Ground for dual battery

BurbanAZ

Explorer
I'm hooking up my dual battery today and was looking for a solid ground for the accessory battery. Would the hook that's there on the engine be a solid ground? It's on an 04 4Runner.
 

DaveNay

Adventurer
Most every installation I have ever seen suggests connecting the neg of the aux battery directly to the neg of the primary battery using the exact same size cable as the pos connection.
 

BurbanAZ

Explorer
I've done a few dual battery setups before and I always just grounded them separate from the main batter. I'm not sure if there would be an advantage to running negative back to the negative of the main battery.
 

WagoneerSX4

Adventurer
Depends on the vehicle. If it's a full frame vehicle you're probably fine. But my unibody suzuki is a huge pain to ground properly.
 

BurbanAZ

Explorer
I just grounded it with a large bolt to the frame. I sanded off the paint and checked for a good ground with a meter so that should be good I think.
 

4x4junkie

Explorer
I would suggest running another ground cable (same size as your positive cable) straight from your primary battery to the frame also.

Without that, I could see current trying to find it's way down some thin little factory ground wire somewhere and smoking it (along with something more expensive), as the factory battery (and alternator) is normally grounded to the engine block, rather than the frame.
 

doug720

Expedition Leader
I don't think you can have too many grounds. I tie both of my batteries in my 60 to the body, frame and engine. With one ground to the starter. This is how Toyota wired them stock and Isuzu grounded the battery to the starter stock also.

Many odd electrical problems - intermittent lights, odd readings, etc, are often ground related. Make grounds to solid connections and tie all the isolated parts - body, frame and engine together.
 

wrcsixeight

Adventurer
Frame grounds tend to deteriorate, and yet appear fine and tight upon visual inspection.

When Unthreaded one finds the mating surfaces white and oxidized.

Make super shiny both mating surfaces, and cover with grease after rethreading to prevent oxidation.



+1 on adding an additional battery to frame ground, or even an engine to frame ground.

When the big grounds fail and large currents seek a return path to ground through thinner wires, bad things can happen.

Reduce the likelihood of this occurrence.
 

Borrego60

Rendezvous Conspiracy
I would go where the factory ground wire is located. On the 03 Tundra it is on the engine block left side low mid block. I did a dual battery system in the truck and that is where I ran my ground wire to.
 

Quest4ADV

Adventurer
You could try something like this...
rbAo0Vc.jpg
 

CaliMobber

Adventurer
If you Have not done the BIG 3 grounding mod I highly recommend it. I saw a good voltage increase from it.

Ground battery to the frame/ engine block and alternator.

My second battery is just grounded to the frame since i have so many grounds off the main battery.
 

BurbanAZ

Explorer
If you Have not done the BIG 3 grounding mod I highly recommend it. I saw a good voltage increase from it.

Ground battery to the frame/ engine block and alternator.

My second battery is just grounded to the frame since i have so many grounds off the main battery.

Yea I've seen other people talking about that but I haven't done it yet. I'm going to have to now that I'm adding a bunch of electrical stuff.

I was going to mount to the same point that the frame is connected to the engine block but I didn't see it. Plus if I do the BIG 3 upgrade than I'll have a better ground to frame.

Are these vehicles just badly grounded from factory?
 

CaliMobber

Adventurer
Not any worse then other cars. The BIG 3 is a popular mod for all cars. They just ground it well enough for stock but once we start adding more and demanding more the grounding becomes a chock point.

I would say dont worry to much on where its grounded. the frame is a tough one. The bolt I used was pretty small, just be sure to sand it down before you add the wire. You can use a little spray paint over it once it tightened down to protect from rust.
 

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