That's a feature of some models of "smart" chargers too - if they don't see a certain minimum voltage they won't charge. Paralleling another battery will get things going.

 

Can honstly say that thought hadnt crossed my mind... I certainly wouldnt wanna run anything of value like that and ruin it. Pretty much the only thing I run off the old batteries is my ancient 10,000lb winch thats bolted to my car trailer. I wouldnt trust it to pull me out of a hard spot but it does an alright job dragging new projects up onto the trailer, usually just take 3 or 4 batteries along and run em til it stops moving. Ive thought about using some forklift battery cable quick disconnects and making a harness to run back to the winch to so I can power it off of the aux truck battery while the truck is running. Will probably be my next rainy day project.

 

I can honestly say that the thought didn't cross my mind either... until I was at a motor rebuilder asking why my compressor didn't work and what could be done to fix it

You probably aren't taxing your 10,000 lb winch much (I was running my wimpy little compressor motor at it's full rated load). And your winch probably has a better cooling system (my compressor is rated for 100% duty cycle, but I'm guessing it's not with much safety factor). So I'm not surprised you haven't had any trouble. I just wanted to give people the chance to learn off the tuition I already paid.

 

jimbo beam-
Warn makes a setup like you're talking about. It's pricy, and I remember reading somewhere on the interweb that people with portable winches had configured just as good a harness with simular ends for a lot less $. Here's a link to the battery-to-vehicle-rear kit and some cables you could use for other things:

https://www.warn.com/truck/mounting-...nect_kit.shtml
Warn Industries - Electrical Accessories for Jeep, Truck & SUV Winches: Booster Cables

 

I've seen those in the past, and yeah they're quiet pricey. I do like the idea of quick connect jumper cable ends. I've got a couple heavy duty drag race style master disconnects. I'd have maybe 30-40 bucks into bulk 2 gauge cables and connectors. I'm considering mounting a master disconnect near the aux battery on the drivers inner fender (since the idea of a constantly "hot" wire running under the truck doesnt sit well with me) I could run the positive along the frame under the truck and back to a quick disconnect plug under the rear bumper, with the ground bolted up to the frame. Would then need to run about 6 feet of cable off of the winch with a quick disconnect so I could simply just plug the winch in and toss the master switch under the hood.

On a side note: after tackling the cold weather hard start/no start on my F150 I decided to go overkill on my '99 Escort ZX2 work car as well. After some creative rearranging under the hood I was able to shoehorn a huge 880CCA group 65 battery where the tiny stock one used to live. I also made a set of cables for it out of 2/0 gauge and marine terminals. It now spins over beautifully as well.

 

Jimbo...I live in west-central Wisconsin, and "hard starts" are in order here, too. I do love the overkill feature of your second-battery project.

I have a '92 F-250 which I believe needs the second-battery overkill treatment you gave to your F-150. If I can't gleen enough from your many posts and video, I may beg for more detailed info (although, I do believe you have covered everything with the make/model/part information one can use to follow your project.

One question I have regarding "isolation." I contemplate some no-so-heavy use with truck/trailer lights plus sound system, etc.. While wanting to MAKE SURE there is juice for starting, do you (or anyone else) consider re-wiring the completely separate the starting system from ALL other systems a prudent move? Say, staying parked all night with marker lights and sound system (engine off). This would put drain on the main (starting) battery--unless one could re-wire to have these systems run from the auxiliary battery. Is this any better than the isolator you mention which puts both batteries in parallel for starting, while leaving the main (starting) battery to power lights, etc., in all cases?

It seems using a dual battery system (NOT hard-wired in parallel as on my '99 F-250 7.3L diesel) uses the auxiliary ONLY for starting. The main battery remains in use (engine off or on) as if there were no second battery.

Yes. I'm really a novice!!

Do I have a grasp on the single vs. dual battery situation--and (basically) how the add-on-with-isolator operates?

I will appreciate all comments/suggestions/thoughts/recommendations.

Thank you!

 

Not a bad idea, but difficult to COMPLETELY implement. You can run the starter power off the aux battery, but the power to the ignition switch will probably be off the main. It might be possible to isolate that, but the radio and so forth generally get power through the ignition switch too, so that will take some creativity if you want to go that far.

But even so, as long as the main battery isn't run down so far that it won't even pull in the solenoid, you'll get a solid aux battery powering the starter. And even if the main battery is completely dead, you can "jump" it from the aux battery.

But keep in mind that the fuel pump and computer are also running off the main battery too, so they will need a jump from the aux as well if the main goes completely dead.

If you expect to run one of the batteries that low, it might be better to put everything you want to run without the engine running onto the aux battery and leave the starter on the main. That get's a little messy too, but it shouldn't be too hard to rewire the lights to the aux. And if you're talking about an aftermarket sound system you can wire it to the aux battery (again, this gets more difficult if you want it to shut off with the key). This way if the aux battery goes completely dead you can keep the batteries isolated as you start it on the main, so the dead battery isn't draining anything. Then once it's started you can turn on the aux so it will charge.

Keep in mind, starting batteries don't like being deep-cycled, they won't hold a charge very well after one or two deep discharges. You can use a deep cycle battery for your aux, but then it won't be as effective if you need it to jump the main.

 

Nothing Special...Thanks for your information. If I can get this right--keeping starting (and its elements) on the main and having lights and sound (and other non-starter elements) on the auxiliary is probably "best." The trick, then, is to have the non-starter elements switched with the ignition key without being wired to the main (guess this may take a bit of contemplation!). If the starter battery is used only for starting, then chances are slim of it being drawn down too far. The auxiliary is the battery which might be "used" quite a bit more. If the isolator joins the batteries for starting and then separates them, all should be well.

