How-To: Install Dual Batteries.

-Devil- · December 30, 2007

once i get around to adding my ham radio and such into my truck i will be adding an isolator and a second battery ...

just using the isolator .. so i can have my radio's hooked up to the second battery .. and dont have to worry about the 'oh s**t i talked to much and now truck is dead' syndrome...

BigJayDogg3 · December 30, 2007

'oh s**t i talked to much and now truck is dead' syndrome...

-Devil- · December 30, 2007

'oh s**t i talked to much and now truck is dead' syndrome...

hey it is followed by a close second to the

'who left the keys in my truck on so the radio could play while i was out drinking by the bondfire' issue...

j.roffel · January 18, 2008

Great article, I dunno about the 2500hd but my 99 1500 will turn anything you leave on off 15 minutes after you open the door with the keys out. This includes cargo lamp, all the interior lights, and I've never checked but I believe it's the headlights too...

Just FYI.

MILEPOST · January 21, 2008

Question for fourwheelinfool.

I have installed the dual batteries in my 98 tahoe and it works great.

My question is about my 01 silverado. What did you do about the firewall to fender brace where you put the 2nd battery? There isnt room under it for the battery.

thanks

MILEPOST

fourwheelinfool · January 30, 2008

You're absolutely right... there isn't enough room.

My brace is now tucked away in a workbench drawer!

(The factory equipped dual batt trucks lack this brace as well)

Good question tho... I didn't mention it in the write up.

~Stan

Shawn84 · January 31, 2008

Any suggestions on where to look for a battery tray. I see the space but there is what looks like 1/2 a tray already bolted down. Just curious on what to buy and how to install the tray.

EDIT:

Now i found this on GMPartsDirect.com

http://www.trademotion.com/partlocator/ind...playCatalogid=0

which parts will i need to build the entire tray. I'm guessing at least the retainer and tray left. What are the support, bracket, and reinforcement for? and are they needed?

MILEPOST · February 11, 2008

THANKS

I have done the same thing with the bracket. I made a tray from 1" angle iron that supports the battery on all four edges and used only 1/8" of height. I did however put a selenoid in the hot cable to prevent me from running down both batteries. I just have to remember to flip the switch once in a while to freshen up the charge. It should also be mentioned to use side post batteries only to prevent using your hood to check your charge.

Thanks again

CasualButJiggy · January 7, 2010

This is a good thread.

Is there a good place online to buy the wire and accessories for this setup? The 2 guage wire, lugs, etc?

R3Wood · October 27, 2011

I know this is an old topic, but I used it to install a second battery in my 2007 Yukon XL Denali. I appreciate this great post with pictures. I followed Stan's directions to the letter, except I ran my positive to the rear along the firewall and grounded the 2nd battery to a post on the firewall, to avoid two cables running to the passenger side (factory battery).

We've had problems sitting at football practice, just having the radio on. Then, click, click, click, battery dead.

I did this yesterday and went to practice last night, and no problems. The batteries I used were two new Interstate Mega-Tron Plus 85's.

It will be nice going into the winter months with 1540 CCA's and being able to sit places with the radio on without fear of needing a jump.

p.s. Thanks Stan!!!!

Rich in NJ

cgalford · October 27, 2011

I chose not to ground the second battery to the chassis and run a cable between both negative terminals. I chose this for ease of installation and no *good* reason. Alternatively you could run to ground on the second battery with no cable between terminals or do both. This is probably the proper way to go, but I didn't want to unhook two grounds when I service the vehicle… so there. An electrician may now tell me if I'm wrong or right. Never-the-less, it is what I did and I can't recommend anything else.

I had a similar setup in my 07 Tahoe and would get charging errors every so often when I grounded each battery independently. I later found out there is a current sensor on the OEM battery ground (induction loop) that helps the system determine how to regulate the alternator. After combining both grounds the errors went away and the system seemed to perform better when charging.

I would also recommend deep cycle batteries for this setup (IE Optima Yellow Top). Even having two starting batteries they're still not designed or rated for a depth of discharge past %10-%20.

R3Wood · October 28, 2011

I chose not to ground the second battery to the chassis and run a cable between both negative terminals. I chose this for ease of installation and no *good* reason. Alternatively you could run to ground on the second battery with no cable between terminals or do both. This is probably the proper way to go, but I didn't want to unhook two grounds when I service the vehicle… so there. An electrician may now tell me if I'm wrong or right. Never-the-less, it is what I did and I can't recommend anything else.

I had a similar setup in my 07 Tahoe and would get charging errors every so often when I grounded each battery independently. I later found out there is a current sensor on the OEM battery ground (induction loop) that helps the system determine how to regulate the alternator. After combining both grounds the errors went away and the system seemed to perform better when charging.

