second battery?

timmyb457 · **Posted:** Wed Jun 10, 2009 4:08 am

has anyone added a second battery for lights/winch/subs? i was thinking about it but just seeing what others think

jeepkj02 · **Posted:** Wed Jun 10, 2009 8:46 am

I don't think anyone has done that. But another battery will do nothing if the alternator can't handle it.

tomsjeep · **Posted:** Wed Jun 10, 2009 10:09 am

I keep pondering this as a mod.
For TJs, there is a battery tray (Kilby I think) that turns the battery 90 degrees and scoots it over so a second Optima can nest in right beside it.
I keep looking at the rat's nest of stuff under my Libby's hood and trying to visualize making something like that work.
There is also a small battery pack that mounts on top of the existing battery (offered by JeepersandCreepers) but it requires another 4 or so inches of clearance, and I don't think that will fit up there.

JL Rockies · **Posted:** Wed Jun 10, 2009 11:23 am

Keep in mind that a 2nd Batt will REDUCE available power to everything else you use everyday. The only thing a 2nd Batt is good for is powering items when the engine is off. If you don't plan to use your lights or winch with your engine off, it makes no sense to do it.

tommudd · **Posted:** Wed Jun 10, 2009 11:28 am

Agree with JL, unless you are going to use it as say an Expedition rig with lights at night , fridge running all the time and things like that no reason to really run an extra battery with all the headaches it would include on something like the KJ.

KJ 119 · **Posted:** Wed Jun 10, 2009 3:46 pm

http://www.lostjeeps.com/forum/phpBB3/vie ... 8&start=20
The only difference is I swapped the red for a yellow.

Am I the only one with a dual batt. setup in a KJ? :roll:

JL Rockies · **Posted:** Wed Jun 10, 2009 5:51 pm

Interesting pics. I am sure there are fuses there somewhere protecting the wires at each battery but you just didn't take pics right? If not, your KJ is one big rolling fire hazard. It's also a really bad idea to mix different types of batts in the same system unless you're going to put in a 2nd alternator as well. I've had two vehicles catch on fire on me while I was working on them due to poorly executed wiring practices. Once it was in the shop and the other time I was test-driving the vehicle. I can tell you from personal experience, that its no fun being in a vehicle when it suddenly catches fire. I have no sense of humor about such things. Nothing personal.

I have a black belt in the 12V arts, I know these things. Heck I'm even ASE Certified in Automotive Electrical if you can believe that.

jnaut · **Posted:** Wed Jun 10, 2009 7:34 pm

KJ 119 wrote:

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=32018&start=20
The only difference is I swapped the red for a yellow.

Am I the only one with a dual batt. setup in a KJ? :roll:

How's the venting of that second battery being in the passenger compartment?

KJ 119 · **Posted:** Wed Jun 10, 2009 9:49 pm

JL Rockies,
I've run this setup in three vehicles over the past 13 years with all different battery combo's and no problems.
I'm an electrician and know the importance of fusing electrical equipment,yet have never fused my duals.
I could tell you to use a #2 awg wire for 100A 3phase 208vac ,but wouldn't know what to fuse my #2 awg wire running between my 12V dc batteries or where I would find such a thing.One that would hold up to the elements.
Allright Mr 12V,help me out.

jnaut wrote:

How's the venting of that second battery being in the passenger compartment?

Batteries are sealed.No problemo.

tjkj2002 · **Posted:** Wed Jun 10, 2009 10:24 pm

KJ 119 wrote:

JL Rockies,

jnaut wrote:

How's the venting of that second battery being in the passenger compartment?

Batteries are sealed.No problemo.

Not fully sealed,Optima's do have vents(the little gray circles on the top of the battery).They are labeled sealed since the AMG contruction can not leak through those vents.

jnaut · **Posted:** Wed Jun 10, 2009 10:51 pm

tjkj2002 wrote:

KJ 119 wrote:

JL Rockies,

jnaut wrote:

How's the venting of that second battery being in the passenger compartment?

Batteries are sealed.No problemo.

Not fully sealed,Optima's do have vents(the little gray circles on the top of the battery).They are labeled sealed since the AMG contruction can not leak through those vents.

So is that a potential problem?

JL Rockies · **Posted:** Wed Jun 10, 2009 11:57 pm

Inhaling poison is about it.

icarl · **Posted:** Thu Jun 11, 2009 12:57 am

I would think a second alternator hooked up to the second battery would be sweet to power all those 'extras'.

