Big Three Wiring Upgrade - 2nd Gen Tacoma - Writeup with pictures!

it comes in rattlesnake!!

 

but then it’s gonna look like a snake crawled in the engine bay

 

Theft deterrent.

 

Is there a common problem with wiring or just trying to support a larger electrical load?

 

For me it was replacing the corroded stock wiring. After 16 years the corrosion had made its way through most of the wires. If I remember right, I cut like 6 or 7"s down and there was plenty of crap. So I wanted to hopefully gain some efficiency in the conductivity..

 

Ok thanks, that makes a lot of sense

 

FYI to all, instead of having to go into the engine bay fuse panel to remove old cables and attach new you can leave those cable ends attached because they are rated for feeding everything factory on each side of the 120A fuse (or 140A fuse if you have tow package)

The point of the big 3 and the higher current alternators is for feeding things beyond the battery terminal positive post. so save yourself time and just add a new external fuse holder rated just higher than your new alternators amp limit and make sure you remove the old fuse and leave that holder empty (or easier leave it in place but break open the fuse ) the diagram I modified and attached doesn't show it but anyone that looks at the factory engine bay fuse/relay box internal diagram (the second picture) that shows all the bus bars to the fuses and relays will see that each side of the existing fuse feeds a whole lot of other things too....... so leaving the existing battery terminal to 2C cable as is, is an adequate gauge for everything on the one side and leaving the old alternator to 2E cable gauge on the other side but cutting it short and attaching it to the new fuse holder is adequate to feed all the other things in the panel common to 2E (blue wire shown on the 1GRFE engine diagram) that was connected from alt - B to the 2E of the engine bay fuse box (these pictures im showing are specific only for a 2nd gen V6 whether tow kit or not, this may NOT be for a 2.7 liter truck but you could verify that or do similar design on a 4 cylinder electrical system if need be)

1) I disconnected the main factory feeder cable from just the B terminal at the alternator, cut it short , crimped a new lug and attached it to the new fuse holder i mounted external from the factory fuse box.

2) i ran a new 4/0 gauge wire from the alternator B terminal to the same attach point on the fuse holder as the rerouted old cable discussed in step 1

3) i ran another shorter 4/0 gauge wire from the other side of the external fuse holder to the main batt terminal

4) i removed the old ground wire and then ran a 4/0 gauge ground wire from alternator to frame and removed old frame to battery cable and ran a new 4/0 in its place too

this keeps the system design 100 percent intact as factory designed except for increase wire gauge, alternator output and fuse matching the alternator

the people who sell big 3 kits limit the cable to a maximum of 1/0 gauge which truly isn’t rated for full length if you are including a 2nd battery in the bed area. The reason they sell those is because you can’t really get larger than 1/0 to fit into the connections on the engine bay fuse box. With my design you can run 2/0 or even 4/0 to handle the 320 amps not just to the main battery but also any additional wire needed to reach a 2nd battery and a even a power inverter up to about 3000w where if you have one in your smart cap like I do. I needed a total cable run from alternator to main batt to aux batt to inverter that that can handle 238 amps at 22 feet including the ground cable so I have 4/0 everywhere

NOTE REGARDING INVERTERS. A 3000w ac inverter with the DC input voltage as low as 12.6v requires 238 amps to output the full 120 ac at 3000w. Every 0.1 volt above that on the dc input reduces the amp draw on dc sources feeding it so thats the lowest voltage that my automatic battery isolator can pass down the long cabe to the rear battery and to the inverter in the back of the truck while staying connected to the front battery and/or alternator sources. Thats is worst case scenario on that long cable run charging and maintaining the battery and the inverter when the inverter is at full. my automatic isolator between front and back battery cuts out at 12.5v so I have to have the engine idling to use up to the full 3000w without putting a draw on the rear battery. hence, this is why I chose a 320A alternator for times i want up to a continuous 3000w without depleting batteries, for engine running operations the 320A was the correct choice i have to advise that you cant get the alternator to reach the full potential of 320 amp while spinning at the rate it is turning with the engine at idle. It’s more like 250 amps with the engine at idle But mine at idle easily supplies the needs of the main batt and factory fuses and systems and keeps both batteries topped in addition to being able to supply the additional 238 amps sent to the back battery to keep it from depleting while the inverter is continuously operating indefinitely at full rating. (3000watts of pure sine wave 120vac).

