Dual Alternators - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 05-09-2005, 03:25 AM Thread Starter
 
Join Date: May 2001
Posts: 3,501
Thanks: 0
Thanked 0 Times in 0 Posts
 
Dual Alternators

Not that I need to do it, but I was just thinking about dual alternators.

Someone said that they would interfere with one another because they would be trying to compensate for one another..

Technically wouldn't it be the same setup as when you have two trucks hooked together with jumper cables? There aren't any odd side effects when they're hooked together, but maybe it's because its not being driven.

So is there a reason why dual alternators wouldn't work? (assuming stock alternators without modifications?)
Infernozx is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 05-09-2005, 06:51 AM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: Dual Alternators

If the alternators were trying to feed the same battery at the same time, I think you'd find only one does all the work, while the other one loafs.

Remember, a battery can only accept about a maximum charging current of about 30 amps. More than that will destroy it. And, since a battery has internal resistance, it "self regulates" how much it can absorb anyway. To get more than 30 amps into it, the voltage has to be way up - like 17 volts or more. Both alternators would have voltage regulators in them to prevent them from going that high anyway.

But dual batteries each fed with it's own alternator could be handy for winching or as a back-up.

I mounted a second battery in my Rubi - so I can use a Ready Welder -- now THAT'S been real handy!
RRich is offline  
post #3 of (permalink) Old 05-09-2005, 09:13 AM
Official Historian
 
WILL's Avatar
 
Join Date: Sep 1999
Location: Hot Springs, AR
Posts: 8,339
Thanks: 1
Thanked 5 Times in 5 Posts
 
Re: Dual Alternators

I bought a high output alternator from www.4alterstart.com 2 weeks ago. It was the 130 amp one. At idle, it will run my electric fan, lights, wipers and heater blower on low and still stay above 12 volts.
WILL is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 05-09-2005, 09:19 AM
Keyboard Implanted
 
JeepnGreg's Avatar
 
Join Date: Mar 2000
Location: Eureka IL
Posts: 4,676
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Dual Alternators

Are YJ alternators the same as TJ alternators?

If so i know theres a cheap junk yard swap for a 136amp for TJs out of certain Dakotas and Rams, but you have to change the pulley (they have a 7 groove serpentine, TJs have a 6 groove)

not sure if they are the same...but its a good option if they are
JeepnGreg is offline  
post #5 of (permalink) Old 05-09-2005, 12:27 PM Thread Starter
 
Join Date: May 2001
Posts: 3,501
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Dual Alternators

I've got a Buick 90amp sucker on my SBC right now.

As it turns out, the reason my voltage gage takes a dive every time the trucks been running for 20-30 min is a combination of the taurus fan, and some bad grounds somewhere.

The system holds 14volts even when its fully loaded (except the winch) when checked at the battery with a known good multimeter.

I was just pondering dual alternators.

Isn't having the two vehicles tied together with jumper cables identical to dual batteries that are not isolated from one another?

I was just curious about the theory... wasn't really going to put it into practice... besides the other alternator is reserved for an OBW one day. [img]/ubbthreads/images/graemlins/grin.gif[/img]
Infernozx is offline  
post #6 of (permalink) Old 05-09-2005, 01:11 PM
Way Outta Control
 
Join Date: Sep 1999
Location: usa
Posts: 10,815
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: Dual Alternators

Yes, jumpering 2 vehicles together would be about the same.

Most likely one's doing all the charging in that case too.

I wouldn't think it'd be good practice to have both vehicles running at the same time for long tho. There could be some interaction between the 2.
RRich is offline  
post #7 of (permalink) Old 05-09-2005, 02:11 PM
Moderator
 
Jim_Lou's Avatar
 
Join Date: Dec 2001
Location: Belleville, Illinois
Posts: 11,487
Thanks: 15
Thanked 22 Times in 17 Posts
         
Re: Dual Alternators

[ QUOTE ]
Most likely one's doing all the charging in that case too.

[/ QUOTE ]

When a battery is really low either alternator by itself might not have enough output to bring the voltage up to the regulator set point. In that case they will both put out as much as they can. That situation is likely to last a very short time however.

All voltage regulators are set about the same, but they aren't exactly the same, even if they're supposed to be. Whichever alternator has the higher set point will do all the work. The other will see that the system voltage is higher, even if only a hundredth of a volt, than its set point and so will shut down.

That won't cause a problem by itself, but the complexity of wiring, belts and mounting won't buy you much either. You will have more output, but you can get that with a bigger alternator. You will have redundancy in case one fails, but the complexity is a poor tradoff IMO. Plus, there's the issue of maximum charging rate.

I have an ammeter in my Jeep with a 56 amp Delco. I almost never see the alternator putting out full capacity. The only time is if the battery is really run down from leaving lights on or something like that, and then it only puts out for a minute or two before it starts backing down.
Jim_Lou is offline  
post #8 of (permalink) Old 05-09-2005, 03:07 PM
Keyboard Implanted
 
lomodyj's Avatar
 
Join Date: Jan 2002
Location: Chapel Hill, NC
Posts: 3,761
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Dual Alternators

Just because nobody has mentioned it in this thread. You could hook it up and drive down to the bash and we all could see it at the Bash. [img]/ubbthreads/images/graemlins/grin.gif[/img]
lomodyj is offline  
post #9 of (permalink) Old 05-09-2005, 03:10 PM Thread Starter
 
Join Date: May 2001
Posts: 3,501
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Dual Alternators

With the way my tranny is slipping now, I'd probably go through $400-$500 in fuel just to get there.
Infernozx is offline  
post #10 of (permalink) Old 05-09-2005, 11:28 PM
Official Historian
 
WILL's Avatar
 
Join Date: Sep 1999
Location: Hot Springs, AR
Posts: 8,339
Thanks: 1
Thanked 5 Times in 5 Posts
 
Re: Dual Alternators

I didn't swap in a high output alternator for the top end output, I did it for the idle output.
WILL is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome