Chevy Astro and GMC Safari Forum banner

Dual Battery setup

40K views 53 replies 34 participants last post by  Wavelength 
#1 ·
Here's a write up of my dual battery setup:

Before I went forward with this project, I searched the heck out of the AS site and, other forums and got a zillion different opinions. I went with a simple, non electronic solution.
Here is a short write up and pics of the installation of my auxiliary AGM Deep Cycle Marine Battery and isolator switch.

About The Battery:
12V AGM, Group 24, 79Ah, 10.9"L x 6.8"W x 9.9"H, 53lbs
Around $200.00 US


The AGM Deep Cycle battery from West Marine is an "Absorbed Glass Mat" battery.
AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:
Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. Most AGM batteries have no charge or discharge current limits.

AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries.

AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

More info here:
http://www.westmarine.com/webapp/wcs/st ... assNum=208" onclick="window.open(this.href);return false;

About The Switch:
Around $40.00 US
Make-before-break contact design allows switching between battery banks without power interruption.
Ignition protected - Safe for installation aboard gasoline powered boats
Case design allows surface or rear panel mounting
Meets American Boat and Yacht Council (ABYC) requirements for battery switches
"Blue Sea Systems' switch (9001e) is our choice for best value in a standard-duty battery selector switch. It's made in the U.S. with high grade materials, comes with a lifetime warranty, and is the least expensive switch in our test." - Powerboats Reports, June 2005





More Info here:
http://bluesea.com/category/1/products/9001e" onclick="window.open(this.href);return false;

Connecting The Switch
1st thing we did was disconnect both the positive (+) and negative (-) post from the vans battery.
Using the existing positive cable, we removed the protective rubber boot and connected this to the "common" terminal on the switch. [see back of switch]
Next we took a standard 6 inch side post battery cable (purchased from Advanced Auto for about $6.00) and connected this to the "1" terminal on the switch using a ring/crimp connector on the end of the side post cable. Then we connected the side post cable to the (+) Positive terminal on the stock battery.
Next we used a ring/crimp connector and connected the auxiliary battery cable to the "2" connector of the switch. [see back of switch]
We used tie wraps and secured the switch to the existing conduit. It is very secure, and very easy to remove if you need to.







The battery currently is placed behind the 1st row rear seat.
I bought a top post battery cable, 24", and used the seat belt mounting bolt for the ground. [see pic below]







We ran a 6 gauge cable through the firewall close to the steering column.
The cable is from a 16 foot jumper cable that we split and removed the clamps.



When we were finished, I flipped the switch to "2" and started the van using the Aux Battery. Not what I would usually do, just wanted to test it. Switched it back and fourth a few times and everything seems fine. Let it run a while, turned off the ignition, flipped the switch to both "1" and "2" and she fired right up.

I have only been on one road trip so far and the battery has powered my stereo for 8 hours at a time with no issues. To save power I disconnect two of the three amplifiers and run my external speakers.





I use the switch set on "1" + "2", [both batteries in parralel] full time. This way the battery is being charged as needed using the vehicles charging system.

I switch to battery "2" [Aux battery]for when I am running the stereo with the engine off.
The next morning, or after an evening of partying, I turn the switch to "1" [car battery] for starting the engine. After a minute or two, with the engine running, I turn the switch back to "1" + "2" and let the battery recharge.

Of all the deep cycle batteries out there it appears the AGM is best suited for my needs. It can be used inside the vhicle. It can be used as a starting battery and a deep cycle battery and the vehicles charging system will work OK. However, if you run this battery down stone dead, an external charger is recommended to save your alternator.

I hooked up my 3 amplifiers directly to the Aux Battery. The CD player is hooked up normally. As most of you guys may know, a battery is like a big *** capacitor, and hooking an amplifier directly to the Aux battery is an ideal set up. I have a 15" subwoofer between the seats, and this new setup really provides the power when it's needed.



Here's a couple of pics of the stereo and sub.
The armrests had to come off to squeeze the sub enclosure between the seats.
It is actually more comfortable setting the armrests on the sub.





 
See less See more
16
#2 ·
:text-threadjacked:
Wow, great write-up. However, because of the amount of content and the fact that the post deviates from the original topic... I'm going to move it to its own topic.
 
#3 ·
Makes sense....
update:
It's been 13 months and lot's of trips, camping, etc...everything works perfectly.
I have run the stereo for 12 hours or more at a time on the deep cycle battery...have never run it completely down.
 
