Dual Alternator on a desmogged 2F

[lovetoski]

25 year rule kicked in for me recently, and I won't have to go through the smog test anymore. Time for a desmog. I've installed a Trollhole carb, and will post pics of how this turned out in another thread.

The purpose of this thread is to document a long-planned dual-alternator install. I've had a dual battery system in place for 5 years, using a VSR (voltage sensing relay). This is a very reliable and simple setup.

But I was inspired and intruiged by some of the dual alternator installs, and now that I'm doing the desmog, it's time to give the dual alternator install a shot.

Here are two threads that were key in inspiring me...

https://forum.ih8mud.com/60-series-wagons/222516-130-150-extra-amps-2f.html

https://forum.ih8mud.com/60-series-wagons/94294-fj60-dual-alternator.html

Some notes on what parts I used...
Alternator is a stock 55amp from a 2F
Alternator bracket is from a 3FE (but modified)
Tension bracket is from the smog pump in the 2F (slightly modified)
Belt is a 17mm X 1095 (11/16" x 43 1/8") - stock is ~ 44 1/2".

I cut a lot off of the 3FE bracket. Pics attached.
The tension bracket only needed slight modification...I opened up the hole towards the engine so that the bracket would rotate down further.

Wiring is not done, mostly because I don't have it figured out yet. This system will use a marine switch...so that I can switch from batt 1, batt 2 or use both, or neither.

There are three wires on the 2F alt.

1. Battery - easy, run a 6 ga wire from the alt to the battery +
2. Ground - easy, run a 16 ga wire from the alt to battery - or nearby ground.
3. Sensing wire is where I am confused:

The "sensing" wire (white) is 10 gauge. I can't figure out why it's such a heavy gauge wire. It's function I believe is to tell the alternator to turn on, I don't think it carries high amps. It needs to be connected to a switched hot wire (engine charge lamp, radio, cig lighter, etc). The closest switched hot is the carb fuel cut solenoid...but it's an 18 ga wire. Why the heck is the sensing wire so fat? Does it carry a lot of amps...or is it this size only to minimize voltage drop? Would it work to connect it to the sensing wire on the stock alternator?

Appreciate any input on this...I'm keen to get this done.

Here are some pics...more to come tomorrow.

You'll notice that I had to grind off a lip on the front side of the 3FE bracket. This is because otherwise the alternator pully rubbed into the other belt. By grinding off the lip, it moved the alternator backwords, away from the other belt. This was perfect, since the spacing between the ears of the alternator was too narrow for the 3FE brackt, and by grinding off the bracket it allowed the alternator to fit.

 

[Kynot62]

Doug

I have to ask, just what is it that you are running that requires that much juice? Short of the benefits of having a backup are there others?

Reason I ask is that my BJ60 came from the factory with 2 batteries wired in parallel with an alternator that only puts out 45 amps if I got the numbers correct. I run winches front and rear, a large fridge, an air compressor for my lockers, lots of DC accessories and I have never had an issue with my power.

My alternator also gets the privilege of running my vacuum pump.

Just want to learn more about the why's and reasons. Also wonder if there is something I am missing...

Tony

 

[lovetoski]

I have to ask, just what is it that you are running that requires that much juice? Short of the benefits of having a backup are there others?

Hi Tony,

If you add up the amp draw during a typical winter day in the nw (headlights, heater fan x2, rear window defog, windshield wipers, stereo) it's enough to cause a pretty good voltage drop at lower rpm...ie the stock 55amp alt can't keep the system at 14/14.5 volts. Everything electrical works better at 14.5v. If you add a second set of driving lights, especially for night wheeling where you're going slower, you're pushing the limits of the stock system even further.

In my opinion, the stock electrical system is just adequate, but if you add stuff it's no longer sufficient and needs an alternator upgrade.

Also, with a desmog, the space occupied by the smog pump is available to do something with. I have a jim-c pully, and that's a much easier/quicker way to replace the smog pump.

