Need help understanding Dual Battery Systems

[4x4freedom]

Hello,

I've been looking into Dual Battery systems lately and I seem to be having a hard time understanding just how they work. I get the systems that use a manual switch to control battery banks, but I don't really understand how the isolating solonoids work.

If I were to install a National Luna for example, the minute I shut off the truck and then turn on my radio, does the solonoid automatically shift power over to my aux. battery, or do I have to wire all my accessories to a fuse panel wired to that aux. battery?

I ask simply because I don't want to rewire my truck and the mods I've made to it in order to get the benefits of a dual system.

Thanks for the help,
Tim
www.4x4freedom.com

 

[Hunter]

OK,

This is a pretty watered down, "back of the box response", but should help understand how it all works.

There are several different set ups and variations out there that people like to do, but this probably the common and easiest.

You have your factory battery, then add a second battery, contorled with a isolation switch or solenoid. The battery in the factory location stays the primary. Meaning all of your factory wiring and accs. still run off it. But the 2nd battery would sit in reserve. It would get power in to keep it charged but there would be no draw on it. You would only activate, via switch when your other battery has died. Say you left the radio on all night or a lap top plugged into a power port. Or heaven forbid, you bump a light switch during the day, in th emiddle of nowhere and have to wait hours from some to come by to give you a jump. (That hasnt happened to me... it was uh.. freind) You would hop in, hit the switch, getting power from the reserve battery. Basically, jumping your self.

With this set up, you have the saftey of another battery without the headache of a bunch of rewiring or transfering of power leads.

 

[Speaker]

Oh, interesting. I thought the second battery was used to power aux lights, fridge, gps/computer, and other accessories. If jump starting is really all the second battery is used for, why not just carry one of those jump starter things?
Poor man's dual battery setup, that's all I've got.:sombrero:

 

[Hunter]

Speaker,
You can if you want. What I describd is just the easiset way that it sounded what FreeDom4x4 was looking for. With good switch, you can hit and get the power of both, say if you really needed to do a heavy pull on the winch and wanted them both.

Several different ways to do it, but in the end, it all breaks down the same... protect one battery so you can get out of a jam.

I carry a small jump box with me. It doesnt help if I really run down the abtery, can it can be enough if I am close. Plus, it has a built in 12 power plug so I use the run camp lights or the DVD player.

 

[tdesanto]

My setup is as Hunter describes it in concept. Main battery supplies power to everything and the extra battery is a reserve battery.

The benefit is as he describes--no need to rewire anything and I have no fear of running anything...fridge, aux lights, laptop, camera battery charger, etc.

The extra benefit of this system over a jump-start battery is in winching situations you can combine the batteries while the engine is running in order to provide that extra power. Winches can easily pull over 300 amps and this helps in those sitations. Imagine the other way around: you run your fridge, stereo, lights, etc. off of your reserve battery. Then you start out on a trail and need to winch. You end up draining the main battery; now what? You've got 2 batteries with little reserve.

I went with this unit: BIC-95300B. I've been very, very happy with it. I've got no ties to the company or owner. Just a happy customer. Great service and the product seems very reliable.

 

[Mike S]

Various dual battery set-ups...

I have worked on a couple of dual batt configurations. A very good source of information is on the West Marine website, and on battery controller manufacturer websites... a solenoid or solid state controllable automatic system usually allows the user to select one of three operating modes. The best systems have dash switched which allow the following settings...

1. Automatic - will combine or isolate the aux batt bank automatically depending on state of charge and power demands.

2. Manual combine - will allow you to manually combine both batteries when needed.

3. Manually isolate - allows you to manually isolate the batterires - i.e.: when winching.

Here are couple of popular ways to configure with an automatic control system:

AUXILIARY ONLY - configured as a standby battery where all the electrics are connected to the primary battery. This will automatically isolate the standby from discharge, combine for charging when running, and combine when starting power is needed - basically a built in jump start.