JeepinJarhead03 · **Posted:** Thu Jun 11, 2009 1:07 am

a dual batt setup deserves a battery isolator which prevents winches lights etc from draining your vehicles main battery and all the alt does is keep the 2nd battery charged which isn't hard because unless you use your winch or roof lights or whatever it doesn't get used and thus you can't kill your vehicle main batt with those accessories and depending on where you put your secondary can operate a much larger battery than underhood space allows, at the same time it can kill your alt by working it to death if you do kill a big battery while draining your main at the same time, at which point (hopefully you've winched yourself out and got off the trail, you turn your isolator to main batt only, and take the secondary out and charge it on a trickle when you get home

it appears that he's got one which breaks the argument back down to fumes and fuses

don't know how big they make such batteries but can't remember what it was but was lookin at a car, looked under the hood and the battery was under the back seat.. i believe i remember someone on the forum mentioning the same situation as well

JL Rockies · **Posted:** Thu Jun 11, 2009 1:33 am

We're still back to the fact that dual batt set up reduces power overall and only makes sense what you're using things with the engine off.

Isolators themselves are very lossy. Why do you think that they have those heat sink fins on them? The charging system normally has to keep the batt charged (load #1) and run the power demands of the vehicle (load #2) and any accessories (load #3).

In the dual batt set up with isolator (load #1) the main batt (load #2) and the 2nd batt (load #3) are always connected to the charging system but isolated from each other. When the vehicle is running (load #4) the charging system is trying to keep up with all of this. When you add your accessories (load #5) you have far less energy available that if you did nothing.

If you needed a 2nd battery for off-engine use (the only good reason for one) it's better to use a isolator relay like this: http://www.autotoys.com/x/product.php?productid=8631

The nice thing about the relay is, the 2nd batt is isolated from the charging system until it needs charging. Once the 2nd batt is good, the relay closes and only the primary batt is connected to the charging system.

JeepinJarhead03 · **Posted:** Thu Jun 11, 2009 2:11 am

Quote:

The nice thing about the relay is, the 2nd batt is isolated from the charging system until it needs charging.

that's the type of iso was talkin about actually

i've seen them with secondary knobs that trip another sort of idle circuit that additionally allows you to choose whether or not that 2nd battery gets charged or used, or not

i kind of assumed that was the type he had, but then again i'm not an electrician

hehe

Fouros · **Posted:** Thu Jun 11, 2009 2:16 am

there are a few guys running around in aus with a second battery

JL Rockies · **Posted:** Thu Jun 11, 2009 2:33 am

The first vehicle that caught on fire while I was sitting inside of it was owned by an electrician.

Boiler · **Posted:** Thu Jun 11, 2009 2:36 am

How is it that dual battery setups decrease power? If they were wired in parallel (they'd have to be, or on seperate circuits) you'd have more available amps / amp hours. You'd of course want to use the same battery if you were doing them on the same circuit in parallel.

I'm not sure about typical car batteries or the ones you used, but someone designed a battery box where I work that used "sealed" AGM style batteries (glass mat). They are very sealed, as they can be left in any position, these were installed on end. Someone used the wrong charger setting, charging them for typical style batteries which took them about a volt too high, causing them to gas (hydrogen). They do have little pressure relief valves in them. For electromagnetic insulation, the box it was in was sealed with EMI gaskets and blew up...

I forget the % of hydrogen in the air that is combustable, its like a 5 or 10% range, and its a low number. Below that won't blow up, and above it won't either. Either way, I'd be weary of putting a battery in my passenger cabin. There is probably enough air volume for it to not matter, but being a clumsy smoker I think I'll pass :wink:

KJ 119 · **Posted:** Thu Jun 11, 2009 4:08 am

My Perko acts as the isolator,don't need one of those.
The dual batt was actually my first mod to my jeep,and the extra batt in cab has never been a problem.
The setup I run is TRIED AND TRUE,and would advise anyone to mirror my dual setup,for it has worked fine
for MANY years.And yes it's mainly for use when engine is off,but has saved my can many of times when I run down the main batt(radio),and switch to all for jump start(all by myself in the woods).Your batt runs down and you're making a phone call.

Question was about fuses. :wink:

second battery?

Who is online