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Duel battery ????????

rjm7263

NAXJA Forum User
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Hey y'all ok so I want to install a duel battery setup my plan is buy a second batt and sence I have all my extras hooked to the main battery now I was just gonna move the two original positive and negative cables to my new battery under the back seat and just make the main batt now only have all my extras on it basicly only using the new batt for starting will this work or make anysence I just don't want to remove cut and lengthen all the extas and run them to the new batt any help would be graet pictures and I fo on a realy well desinged duel system would be greatly appreiated rhanx bo
 
kinda hard to make out what your plan is... but you gotta have those batteries hooked up together. you can run everything off of your normal battery and just have a postive and ground run to the new battery and that way they are linked and everything you run pulls off of both batteries, but more importantly your alternator charges both batteries. from what i made out of your post it doesnt sound like one of your batteries are gonna get charged.
 
1) Punctuation, please. It does make your questions easier to read (I generally don't answer questions when I can't read them!)

2) Don't forget (1).

Now that that's out of the way...

How many "extras" do you have that make you think you need a second battery, and how much do you run them without having the engine going? I'm only asking because you may not actually require the secondary battery, and upgrading your alternator (which is usually easier) may be a more productive use of "mod money."

Having said that, an effective dual battery setup (starting and reserve bank) isn't as simple as wiring a secondary battery in parallel. Look up "battery isolators" for more information on what I'm about to talk about...

If batteries arranged in an "open parallel" bank (meaning that they're directly wired together - positive to positive and negative to negative,) they must be the same type, capacity, and age. Period. If one of them fails, replace all of them.

Why is this so? Because, if there is one battery in the bank that the bank will think is "weak," the bank will spend most of its time (when not being directly charged) in trying to charge the "weak" battery - which will drain all of the batteries in fairly short order!

This is why isolators are important. The isolator allows all batteries to be charged when the engine is running, but will "isolate" the deep cycle battery from the starting battery when current is not applied, which allows you to run your accessories off of the secondary battery - which is usually a deep cycle - without draining your starting battery. Treat this point as important.

There are two essential types of isolator in common use:

Solenoid Isolator - You may not have heard of a "solenoid" before. Ever hear of a "relay?" In an automotive sense, a "solenoid" is the same thing only moreso. The typical small automotive relay is good for 20-40A, while a solenoid switch can be had up to 200A in capacity.

NB: These are not the Ford starter motor solenoids that people like to try to use. There's a reason those Ford parts are so cheap - their current capacity sucks, and they're designed for a duty cycle down around 20%. So, for every minute they are ON, they must spend four minutes OFF. Failure to run intermittent duty on these solenoids will lead to failure of the part.

The solenoids that are used as isolators (I've used them in industrial settings - both as battery isolators and a high-current switches for hydraulic motors and such...) are rated for a high current load at a 100% duty cycle - meaning it's not going to cause them any trouble to be "always ON." This isn't a common part, you're not going to find it at Kragen's or Autozone. However, they're compact (about the size of your fist,) cost less than a comparably-rated solid state isolator (more on that in a minute,) and are easier to mount (being small and not generating as much heat.) However, you do have to find a "Hot in RUN" lead to trigger the thing to close once you've started the engine, or wire in a manual switch to control it (and don't forget to turn it off when you turn off the engine!)

Solid-State Isolator - Ever hear of a diode? How about a "check valve?" A check valve is a device that allows fluid flow in one direction only - a diode is the same thing, only for electricity.

So what you get with the solid-state piece is a larger device (book-sized or so) that contains a network of diodes. The alternator's output feeds into the isolator, and then there are two feeds out of the isolator - one goes to the starting battery and vehicle distribution, and the other goes to the auxiliary battery. Nice thing about the solid-state units is that no user intervention is required, and you don't have to track down a "trigger" lead for the thing.

But, anytime you run current through a semiconductor (like a diode,) you generate heat. This is why the case of the thing has all of the aluminum fins on it - they're for heat dissipation. This means that you'll have to mount the isolator somewhere that it can have free airflow over it - if you don't want it to melt down.

And, since it runs on diodes, the current throughput rating can be somewhat limited (I think they're up to 130-150A. I can get solenoids easily up to 200A.)

Either way, selection of the isolator is going to be primarily driven by the alternator's max output, less the expected "overhead" used up in engine management (figure this one without any accessory systems running - like radios and lighting - and don't count the electric fan(s), since they're not always on.)

Also, it should be noted that there are no real "standard" designs for auxiliary battery systems - there are too many variations. Yes, you can get some kit solutions out there (secondary battery tray, or a tray that will take two, or ...) but those can vary heavily by vehicle - and still presume a setup that is still OEM (or somewhat close to it.)