Usually, if my batteries have recovered from starting and are mostly topped. I can run the inverter at full 3000w and at that draw. The dc input voltage after drop over distance is about 13.5. (My alternator is set at 13.8 (1 volt over a nominal 12.8v flooded lead acid battery) so my nominal current to run the inverter at full rating and the alternator maintaining it is 222 amps on that cable run to it. ( I’ve had this installed with both batteries and the inverter for 3 years now and both my group 27 battery’s are as good as new and sit at 12.8 when topped and then the engine turned off.

Also note that my cables coming off the back battery to the inverter are about 1 foot long each. Power and ground both, so if the engine happens to turn off or someone shut it off while the inverter is running at full watts feeding some device , then the automatic isolator cuts off connection from the front battery therefore the rea the rear batt is feeding inverter and draining at whatever watts im demanding from the inverter. The voltage on the DC input will drop because of that loss of battery amp hour capacity and loss of alternator feeding it all, and that therefore causes a rise in current. but those cables being only a foot short can handle the increase which even at 12.0 volts it still would jump to 250 amps but 2 feet total of 4/0 from rear battery to inverter dc in and then ground out back to frame can handle that. Plus I have a 250 amp circuit breaker right inline in the 1 foot of cable from aux rear mounted battery to the inverter DC input so if I drop to 11.9v it’ll go over 250 amps and trip the breaker to protect that battery when it’s the solo feed source and engine not running.

Gotta consider everything for safety and no fire or overheating of feeder cables

so in summary, the inverter system has a engine on scenario and a engine off scenario

engine on scenario: start engine, and then wait a minute for batteries to recover from engaging starter. then i can indefinitely and continuously run the inverter at its full rating without depleting any battery levels

engine off scenario, i can run the inverter just off the back battery until that battery drops to 11.9 then it cuts out by breaker trip long before that short cable run can get anywhere near a current draw to cause concern on those short cables. of course when using this scenario, itll be times where i just want to plug something in thats lower watts for a short period without having to start the truck. like my insta-hot water boiler, that i can quickly make two cups of 212F hot water for instant coffee and it uses only 250 watts and takes maybe 5 minutes to bring the water to that temperature. short term use of low power ac pwoered devices. but as i said i can run a full 3000w but that battery will drop to below 12.0 pretty quick the highe the draw on it with out it being fed by the alternator. the wife can run her hairdryer which is 1650 watts for about 5 to 10 minutes without having to start the trucks engine.

under normal conditions, i cant draw from both batteries when the engine is off because of the automatic isolator between the front and rear batteries disconnects them when the front is less than 12.6 volts so i dont cause my main battery to go low to where i cant start the engine.

yes, the automatic isolator has a manual bypass button so i could force them connected without the engine running but i dont plan on ever doing that as a third scenario, ill just stick with the engine on and engine off scenarios i previously described and call that good.

Of course, that manual override button on the isolator comes in handy if i ever accidentally ran my main battery down a bit to where the start solenoid wont engage. With it manually override enabled, i could connect them at any voltage potential between them and augment the front battery by connecting the back one to it, reversing the flow for a bit, trying to bring the front battery's potential up a bit, before attempting a start

 

@ramonortiz55 Where did you get your cable terminals?

 

there was a guy on here that would build them, he's no longer around sadly

 

I think your diagram just saved me. I have the 1/0 wire upgrade. Im getting my 240amp alt installed soon but i wanted to get everything else done beforehand. A few months back I took the route that a lot of guys go and put in a jumper in place of the factory alt fuse to run to an external ANL fuse terminal. This worked, but really seemed unsafe. This weekend I went through the hellish task of taking apart the fuse box again to remove the jumper and leave it blank like you did.

My alt cable now goes from batt to ANL fuse terminal to alt. I also have a 1/0 going from the batt to the factory fuse box through the side entrance. Now my truck won’t crank. The dash light comes on when the key is turned but no clicking at all.

I spent a while trying to figure it out but I gave up for the day.

I don’t have the light blue wire from the ANL fuse terminal to the top factory box alt wire terminal. Is this what is stopping the truck from cranking? I was planning on hooking up this wire tonight when the heat dies off, but I wanted to see if you can confirm that this is the cause?

 

Update: I added in the light blue wire I mentioned in my previous reply and it cranked right up! Thank you for that great post man.