Perhaps what would work is a switch. When the engine is running, the starter battery would be supplier to all systems (unless, as you indicate, hard-wiring an after-market sound system to the auxiliary). Charge level should be OK because the alternator keeps the battery "juiced." With the engine off, a switch would direct all the non-starter systems to the auxiliary from their "normal" route of the ignition key. The auxiliary would get its status back when the engine is again on.

Am I still "on track"? The "switch" system, combined with the isolator, would put the auxiliary into duty only as a starter amplifier and as an engine-off non-starter source. The "switch" system might be a more straightforward way to "separate" the non-starter elements from the main battery.

Again, I will appreciate all comments.

 

You're going to want the batteries hooked together any time the engine is running, otherwise the aux battery won't charge. You only isolate them when the engine is off and possibly when it's cranking.

I wouldn't try to switch things back and forth between batteries. That gets awfully complicated awfully fast. I'd keep most things on the main except the lights and whatever else you want to be able to run with the engine shut off for a while. Those I'd always have hooked to the aux battery.

You could use a relay, switched by the "aux" output from the ignition switch, to make your accessories draw power from the aux battery but go off when the key is off. But you'll need to figure out how to turn the relay on when you want them on with the engine off. Turning the key on will bring the main battery back into the picture, so you might not want to do that for long periods. Maybe have a diode between the key switch and the relay I mentioned, and then another switch, drawing power from the aux battery also switching the relay through another diode. That would let you turn your accessories on the normal way (with the key) when the engine is running, or with the switch when the engine is off.

 

Nothing Special...

Thank you. I think you provided the solution with the switch, relay and diode setup. Keeping everything simple (as possible) helps keep "Murphy" out of the picture and trims down the number of things which could go wrong.

I do hope you're enjoying the snow we're getting today. I suspect you and I pretty much share the same weather patterns. I'm about due east and a few miles from the Twin Cities.

Again. Thank you to you and the other "posters" who have shared so much information and advice.

 

Dual batteries take 2...

Howdy all, my old white zombie is still running great and starting just fine on the coldest mornings, no issues to speak of with the dual battery setup. I've recently gotten another 94 F150 4x4 and decided to give it the dual battery treatment as well, but this time I've done it a little differently...

As was stated earlier in the thread on my white 94 F150 I used the drivers side tray for a 92-97 era powerstoke, I also had to use the powerstoke overflow tank and washer fluid tank, I also had to modify the the factory air intake and tubing. All of this was necessary in order to fit the additional battery tray on the drivers side.

my setup in my white 94 F150...



This setup require fairly long runs of wire from the secondary battery clear over to the other side of the truck, it also required modification of the coolant bottle and air intake.

The setup on my green 94 F150 has nowhere near the wire used, and all the drivers side factory components remain in place...



Pretty much the first thing I do when I get one of these trucks is give it a good tuneup, bump the timing to 13btdc, and delete the smog pump... What I had never considered apon deleting the pump is the space that is cleared up on the passenger side inner fender after the smog pump's air feed is tore out. Removing the smog pump air feed clears up some room, but then theres still the issue of the big ugly coffee can vacuum reservoir sitting there... After brainstorming over a couple beers I remembered the small little plastic "bubble" reservoir that is on my '95 ranger (w/ the 2.3). Since my poor little 2wd Ranger is helplessly buried in a 10 foot snow drift and not going anywhere for awhile I didnt think it'd mind if I snatched it's reservoir for a experiment. After removing the big ole coffee can reservoir from my green 94 F150 I was able to connect the Ranger reservoir and I mounted it outta the way back by the blower motor.

With the air pump feed outta the way, and a tiny little reservoir replacing the big ugly coffee can I now had a nice big flat area to mount a cheapo $5 plastic battery tray from the parts store. I drilled 4 holes through the plastic inner fender and secured the tray down with some bolts and nuts. For this project I again used the BWD 3098 isolation relay, and I made my own cables from from the primary battery out of 2/0 gauge, and made the cables for the aux battery out of 2 gauge. This 94 now spins over just as fast as my white 94 does.

For anyone unclear on the process of making cables I buy bulk cable and copper ring lugs. After cutting the cables to length I strip back approx an inch of wire on the ends, I apply a liberal amount of flux and I slide the lug over the end. I then use a hammer crimper to crimp the lug to the wire. Once the lug is crimped I then fire up my torch and heat the lug until the copper starts turning greenish, I then melt solder through the exposed end of the lug until it puddles out the other side. I then use heat shrink (2 to 1 ratio heavy duty stuff with the glue) and I heat shrink the lug ends.

If the idea of making ones own cables is over your head (but if you're mechanically inclined enough to swap out premade battery cables) you could still do a dual battery project easy enough. Most every auto parts store will have an assortment of premade cables. For dual batteries you'd certainly wanna use atleast 2 gauge cable.

Not counting the cost of a second battery a project like this could be done easy enough for around a $100 using a $5 junkyard ranger reservoir, $5 tray, $30 relay, and some premade cables from a parts store.

 

Everything sounds good, except for this part:

I'd be concerned about relying on the plastic fender liner to support the weight of a battery over time, not to mention what could happen in an accident. It would be worth installing at least a couple of diagonal braces to the fender, IMO.