Since you're thinking about putting the secondary battery in the passenger cabin (if I'm reading right...) pretty much none of the current kit solutions will address what you're trying to do. You'll need to get an isolator yourself, you'll need to mock up the cable runs yourself and decide what to get (if you're stuck on this, I can help you. Hit me backchannel...) you'll have to pass the cable safely through the firewall, you'll have to find a deep cycle AGM or gel cell battery (so it won't leak,) you'll have to get a battery box for it, and you'll have to make sure that the battery box is vented to the outside of the vehicle (no matter what the technology, all rechargable batteries will outgas when they're being charged. Even Ni-Cd, Ni-MH, and Li-Ion compact rechargeables. Don't believe me? Take a look at a AA Ni-Cd - you'll see small vents on one end. They're not there just for looks.

(Automotive batteries will give off more gas volume, and the gas is typically hydrogen. You don't want to breathe the stuff, and you don't want to smoke anywhere near it. Recall the Hindenburg...)

So, consider all of this and then think about what you want to do. I'm not trying to discourage you - I just want to make sure you get an effective solution for your needs.
 
Thanks guys sorry I was late. Yes the second battery will be hooked up with a isolator and all the proper wiring . I realy just want this new battery to be for starting purpose only ( the main battery) if u would, sorry for the confusion
 
Thanks guys sorry I was late. Yes the second battery will be hooked up with a isolator and all the proper wiring . I realy just want this new battery to be for starting purpose only ( the main battery) if u would, sorry for the confusion

?!?

Leave the OEM wiring in place, and the starting battery in the OEM location. Rewire accessories PRN to the auxiliary battery - but it would generally be used for significant add-ons.

You still haven't answered my questions tho - and those answers may be more help to you than you would think...
 
All good points, Fnord, especially regarding the isolator. Your tutorial is excellent and outta be posted permanently.

I don't think one needs to trash a good used battery if its brother in crime fails, though. At least I got by without trashing it once. Most battery shops can put the used one on a charger that uses some charge pattern to drive the lead sulfate crystals out of the cells, essentially making it a new battery. At least in terms of capacity...I don't think it extends the cell's life any longer than it would have been originally. I've only done this once, so I can't say that I have lots of proof to back that opinion up. The local Batteries Plus owner recommended trying it first, before I replaced both batteries, and so far it's worked good for about a year.

I sort of disagree regarding the off-gassing, but this is a minor technical point. You are right essentially, of course. Batteries under charge create gas (the battery type and the location of overcharge drive the gas released). It's *how much* gas they create that I differ on. For example, the NiCad battery is vented, but since it normally creates miniscule amounts of gas that vent is not there to let the gas out. It's there to protect the outer casing from rupture. Internally the cells are sealed...inside the casing...with simplistic safety valves on the seals to protect the seal from failure should there be high gas pressure further inside. The gas developed on recharge is inside that seal. If you put a huge voltage on it, it'll bulge and rupture and even spew bits of crap. But under normal conditions it's okay without a need for gas release. As for lithium ion batteries...never had to deal with them professionally so I don't know much about them. But the same logic would follow for them, I'd think.

A normal lead-acid battery, under a severe overcharge condition, will spew hydrogen. But given the battery's size and the fact that they're normally installed an open area (even under the hood) - you'll not reach the necessary 2-4% hydrogen saturation of atmosphere required for LEL (lower explosive limit) conditions. Perhaps inside a vehicle, doors and windows shut and vents closed, maybe then you could reach LEL. If you look at alternate vehicle batteries, like AGMs, the offgassing is almost immeasurable. Yes, it exists. But for the closed system to work the hydrogen and oxygen have to be available to recombine inside the battery. At least the vast majority of it does. Some leaks out simply because stuff leaks. Gel cells...again, no experience. So I won't pretend to know the specifics of their functions.

The only place I've seen real hydrogen buildup is with industrial batteries, such as those used at nuclear power plants for emergency flow DC motors and control power, or on submarines for the DC bus. But those batteries fill large rooms, with the small cells being about 6"x12"x24", then varying larger and larger up to about 2 foot by 2 foot by six feet tall...and even larger. With those we have hydrogen detection systems in place,with remote alarms and emergency ventilation systems for the rooms the batteries are in. This is all because hydrogen explosions, as you pointed out with the Hindenburg reference, are bad. Especially on submarines...they have about as much luck as dirigibles when it comes to making it home after a hydrogen explosion.

-Mikey-
 
^^^

Which is why I'd said "outgassing," not "pressure buildup." The cells are, as you noted, relatively small. But, increasing the partial pressure of hydrogen in any enclosed or semi-enclosed area, without ventilation, and with the potential for sparking, just is Not a Good Thing(tm).

