Can you start your car with your secondary battery (National Luna)

[ssssnake529]

I've got a National Luna dual battery kit.

If my main battery goes dead, is there a way of starting the truck using the secondary battery?

I didn't see anything about this in the instructions, but it seems like something I should be able to do.

 

[AndrewP]

How much wiring do you want to do?

You could wire around the solenoid and control that with a Marine switch.

Or, just carry a set of jumper cables.

 

[ScottReb]

I believe you can do it with the controller. The optional piece on the NL kit. Otherwise jumper cables. Check the NL site it shows you how to do it with the controller

 

[AndrewP]

While I don't own 1 of these, it is only an 85 amp continuous duty solenoid. Running starting currents through it seems like a bad idea. The literature from National Makes no mention of self jumping with it.

Reading the instructions, there is a way to defeat the "intelligent" part of the electronics and close the relay, but I still would not recommend this for starting. Jumper cables would be safer and easy. You're probably carrying them anyway.

The 500amp Blue Sea ML-ACR would be a better choice if your goal was self jumping with an in cab switch.

 

[dstock]

I would definitely keep jumper cables handy, I had the NL system and there were times when the "override to connect" button on the controller would not connect the 2 batteries.

I now run the 500amp Blue Sea ML-ACR, which has an in cab switch and the ability to do it manually at the relay.

 

[MANUCHAO]

You better off doing a BSS ML-ACR 7622 with the inside cab switch.......

 

[mep1811]

Have you thought of using jumper cables ?

 

[Martyn]

You can link both batteries for starting using the button on the remote display.

 

[anickode]

Stop at your local auto parts store and get a 200 amp battery disconnect switch for 20 bucks... the kind that uses the big red key to close the circuit. Wire it in parallel around the isolator. Main battery goes dead, pull the key out of the glove box, close the circuit, let the batteries equalize for a couple minutes, and start your engine.

My isolator is just a basic solenoid setup. I can jumpstart the truck with a 12" long 16awg test lead with alligator clips by hooking from the aux battery side of the solenoid to the positive coil terminal. I haven't wired a self-rescue switch in yet, but I plan to do so with a momentary pushbutton switch so I can't forget to shut it off and end up with 2 dead batteries.

 

[unseenone]

You could accomplish this with a Traxide battery isolator if you were so inclined.

My primary goal is not to kill the starter battery, which it also accomplishes.

You won't do it for 20 bucks, but it's a little more elegant.

 

[AndrewP]

You could accomplish this with a Traxide battery isolator if you were so inclined.

My primary goal is not to kill the starter battery, which it also accomplishes.

You won't do it for 20 bucks, but it's a little more elegant.

Well, even if he did want to re-do his dual battery system, he could accomplish a lot more for less money with the Blue Sea 7622. Assuming he actually wants to keep his national Luna system, he just needs to remember to bring his jumper cables.

 

[unseenone]

Yes, someone else might though.

 

[rambrush]

I solved this issue with the Hellroaring kit. Left my inverter on overnight resulted in dead main battery. A quick flip of the switch and I was up and running again. No mess no fuss of jumper cables etc.

 

[Scott Brady]

It works fine for jumping. Have done it dozens of times. Press and hold the right button on the monitor.

The 85amps solenoid does not limit jumping. Keep the batteries joined for about a minute and then turn the motor over.

 

[DiploStrat]

Many Ways to Do This

Each intelligent relay controller has a slightly different way of doing grossly the same thing: Closing a relay (solenoid) when there is a charger present at either or one one of the batteries and opening the relay when there is not. The one that is best for you may depend on many things:

-- Manual or semi-automatic relay. The Traxide has some clever options here; a winch mode that times out is cute.

-- Size of relay. I tend to think that 100A is about the minimum you should have, and Blue Sea, with a 500A relay is the clear winner here. But, as noted, even a jump start may not require that large a relay as the actual surge can be limited to be of short duration. And, as my colleague dwh loves to point out, as lead acid batteries charge, they take an ever lower amp flow, so even if you start out with a massive charge, say 200A, it won't last more than an hour or so before it drops.

-- Weather proofing.

-- Size of vehicle, presence of winch, and size of battery banks. The Traxide has an interesting mode designed to pull down the starting battery to give you the benefits of a larger bank - more current, less voltage sag. But, at the same time, this implies letting the starter battery drop to about 12.5v. Some would consider this a no-no, not because you won't have enough current to start your vehicle, but because a 50% discharge can be hell on a starter battery. BUT, equip your vehicle with deep cycle batteries at both ends ... And that might be really slick for a smaller Jeep/Toyota where the whole mess is under the hood and you don't have room for hundreds of amps of camper battery.

Some models have extra time built in to allow the starter battery to fully charge first, some keep the batteries from combining during engine start, and some are designed to work with two engines or alternator. There are many ways to do this. While I like the Blue Sea, I actually use a Magnum SBC driving a Blue Sea relay. The Magnum opens the relay if the charging voltage exceeds 15v, possibly an issue with a Chevrolet that may have lead calcium or calcium/calcium batteries and which raises the charging voltage to 15.5v in cold weather. (I also have a dash override switch which allows me to force combine or force separate the batteries.)

Most folks will be very happy with either the 120A or the 500A Blue Sea ACR.

All of this is moot, however, if your cables are not up to the task of jump starting - wire everything up with 10 AWG and you are wasting your time.