fill the available space... The size of your cooler may make it hard to fit everything.

I have long camped using a 2 door Jeep so available space is always cramped; my two most desirable things have been a tent that I can stand up in and a bed that is comfortable.
First layer only; the tent, ground tarp, mattress pad, table and chairs & maybe some other stuff, have been unloaded.

The tent was initially solved by a dome with a 6 foot interior height; its still cramped for forced stays during inclement weather but it works (my preferred tent is much bigger and consumes much more transport space).
The comfortable bed evolved over several years and happy happenstance; it consists of a Coleman cot with springs supporting the cloth sleeping area, and the standard Coleman foam pad (in themselves this is an ok combination but not luxurious.

To get the best comfort I added a hospital mattress pad (3 inch if I recall correctly)
which was trimmed to fit the cot.
Together they give me more comfort than almost any other bed that I have had. Note the pad forms a very space consuming LARGE roll and is best vacuum packed to conserve space.

A good sleeping bag is essential for warmth; I recommend an intermediate temperature rectangular bag with additional layers for fine temperature adjustment (I cant really help you with brands since thie current bag was made in the 1950s and has a GI poncho liner and a very light, fuzzy/plush overnight bag from wallymart ~$20 for layers... when you get cold cover your head with a wool stocking cap.
When my feet get really cold I throw a fake fur bathroom rug over them (wallymart again).
the pillow is a wallymart travel pillow and pillow case.
Except for the rug, It all rolls up and fits in a military wet weather bag (try the internet or surplus dealers)...

Cooking is for me best don on the campfire but I usually have a single burner propane stove and cooking accessories.

Gotta go now; I will try to add some more things later...

Enjoy!

So a few quick questions are you camping or living/camping in your car. Are you moving around or are you staying in more or less one place? If you are moving around and sleeping in your car and then moving again in the morning type thing it would be a different set of things you might need.
Also you will have a harder time keeping a BIG ice chest cold enough, maybe try 2 smaller ones. We do that and even have a small lunch sized one for when we drive. Tons less open and close for the ice to melt.
You will need things to keep yourself organized. Bags, baskets or ?.
A way to charge phones etc.. I like my Jackery that charges with my car and solar panels.
A way to keep yourself semi clean. Water for brushing teeth and washing hands and face etc.
How to cook your foods you could just eat cold goods and not worry about it or set yourself up a full on gourmet kitchen.
This is one area that really is depending on how much you move around. IMO.
A place to sit when not inside your car.
A hobby, books, games, camera, or whatever for the down time.
Really important a safe place to keep and easy access to important papers that you may need to have ready. Meds you take or who to contact if the need arises etc..
A good first aid kit. I am a big believer in Murphy's law if you don't have the umbrella it will rain, if you have one you are less likely to have rain at least on you.

Vanbrat has some good points;
My personal style is to basecamp in one place for a week or more, I really don't care to be totally rootless . Folks that move every day or so often call themselves overlanders and favor things like rooftop tents instead of the longer setup time ground tents...

For short term personal cleanliness, I favor a sponge bath at least once a day to keep the funk level down.
I also shave every morning. Personal cleanliness helps keep my spirits up. Doing a sponge bath in the evening before bed, does a lot to keep the bag clean, as does an, easy to wash, bag liner.
A small table helps keep the wash basin from getting dumped on the ground.
Being able to heat the water helps on cold mornings and evenings.
Showers are often available, for a fee, at truck stops.

Sanitation is another thing that is high on the list for longer campsite occupation; there are only so many trees and bushes in an area to dig cat holes behind (a GI tri-fold e-tool works well for this).... I started carrying a porta potty to improve the sanitation issues. Be sure to get one of the larger sizes since the average size lasts less than a week, for one person, before becoming full and needing to be emptied at a dump station or toilet.. (yes it smells ...an odious chore...)
A small squirt bottle of soapy water helps keep it clean and the (special, required) paper (wallymart sports/camping/RV section) prevents clogs and clumps in the holding tank.
It fits at the foot of the cot under the small table.

I, too like to have electrical power in the tent; for lights and to recharge the toys & tunes but also to rid the tent of tiny vampires before bed. (A small mosquito zapper running for 15 minutes; does the trick).
cheaper power stations can be built/assembled by the technologically astute; cheaper than the high priced power stations and better than the lower priced ones.

I carry a chair and a spare (in case of breakage or a visitor). They are much better than sitting on the ground, rocks, or stumps etc.

a small folding table is also handy as an end table, night stand or a place to make coffee in the morning...


More coming...

Enjoy!

A word on power stations; they are essentially batteries with an attached inverter (to convert the battery voltage to 110 volt AC power. Some include other capabilities like a battery charger or compatibility with solar panels.
After much experimenting I got rid of the MPPT solar controller, shown, in favor of a smaller PCM controller. I also normally carry a, more portable, 50 amp hour Lifepo4 battery rather than the larger heavier 100 amp hour battery in the pic.

Like all batteries they will run out of energy and like all rechargeable batteries must be recharged.
On trips longer than a week, or so; I bring solar panels (100 watts is more than enough for my needs) but I also have a DC to DC charger that allows recharging from the vehicle (vehicles make very poor generators/re-chargers due to their pollution and inefficiency). Shade is the enemy of solar energy; but I prefer shady campsites so I end up having to carry the battery & panel(s) to a sunny area, then having to baby sit them so that they can be re positioned when they are in danger of becoming shaded. Only when camping in the desert or a hot treeless pasture does this become unnecessary.