The point I was making was that all rechargeable batteries will outgas when charged - and if it's enough of a problem to warrant vents on a small AA cell, how's it going to be with a big automotive battery?

And, LEL isn't the only hazzard with flammable gases. You've got hydrogen already present in the atmosphere, you're increasing the partial pressure of hydrogen - which can cause a flam hazzard. Which is entirely avoidable. Which is why I say what I do (I don't like to assume hazzards that can be avoided - even if they're statistically or logistically minor hazzards.)

And, the chemistry of the conventional lead-acid battery, the AGM, or the gel cell is essentially the same, it's just a different physical state. (I've spent some time talking to Exide, International, Optima, and Odyssey, as you can probably guess...)

OK - maybe you don't have to scrap the whole bank. But, you'd end up tossing the battery that went TU on you and you'd now be one battery short (and therefore lose that current capacity.) In most automotive applications, this isn't a problem - since there's just the starting battery and the auxiliary battery. It's a bigger problem with buses and motorhomes - since they actually can run deep-cycle banks.

And yes, if you put a new battery in with a bunch of older batteries, you're going to end up killing the new battery in fairly short order. I've run into this before - replace one pack, it gets clobbered, then I got bitched at for not replacing the whole thing the first time (of course, I'd made the owner sign off saying that they'd been warned and still wanted me to replace only one. CYA is the Name of the Game...)

So, "nukegumby?" Is this because you glow green and bend easily?:D
 
Sorry I'm late getting back - I'm an irregular visiter because I try to keep from spending my life online. I spent hours a day online from the early 90s (with a screaming 1200 baud modem) up til a couple years ago, when I finally broke the addiction. Now I try to force myself away from the computer. Anyway...

Fair enough on your points...your "outgassing" position is accurate, as is your point regarding free H2 in the atmosphere. There's no point debating the greater/lesser hazard positions, since we all have our own (subjective) line of "okay" [similar to Not A Good Thing(tm) but better] Besides having been through what feels to have been a few million slooooowww years of college in electronic engineering and doing graduate studies in HF/HP, I was an electrician on nuclear submarines. I have also been running sundry other nuclear facilities for the last 25 years, to the point where I started a biz and now whore out others besides just myself. This is only relevant because it explains (probably) why I draw my caution line in a different place than you. I've been deep in industry and shipyards since the 70s.

Nukegumby...it's an odd name, isn't it? I made it up on AOL back in the early 90s because I wanted a name that "fit" me and wasn't taken. As I said, I work in the nuclear industry. There's the "nuke". Back in the military a couple of the barracks monsters nicknamed me "Gumby" for reason I won't explain here...but it did have something to do with bending easily. Good guess. I expect now that you'll probably have to go wash your imagination out with boiling Chlorox bleach. Sorry about that.

:attom:-Mikey-:attom:
(we need a Smiley with just one eye...a nuke mutant Smiley)
 
Re: Dual Battery - YES!!!

I installed a second battery in my rig with components that I found at the local auto parts store & a dual battery isolator/dash indicator on EBay (Vortex Brand ≈ $125).

The dual battery isolator kit came with the solenoid, cables, and most importantly - a display to mount inside the cab that indicates each battery's strength. It also has the capability to toggle between batteries, so if the primary battery is dead, I can "jump start" myself via battery #2. Or if I need some extra OOMMPFF, they can be tied together (such as when the wench is under a lot of load). Come on, doesn't your wife get out & push when you're stuck?

To make room for the second battery, I removed the OEM air cleaner box & installed a "free flow" aftermarket air filter. The filter now, turns down & tucks neatly in front of the brake master cylinder.

I installed a plastic battery tray (corrosion) in the space where the air box was. The battery tray required some leveling, so I leveled it with some SS bolts that pass through the inner fender wall. I used some nuts, fender washers & lock washers to hold the tray at the right height.

An auxiliary fuse box was installed on the inner fender wall below the master cylinder, to feed all of the new components. an 8 Ga wire feeds a small fuse panel under the rear seat. The winch has her own dedicated cables. The ground for the winch & battery #2 are tied to a dual copper grounding lug on the chassis below battery tray #2 (Home Depot electrical department). There was enough spare cable between the winch & the dual battery kit to even upgrade the OEM battery, battery and fuse box grounds, & positive alternator output cable.

There are some additional relays to control auxiliary lighting, power sockets, and a power converter under the rear seat - driver side. I installed some power sockets (under front drivers seat & under rear seat on the face of the kick panel), to power spotlights, & recharge stuff. They are fed from battery #2, so that the main is not drained to power a cooler, tv, radio, space heater, etc.