ACCESSORIES ONLY - primary battery runs the starter and standard electrics, and the secondary batt bank directly supports all accessories - winch, lights, fridge, etc. This is a pretty common set-up, but can seriously discharge the reserve capacity of the second battery to assist in starting, if needed. The system will usually charge the primary first, switching to charge the secondary bank only after the primary is fully charged.

WINCH ONLY - This uses the second battery for winching only - all other accessories run of the primary battery. Also a popular set-up with people who use their winch a lot. When the secondary is discharged from extended use winching, the vehicle will still start and run accessories, and the system will recharge the secondary battery when the vehicle is running.

It would be good to do some research and thinking about the best way to use the secondary battery,and arrive at the best type of system based on YOUR needs.You need to pay particular attention to cabling, fusing and connectors, and select these items based on the max anticipated load for each component. Not difficult or complex, but some thought in advance and a good diagram will help you do a smooth and effective job.

These are photos of the set up on my FJ60. Basically the same on all vehicles, particul;ars of mounting, etc. may vary. Top is the mounting and primary cabling, lower is the BlueSea ACR that I used in this set-up.

Mike S

 

[UK4X4]

Thanks for the link...that looks like a sweet unit, almost fit and forget, rather than remebering to switch things on off 1 batt or two battery

 

[jatibb]

i prefer a manual switch for duals. run on #1 most of time, when that battery goes down a little change swith to both, effectively jump starting yourself. electrical current flows the path of least resistence, ie to the weakest battery first. the dual battery switches with a built in isolator are made so you can switch from 1,2, or both while engine is running w/out harming the alternator.

 

[ntsqd]

snip.....
the dual battery switches with a built in isolator are made so you can switch from 1,2, or both while engine is running w/out harming the alternator.

This is true so long as you Never go past the "Off" position.

 

[BajaTaco]

A couple points to add:

1. If you decide to go with the setup whereby your primary battery (starter battery) is used to run your accessories, then make sure it's a robrust model that can perform both powerful cold-cranking amps, and withstand deep discharges. Typical AGM deep-cycle batteries like Lifeline, Deka, Odyssey, Optima, etc. are capable of this these days.

2. If you want to combine both batteries for winching, make sure you use a switch that can handle the heavy currents for sustained periods without degrading.

 

[Mike S]

This is true so long as you Never go past the "Off" position.

In the marine industry, this is called a 'make before break' switch. It NEVER disconnects the alt from the battery. OFF is a no-no when the engine is running..

Word to the wise.

M

 

[Mike S]

2. If you want to combine both batteries for winching, make sure you use a switch that can handle the heavy currents for sustained periods without degrading.

If you do not want to use a switch, an option is to connect through a automatic or manually switched continuous duty solenoid. A good model (but more sophisticated) is the BlueSea ACR.

M

 

[NothingClever]

Hello,

I've been looking into Dual Battery systems lately and I seem to be having a hard time understanding just how they work. I get the systems that use a manual switch to control battery banks, but I don't really understand how the isolating solonoids work.

If I were to install a National Luna for example, the minute I shut off the truck and then turn on my radio, does the solonoid automatically shift power over to my aux. battery, or do I have to wire all my accessories to a fuse panel wired to that aux. battery?

I ask simply because I don't want to rewire my truck and the mods I've made to it in order to get the benefits of a dual system.

Thanks for the help,
Tim
www.4x4freedom.com

My Volkswagen Westfalia had an excellent dual battery set up.

The primary battery started the vehicle and powered accessories while under way.

While underway, if the primary battery was fully charged, the auxiliary battery would charge.

When I switched off the ignition, the solenoid switched all demands over to the auxiliary battery which powered all the accessories and the power inverter.

I also had a solar charger to keep the auxiliary battery topped off & a nice little digital battery monitor plugged into the cigarette lighter to monitor my usage.

I'm not sure how the folks at GoWesty wired the Vanagon but it was a slick set up, IMO. I do know that they did NOT have to get knee deep into the loom to re-wire everything.

 

[NothingClever]

This should explain everything....

http://www.equipt1.com/h/component/page,shop.browse/category_id,151/option,com_virtuemart/Itemid,31/

 

[ntsqd]

No you haven't, but it is not always adhered to.