1st I know there are a million battery posts, but there is so much info its like trying to drink from a fire hose. and most threads focus on running fridges etc.

2020 model
Installing a Warn vr evo 12s winch. max amp draw is 396 amps.

Not factoring in any fridges or other stuff...Winch operation and starting vehicle.

Do I need to upgrade the battery?

if so, what specific model to use in stock location without mods.
The one mod I think I may need is the diode mod if an AGM is recommended.

Thanks for your input.

I use the OEM battery size. I've replaced once in 7 years. I use my winch quite a bit. IMO you don't need to upgrade your battery. The 4Runner has a relatively large alternator by historic 4x4 standards at 130 amps. Unless you're doing multiple full line pulls, the OEM battery will be just fine. It really depends on how you're going to use the winch and some of that is going to depend on the terrain you spend time in. If you're stuck in rocks, you'll rarely ever pull more than a few feet. In mud it might be a longer distance. If you're bogged in the salt flats or sometimes in deep snow, it might be dozens of back to back full line pulls and waiting while the winch cools down.

In theory if you were pulling the full 12k max load at 4 feet per minute, and getting 100 amps from the alternator, you'd deplete a typical Group 24 battery in about 6.6 minutes to 10.5 volts where you should stop and wait to recharge. So that would be only about 26 feet of line pull. But in reality you'll likely never come anywhere close to reaching the full 12k lb line pull, and if you did it would only be for a few seconds. In my normal 4runner offroad use, it's usually short pulls of far less than fully maxed out capacity. And then most of the use is just winding up the rope. You'd see more like 200 amp draw to pull say 6k lb line tension at more like 10 feet per minute. So even under a decent winch pull that you're more likely to see, you'll be closer to 3-4 full 80' line pulls before you'll need to stop and let the alternator charge the battery. You might be seeing the winch get pretty hot at that point too.

If you're guiding an offroad group or going somewhere you'll be doing a lot of winching, then it probably makes sense to upgrade to dual batteries. For trail use, I'd just stick with what you've got. That's what I've used for the last 7 years without issue.

In my trial rig - I go with dual batteries and a high output alternator, but it also uses an 8274 winch that has 150 feet of line and pulls a lot faster/harder. So the draw is high, but often for shorter duration. With the fast line speed, I also tend to end up as the anchor vehicle at the top of a tricky obstacle to pull everyone else up. It's just more convenient even if the other vehicles have winches to use one with fast line speed and sometimes that long rope helps being able to park in a more favorable anchor location. I've also used it for skidding logs over to the road for firewood and general utility type tasks like that. If you're doing that sort of duty, then dual batteries are more useful as well a high idle option to keep the alternator output up. So there's certainly a time and place for higher battery capacity. I just don't think most 4runner users are doing that kind of winching regularly. So I would suggest using the OEM battery size unless you know that you're going to need more for your use profile.

Good luck.

Heavy plus on this, I winch A LOT during the winter because of my love of snow wheeling and getting stuck apparently. Even in scenarios where I am doing repetitive pulls to get myself or others out I have never run into a situation where I've drawn down the battery. Don't let the IG influencers and Expedition Overland actors fool you. Your stock battery is just fine.

Just to add a point of reference. Most planetary style winches have around a 30-45 second duty cycle at full load before overheating. Then require around 20 minutes of cooling. The stock battery can easily put out full 400 amps for 40 seconds and the 130 amp alternator has no problem returning to full charge by the time the winch is cool enough to use again.

thanks all for your replies....i will stick with the OE setup. I only "plan" to use it intermittently mostly because I often explore solo.

The rabbit hole of upgrades gets quite expensive, so im glad i should be ok..
adding a winch =

winch 900$
Bumper 1000$
Springs 400$
UCAs 600$ (figure might as well since i will be in there)
Misc extra recovery stuff...$100.

total 3000$

Thanks for help full information about the winch, Bumper, Springs, and UCAs.

I dunno.

I drained my OEM battery winching, but probably due to me turning off the vehicle shortly after winching and taking a break, which then required a jump start from the vehicle I was recovering.

I upgraded to a AGM group 31 soon afterwards, but that was mainly due to the OEM battery being on its last legs, and I wanted to upgrade the electrical system as a whole to support the winch, fridge, lights, lockers, comms, etc.

So I wouldn't replace your OEM battery if its in good condition, but if you HAD to replace it, then I would go with an AGM battery.