Dual battery cheap solution Q's

[Kiel]

I have been figuring out how to do a cheap dual battery in the cherokee, but being the low budget guy I am on this project I don't want to buy a high end isolator for over 150 dollars. I want the ability to have 2 batteries for instances like extended winching, fridge and electronics usage. Not to mention if I leave it sitting for a couple days with the accessories on be able to start it back up, so here is my idea. Can I just hook up the batteries in series or whatever the correct wiring way to do it is, then put a cheap battery disconnect or knob isolator on one battery when I leave it sitting for a couple days or camping etc. and come back and when it could be dead turn that one back on for starting ability? I would be in the setup around 30 bucks for the cables and disconnect. Ideas and thoughts?

 

[I Lean]

The only issue I see with that, is the one dead battery will suck the juice from the live one, so you may still not be able to start.

If you can turn off the dead one, then turn on the charged one, you'll be able to start--then connect everything back up to charge it back up.

The one in my boat lets you select Batt 1, Batt 2, Both, or Off. (or maybe that's the high end $150 isolator you mention?)

 

[Chevycrew]

If you ran the main ground wires to each battery seperately with a disconnect on each line, then hook the 2 positives together it should get what you are after.

Would give the options carl is saying, just have to manually turn the disconnects.

 

[JL Rockies]

Series would be bad unless you're converting everything to 24V.

The problem with a manual switch is you will forget to flip it eventually.

The high dollar kits are just left of rediculious in my expert opinion. You can buy a battery separator from any autoparts store. You can pay extra for a smart isolator or not. I'm not of the opinion that there's a benefit to linking two batts together for winching unless the motor doesn't run anymore. Eventually, the voltage will still sag creating a greater load on the charging system and reducing available voltage to the winch. Some will dissagree believing that the Enterprise is in orbit and will beam down extra power when batts are in parallel.

You can buy the wire at audio shops or buy the cable from welding supply. ANL fuses on both batts are very important; most skip the fuses.

I am also of the opinion that dual batts are a waste of time, space and resources more often than not.

I am currently working on a system that would be more efficient and simple than a dual batt system but I'm not ready to discuss it. It's kind of a big deal... Star Trek schizz yo.

 

[I Lean]

I'm not of the opinion that there's a benefit to linking two batts together for winching unless the motor doesn't run anymore. Eventually, the voltage will still sag creating a greater load on the charging system and reducing available voltage to the winch. Some will dissagree believing that the Enterprise is in orbit and will beam down extra power when batts are in parallel.

How would the Enterprise NOT beam down extra power? Two batts in parallel = double the winching time before the voltage gets low enough to be problematic, no?

That said, I've only been in a situation one time where winching lasted more than just a couple minutes....and that was a man-made scenario that probably wouldn't happen in nature. (Top Truck Challenge, the Tank Trap....with two broken front axles. All forward progress was by winching)

 

[2INSANE]

Captain, we don't have the power!!! Lol!


You could go to a junkyard and pull off an isolator from a duel batt truck. Might as well get some wires and connectors too? Just saying... Keep it cheap and simple.

 

[Taconut]

I believe the point in a dual battery isolated system is for one battery to be used for starting and the other for winching, added lights, Fridges, etc. That way you always have a starter battery. The winch can pull down the one without affecting the other. If you use a deep cycle for the winch battery it will winch longer withouit damaging the battery. If you wire two batteries in parallel, if one of then is weak it will discharge the other, eventually causing damage to the better battery. That alone is a strong argument for buying an isolator. As for buying one from a parts store, you can go that route, just make sure it can handle the expected amperage. I,m of the opinion that sometimes you get what you pay for!

 

[BCGPER]

Your cheap switch idea will work fine, it's how I used to wire my campers, but your theory of operation is a little skewed.


What you'll do is wire all of your added accessories to the newly installed auxiliary battery. Leave the Jeep battery and wiring the way it came from the factory. A heavy wire (say 2.0ga or larger) will run from the positive of the Jeep battery, through the switch and to the positive side of the auxiliary battery. Keep this wire large, you may need it one day to "jump" the Jeep battery if it ever fails you.


How it operates will be a little different than what you described. Normal day to day use, you'll leave the switch closed, charging both batteries whenever the vehicle is running. When you camp, you'll open the switch running all of your equipment off the auxiliary battery leaving the Jeep battery sitting there fully charged. when you leave, start the Jeep, then close the switch to re-charge the auxiliary battery on the drive home. Make sense?


Any auto parts store should have the cheap knife switch you're looking for. If not, I'm sure a place like State Trailer has it.

I have been figuring out how to do a cheap dual battery in the cherokee, but being the low budget guy I am on this project I don't want to buy a high end isolator for over 150 dollars. I want the ability to have 2 batteries for instances like extended winching, fridge and electronics usage. Not to mention if I leave it sitting for a couple days with the accessories on be able to start it back up, so here is my idea. Can I just hook up the batteries in series or whatever the correct wiring way to do it is, then put a cheap battery disconnect or knob isolator on one battery when I leave it sitting for a couple days or camping etc. and come back and when it could be dead turn that one back on for starting ability? I would be in the setup around 30 bucks for the cables and disconnect. Ideas and thoughts?

 

[Tacoma]

Those knife switches work great.

Boat stores also carry battery switches.

I got an isolator from some farm store for my old box van, ran the lights and TV and whatnot off the aux. battery.

If you want to spend money, Kurt has the most awesome smart tender every. But I think it was like $300, which is actual money.

 

[gijohn40]

you can always put a relay in place of the switch and run the control cable into the cab so that you don't have to open the hood everytime to close the switch... and if you put a light on the control button you can see when the relay is closed and the second battery is connected to the main battery...

