Huge battery vs two medium sized ones

[Jack5885]

I have been looking into getting a dual battery setup for my '02 Xterra and I was thinking of getting a Kodiak Industries Dual Battery Kit like this one:



Then I started wondering why I needed two batteries instead of just one bigger one. That setup comes with two Odyssey PC1200 batteries. The total dimensions of the two batteries measure 200mm wide and 340mm long. Instead of two PC1200s should I get a single PC2150 that measures 170mm by 330mm? The PC2150 is a Marine Dual purpose battery while the PC1200s are regular automotive batteries.

Here are the specs of the batteries:

PC1200
Keep in mind there would be two of these:
530 CCA
44 amp hours
78 minute reserve capacity
$200 each (also need to buy an isolator)

PC2150
1150 CCA
100 amp hours
205 minute reserve capacity
$390 (Only like $300 if I get a DieHard Platinum which is the same battery)(Don't need to buy an isolator)


I know that with two batteries I can use one to jumpstart the other, but I don't see any other advantages, especially given the specs above. Seems to me like a single big battery is cheaper and gives better performance.
I will be using the batteries to power a fridge freezer as well as campground lights as well as an inverter for as long as possible without running the engine. I also plan on upgrading my stock 80ish amp alternator to one with 175-200 amps.

So what setup would be better for me? The two PC1200s or a single PC2150? I don't plan on discharging the batteries very often, just maybe once a month while camping.

One the car is off and the batteries isolated, there isn't very much power to play with on the AUX battery.

 

[Xterabl]

Hmmm...this is an interesting question. I think the key thing is $/amp hour...and the single big battery is 15% cheaper for Odyssey and 33% cheaper for Diehard version. Makes me 2nd guess some of the "restructuring" I did to fit 2 batteries in my 1st gen X.
BUT, you also must consider the isolating nature of dual battery setups...they provide for those "what if" scenarios where you forget to turn something off, etc. Point is, certain dual battery configurations protect the starting battery. And so, while the food in your fridge might spoil due to the aux battery draining; at least you'll be able to start your rig and drive to the market for more supplies.

Thanks for raising this topic...am very interested to read the replies....

 

[McZippie]

No problem with having only one battery. Two batteries or one battery isn't the issue. It's getting the most amp hours into a given space and for your situation one battery is best.
Purkert Effect benefit and more amps for house use with not separating starting and house batteries.
Click my first signature link below for more info.
Consider wiring in an automatic low voltage disconnect LVD battery protector so there is enough reserve capacity to start the engine.
Wire LVD into the fridge and light circuit. The Inverter should already have a LVD built into it, but the disconnect voltage may be below engine start level.

http://www.powerwerx.com/fuses-circuit-protection/dc-low-voltage-disconnect-lvd.html

 

[FellowTraveler]

Consider, the increased weight compared to original battery (s) if installed in engine bay and extra load on the front suspension, then can the alternator/generator you have handle maintaining/charging the battery (s), or?

I'd stick to largest highest capacity battery (s) that can fit in any given area.

My setup uses two (2) 34/78 PC1500 batteries in engine bay and two (2) CS130D alternators/generators which include pulse width modulation (PWM) for charging which is great for charging absorbent glass mat (AGM) batteries then another much bigger 120 ah AGM battery inside vehicle.

 

[McZippie]

Consider, the increased weight compared to original battery (s) if installed in engine bay and extra load on the front suspension, then can the alternator/generator you have handle maintaining/charging the battery (s), or?

I'd stick to largest highest capacity battery (s) that can fit in any given area.

My setup uses two (2) 34/78 PC1500 batteries in engine bay and two (2) CS130D alternators/generators which include pulse width modulation (PWM) for charging which is great for charging absorbent glass mat (AGM) batteries then another much bigger 120 ah AGM battery inside vehicle.

OK lets talk theory, assume all your batteries are 100 amp hour and you have 3 batteries.
2 batteries are dedicated for starting and 1 battery is dedicated for house use. So there is only 100 amp hours for house use.

Wire in a LVD, eliminate the one house battery and use the 2 remaining batteries for both house and starting. Now there is 200 amp hours for house use with only 2 batteries instead of original 3.

 

[keezer37]

Hmmm...this is an interesting question. I think the key thing is $/amp hour...and the single big battery is 15% cheaper for Odyssey and 33% cheaper for Diehard version. Makes me 2nd guess some of the "restructuring" I did to fit 2 batteries in my 1st gen X.
BUT, you also must consider the isolating nature of dual battery setups...they provide for those "what if" scenarios where you forget to turn something off, etc. Point is, certain dual battery configurations protect the starting battery. And so, while the food in your fridge might spoil due to the aux battery draining; at least you'll be able to start your rig and drive to the market for more supplies.

Thanks for raising this topic...am very interested to read the replies....

I'd go with the single large battery and the LVD for now. You can always up it later. Easy, quick install.

But if you don't,
Being able to crank the engine is job one for me. This is why I went with a backup configuration in lieu of an accessory one. Down side, if you are running a lot of acc, you beat the hell out of one battery. Up side, your engine cranks. You can view a variety of configurations at Hellroarings website. There's also good info there about sizing. You have to do some digging. The website is not very well laid out or updated.
I've a Tripp Lite inverter, it has a LVD adjustment screw so you can set the threshold level. For my setup, I don't bother with it much.
I put my backup batt (Odyssey PC1500) in the back passenger side due to space avail/weight reasons. Nail down your configuration/location of your biggest drain first, then decide on battery location. Common opinion says to have the same ground point for both batteries. Once upon a time a forum member brought up something called the "see-saw effect" that occurs when batteries have different ground locations. I never found a write up about this phenomena nor could I prove a difference of potential between ground points on my setup. But it sounds like good practice.
Take your time and plan well. When you think you have it all figured out, set it aside for a few days and see if you come up with any other questions before you begin.

