Larger alternator vs dual battery
 

While winching a Jeep (again) I hit a point where my alternator wasn't able to kick out enough juice to run the winch and my truck and the same time, even with my engine at 3000 RPM.

So, in my V6 94 4Runner, what will give me the most benefit in these situations, a larger alternator or a dual battery setup?

A second battery, without a doubt. Since your winch can draw 400+ amps, there isn't and alternator out there (without spending serious $$$) that's gonna keep up. It's much better to a have a second pool to draw from. Run the engine off one, the winch off the other.

Why not go both? The dual battery setup (with a good isolator) will be a lot more expensive than a bigger alternator. You can get a bigger alternator that's a direct replacement from Mr. Alternator (which is what I have) or you can swap in a GM alt (which is what I'm going to do later). Both can be had for about $230.

If you can only do one, I'd also go with the dual battery setup. The bigger alternator will prevent the batteries from draining as quickly though.

I happen to have a dual isolate switch for my boat, that I don't really need there, so I guess my challenge is finding a suitable mounting location for the second battery.

I would vote for the second battery, but don't bother with the switch and associated crap. Mine just turned into a headache. Mount the batteries as close together as possible, and wire them together with nice, heavy gauge wire. One positive thing about having extra battery power is that you can use the winch to pull the truck on to the flat bed trailer when it craps out completely and won't run. I'll let you know how well that works in a couple days when I go get my dead truck.

yeah, just get 2 GOOD batteries, and forget the isolator crap. my blazer came from the factory with dual batteries, and there is no isolator, they are just wired together. and mine are on opposite sides of the engine bay. it works fine. it even makes it easier for me to use the readywelder(thanks again MNBOY).

I have been running 2 batts for a # of years with a master battery switch. Don't mess with an isolator setup, too prone to having problems vs. a good marine master battery switch. I also run a gm 100a alt...

I'll have to see what my setup is in my boat. I do believe that is was an isolater. It seemed simple enough in my boat.

If I wire this with just the switch, what's the wiring pattern?

A guy on the pirate board wrote a tech article on doing this exactly:

Dual Battery Setup

Not really a good idea. If one battery begins to fail it will take the other with it. Even when they're good one will always be lower than the other and they will fight eachother over time until both are drained. You have to have some way to seperate them, either through a switch or an isolator.

well, its been working just fine for 19 years in this truck, and according to the reciept, the battery's are 4 years, 7 months, and 12 days old, and still kicking. i admit that it isnt the best way, but (and im setting myself up here) GM and ford used it on their diesel trucks for a long time, and thats good enough reason for me to keep it the way it is.

Interesting. If it was a factory job I'd think they would put some sort of isolation device in there. Is it a 12 or 24v system? If it was wired up for 24 it wouldn't need it, the problem only occurs when you wire the +'s and -'s together.

Shane, you ever seen how a diesle is setup? They run 2 batteries in paralell. I have had my setup, with amaster battery switch, for like 3 years now, and yes, I had one battery fail. But once it did, it wasn't hard to figure out... I totaly dissagree running any kind of electrically controlled isolator setup. They are prone to failure, and the way you would have to set the system up, you would not5 be able to use one or the other battery to start the rig, use it for a winch ect (you have to sit down and draw the schematic to show it)...

But what I say comes from 15 years of doing this stuff...(at a profesional level)

crash, what do you have?

and crash explained it all better than i could have. i just know that the diesels need the extra juice running them together to turn against 21:1 compression, and 330 psi.

It has to do with the amperage capability and like you said the flippin high compression ratio's.

My rig has 2 optima's with a marine master battery switch
So, it has setting for
Battery A
Battery B
Battery A&B
Off (and its lockable in the off position)

I always just keep it in the both position, which lets both batterys be constantly charged, and helps with starting/operation of any high amperage electrical parts. And If I was ever in the situation where the motor stalled, turn it to one battery, and have the second fully charged and ready to...

Keep it simple, and I have replaced a # of those blue isolator setups because, well, they are junk...

Yes, actually. I've seen a small diesel car with a single battery setup, duals like you're talking about, and 24v and larger systems on logging equipment. I was just always taught that having + & +, and - & - connected all the time would drain them over time. :dunno:


I'm not saying I disagree, I also think the marine battery switch setup is the most robust.