I went this route for four reasons: redundancy, to increase the reserve capacity of the electrical system, to see how it would work, and to document the results.

 

[lovetoski]

Here's another pic of the alternator installed. Note I had also to add a spacer (a nut) between the tension bracket and the alt.

 

[lovetoski]

I've also installed a battery cut-off switch in line with the 2 ga wire that runs over to the DS of the engine bay. There will be an identical battery cut-off switch on the primary battery.

 

[lovetoski]

After reading lots of posts about whether to fuse an alternator, it seemed that doing so made more sense than not. Here's a pic of how I did this, though the fuse itself is not yet installed (I purchased a 60am fuse).

 

[lovetoski]

And here's where I still have a question...where to connect the sensing wire? (It's the white wire in the attached pic. The yellow wire is ground.)

The concept as I understand it is to measure system voltage somewhere far from the alternator. This allows the alternator to compensate somewhat for voltage drop w/in the electrical system. But that's for a single alternator system.

I've not (yet anyway) found a good explanation of where you might connect the sensing wire on a dual alternator system.

I could run it to the fuse box. That's easy, and close by. However when I have the battery switch on "battery 1" then the 2nd alternator would be looking to the primary alternator output to sense what it should do. This doesn't seem right to me. My current thought is simply to run the 2nd alt sensing wire to the secondary battery positive. On single alternator systems, I've read that some people wire up alternators this way and it works - it's not optimum, because it doesn't compensate for voltage drop w/in the electrical harness, but it works...that is, the alternator will put out 14/14.5 volts.

Any and all comments are welcome...

 

[RockDoc]

Good to see some current discussion on dual alts.

I'm planning to add a second 3FE alt in my truck, but I think I'll run two separate alt-battery pairs with the second being a deep cycle system for fridge/lights/radios etc. that will only be linked to the primary electrical for self jumping and winching. I first need to build some welding experience, though, to tackle a mount for it (in place of smog pump like yours).

 

[ntsqd]

Delco 10Si's, 12Si's and 17Si's all have such a sensing wire. Most conversions simply loop it back to the output post. Seems to work, and work on many, many different applications.

 

[Kynot62]

Doug

Nice job with the write up and pics

Tony

 

[lovetoski]

Good to see some current discussion on dual alts.

I'm planning to add a second 3FE alt in my truck, but I think I'll run two separate alt-battery pairs with the second being a deep cycle system for fridge/lights/radios etc. that will only be linked to the primary electrical for self jumping and winching. I first need to build some welding experience, though, to tackle a mount for it (in place of smog pump like yours).

I haven't decided yet how I'll use this. I've designed the system so that I can use it as you describe above, or could run both batt/alt pairs connected together all the time. A marine switch makes these choices possible...here's a link...
m-Series (Mini) Battery Switches - Blue Sea Systems

I know I'll connect the two for winching.

I am pretty sure I'll connect the two during the winter (when the stock system is not quite enough.)

So, it maybe that I'll just leave the two connected most of the time.

However, I do plan to have it set up so that at camp I can run lights/fridge/etc just from the aux battery, saving the primary one for starting duties in the am.

Time will tell how it works, and how I use it.

 

[ntsqd]

If you're going to pair them together for any extended period I strongly suggest that they share the same ground bolt. Just the resistance from one side of the engine block to the other in my old Sub caused me no end of battery grief. Moving the grounds to the same bolt made it magically go away. I didn't move them as part of the problem solving process, I moved them as part of a battery switch install.

 

[lovetoski]

If you're going to pair them together for any extended period I strongly suggest that they share the same ground bolt. Just the resistance from one side of the engine block to the other in my old Sub caused me no end of battery grief. Moving the grounds to the same bolt made it magically go away. I didn't move them as part of the problem solving process, I moved them as part of a battery switch install.

I have a 2ga wire running from batt #1 t o batt#2, connecting the neg posts (as well as various ground wire to the engine/block/etc. Would that suffice?

