How to wire dual alternators.

[Nick_R_23]

So the charge each other was a little fib. Example- my Duramax battery is not carrying load anymore. Repair is 2 new high quality batteries correct group size and amperage rating of at least what GM requires. Same size, same cca. Connected in parallel. Are you talking about multi battery power banks, backup power supply or dual battery trucks and dual alternators? " charging system will be based on weakest therefore thats your power level" ? Didn't you just say the charging system will keep trying to chargethe weaker battery resulting overcharging good batteries?

I think you’re trying to massively over complicate this. The OP is talking about dual alts/dual batts in a parallel system. I don’t know why there is talk of wiring in series and 24v systems as it is not what the OP is working with.

You’re also confusing battery voltage and amp loads. A battery can show 12.8v and be considered fully charged but have dead cells and carry a low amp load rating. You can have a 12.8v charge and on two different batteries, but one may be a faulty battery only produce 1 amp and the other is a working battery producing 800 amps. Both show good on a tester, but one will function under a load and the other won’t. That’s why you can’t just put 8 AA batteries together and start your car, even though it’ll read 12v.

Batteries will always want to equalize to the weakest battery in the system.

 

[Ken K]

The "L" terminal needs to be powered through a 100 ohm or 50 ohm resistor depending on who you ask.

This makes it easy!

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The OEM dash alternator or battery symbol on the dash is a 194 peanut bulb. In the schematics it has B+ from the key during crank and run. It goes to the bulb and the to the exciter terminal of the voltage regulator. The bulb acts as a current limiting device and allows only 0.25 amps to pass thru. This is where many damage the regulator as the dash bulb when lit has the same resistance as a 470 Ohm resistor. On passenger cars (Maybe some trucks) but they ran a parallel circuit around the bulb so if the bulb went bad, the alternator would still work. In a parallel circuit and resistors, current flow is higher if one resistor is lower. The 194 peanut bulb is the same as the 470 Ohm resistor. (Note; Either 460 ohm or 470 is sold/made not both. 1/4 of an amps is limiting current to the regulator but still gets full B+. Otherwise the regulator will be damaged.
Wired to “Hot All The Time” will keep the alternator on. Place a large screwdriver on the pulley shaft and it is magnetic. Only got with crank & run should be used. If for some reason the dash if heavily modified and has no “Battery” or “Alternator” symbol on it, you have to solder a 460 Ohm resistor in line (Called in Series” and shrink tube over it. It you use regular tape that unravels, place a drop of Black Weather Strip” adhesive on the end, it will stay. Another trick when cutting open a harness with tape or tape over convoluted harness cover is using a “Seam Ripper” sold at a sewing store. It has a long point that has a plastic ball to protect wire from poking holes in. The center is sharp and does the cutting and has a tiny point on top to guide your cut. I buy 6 at a time as the used to be 50 cents. They are all the same and do get dull. Unless you have a small stone rounded to fit, used on wood planes, it’s call a “Slip Stone”. A wood shop may sell them but I just grab a new seam ripper and go.
ASE Master Tech - Retired

 

[Jesse_Wenting]

Typically while I'm plowing the plow it self is a 200amp motor

Do you mean plow or snow thrower? Either way 200amps jeeeeeeeeeeeeezzzzzzzz

 

[Duallylife]

Sorry for not replying I was out of town then got busy. The plow I use most on this truck is a Boss, it's it's 200amp motor Idk what the tag says but I know the motor is 200 I had to replace it 2 winters ago. The sander is a Fisher polycaster. Also electric motor, actually its a newer dual electric, one for conveyor one for spinner. I'll say the plow draws the hardest, followed by my heater then 4wd is very close behind then my marker lights. The sub I don't notice any gauge fluctuation but if I'm "blasting" the tunes I cab sometimes watch my marker lights flicker. The heater and 4wd I can watch the gauge dip with both, same with the markers. The sander I actually don't see any voltage drops on the gauge or lights flicker, seems to be very good on power.

So I need to wire a resistor somewhere along the line on my exciter wire that runs to wherever I bring it?