I guess I'm confused now. To me, it sounds like Shane is talking about running two batteries together in series, ie. the two +'s connected, and the two -'s connected, with one set of leads running to the alternator. Crash is talking about running the two batteries in parallel, which to me indicates that each battery has a pair of leads running to a marine switch, with one set of leads running from the switch to the alternator. Is this right? Series wiring would give 24V, versus parallel that would still put out 12V total, draw would be split equally between the two batteries? Its been a while since I've done wiring/electricity.

google is your friend David :D

http://ourworld.compuserve.com/homep...tt/elect27.htm
http://www.google.com/search?hl=en&i...arallel+series

Thanks for the links Shane- it was reassuring that I remembered something right from physics!

This has been interesting, and I am curious to find how it ends for those involved.

It appears that you remembered backwards.

Parallel is positive to positive, negative to negative.

Series is positive to negative, positive to negative.

Good thing I'm not an electrician!

You're right that without a switch or an isolator, when and if one battery goes bad it will drain the other one. If both batteries are good, there is no problem running them without a switch or isolator, they will both settle at full charge and then discharge equally when a load is applied, provided the batteries are of similar size and capacity. The switch is a good idea, is easy to install, and doesn't really have any drawbacks beyond the added cost. An isolator on the other hand will mean the batteries are never fully charged unless you have a regulator with remote sensing capability, something most cars and trucks will not have.

Hey Gibby

Thought you might be interested...

http://www.excessiveamperage.com

Do both!

High power alternator install on a '85 Toy 4Runner, 140 amps for $140:

http://news.yahoo.com/news?tmpl=stor...r_050128235115


Dual battery installation:

http://www.rocketcityrockcrawlers.co...20Part%20I.pdf

Thanks,

Al

You Need An Isolator
 

Here's my set-up....
https://www.yotatech.com/forums/show...dual+batteries

This computer is messed up, that should take you there....

I would put some sort of isolation device no matter what. Obviously you're not going to run them together for a 24 volt system. If you simply "hook them together" they will kill each other in a short time. I've spent years with in the stereo scene and on my way as a mechanical engineer (not electrical!) but I think I can explain why easy enough. Electricity flows from areas of higher concentration to lesser concentration. I could go into details and yadda yadda yadda, but it's a basic law of physics. When you put those 2 batteries together and they're sitting there, freely exchanging current, they really do kill each other. You can have 2 of the same battery from the same batch built on the same day, essentially THE SAME 2 batteries. BUT, one is going to have slightly more charge than the other one. So, since electricity moves from greater to lesser concentrations it's going to transfer that extra juice to the other battery. And once that gets it, then it will have more energy, so that energy will go back to the original battery. This continues indefinitely, they are basically shooting that small charge back and forth which after time (a few days usually).... kills them both. I've tried it once despite knowing this, and after the car sat 3 days I came back and both batteries were dead, and wrecked. For a winching setup, you're best to have an isolator to let those batteries be charged by the same alternator. Picture this: You're in the middle of nowhere and stuck. You have to winch yourself out but it was a tough spot and all of a sudden you don't start. You are SOL.... With that isolator you can keep them seperate, say you do kill the one battery from winching (a deep cycle of course), you simply wait a bit for it to charge.
I don't have a winch, but my situation is this: I have the tunes cranked and the battery goes dead after an hour. I just walk up, flip a switch in the cab and start the vehicle up with the other battery. Check out Hellroaring for an isolator. Sorry for the long post, I don't claim to be an expert but I know what I'm talkin about. Good luck!

Jus wondering about this whole suggestion of two batteries I ain't a real rock crawler I used to jus build small yotas for speed and crap n help around with my uncle with the big ones for mudding...aaaaanyways I jus moved to Cali n bought a 94 4runner and don't kno what the hell went rong but i tested my alt n its good and I put in a brand new battery but my voltage meter drops wenever I turn on a blinker or roll down a window! Anybody can help me please I'm a not a real electrical man n I checked grounds and all but all I can see is my alt cable being a little blue but I don't kno if it's the prob? It aint even corroded...I wanted to put in another battery but not sure how to wire it...jus for som sounds so my lights dim on me...and thinkin bout the gm alt swap..anyone suggestions or advice