Inevitably, clothing will become dirty. Solutions include doing laundry in a bucket or making a trip to the laundromat, in town; as a part of the weekly, or so; port-a-potty dump, shower, grocery, ice & potable water run (yes; filters work, but filtering 2.5 to 5 gallons, for potable use is a bit of a pain).
Laundry in a bucket needs to be accompanied by hanging them on a cloths line to dry. A 100 foot hank of para cord with some clothes pins comes in handy here.
Hopefully you can camp next to a clear stream/brook and use the water for things like cleaning and laundry. If not; better figure on being able to transport more water.

Enjoy!

After erecting the tent, it will get dark eventually; If you have selected, procured or assembled a power station: you can light the tent and area with electric lighting. If not you are stuck with living in the dark by the light of a campfire or the (to me) less desirable independent battery powered alternatives, or even fuel powered lighting with all of its problems.
I have long relied upon 110 volt tent lighting hung from the ceiling or a tent support.

using a 350 to 400 lumen bulb this is adequate to light the entire tent and provides enough light to read by or perform moderately fine tasks.

The larger (preferred) tent can also be illuminated by either a second hanging globe light or a DIY collapsible floor lamp.

Personally I dislike fuel powered lanterns (because they require new mantles and the glass "globes" are fragile. They present a burn hazard and the flammable fuel must be replaced (consuming valuable transport space). Their only redeeming characteristics are that they are portable and can provide a lot of light (when the mantles aren't broken).

Chairs for me fall into two categories the typical very portable camp chair which are not the most comfortable and a more comfortable chairs with more padding (I usually have one or the disc /moon chairs along in case I need to sit for long periods; during inclement weather (its biggest downside is that there are no cup holders). There are many other styles of folding camp chairs available for those that have the room to transport them.

Furniture arrangement in the tent; for one person it gets arranged like a mini living room; so that visitors can be accommodated.

if two people are on the trip both extra chairs and one end table are replaced by a second cot; this results in much more "together" living... with little space left to spread out.
The same or similar set up is used for the larger preferred "standing room" tent however the cube shape frees up a lot of overhead space and alleviates the cramped feeling.
the larger tent is more difficult to transport and setup/breakdown, however; so it is only used for longer trips and longer stays at a base camp site.

Both the dome and the cube tent use the same ground tarp and have very similar footprints.

Enjoy!

There are obvious alternatives to much of the equipment covered so far.

Stoves; I have changed from the old 2 burner Coleman propane stove to a single burner Gas one. (There are may others on the market) Since I no longer cook for more than myself.
I did find this past year, a small, temporary, heater attachment for the stove tha helps take the edge off the cold tent just before entering the sleeping bag (it then gets turned off).

I have basically given up on trying to heat a tent, due to moisture/condensation, air quality and fuel quantity issues. A good sleeping bag renders a heater, mostly, redundant.

I have found wood heat to be excessivly dirty/sooty; especially when transporting the components home.

12 volt refrigerator vs cooler:
It doesn't take many trips to town for ice replenishment to provide an incentive to look for alternatives.

An ice maker was considered early in the search and could be viable IF a generator is in use (generators require a lot of fuel; so this is a trade of a weekly trip to town for (cheap) ice for a trip to to to replenish expensive fuel supplies, IMO. Running the numbers, several years ago indicated that a relatively large solar electric system is needed to power the ice machine with sunlight. Note; this was quite some time ago and newer technology may have moved the break even point.

A compressor type refrigerator freezer can be run from solar panels and a battery (the base numbers, usually given are a 100 watt panel and a 100 amp hour battery.)... Technology is constantly changing and these numbers may have improved.
I have done this and it works. However, it does require that the camp be sited with access to direct sunlight over most of the day. (As mentioned before; I prefer cool, shady campsites). Like the large tent I save the refrigerator/freezer fo longer than normal trips (1 1/2 weeks or more; the additional transport and set up hassles are simply not worth it to me for week end trips).

I tried solid state (Peltier) coolers and they are, for me, a waste of time. They do not cool well enough to keep ice cream frozen on a hot day.

For port-a-poties; get one with a very large holding tank (cassette) at least 5+ gallons, and, consider getting a second spare/reserve holding tank.
Alternatives include bucket or bag based portable toilets.
for a while I was using a post hole digger a cheap tent with a hole in the floor and either a chair with a hole in it or a padded 5 gallon bucket with the bottom cut out... (honestly, I prefer the port-a-potty).

Lanterns are a thing of personal preference.
As are flashlights/headlamps.

I do still use a tap light on the end table next to the cot; it has the advantage of being easy to find and light in the dark when big foot is making noises out side at O-Dark-thirty in the morning... just tap it to light.


There is also usually a clock and a thermometer on the end table also.

In terms of security (intruder alarm) and companionship a dog is can be hard to beat. (You will, however, see almost no wild life).

IMO Firearms require professional training and while I usually have one available; near "civilization", I can whole heartedly, recommend bear spray with dye to discourage both 2 and 4 legged varmints.

If there are 2 or more people games can help pass slow periods; Chess, checkers and backgammon are favorites.

Some folks are known to camp to hunt and/or fish.

Day hiking hand wood gathering are usually part of my trips.

Running out of things to say, today...

Enjoy!