I would also recommend deep cycle batteries for this setup (IE Optima Yellow Top). Even having two starting batteries they're still not designed or rated for a depth of discharge past %10-%20.

Chris, I have not seen an error (yet) in my Yukon XL. Good information though, if I do get any errors, I can just run another ground from battery to battery. The 2nd battery (negative) is connected to the engine ground strap bolt on the firewall. So far, so good.

R3Wood · October 28, 2011

I chose not to ground the second battery to the chassis and run a cable between both negative terminals. I chose this for ease of installation and no *good* reason. Alternatively you could run to ground on the second battery with no cable between terminals or do both. This is probably the proper way to go, but I didn't want to unhook two grounds when I service the vehicle… so there. An electrician may now tell me if I'm wrong or right. Never-the-less, it is what I did and I can't recommend anything else.

I had a similar setup in my 07 Tahoe and would get charging errors every so often when I grounded each battery independently. I later found out there is a current sensor on the OEM battery ground (induction loop) that helps the system determine how to regulate the alternator. After combining both grounds the errors went away and the system seemed to perform better when charging.

I would also recommend deep cycle batteries for this setup (IE Optima Yellow Top). Even having two starting batteries they're still not designed or rated for a depth of discharge past %10-%20.

Chris, I have not seen an error (yet) in my Yukon XL. Good information though, if I do get any errors, I can just run another ground from battery to battery. The 2nd battery (negative) is connected to the engine ground strap bolt on the firewall. So far, so good.

P.S. I wonder, instead of re-running the 2nd Battery ground (which is currently connected to the firewall with the engine strap), I could just run a short cable from Battery 1 Negative to the firewall and bolt it on with Battery 2's ground?? Effectively connecting the two terminals while at the same time grounding to the chasis.

refueler83 · March 22, 2012

Hey everyone, names Will new to the Forum but been around chevys since I was a lil kid. I have a '00 chevy silverado Z71 5.3 and I want to do the dual battery install, but the one issue I am having is that the secondary air pump (smog pump) is located where the second battery is suppose to go, How to relocate it? is there another location for it? or do I gotta fab and relocate myself where i find fit?

69camarorag · March 24, 2012

Installing Dual Batteries on a 2002 Chevy 2500HD:

For some reason installing two batteries where there was only one original seems to be a difficult problem. Many people don't like dealing with electricity and prefer sticking with projects that require a ratchet and a ball peen hammer.

Running dual batteries is a great project for your truck and not that hard to setup. That being said, I don't want any of your loved ones suing me, so be careful. If you have any doubts, don't. If you think for a second you're going to hold me liable for blowing up your truck (or family blaming me for your death), stop right now—It's your fault for trusting what you found on the internet. Yes, this is a disclaimer.

Did it, loved it, sold it, then ordered it from factory on my 2011! Great write up......order the factory tray, it's cheap!

Anyway, I myself did some research on dual battery installation before I set out to conquer the beast... there are a lot of "good" ideas floating around about how to do it, from isolators and constant-duty solenoids to switches, even flux-capacitors. Forget about them, most are from people after your money or from others who have already paid those people. Wire them in parallel and be done with it for a minimum of cost and all the benefit. If you disagree, spend your money on some of these wonderful pinball machine parts I have and leave this advice to people who just want a truck to start in the winter.

Above: New batteries at top and lower left. Cable routing can be seen on the right side, running along the radiator support. Terminal extension bolts for the original battery location, top.

Things you must have:

Minimum length of appropriate cable

Copper "automotive style" crimp lugs

Electrical (vinyl) tape

Battery terminal extensions

Two batteries

Procedure:

First I went out and bought 12' of 2 AWG THHN cable, which happens to be gasoline and oil resistant. Measure your route before you buy wire! I chose 2 gauge as it was the smallest cable that would provide a voltage drop of no more than 2% at maximum charging current (in my case 160 amps). This is to prevent damage to the alternator and to keep the batteries from "fighting" and wearing themselves down. Calculated out, I ended up with a 2.5% drop over 6' of cable for 2 AWG at 160 amps. You may want to choose a larger cable diameter. I'm glad I didn't.

Second, you need to identify where to put the second battery! In many a Silverado the choice is simple. I located mine on the passenger side directly behind the coolant recovery. This is where the second battery from the factory is located. Some trucks are equipped with MAP sensors in this location.

I wanted to get this project under way, so I fabricated a support of 1/8" plate and bolted it down. The battery is supported off the bracket with neoprene rubber and rubber tape. To hold the battery down I fashoined a strap out of 1" webbing. You may choose to get a battery tray from a parts store / dealer. I will eventually but my old battery was dieing! I passed on the plastic trays from the local parts store.

