Too good to be true dual batt setup?

[Schattenjager]

I was in my local NAPA talking dual battery setups when one the guys asks me outside to look at his nicely restored bronco. He is running a simple heavy duty relay with remote on from his primary battery's positive to his deep cycle. He turns the key and she starts to charge. Cuts off the truck and the connection between the batteries is broken and he runs his accesories off the deep cycle. Says he has had it this way for years and works fine. Realy and wires cost about $80 and he has a set of jumper cables in case he needs to jump the primary. Worse case he can swap batteries.

Is this too simple? I like the idea and certainly don't need an led pandle and digital switch if this will work.

Thoughts?

 

[john101477]

sounds like a simple battery isolator. keeps the starting battery separate from the acc. battery. charges when the vehicle is started. I used this quite a bit when building large multi amp sound systems and they always seemed to work fine.

 

[vampli]

It's works. That's how i did it on my last 2 cars. Simple and cheap.....:victory:

 

[tremors834]

Sounds like a basic set-up. To make it even more simple, just use a manual battery isolator switch found in marine applications.

 

[goodtimes]

Yes, it can be that simple.

There are advantages to the more sophisticated systems -- but that simple relay will indeed work.

 

[Bullseye240]

Just make sure it s continuous duty solenoid and not just a relay or worse yet a starter relay. They aren't rated for holding a connection constantly like the solenoid is.

 

[LandCruiserPhil]

GM has used that system for years for there factory dual battery set up. K.I.S.S.

 

[ntsqd]

Simple Cole-Hersee constant duty solenoid. I used one in my '66 Econoline tow rig. Simple, robust, and it worked. Per a recent thread I understand that NL uses one of these in their systems, though with smart control system rather than simply an ignition-on signal.

The next step up in service and complexity over the simple relay would be a relay that senses when the starting battery is fully charged and waits until then to connect the 'house' battery to the alternator. They're known as "Voltage Sensing Relays" or "Automatic Charge Relays."

 

[Pskhaat]

I've been doing this for about 10+ years in my FZJ80. The solenoid closes based upon the Toyota OEM "Alternator Good" signal (asserts once the alternator is producing sufficient power).

The solenoid can also be closed (batteries connected) from a switch inside the cab for auxiliary starting.

 

[crawler#976]

http://www.pirate4x4.com/tech/billavista/dual_battery/my_dual_battery_setup.htm

Here's a very simple but slightly unattractive solution. I saw lots of these type setups while serving in the USCG - they work very well.

 

[matt s]

You could always just tie them together with some #2 (or bigger if that makes you happy) wire just like a diesel set up. Works great, although if you already run a deep cycle for one battery this is not a great idea.

I carry a full size jumper box anyway, so I never saw the need to isolate my batteries.

I also am not trying to run fridges or other long draw items.

 

[ntsqd]

Running two batteries permanently in parallel is how my '79 gasser Suburban was wired by GM. I always had battery problems with that truck. Ironically the totally mismatched pair that came in the truck when I bought it lasted the longest. I never did figure out exactly why, but I suspect that it was because the two ground cables where not on the same bolt. Spanning the engine block may have been just enough resistance to set up the self-discharge downward spiral.

My advise for anyone considering a permanent parallel battery lay-out is to connect both batteries together directly, then from there run the power & grounding cables.

 

[lostworldexpedition]

I have the setup you mention in the original post, very simple and inexpensive. However, I must say that if you plan on doing extensive camping get a battery monitor or keep the multimeter handy. I inadvertently dropped the "house battery" below 10v once or twice when we where having too much fun at a campsite... So a monitor with alarm would be pretty nice. Now that I have been on the road for 8 months I really wish I had a National Luna set up or at the very least their nifty battery monitor with alarm. They even have a single battery monitor that is about $40... If only Paul shipped to Central America

Here is the current set up, you can see the solenoid right next to the charge controller.

The 90w solar panel is now allowing us to camp without worrying about the fridge killing the "house" battery...

 

[goodtimes]

Voltage monitors are a good idea. Signal Dynamics makes some simple (to install) units. I have one of their 'single' units on my motorcycle (well, it's on the workbench, waiting to go on the bike), and one of the dual units in the Jeep. Simple 2-wire installation.

Simple single-LED display (two LEDs for the dual battery unit -- one LED for each battery).

Flashing Green - Voltage Above 15.25 VDC

Steady Green - Above 12.9

Steady Amber -Above 12.6

Steady Red - Above 12.1

Flashing Red - Below 12 VDC

 

[ntsqd]

GT, That is a very interesting product. I hope that you'll do an evaluation post after you have some time in use.