mount dual batteries under frame (1 Viewer)

[daytrader]

I'm considering installing two batteries from under the hood to where my spare used to be. Main reason would be weight. For the sake of argument a battery weight 50 lbs so thats 100 lbs from the front to the back.

I would be installing the AGM batteries on their sides in suitable reinforced boxes.

I would be running high quality low resistance cables from the rear to the front.

I'm eventually going to do a 6BT swap so the battery weight shift will offset the extra weight of the cummins.

Has anyone else done this and how did it work out.

 

[nukegoat]

I considered it but its a long run for the alternator and winch and so on. I was looking at 2/0 gauge and decided it wasnt worth the effort.

 

[1973Guppie]

completely possible but difficult, I would use the largest wire possible to compensate for voltage drop, I would also not mount the starting battery back there, too long of a run for starting purposes. If possible keep the 2 in the rear and a starter in the engine bay.

 

[ZackR]

Both of my BMW's have batteries in the trunk (factory location). I'm not sure of the wire gauge but its definitely doable.

 

[Bigdrewbowski]

I was about to mention the same thing about BMW's. Some Mercs have them under the passenger seat. You would want terminals under the hood for jumping off and running the winch to. There has to be a calculator online to help you figure wiring gauge and voltage drop.

 

[White Stripe]

Im currently doing this in my 40 but won't be done for a week or two. Im using 3/0 gauge cable. I can send you a link to my process if you want.

 

[Biggreener]

Rezzing an old thread here, but I’ve been thinking about adding my second battery in the spare tire void as well. Any update on this @daytrader @White Stripe ?

 

[RS6tofj80]

my C63 Merc and Old RS6's had it in the trunk 1/0 wire run is fine..... I debated doing this and running a Odessey 825 under the hood for starting but decided it wasn't worth the hassle and I'd like to leave that space open for a rear tank someday...

E

 

[Sc0-]

Metaltech has a bracket to mount a battery or batteries to their slider under the truck... Depending on how you look at it, the battery cable isn't much longer than in the OEM location.

 

[maxamillion2345]

Did this with the main battery on my buddies 95 toyota pickup. We ran 2/0 cable. Mounted batt under bed. Ran negative cable back through cab with a batt disconnect. Works great.

 

[fz1boxer]

back in my drag racing days it was 2 batteries in the trunk and 1/0 cable.
you can run a lighter gauge if you can find continuos strand railroad cable$$$$$$$$$

1 Awg Battery Cable - Wiring Products

 

[Golgo13]

Current production Toyota Hybrids do this exact thing for better balance. Lexus does the same thing too. But they both keep the battery inside where it is dry/safe to eliminate the need for a special reinforced, weather tight box. A lot more crud gets sprayed in that area compared the the current F(Z)J80 battery locations with their half-sealed carrier boxes in the engine compartment.

 

[Red Merle]

Current production Toyota Hybrids do this exact thing for better balance. Lexus does the same thing too. But they both keep the battery inside where it is dry/safe to eliminate the need for a special reinforced, weather tight box. A lot more crud gets sprayed in that area compared the the current F(Z)J80 battery locations with their half-sealed carrier boxes in the engine compartment.

Having dealt with the rust on my truck's undercarriage over the course of the last couple of years, I can say for sure that the area that the spare tire is in gets the brunt of the salt, dirt and other crud that gets caked up on an 80. From the rear wheels back is a bad area for something that probably won't like those conditions. I think some sort of sealed box would be the only way it would work, especially if you have winter where you live.

 

[fz1boxer]

if i was going to put a battery underneath i would use a sealed box and mount it where the spare tire used to sit,my spare resides inside for now.
you already have mounting points and a crossmember,or fabricate a custom mount.

 

[Red Merle]

if i was going to put a battery underneath i would use a sealed box and mount it where the spare tire used to sit,my spare resides inside for now.
you already have mounting points and a crossmember,or fabricate a custom mount.

I think making it so you could access it would be key. Big enough to work in there too, without having to pull the batteries out. Some sort of a door with a stainless piano hinge type operator panel with a fold on the edges so you could install some self adhesive weatherstripping. Maybe even a dome light in the box for true pro jock engineering?

Maybe that is too far out of the box though...

 

[White Stripe]

Mine does not use a sealed box, but I only drive on mag chloride roads once a year at most and then I wash everything. I raptor lined the entire box and used stainless fasteners. I like having it open as it's easy to work on and wash the crud off of. I gained a lot of need engine compartment real estate doing this. The 31 series battery turns the motor over with ease.

 

[Tapage]

you are not on a wet / humid / salty environment ..? that would be a concern to me ..

 

[Red Merle]

you are not on a wet / humid / salty environment ..? that would be a concern to me ..

Honestly, in my area, you would need some sort of like mini dorm room fridge level of seal to keep that from just getting soused with salt water mixed with sandy road grime knarlyness.

 

[White Stripe]

you are not on a wet / humid / salty environment ..? that would be a concern to me ..

The only concern I can think of is moisture working it's way into the cable at the point where the cable meets the battery clamp, which with these clamps is pretty easy to seal up that connection point. The clamps themselves are pretty decent quality and should not corrode easily at the battery terminals. A little grease on the terminals would give even more corrosion protection which I may add.

 

[RFB]

back in my drag racing days it was 2 batteries in the trunk and 1/0 cable.
you can run a lighter gauge if you can find continuos strand railroad cable$$$$$$$$$

1 Awg Battery Cable - Wiring Products

great link