#5 ·
Yes, that is great write for sure, thanks WVKayaker. Amazing.:)
 
#6 ·
a music lover, nice post!

I've just installed a second battery (100ah AGM) and a 40w solar panel on the roof.

Im wondering if you have had issues with over charging the AGM? my stock altenator puts out 14.7 volts when charging and the AGM battery specs says charging must be limited to 14.1 volts and over that decreases the lifespan of the AGM.

the solar does the charging for me but I have also added an automatic isolator that switches to the AGM after the altenator has fully charged the starting battery and it can also be manually switched so I can jump start if needed (kinda cool with no jumper cables)

anyway now Ive got it all wired up I found the stock altenator is a little too much so I have the auto part disconnected for now. it will be fine for emergency when several days of bad weather dont allow for solar charge but Id like to find a a way to limit the voltage into the AGM to 14.1 without buying a new altenator.

I'll try to get some photos, I mounted the AGM under the van just ahead of the fuel tank.
 
#7 ·
Hey ratmoto could you post a couple pics of your 2nd battery and mount system...I have a Wallyworld battery=125AH and am gonna hook it up in series for my amps (3) and the DVD/LCD w/inverter...and since i already have battery need a place for it (not inside with kiddies) I already have most of wires ran to back with an isolator switch mounted by e-brake :confused:
 
#8 ·
astro355 said:
That is a good write up. I am glad that you knew to use a sealed battery in the passenger compartment. Some of the things I have seen in the past, :eek:
What have you seen?
I'm planning on running dual batterys , i ussually would mount both under the hood but i only have room for one , i have a xtra normal car battery laying around that i thought i'd use , is this a bad idea? I dont know what a sealed battery is!
Also if i was to use a deep cycle as a second battery , could i keep it hooked up at all times or would i need a switch like WVKayakers to protect the deep cycle battery from the cranking circuit?
I was just thinking maby i could get a plastic box that i can seal and run a hose from it to the outside to let it vent / breath!
 
#9 ·
webcat said:
astro355 said:
That is a good write up. I am glad that you knew to use a sealed battery in the passenger compartment. Some of the things I have seen in the past, :eek:
What have you seen?
I'm planning on running dual batterys , i ussually would mount both under the hood but i only have room for one , i have a xtra normal car battery laying around that i thought i'd use , is this a bad idea? I dont know what a sealed battery is!
Also if i was to use a deep cycle as a second battery , could i keep it hooked up at all times or would i need a switch like WVKayakers to protect the deep cycle battery from the cranking circuit?
I was just thinking maby i could get a plastic box that i can seal and run a hose from it to the outside to let it vent / breath!
Sealed batteries don't emit vapors. If you put a normal car battery in the passenger compartment regardless of how you set up the box, you run the danger of leaking those vapors in the passenger compartment. There is no good way to completely seal a battery box.

And you would have to isolated the batteries. The problem is in the amps required to charge both batteries.
 
#10 ·
astro355 said:
There is no good way to completely seal a battery box.
What would be the differance from it being in a sealed box vs under the hood of a van?
I would think if i had a sealed box with a good vent (large tube that led to the exterior ) that the fumes would take the path of least resistance and escape.
I was looking at battery setups in RVs and they had 6 -6volt batterys in a box , the box had 2 small 3" round vent holes in the floor and one small round 3" vent in the middle top of the box , i was thinking since i would have one 12 volt battery in a box , i would put about a 5 " tube up and out the side of the van and i could put another vent in the floor , since my floor is wood it would be really easy to secure everything so it dont develop leaks.
Here's a picture of the battery box i made , i hav'nt cut the hole in it yet to run my vent tube
I was going to buy a plastic box from walmart but they all had big vent holes in the top like they would be better for under hood application.
1.JPG
 
#11 ·
webcat said:
What would be the differance from it being in a sealed box vs under the hood of a van?
Because under the hood of a van is NOT in the passenger compartment. :confused:

If you really want to, go for it. There is just some things I won't put in the passenger compartment such as batteries and fuel tanks.
 
#14 ·
You don't want to breath the fumes from a battery, they are also flammable and can cause a battery to explode. Going with a dry cell battery is the way to go.
 
#15 ·
I'm back to say it's still working great...no issues...
 