 

[ntsqd]

I would think so.

When I added the marine switch (so that I could the truck off in the hopes of keeping the batteries alive) I added it on the ground side as it was the easier side to work with. Then after forgetting to turn it off a couple times I realized that the problem was gone.

Be careful to not create a ground loop. Can and should be branched, but no loop(s).

 

[Kynot62]

I had to ground my dual batteries seperate because I have the capability of swithing my batteries from a parallel 12V to a 24V series connection for my ready welder. I also can reverse the polarity when welding. Switches completely isolate the vehicle system when it is switched to 24V and no I can't run the vehicle when it is switched over to 24V.

As far as I know, older Toyota diesels, which all run dual batteries are grounded seperate from the factory. There was no direct connection between the Neg posts on my BJ60.

Ntsqd could you explain ground loop for me, I'm a bit of an electrical peasant and want to know more

I am also curious about using the switch on the neg side. How does this isolate the two systems? Reason I ask is that my older Ramsey winch does not have a ground wire, it uses the mounting bolts to the frame as the ground for the motor. If the isolation switch is on the neg side it wouldn't effect my winch. Don't you need to interupt the Pos side to truly isolate the batteries? Or am I losing it in my old age.

Tony

 

[ntsqd]

Switching on the ground side does the same thing as switching on the + side. It breaks the circuit. Ground side switching is sometimes preferred because the voltage drop across the load has already occurred. Note that most EFI systems switch the ground side of the injectors, not the + side. V = I * R, so where the voltage has dropped the most is the greatest consumer of current. Switching on the ground side means that it is low current switching rather than the high current switching that would happen on the + side. Printed circuit boards generally don't like high currents in them.
In my case it was simply more convenient to do it that way.

Ground loops are an interesting phenomenon that I don't fully understand. I suspect that anyone who claims to fully understand them is lying. Even the ground loop expert that we called in to consult on a problem that we were having in the dyno facility commented that he learns something new on nearly every job.
If you arrange the ground cables such there is a circular path, rather than a branched path, then what happens is that each 'station' in the ground loop can be at a slightly different potential due to the small resistances at each connection. For normal 12 VDC operation this isn't too much of an issue, but it can cause no end of trouble to electronics. Low voltage electronics, like say some EFI sensors, are intended to operate with the same reference ground. If not all of the 'stations' in the ground system are truly at Zero potential then those references are thrown off and the ECU may or may not be able to compensate.

There is also the possibility for electronic noise due to a ground loop. I'm not really up on how this happens, what the mechanism behind it is, but I can say that having seen it in action that it can vary from mildly disruptive to what you're trying to do, to destructive to hardware, and anywhere in between.

 

[lovetoski]

I read the wiki article on ground loops, and you're right it's not easy to understand (and I don't really understand it) though I can "kinda" see how you'd get noise/crosstalk in sensitive electronics.

In the case of my 12v dual battery system...I have multiple grounds from battery to frame, frame to engine, etc. Is the grounding from battery to battery overkill/risky?

 

[ntsqd]

The way that I would do it it to ground both batteries together. Where they're grounded isn't of importance to anything, though common practice is to ground to the engine. I think this is a good idea, shortest, least resistant ground path for starting current - which is typically the highest current in a vehicle.

From the engine I would ground to the body, and also from the engine to the frame. Can have multiple parallel grounds (i.e several engine to body grounds and/or several engine to frame grounds), but do not then also run a ground cable from the frame to the body as that creates a loop. Can go to a point and then branch out from there, just do not connect any of the "tips" of the branches together.

 

[nikos8]

are you adding the second alternator to charge the second battery?


Never mind. I just read the threads posted on your first post.

 

[lovetoski]

Here is a thread from a couple of months ago with my initial wiring diagram and some discussion around this topic. Thought I'd combine it into one for ease of use.

https://forum.ih8mud.com/60-series-wagons/476463-questions-dual-battery-dual-alternator.html