Next, I routed the cables. This is why I'm happy I chose 2 AWG. Any larger and it would have been a difficult task. Bend them to fit kind of like you would when running brake line. At first I was going to be fancy but then reason took hold. Go easy and simple. I routed the cables from the new battery location, back to the fender, along the coolant recovery, past the air filter, turn 90 degrees, along the radiator support, down under the radiator hoses and finally to the stock battery location. Have fun! Make sure that your wires don't rub on any hoses / lines or you'll regret it later.

After you have the cable routed, crimp your lugs on. Make sure that they line up with the terminals properly or you'll have to twist the wire. Also make sure you get the correct terminal size which would be 3/8" for GM side terminal style batteries. These are available cheapest at you local hardware store in the "hardware" section in the little bins. Stay out of the electrical section or else you'll over pay or won't be able to find the right size.

Now slip on your loom (optional but highly recommended). This is the black corrugated tubing you see snaking all around your engine compartment. You can get it cheap at the hardware store. Its purpose it to protect the cable from rubbing, don't pass it up. Not to mention the installation looks much more professional this way… which is enough of a reason to warrant the extra $5.

Before you can install the system you have to secure the cables. I used nylon clamps also available at the local hardware store. These I fastened behind the bolts holding the fan duct. You may find a better location.

Now for the fun part, connect the batteries! Remember, red goes to red, black to black, not the other way around! This is called parallel. Put your extensions on the stock battery. I transferred the stock terminal bolts to the new battery. If you can't figure this out you've probably electrocuted yourself by now. The sequence I used (which I believe is correct, please someone correct me if I'm wrong):

Positive from vehicle to battery #1

Positive from battery #2 to battery #1

Negative from vehicle to battery #1

Negative from battery #2 to battery #1

You MUST connect your 12 volt batteries in parallel on a 12 volt system. Doing otherwise is called "series" and you end up with 24 volts which results in no more truck—it disappears in a flash of fire and a puff of smoke. Parallel results in the same voltage, twice the amps, and twice the reserve capacity. It's like going out and buying a battery with 1200 CCA that lasts twice as long (reserve capacity) than your stock 600 CCA battery. Old man winter is now shut out far away from your starter!

I used red vinyl tape to clearly mark the positive ends. I also used rubber splice tape and vinyl tape to wrap the copper lugs up to the terminal spade for personal safety. Rubber splice tape was also used to fashion positive terminal covers. If you can find manufactured covers for side terminal batteries, let me know, I'd like to buy some.

Estimated Cost:

(12') 2 AWG Stranded THHN Cable = $35

(4) Copper Lugs = $9

(2) Battery Terminal Extensions = $9

Vinyl Tape (Red and Black) = $5

Rubber Splice Tape = $4

(2) 10' Loom = $5

Nylon Hold-Downs = $3

(2) ACDelco 78-6YR Batteries 675 CCA = $230

Total = $300

Done properly my setup would have only cost $300. It does not include tools like a wire cutter or crimper. Get good ones if you don't have them… go to Sears and buy Craftsman or better and make sure they're made in the USA. I probably spent $50 more in stuff I didn't need like crappy lead lugs from Wally-World. Get good stuff! My extensions from AutoZone will need to be replaced shortly; the threads were damaged just by trying to tighten them. Coincidently I have vowed NEVER again to shop at Wal*Mart or buy anything MADE IN CHINA no matter how small (except for disc brake rotors which is another story... arg).

Other things you must know:

SAFETY! You must have a grasp on basic electrical concepts. If you haven't learned series vs. parallel wiring, go learn it! Also, if you don't feel confident performing work on your own vehicle bring it somewhere to have someone else install this mod. Most of what we do to our trucks is fairly safe to implement, resulting at the worst some bloody knuckles. Messing this up can KILL you. Whoever said a little fear isn't healthy? You wouldn't go sticking a fork in power outlets would you? That's essentially what you're doing every time you disconnect a battery.

Batteries have a code stamped somewhere on them indicating the month and year they were manufactured. This code differs by manufacturer and you may want to learn how to read it. It is highly recommended that you get batteries made during the same month. Mine have consecutive serial numbers. I don't know if it still holds true or not, but it is also recommended to purchase batteries that are no more than 3 months old.

I chose not to ground the second battery to the chassis and run a cable between both negative terminals. I chose this for ease of installation and no *good* reason. Alternatively you could run to ground on the second battery with no cable between terminals or do both. This is probably the proper way to go, but I didn't want to unhook two grounds when I service the vehicle… so there. An electrician may now tell me if I'm wrong or right. Never-the-less, it is what I did and I can't recommend anything else.

Finally, you don't NEED a constant-duty solenoid or any other fancy $300 crap. You can choose to get it if you want, but my setup works and will work fine as long as I heed standard auto protocol like "Don't leave your dome light on."

Now listen to it crank! My-My, faster than your girlfriend!

Good luck and muddy tires!

Stan