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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.





 
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#28 ·
I am setting up charging the dual battery using the solenoid but I am having a hard time finding a power source that I can hook it up to that goes on with the keys, under the hood everything I hit with my meter has power with the key off anyone have an idea what I could try for keyed power that I can reach? 99 astro
only thing I can think of but do not want to cut in is the headlights power cable as they go on at the turn of the key...
would rather find another power source thats keyed...
 
#29 ·
Where's your 2nd battery, SurBill?

If you're going to start splitting power between main and aux batteries, I recommend you bring a dedicated KEYON wire to a fused relay in the eng compartment. Since it runs to a relay you can use very small gauge wire, not much current handling capacity needed.

But run it to a relay and then you can run everything from that relay to their individual relays with a large gauge power source to each auxillary gizmo.

I also recommend running a very large gauge, FUSED 12vdc+ wire to the rear of the van as well as a FUSED KEYON switched wire. Terminate both of those in a fuse block and run all your rear of th van gizmos from that.

Lump
 
#30 ·
Aux Battery is at the back of the Van.

yes I understand I can use small gauge wire its finding that darn KEYON wire I can tap into that causing me a headache..

neat idea to run other relays off that it is an 80 amp relay so plenty of juice to run other things off it...

yes I have a fuse I will put on before it gets to the aux battery....

Now I can get a one time fuse were you can just replace the fuse itself then their are fuses you can get that auto reset themselves to me that sounds good but if their really is a problem of something shorting out then not so good to have one of these auto reset fuses..

I have the relay in on the firewall just above the main battery and then ran my power to the back from that but I still cant find that darn keyon wire other than the daylight headlight wire do you think it would be ok to tap into that if I dont find anything else?

I have a cutoff main switch right at the aux battery..

Lumpy said:
Where's your 2nd battery, SurBill?

If you're going to start splitting power between main and aux batteries, I recommend you bring a dedicated KEYON wire to a fused relay in the eng compartment. Since it runs to a relay you can use very small gauge wire, not much current handling capacity needed.

But run it to a relay and then you can run everything from that relay to their individual relays with a large gauge power source to each auxillary gizmo.

I also recommend running a very large gauge, FUSED 12vdc+ wire to the rear of the van as well as a FUSED KEYON switched wire. Terminate both of those in a fuse block and run all your rear of th van gizmos from that.

Lump
 
#35 ·
survival bill said:
I found a fuse here that is keyon yee haa now how do I tap into this fuse?
With a little gizmo called an "Add a Circuit". It's a couple dollars at the LAP store. It plugs into your existing fuse slot, then you plug your existing fuse into it, and there's a second spot for you to use for whatever you like. Add a fuse right there at that 2nd slot. Very handy little device.

Add-A-Circuit.

Lump
 
#36 ·
I just happen to Napa Auto Parts and asked them yup thay had that cool fuse part its all setup now for me IM a happy camper this setup is for my Koolatron cooler for this coming summer so will be interesting to see how well it works I still have to install the 120 watt solar panel to the battery but I still need to find/want 20 amp charge controller....
Will still have to unplug the cooler overnight though as I think it will drain battery down to low but should be ok to keep things cool overnight anyways....
 
#37 ·
ratmoto said:
..
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.
...
I know this is ancient but we do get new people (and others) reading these posts so I'll say it anyway: If you use a solid state isolator, it has an inherent voltage drop across it of ~.7 volts, so using one of them means your AGM would be getting 14 volts, instead of the alternator's 14.7, sounds about right to me...
 
#40 ·
I'll just mention my dual battery setup:

I have a battery isolator and after-market 220A alternator. If I were to do this again, I might get a voltage-sensitive relay instead. I use two golf cart batteries in series (big cells) and made a battery cage for them which I mount underneath the body, under the driver's seat (between the door well and fuel fill hose). It's a tight fit but the best place as I can keep my spare and it's away from the exhaust. I then routed 1ga wire (overkill but I had some laying around) from the battery to and through the firewall, hiding it elegantly inside the floor plastic conduit thingy (don't know what it's called, but it's just big enough for 1ga). Warning: be careful of where you choose to poke through the firewall; I nearly lost 1st gear because the gear selector moves down when you downshift!

Anyway, this is easily the most useful upgrade I've done.
 
#41 ·
heres my multiple battery setup. I run a 250 amp alternator to a 270 amp diode style isolator that charges the front optima battery and 4 rear batteries, two being kinetic 600's and two being xs power D2700's. all ran with 1/0 cables. works awesome for me.

isolator setup


rear batteries, small box to the left of sub box is where the kinetics live.


 
#43 ·
five10freak said:
isolator setup
Exactly the setup, i've been planning on.... Except i've been planning on a 200 amp alternator, and a 240 isolator.... Didn't think they were that big... WAS planning on mounting my isolator in the engine bay next/near the batt

Thanks for the photo,
~Junior
 
#46 ·
jrsride2002 said:
Exactly the setup, i've been planning on.... Except i've been planning on a 200 amp alternator, and a 240 isolator.... Didn't think they were that big... WAS planning on mounting my isolator in the engine bay next/near the batt

Thanks for the photo,
~Junior
yeah, after you go above 200 amps, these diode based isolators get huge fast,lol. some day I'll upgrade to a Mechman alternator @ 370 amps and get a 400 amp isolator, now that will be Fín huge.

markmitch said:
never really had a need for two or more batteries but I like the injunuity, if I ever do I know I will come back to this forum.
yeah, I'm a power junkie,LOL. need more power :rockon:
 
#48 ·
Ball said:
I'll just mention my dual battery setup:

I use two golf cart batteries in series (big cells) and made a battery cage for them which I mount underneath the body, under the driver's seat

Anyway, this is easily the most useful upgrade I've done.
you have a photo of them under the van kicking around would like to check that out....
 
#50 ·
If you mount solar panels make sure you leave a nice space between them and the roof, will cut down on the heat gain quite a bit. I have a CTEK that has dual inputs, one for the alternator and one for the solar.

They do have battery isolation available that don't have the voltage drop like the diode based ones.
 
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