Can you jump start off a dual battery?

Q: Can you start a car with a second battery?

A four-way switch allows the vehicles first or second battery to perform either of two roles: starting the vehicle, or powering equipment while totally isolating the other battery. Thats great if at camp you wish to operate your vehicles radio or other accessories, without risking flattening both batteries.

Q: How do you jump a car with a second battery?

Open the positive jump-starting points cover (2). Connect the red jump leads other clamp onto the cars positive jump-starting point (2). Connect one of the black jump leads clamps to the donor batterys negative terminal (3). Connect the black jump leads other clamp onto the cars negative jump-starting point (4).

Q: Can you jump a diesel with both batteries?

Youll need to determine which battery on the diesel truck has thicker cables. The thicker cables will be the battery you connect the jumper cables to. If both cable thickness is the same, either battery can be jumped.

SentoZD30Di

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Discussion Starter · #1 · Jul 16, 2020

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This is the kit I want to get to setup my dual battery( image below).
I’m just wondering if one day my main battery dies can I start my car by jump starting the second battery?

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rumcajs

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#2 · Jul 16, 2020

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In theory you can as long as that voltage sensitive relay pictured supports that function.
Thing to consider is the size of the wiring between batteries (should be equal to your starter battery to starter motor wiring) and also being your secondary battery deep cycle nature.
You can just use external jumper leads to connect as well in case of emergency.
Redarc SBI series battery isolators (aka voltage sensing relay) Dual battery isolator has the option of "Jump start" built in and can be wired up by to use momentary push on switch to actuate.....
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turps

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#3 · Jul 16, 2020

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My red arc had a momentary switch for linking battery’s for jump starting.
Now I will just use a single jumper lead across the positives if it happens.

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Turps
Well the futures here. And I have a 2010 CRD auto parked in the drive.

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If the "house" battery is fully charged, wouldn't turning on the ignition switch send power to the depleted starter battery? Which would then allow me to start the truck, yes? Or am I missing something?
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I seem to recall learning in the past that in order to send maximum power to the starter, sometimes other circuits are momentarily cut off, so does that mean the ignition circuit that I've tapped into for the solenoid power would lose its power (and open up, disconnecting the house battery from the starter battery) as soon as I turn the key to crank the starter?
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But if that is the case, shouldn't I be able to "charge up" the starter battery, for example, by turning the ignition on (closing the switch and connecting the two batteries together) and then leaving it in that position for a few minutes (so the house battery will charge up by the now-connected starter battery) and then turn the switch to crank the engine?
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I understand this would not work in a situation where the starter battery is 100% dead and doesn't have enough power to energize the circuit with the solenoid, but I'm talking about the (IMO much more common) situation where the starter battery has some power, just not enough to actually crank the starter.

If you recently bought a diesel truck, you’ve made a smart move. The upsides of a diesel truck are tons of torque, rugged construction, reliability and long life. Not much is going to stop that rig. Except maybe a dead battery. Avoid getting towed or stranded by learning how to jump-start a diesel truck with two batteries.

Do Trucks Have Two Batteries?

It’s not uncommon for diesel trucks to have two batteries. The dual-battery setup cranks extra power that can overcome the higher resistance of a diesel engine. Compression ratios for diesel engines are almost twice those of gasoline engines. It simply takes more oomph to fire up a diesel.

How Do I Jump-Start a Diesel Truck With Two Batteries?

Luckily, you don’t need to find a friendly stranger with a dual-battery vehicle in order to get yours moving again. The batteries in your truck are in parallel. This means you can jump-start your diesel engine by connecting to just one of the batteries — usually the most accessible — in your vehicle’s engine compartment. Once you get the engine started, the alternator will do its job, sending a charge back into both batteries, even at idle.

Here’s how to do it:

Put both vehicles in either “park” (automatic transmission) or “neutral” (manual transmission).
Turn off lights and other accessories in the vehicle you’re jump-starting.
Connect one clamp of the red jumper cables to the positive terminal of the dead battery. The terminal will either have a “+” symbol or a red cover.
Connect the cable’s second clamp to the good battery’s positive terminal.
Connect one of the black cable’s clamps to the good battery’s negative terminal.
Find a piece of unpainted metal on the vehicle you’re jumping (the alternator bracket is a great choice), and connect the last black cable’s clamp to it.
Start the engine of the vehicle with the good battery, and let it run for a few minutes. You’re putting juice back into a dead battery, which will take a moment.
Start cranking the engine on your diesel. It may take a while to fire up, so you might need to give it another few minutes of juice from the good battery.
Once the engine turns over, remove the black cables from both vehicles one at a time, making sure they don’t touch metal, each other or the red cable.
Remove the red cables from both vehicles one at a time. Stay careful and alert until the clamps are detached from any batteries to avoid electric shock or fire.

Remember to let your revived truck run for a bit, allowing the alternator to put power back into both batteries. Take your truck for a drive, and try not to shut off the engine for at least 20 minutes.

Keep those jumper cables handy, just in case. Now that you know how to jump-start a diesel truck with two batteries, you’ll know just what to do when someone else needs your help.

Check out all the battery cables available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on jump-starting your vehicle, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

Mike Hagerty View All

Mike Hagerty is an automotive journalist whose work has been featured on radio, TV, in print and online since 1997. He's the Publisher and Editor of MikeHagertyCars.com, and contributes car reviews to the Los Altos Town Crier and losaltosonline.com. Previous outlets have included KFBK and KFBK.com in Sacramento, California, the ABC television affiliates and Hearst-Argyle and Emmis radio stations in Phoenix, Arizona; AAA magazines for Arizona, Oklahoma, Northwest Ohio, South Dakota and the Mountain West and BBCCars.com.

Can you jump

If the start battery is discharged, current from another battery can be used to start the vehicle.

Can you start a car with a second battery?

A four-way switch allows the vehicle's first or second battery to perform either of two roles: starting the vehicle, or powering equipment while totally isolating the other battery. That's great if at camp you wish to operate your vehicle's radio or other accessories, without risking flattening both batteries.

How do you jump a car with a second battery?

Open the positive jump-starting point's cover (2). Connect the red jump lead's other clamp onto the car's positive jump-starting point (2). Connect one of the black jump lead's clamps to the donor battery's negative terminal (3). Connect the black jump lead's other clamp onto the car's negative jump-starting point (4).

Can you jump a diesel with both batteries?

You'll need to determine which battery on the diesel truck has thicker cables. The thicker cables will be the battery you connect the jumper cables to. If both cable thickness is the same, either battery can be jumped.