Exactly what I was trying to point out about battery equalization, if you have dual battery's on something and have a heavy draw hooked up to the one battery check it with a multi meter, it will read lower then the other one. I have checked before, I plowed a driveway (my plow is hooked to my right battery) with lots of plow moving, as soon as I did my last push I shut the truck off, my right battery was at 12.8 and the left was at 13.5, after about half an hour of sitting they started to equal out when I last checked that time they where both around 13.1. I did it again another time but with the truck off the whole time, moved the plow around for a bit then checked my batteries, one was again lower then the other for a while. Even while the truck is running if you put a meter on both batteries and work the plow or any heavy draw you can watch the battery that it's hooked up to fluctuat more while working the plow then the other one on, my truck while it's idling both batteries fully charged and the alt pushing about 14v with a meter on both batteries if I lift my plow one will drop to about 12.8 and the other doesn't drop much unless I move the plow alot. I have parked my truck for the night after a storm, checked both of my batteries and the one my alt feeds was 13.8, the other was 13.4, when I came back out the next morning they settled around 13.3

 

[Wh4t3v3rs]

I have a 93 k3500 that I'm putting dual alternators in. Now for the guys who are going to ask "why? Just get a big single" I have tried, I tried OEM, juiced up aftermarket, and had some built over the years. I just find when they get hot they have a hard time keeping up, then eventually burn out. And at 400$+ for aftermarket or built here by a guy a piece every year or two it gets expensive. I want low RPM output, big singles are good at higher RPM's.

I want this because I use it for plowing and sanding, so there is heavy draws. Typically while I'm plowing the plow it self is a 200amp motor, plus alot of time while I'm plowing I also have my sander on, so another 100 amp? I'm not sure what that motor is. All of my strobe lights, at night all my marker lights, headlights, and light bars. Sometimes I'm using 4wd which draws alot. Heater on, which also draws alot. Sometimes whipers or other misc stuff, of course the usual stuff you know, radio (with a sub), phone charger etc. Alot of times I have to turn stuff off with OEM alternators or it falls too low. Even juiced up ones sometimes, or they get very hot. It's not wiring, as I have re wired most of the lights 2 years ago. And I clean all my connections, grounds positives etc once a year. On the batteries, alternator frame body etc. Also has dual 1,200 cranking amp batteries, less then 2 years old and I test them once a year. I have always had this issue with my GMT400's, even my square bodies. I have had this truck about 12 years, always had this issue just dealt with it. It did help after I rewired the truck though haha. I also plan to do the "big 3 upgrade" on the wires.

My question is, how do I wire it up? Right now my stock alt reads and charges the passenger side battery first, the second battery just adds reserve, (it isn't directly hooked to the alternator) So I would like to hook the second alt to that battery, one alt on each battery. Can I do this? I should just be able to run a wire from the back of the charging stud on the alt to the second battery? What do I do for the exciter wire? Where do I run that to? If I can separate it from the passenger side battery so it reads the drivers side that would be great. Or do I need to splice them together?

If you are looking for an alternator with big output at low RPM and will last the test of time, I've been using them for 20+ years in all of my customers vehicles with bigger stereo systems.....Ohio Generator...... Tom is the owner and they make THE BEST aftermarket alternators! IMO

https://ohiogen.com/

 

[Duallylife]

If you are looking for an alternator with big output at low RPM and will last the test of time, I've been using them for 20+ years in all of my customers vehicles with bigger stereo systems.....Ohio Generator...... Tom is the owner and they make THE BEST aftermarket alternators! IMO

https://ohiogen.com/

I'll look into them, thanks.

 

[df2x4]

If you are looking for an alternator with big output at low RPM and will last the test of time, I've been using them for 20+ years in all of my customers vehicles with bigger stereo systems.....Ohio Generator...... Tom is the owner and they make THE BEST aftermarket alternators! IMO

https://ohiogen.com/

X2. I have one of their alts in my red truck. The shop that recommended and installed it didn't sell me a large enough one so I still have some voltage drop when I'm cranking the subs, but I've been beating the crap out of that thing for over a decade and it still works like new.

 

[Duallylife]

I know plowing will always be hard on electrical systems, especially when you're running over 1800 watts of stereo..(At max), the plow, all those marker lights that GM never really did properly to begin with and always had big power draws. The heater they were also meek on, along with that heavy draw electric 4wd actuator. It would just be nice to either not be burning up expensive high OP alts, or not having to roll ur windows down as you pull up to a driveway (especially with rollies) just so you can turn the heater down/off to save power, and not fog up especially if you need 4wd, and sometimes if you're working the plow hard or running the sander, even having to shut the marker lights off and rely on your strobes souly. The second alt bracket is already built and the alt is already bed in, belt hooked up (original belt too) and running, just need to wire it.

 

[thegawd]

If I was a plow guy i would be looking into alternatives to such high draws. like maybe an electric start gas sander.

do the plows use hydraulics or just electrical power? My dump trailer has a nice little 12v hydraulic power pack, are the plows set up similar? I really have no idea.

 

[Duallylife]

If I was a plow guy i would be looking into alternatives to such high draws. like maybe an electric start gas sander.

do the plows use hydraulics or just electrical power? My dump trailer has a nice little 12v hydraulic power pack, are the plows set up similar? I really have no idea.

The plows are all the same, electric over hydraulic, electric motor spins the hydraulic pump