My problem is finding the negative ground on the block. Still have not found it.

Neither could I, which is why I went to the alternator bolt, which is connected to the block.

lol, I feel ya. Maybe someone will chime in and point us to this mystery ground zero.

I have much more pressing electrical problems though. My voltage is all over the place. Even after new 3 new alternators I'm hovering at 13.1v with no load, and 12.7 with hi beams, A/C etc.. on.

Yikes, that sounds really low. I can't remember what I was at before I upgraded to my 240a alt and big 3, but now I sit around 13.6 at idle in park with no load, and 13.6-14.0 at 2.5k rpms depending on charge. I have a dual digital monitor in cab to watch both batteries and those numbers appear to be my averages.

That seems like a nice upgrade! Where did you get the 240a alternator from, and how much did you end up paying for it?

When you did your big 3, what gauge cable did you end up using? I think the factory cable is 2 gauge...

My electrical system seems fine, but if I can reduce the voltage drop by a couple tenths of a volt ill consider doing it.

Toyota 4Runner High Output Alternators

I paid right around 430ish after taxes, free shipping. They are located out in Riverside, Yucaipa I think, but I wasn't in a hurry. Ended up still being 1 day shipping. Ordered in the morning, had it next day.

1/0 for the Big 3 upgrade and 1/0 for my dual battery setup. I have virtually no voltage loss between both batteries when they're connected except for when my house battery is low. It seems with a simple isolator setup the starting battery (closest to the alternator) will always have a higher voltage than the house battery when the house battery is low. I usually see around 13.8 on starting battery and 13.6 on house when the house needs a charge, otherwise they're typically the same at 13.8-14.0.

Perfect, thanks for that. I actually have some 1/0 laying around I can use up.

Did you do the cable and alternator at the same time? Im just curious how the big 3 upgrade helped the voltage drop with the OEM alternator.

With stock electrical should pretty much eliminate it I would imagine. I did do both at the same time because I was having issues keeping my house battery charged with my fridge running full blast, off road lights, and a/c running in 80-100 degree heat while off road at idle and starting/stopping with a big group over 2 days so I was trying to fix it before the next camping trip I had planned.

Nice, perhaps I should look into an alternator as my electrical load increases... Right now I have a couple light bars, fridge, ham radio, along with a couple plug in accessories but I still have enough overhead for charging...

The issue I am trying to work out has more to do with the voltage my ACR is reading... I installed the ACR on the other size of the engine bay so I am seeing some voltage drop from the distance, and on hot days and when the starter battery is full the ACR takes too long to combine.

If I can rescue a couple tenths of a volt via larger wire my problems should go away. That said, I only used 4 AWG for my house battery, but based on my load figures it should have been more than sufficient plus there is no voltage drop until it combines which is the issue I am working on.

I also checked after it was installed with a DC clamp style amp meter... and it peaks at 77 amps when it combines from a 11.7v LVD cut-off, and levels out to about 33-35 amps after it equalizes for about 20 seconds.

I used 4g originally for my dual battery setup too and was running into the problem where my starting battery was getting 13.8 and house battery was getting 13.1. That was also part of my problem and why I upgraded everything to 1/0.

Then you definitely have more electrical load than I have right now... I dont get that steep of a voltage drop across my 4g cable... ill double check tonight with me meter.

But as I mentioned above, I dont see a voltage drop before it combines... my problem is getting it to combine sooner than later.

Could also have been because I was running an 80a isolator. Also changed that to a 200a w/ 200a fuses at the same time, haha. I made a LOT of electrical changes all at the same time and it fixed about every issue I had. At this point I have more than enough flow for anything and everything else that I may want to connect in the future. I even ran 1/0 gauge to a fuse block in the cargo area from my house battery for rear lights, fridge, and accessories to keep the voltage drop down for stuff in the rear. It's all overkill at this point.

That's actually very helpful information. My girlfriends 2015 RAV4 with 13k miles in drive under the below conditions actually dips to 12.5v:

-A/C full blast, defroster, highbeams, windshield wipers full blast, radio and brake light all applied. (everything that has an on button)

I'm curious if you could test under the same conditions after engine has reached operating temperature, with the batteries isolated?

Would be much appreciated

With the 240a alt and big 3 upgrade I'm getting 13.8-14.2 on the starting battery isolated. Before I really wasn't seeing anything higher than 13.6 at 2k rpms I believe. Maybe 13.1 at idle? I don't remember but I can check my Tacoma though on Sunday when I get back home and see what it's running at with the stock 130a alt and stock wiring on my 4.0 engine. Not quite the same because it doesn't have as many electrical nannies as the 4runner does, but it would be a good baseline for the 4.0 and a 130a alt.

so you dont use a shorter belt with your high output alternator? i know my mechman alternator uses a smaller pulley that required me to use a belt half inch to 1 inch shorter than stock.