 

[AFSOC]

Do you go out solo? Do you camp in austere locations? You have high draw accessories like fridge and inverter, how long do you stay camped at a site?

Single battery set ups are most common and obviously work well. One disadvantage they have over a dual battery set up is that a single battery is a single point of failure. Redundency of a dual battery set up should be given greater consideration if you travel solo or away from passers by who can jump start you or if you camp at a single site for multiple days. If you travel in a group or travel and camp in places that see traffic (potential assistance), a single battery set up's simplicity gets the nod.

 

[1911]

Do you go out solo? Do you camp in austere locations? You have high draw accessories like fridge and inverter, how long do you stay camped at a site?

Single battery set ups are most common and obviously work well. One disadvantage they have over a dual battery set up is that a single battery is a single point of failure. Redundency of a dual battery set up should be given greater consideration if you travel solo or away from passers by who can jump start you or if you camp at a single site for multiple days. If you travel in a group or travel and camp in places that see traffic (potential assistance), a single battery set up's simplicity gets the nod.

^ This.

The only real advantage to a dual-battery system is that you can run a refrigerator or a ham radio, etc. for days at a time without worrying about whether your truck will start or not when it's time to break camp, and the added redundancy in case of a battery failure as stated. I like my dual-battery set-up for these reasons but if you don't have these kinds of accessories or don't camp solo or in one spot for very long, then why bother?

 

[cnynrat]

I think others have hit the nail on the head. For an in-vehicle application the advantage of the dual battery set up is the redundancy of a second battery in the event your primary battery fails.

For a house battery application (trailer, camper, RV, etc.) where you typically are not installing relays to isolate batteries from each other but instead are often permanently wiring batteries together, I personally prefer a single large battery over multiple batteries wired in parallel. There can be some subtle issues that arise when multiple batteries are wired in parallel that result in the real world capacity being somewhat less than you might expect based on simply adding the capacities of the batteries together. You do loose the redundancy element of a dual battery configuration, but unless you've got the ability to isolate batteries from one another that's a somewhat debatable benefit IMO.

 

[FellowTraveler]

OK lets talk theory, assume all your batteries are 100 amp hour and you have 3 batteries.
2 batteries are dedicated for starting and 1 battery is dedicated for house use. So there is only 100 amp hours for house use.

Wire in a LVD, eliminate the one house battery and use the 2 remaining batteries for both house and starting. Now there is 200 amp hours for house use with only 2 batteries instead of original 3.

I need two high quality high amp batteries for starting the diesel I like over kill, as for the house I'm actually going w/2 PC 2250 giving me 252 ah where I'll install them is still up for debate but leaning towards my M101a3/M116 trailer.

 

[Jack5885]

I'm solo most of the time, but I don't go to very remote places with my current setup. With more battery, I'll defiantly be going out farther and for much longer (3+ days instead of 1-2)

I'm currently leaning towards to one battery since it has over 200 minutes of reserve capacity, whereas with a dual battery setup, once I turn off the car I will only have 78 minutes of reserve since the batteries isolate. If I understand how battery life works (and please correct me if I'm wrong), I believe I would have to replace the batteries on a dual battery setup more often, because I would be running the AUX battery through deeper discharge cycles.

I could use up half of the reserve capacity with the big battery and still be able to start, while if I had a dual battery setup, I would be able to start but I would have rotten food. And nobody likes rotten food.

 

[McZippie]

I'm solo most of the time, but I don't go to very remote places with my current setup. With more battery, I'll defiantly be going out farther and for much longer (3+ days instead of 1-2)

I'm currently leaning towards to one battery since it has over 200 minutes of reserve capacity, whereas with a dual battery setup, once I turn off the car I will only have 78 minutes of reserve since the batteries isolate. If I understand how battery life works (and please correct me if I'm wrong), I believe I would have to replace the batteries on a dual battery setup more often, because I would be running the AUX battery through deeper discharge cycles.

I could use up half of the reserve capacity with the big battery and still be able to start, while if I had a dual battery setup, I would be able to start but I would have rotten food. And nobody likes rotten food.

...and when your Rig doesn't start you'll be stranded, get hungry and eat the rotten food and become sick and die.

Don't eat rotten food and die, bring one of these along:

http://www.alten-dc.com/gasoline-powered-dc-generators/item/149-12-volt-55-amp-gas-powered-battery-charger.html

 

[4x4junkie]

I have to side with with the "one big(ger) battery" opinion over two isolated ones also (especially given the small size of the batteries you're proposing, none of them exactly fits the description of "huge" in my book).

I run two 105AH deep-cycle batts in parallel (no isolator, like a single big 210AH batt). I once did have it drain down enough that the LVC on my fridge started kicking in, but with the large capacity of it there was still plenty of juice for the starter to spin the engine over. My truck also has a stickshift, and I now often carry an 85W solar panel or two (depending on where I'm going), which should hopefully keep at bay any dead battery and/or food spoiling issues.

 

[Jack5885]

Well the batteries are huge considering how little space there is for batteries in Xterras :smiley_drive:

 

[4x4junkie]

Get yourself a solar panel. Something 60-80 watts or better should help a lot to keep your fridge running and isn't too big (and even if you did happen to kill the batt, you should be able to fairly quickly get enough charge back into it via the sun to restart the engine).
There are some foldable solar panel options I've seen too, though they're also a lot more $$$ than rigid panels.