Spiral wound batteries was used for both batteries, as they can be installed on their side without any leaking. A hold down strap with j-hooks worked the best in keeping it in place. Battery #1 was a more expensive Optima, #2 an Exide.

As for all of the toggle switches, I found a great place for all of them - between the speedometer cluster & the AM/FM radio. I mounted them in a column & was able to get 6 of them into this location (F-Fogs, F-Driving, Roof-Driving, R-Flood, Brake lights, & a spare).

Yes, brake lights... I want to be able to turn them off when hunting [so we can sneak up on game or drive a ridgeline, without alerting the game (or snipers) when we brake]. There is a red led on the dash that lights up when the brakes are activated when this switch is in the "off mode."

Here are images of the installation. The foam "pre-filter" on the air cleaner is there because I do a lot of off-roading in dusty areas. I can easily remove & rinse the foam filter in any stream or faucet. It is merely a foam "pre-filter" from a shop vacuum. It is pulled back to illustrate the filter underneath.

http://picasaweb.google.com/lh/photo/z-imKpi2OzmCPyHk1XbgDQ?feat=directlink
http://picasaweb.google.com/lh/photo/uGciPT5FuHP5VgwUxE5Odg?feat=directlink
http://picasaweb.google.com/lh/photo/vzqAeH4RgXl_yYPe1i5FNg?feat=directlink
http://picasaweb.google.com/lh/photo/lbKWpu11XTdNHq98etpvjQ?feat=directlink
http://picasaweb.google.com/lh/photo/TZrRVU07eyuYzE3e1-27Cw?feat=directlink
http://picasaweb.google.com/lh/photo/NB0P8UeN7f2FUZDPyUJP2Q?feat=directlink
 
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Sorry I'm late getting back - I'm an irregular visiter because I try to keep from spending my life online. I spent hours a day online from the early 90s (with a screaming 1200 baud modem) up til a couple years ago, when I finally broke the addiction. Now I try to force myself away from the computer. Anyway...

Fair enough on your points...your "outgassing" position is accurate, as is your point regarding free H2 in the atmosphere. There's no point debating the greater/lesser hazard positions, since we all have our own (subjective) line of "okay" [similar to Not A Good Thing(tm) but better] Besides having been through what feels to have been a few million slooooowww years of college in electronic engineering and doing graduate studies in HF/HP, I was an electrician on nuclear submarines. I have also been running sundry other nuclear facilities for the last 25 years, to the point where I started a biz and now whore out others besides just myself. This is only relevant because it explains (probably) why I draw my caution line in a different place than you. I've been deep in industry and shipyards since the 70s.

Nukegumby...it's an odd name, isn't it? I made it up on AOL back in the early 90s because I wanted a name that "fit" me and wasn't taken. As I said, I work in the nuclear industry. There's the "nuke". Back in the military a couple of the barracks monsters nicknamed me "Gumby" for reason I won't explain here...but it did have something to do with bending easily. Good guess. I expect now that you'll probably have to go wash your imagination out with boiling Chlorox bleach. Sorry about that.

:attom:-Mikey-:attom:
(we need a Smiley with just one eye...a nuke mutant Smiley)

Oh my God - it's an AOLien!:shocked:

Just kiddin' - gotta have fun sometime, y'know?

@OP - you still haven't answered my most critical question: What is the secondary battery planned on being used for? If you're adding a bunch of electrical loads, how much help the second battery is will depend on if you're going to go well past what you can get a replacement alternator to put out (you can get up to 200A from Mean Green in a single unit, I think you can get up around 220-225 from Nations, and there's always installing a secondary alternator as well.) If you're going to have the engine running whenever you're doing this, the uprated/second alternator is going to be a more effective expenditure.

If you've got a bunch of stuff you plan on running with the engine OFF (fridge, inverter, heater thingies, ...) then the second battery begins to make sense - depending on anticipated loading.

So, if you want a better answer, we need to be able to better understand the question. We really do want to help you - but we need you to help us figure out what you want to do (and if you're going about it the right way. As I'd said, you may be better off spending the money in another matter, and I know I'd like to help you do just that!)
 
The amperage draw from a Warn XD9000 winch at full 9000# load is a staggering 460 AMPS! It draws around 300 AMPS under the load 4500# of a stock XJ!

Even the 220 AMP output of a MG1382 Mean Green High Output alternator cannot keep up with the draw down on the battery. And dis fool don't sit in the rig & rev the engine while winchin' neither!

Dats why...


Not to mention all of the other loads added to the system. The isolator toggles automatically connects & disconnects the second battery to keep it optimally charged.
 
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