Personally I have an isolator that is rated at 140 amps that I came across years ago... the only problem I have with it is that the alternator needs a supply reference to know to amp up the voltage to charge the battery or not... and if you use the main battery and its fully charged and the second battery is dead then the alternator just slowly charges the second battery... but now say the second battery is fully charged and the main is dead... the alternator goes into full charge mode to charge the first and the second gets overcharged... I know how to fix this with zenor diodes and all just haven't done it...

If you need help let me know and I can draw you up some diagrams...

 

[Kiel]

thanks for the info this sounds like the ticket except to run a switch on each battery if something did happen. I have the need to do some recovery of up to 300 feet of cable on my m8000 warn in the future

 

[Johnny4X4]

when i did mine on the cheap, i bought a relay and wired it to the ignition. when the key was on, both batteries charged, when off the second battery wss used for all the accesories.

then i bought a new thing from painless and wired that in instead.

 

[thenag]

Can I just hook up the batteries in series or whatever the correct wiring way to do it is, then put a cheap battery disconnect or knob isolator on one battery when I leave it sitting for a couple days or camping etc. and come back and when it could be dead turn that one back on for starting ability? I would be in the setup around 30 bucks for the cables and disconnect. Ideas and thoughts?

That is pretty much what I did in my bronco and I transfered it to my xj. When you run batteries without an isolator you buy them as a pair and replace them as a pair. Many trucks come from the factory like this. In theory if they are not identical they will trade charge or something and drain each other, leaving them both dead. (I have read "posible fire" too)

I use a boat switch it is rated at a lot of amps, I can't remember much about it. It has 4 positions, 1, 2, both, off.

I leave both on all the time, but you could switch one off and drain the other with a fridge while camping or whatever. But really if that is your intent you should have them isolated. I have a friend that had a red top and a blue top, had it setup that they were both on while winching. I never really locked at his wiring, I know he had an isolator.

On the trail you can pull 2 batteries from the vehicle, (in the vehicle they are wired in parallel) and put them in series and you have a 24v dc stick welder. (Shane has used my gen one setup, it is much nicer now)

The switch is just plain nice to have, My bronco started smoking after doing some work on it it was easy to just turn the switch to kill all electrical activity, the switch probably saved all the grounding in that truck since I had a dead short to my winch.

I haven't noticed it much with the jeep but with the bronco it ran a hell of a lot better with two batteries, the lights wouldn't dim when you crank the starter, it would start with almost no cranking, it is overkill but most things on our rigs are...

In the xj I have had an optima leak, I think this will not happen once I get some hood vents installed.

full album here;
https://picasaweb.google.com/116333554950363953131/BatteryMount?authuser=0&feat=directlink

Nathan
99 xj with a lot of stuff under the hood...

 

[jdub]

I have the dual battery set-up in one CJ and the other Has only one Optima. I cannot count how many times that jeep has not started, it sometimes sits a while. The one with duals has only not started once. I have had both for at least 6 years. It is something I would look into just for the reliability if the vehicle were to be an expedition type. I'm torn on the duals though. It is expensive.

 

[cruiseroutfit]

Lots of opinions... some I agree with, others I don't.

1. Winching is absolutely improved by manually pairing the batteries. I did a fair amount of winching this last weekend, both self-recovery and recovery of another. With decent load on the winch and the motor slowing to an almost painful pace, I can pair my batteries and the motor picks right up, doubling the available amperage draw from the batteries. I remember winching in my FJ40 on RS years ago, things were slowing down under extreme load even with the engine at high rev's, I flipped the switch and the winch sped right up. Tracy Evans commented "What did you just do"

2. Accessories. I sometimes setup camp for several days without moving the vehicle has a finite amount of amp-hours and short of running the vehicle (which is a slow way to charge a battery considering the absorption rate) either you run all your 12V needs worry free or you don't. I don't run a low voltage shut-off on any of my goodies and don't fear I need to. My second battery is 100% isolated with the key off or if by chance the main battery drops below x voltage when paired, all controllable by me. The math is simple, if you have a 60 amp-hour battery and 10 amps/hour of accessories you have just 6 hours before they stop working and you can't start you vehicle. A fridge pulls ~3 amps/hour to be safe so you can easily make it a full day without starting but add a light, music, charging phones, computers, GPS, etc and you can see how it drains much faster, compromising you start.

3. Other considerations i.e. welding. My trail welder has saved the day and in my mind $1000 worth of batteries and welder would was all worth it if nothing else for the time I used it in the middle of Nevada, saving our group a day's worth of travel and hundreds of miles of detour. With the dual bats I have the ability to utilized the needed 24V. If you've got a group going out on a trip its easy to come up with two loose batteries but as often as I'm out solo, semi-solo its nice to have myself contained.

Does every rig with a winch need duals? No... Does every rig with a fridge need duals? No there too. However for the right needs there is no replacement in my opinion.

Now, as for the kits. You can build an manually selectable setup for under $100 but by the time you get a continuous duty rated solenoid capable of winch loads, high quality ends and cable, fuse setups, switching, etc is actually pretty easy to see just how the prices of the different kits land where they do. I run the NW Wrangler kit in my FJ40 and the National Luna kit in my Tacoma. the NW Wrangler is stupid simple and rock solid reliable, 10+ years without a single issue however it doesn't have nearly the control and monitoring features of the National Luna which incorporates low voltage and over-charge alarms, battery level indicators, etc. Buy once, cry once type of deal where you really get what you pay for. You can peice meal the National Luna kits together, start with the Intelligent Solenoid, add the controller and such as you desire. If you have your own wire sources (keep in mind the kits are generally aimed at those that don't have the time/sources to drive all over town for cable, connectors, etc) then buy a continuous duty rated solenoid and wire it up.