Dual Batt. Cable Specs

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An electrical footnote:

There is a really cool book out there called "Managing 12 volts"
My wife's dad(an engineer) turned me on to it. Anybody who is serious about DC power MUST read it.
 
The cables that conect the 2 bats(to selnoid, isolator or?) needs be large enough to handle the max input amps of the alt(be it stock or 200 amp)

the cables going out off the batts to say a winch must be able to handle the high amp demands of the winch, prolly 400-500 amps. If you undersize the winch cables the worst that I belive will happen is you will not get full power to you winch.

Like others have said, length of the cable run plays into the sizing of the cable.

Well thats how I understand it.

John H
 
Just sitting here thinking on this subject and considering the hassles of 12Volt high current systems.

Anybody ever think about running a 24volt winch (to reduce current and thus cable size). I think you could do it with a second battery in series with the standard battery. It could then be charged with a "fully floating switcher power supply".

It wouldn't meet the other objectives outlined above without more complication.

I guess it depends on how much hassle the thick cable to the winch is. Certainly complexity is best avoided so perhaps not worth considering.

This is basically a twist on the BJ40 24-volt electrical systems used on the diesel engines for the starter. I've never really been sure how they charged the second battery in those systems but a isolated switcher would work.

Riley

Now back to the other threads on oil, grease, bearings, races, curtains and breaker bars.
 
Rich, a thought on the solution for objective 5...most marine battery-paralleling solenoids are designed to parallel the batteries for starting purposes - an intermitant type of use. I would think that a continuous-duty rated solenoid would be necesary to parallel for charging. If you haven't already done so, it would be a good idea to check the duty-rating of that solenoid.

A general comment concerning wire size and voltage drop... Amps = Voltage/resistance.
So when voltage is decreased and resistance(the winch or any load) stays constant, amps increase, possibly overheating, or even burning-up, of the load. So, not only is proper wire size important for safety, it also prolongs the life of the device being operated.

Ed
 
Ed,

You right that the solenoid duty rating is an important design criteria. Here are the specs on the solenoid that I have selected:

Coil Circuit:
Input Voltage: 9 to 36 VDC
Power Consumption:
Inrush, 130ms: 3.8 Amperes@12-36 VDC
Holding 12 Volts: 0.13 Amperes@12 VDC
0.07 Amperes@24 VDC

Main Power Contacts:
Voltage Rating 60 Volts DC
Stud Terminal Size M8 (accepts 5/16” terminals)
Contact Form SPST-NO
Inrush Rating: 250ms (10 repeats)* 2000 Amperes
Cranking Rating: 9.75s (10 repeats)* 500 Amperes
Intermittent Rating: 300s (UL 1107) 275 Amperes
Continuous Rating: (UL 1107) 250 Amperes
Mechanical Life 1 Million Cycles
Make Current@10,000 Cycles: 2000 Amperes@28V
Break Current@10,000 Cycles: 2000 Amperes@28V


It looks like it should work ok.

Rich
 
Rich,
I would like to see you post a wiring diagram if you are creating one for this project.
-B-
 
[quote author=Beowulf link=board=2;threadid=6913;start=msg57978#msg57978 date=1067745994]
Rich,
I would like to see you post a wiring diagram if you are creating one for this project.
-B-

[/quote]

I've got a few projects in the works. When the aux battery install makes it to the top of the list I post some pics.

Rich
 
Rich,

The specs on that solenoid look quite beefy.

Might be a good idea to install a cycle counter so you can replace it on the 999,999th cycle ;)

Ed
 
Rich - Any progress on the dual battery install?

I'm starting to research this topic and would like to hear how your project went.

On another point - for the interm running with simply an isolator seems to make some sense. This would allow me a have a fully charged battery for jumping just in case the main failed. Anybody know if these isolators are true switching power supplies to isolate OR just a relay to strap the batteries in parallel when the ignition is on. Also where would I find one of these isolators?

Thanks
 
I should update seeing how sense this started I have installed the dual batts in both the 86 and 82, I used 1/0 welding cable. Bought the hamer style crimper from NAPA, but McMAster has a better one.

Used 50+feet of 1/0 to do both the Cruisers, redid all the other pos and neq cables at the same time. Welding cable was all black, I used red heat shrink on the + cable ends to mark them. Found the tinned copper lugs for $1 each, vrs marine store or other places for $1.80.........when you need 20+ of em it adds up ;)

used Mil Spec bat terminals and Mil Spec covers, both from Wranger, but McMaster has the Mil Spec terminals for 1/2 the price, on Wrangler has the covers.

Both dual bats are run with the Wranger slenoids and battery manager.
 
Riley,

I have just started the dual battery project. The first step is to work out the wire routing. I will be using at least 2/0 gauge wiring and likely mounting the switches on the drivers side, so there will be a bit of a challange to do a proper job as the space is tight and the placement options limited. Thus the planning for this step will be rather time consuming.

If all you want to do is have two batteries where only one starts the truck and the other is automatically charged when the engine is running and is totally idle when the engine is not runnng with no switchover capability (which is what I think you were asking above) then go to www.bluesea.com and check out their solenoids. Download their pdf catalog. They have two solenoids, one is a just a straight forward solenoid, the other will automatically switch on and off depending on the batteries state of charge. I have not used either one, but their specs are better than most that you will see offered for this purpose. All of the bluesea products that I have seen or purchased are pretty much best in class (which is marine electrical products). The marine environment is typically more severe than automotive due to constant exposure to salt water and hot, enclosed engine compartments. The "good" products seem to be built to better standards than the typical automotive aftermarket stuff.

Rich
 
Thanks Rich. That was my interm configuration until I was able to design and build something better. It only made sense if the cost was very low. I'll check it out and see what the $$ damage would be. In the end I'd like to be able to run equipment on the spare battery while camping. I need to think about my requirements a little more before making that step.

I need to wait a year of so in my "new" 80 to determine if I would ever get a winch or fridge ect... One day it would be nice to be able to start off of the spare but jumping would be ok for now.

It seems that this mod takes much more effort than any other single mod. :rolleyes:

Riley
 
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