#18 ·
I have had an optima yellow top in the van, under the bed for years without issue.
but it has always been connected to the other battery, not on an isolator or anything.

this year I am planning on changing that (cheaper than dual alternators at the moment)
I have had a huge isolator for awhile, just never could figure out where to mount it in the van, but I after talking with several other people, I think I am going with a solenoid option, does the same job as that big red switch in the first post, just does it automatically.

you can see the threads on my site here, Batteries inside the van and here mounting an isolator

I am planning on making a storage box under the van where the spare tire used to be, and making an access panel on the inside of the van to access it, and putting the batteries there (I plan on having at least 2 in the back of the van) and my air compressor in it. freeing up storage space under my bed.
 
#19 ·


That one only had 2 batcaps and a charger. I have the frame somebody made for me for 8 batteries. I will be running 4/0 positive and negative from the engine compartment to the rear of the van, wired to 8 Walmart batteries (can't beat the warranty). Then possibly 8 more stacked on top. Each set of 8 batteries will be linked together with 1/4 to 1/2" thick copper bar. The battery banks will be linked together using 4/0 wiring.

Very simple setup. Hardest part is getting the wiring from the front of van to rear of van. Mine is ran along the frame (one day I need to get it in some PVC pipe).

You do not need an isolator or anything to run multiple batteries, as long as they are wired in parallel (+ to + and - to -). It is recommended to use a fuse within 12" of front battery and rear battery bank. This way everything will be protected from any potential shorting out.

And no, I am not recommending a normal van driver installing 16+ batteries. There are some other things that are involved. 1) A H.O. alternator, possibly 2 alternators, since a factory installed alternator can not keep up with some many batteries (3 batteries for the 105amp is about max). 2) The Big 3 upgrade needs to be done. This actually should be done whether installing 1 extra battery or 30 extra batteries.
 
#20 ·
I was messing around with my project Ole Yellar's battery thinking I want a dual battery starter system.So I had the battery out and was looking at the battery tray that needs to be replaced.I know how many times we have talked about a second location for a battery and then it stuck me,why not sideways with a custom battery tray in the stock location??.So I grabbed a tape measure and that would work.If you tuck the first battery alittle towards the fender and the second one next to it building a battery tray for two batteries.I think sometimes the simplest solutions are right there.Just have to find them.
 
#21 ·
I went with the solenoid option, and replaced the single optima under the bed with 2 exide orbitals.
I made a fancy switch to close the solenoid that includes a warning system so i don't forget to shut it off when the van isn't running.

 
#24 ·
ratmoto said:
a music lover, nice post!

I've just installed a second battery (100ah AGM) and a 40w solar panel on the roof.

Im wondering if you have had issues with over charging the AGM? my stock altenator puts out 14.7 volts when charging and the AGM battery specs says charging must be limited to 14.1 volts and over that decreases the lifespan of the AGM.

the solar does the charging for me but I have also added an automatic isolator that switches to the AGM after the altenator has fully charged the starting battery and it can also be manually switched so I can jump start if needed (kinda cool with no jumper cables)

anyway now Ive got it all wired up I found the stock altenator is a little too much so I have the auto part disconnected for now. it will be fine for emergency when several days of bad weather dont allow for solar charge but Id like to find a a way to limit the voltage into the AGM to 14.1 without buying a new altenator.

I'll try to get some photos, I mounted the AGM under the van just ahead of the fuel tank.
Hello friend can you share some pics of the panel which you have got on the roof? I need a new portable charging system so can you give some good advice.
 
#25 ·
WilburPerez said:
ratmoto said:
a music lover, nice post!

I've just installed a second battery (100ah AGM) and a 40w solar panels on the roof.

Im wondering if you have had issues with over charging the AGM? my stock altenator puts out 14.7 volts when charging and the AGM battery specs says charging must be limited to 14.1 volts and over that decreases the lifespan of the AGM.

the solar does the charging for me but I have also added an automatic isolator that switches to the AGM after the altenator has fully charged the starting battery and it can also be manually switched so I can jump start if needed (kinda cool with no jumper cables)

anyway now Ive got it all wired up I found the stock altenator is a little too much so I have the auto part disconnected for now. it will be fine for emergency when several days of bad weather dont allow for solar charge but Id like to find a a way to limit the voltage into the AGM to 14.1 without buying a new altenator.

I'll try to get some photos, I mounted the AGM under the van just ahead of the fuel tank
.
Hello friend can you share some pics of the panel which you have got on the roof? I need a new portable charging system so can you give some good advice.
 
#26 ·
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top