Dual battery setup, one main and 2 aux batteries???

[osidepunker]

Anybody see a problem with me running three batteries in a dual battery setup? I am looking at using a National Luna or IBS controller. The main battery will be under the hood (Diehard Gold) and for the aux side I was planning on running two group 31 Diehard Marine Platinums connected in parallel mounted in the bed.

As far as I can tell, the battery controller will just view the pair of aux batteries as one single battery.

Anyone with experience see any reason why I shouldn't set it up this way? Running two smaller batteries will allow me to distribute gear weight better on my truck. Plus I already have one so I only need to pick up one more and the battery controller.

 

[Joe917]

The aux bank will be viewed as one battery. Marine batteries are not deep cycle batteries and are not suitable for deep cycling. You would be better off with a pair of golf cart batteries wired in series or a true deep cycle from a company such as Lifeline. Batteries that are advertised with CCA are usually not deep cycle. The more you separate your batteries the bigger the cables you will need.

 

[osidepunker]

The aux bank will be viewed as one battery. Marine batteries are not deep cycle batteries and are not suitable for deep cycling. You would be better off with a pair of golf cart batteries wired in series or a true deep cycle from a company such as Lifeline. Batteries that are advertised with CCA are usually not deep cycle. The more you separate your batteries the bigger the cables you will need.

Thanks for the advice! The Sears Platinum Marine battery is a deep cycle AGM battery. So I am good to go there.

I will be using appropriate gauge wire. Probably 0 gauge or thicker.

 

[4x4junkie]

The aux bank will be viewed as one battery. Marine batteries are not deep cycle batteries and are not suitable for deep cycling. You would be better off with a pair of golf cart batteries wired in series or a true deep cycle from a company such as Lifeline. Batteries that are advertised with CCA are usually not deep cycle. The more you separate your batteries the bigger the cables you will need.

That's a pretty broad statement...

A majority of the 'marine' batteries sold are actually "Marine/RV" batteries, which are infact designed for deep cycle use (marine batteries not suitable for deep-cycling are usually marked "Marine Starting"). The rating a person needs to look for is "Amp-Hours" (Ah), any battery designed for deep-cycle use will carry this rating. The presence of a CCA rating (and sometimes RC) only indicates that it's probably a dual-purpose battery (which these generally are not as robust as say, the golf-cart batteries you mention, but to say they are not suitable for deep-cycle use is incorrect).

 

[Joe917]

Marine batteries will not stand up to as many deep cycles as a true deep cycle battery. A true deep cycle battery has much thicker plates and consequently cannot supply the high cranking amps for starting. I stand by the statement. If you want the best value over the life of a deep cycle battery golf cart or true deep cycle is the way to go.
Starting batteries have thin plates to give a large surface for a rapid discharge and recharge, deep cycles are the opposite. There is no "dual purpose battery" that can do both jobs well.

 

[osidepunker]

I am only considering AGM batteries as they will be subjected to very rough off road conditions. The batteries I have chosen are some of the best and I am happy with the choice.

Accessories I am planning for include:

500 watts of lighting
10k winch
82 quart fridge
2000 watt invertor
1000 watt car audio

I dont plan on running these batteries down. When camped, I will have solar. Most of the time, the only draw will be the fridge. Lights and car audio will mainly be run when driving. Winch will normally be run with the engine on, but in the event that I cant start the engine, 3 batteries will enable me to still winch myself out.

 

[highdesertranger]

yes it will work I have 1 starting battery and 3 aux. I run 2 solenoids. 1 charges the aux that's under the hood, and one charges the 2 aux in the back. highdesertranger

 

[osidepunker]

yes it will work I have 1 starting battery and 3 aux. I run 2 solenoids. 1 charges the aux that's under the hood, and one charges the 2 aux in the back. highdesertranger

Thanks, that was what I was wanting to hear! So you have one solenoid that charges two batteries in the back. Are those two batteries wired parallel? No problems with them "feeding" off each other? I think its called dual battery syndrome or something like that? I guess thats my main concern.

 

[poriggity]

The only problem I see with it is that it would be a triple battery setup and nor a dual battery setup, as mentioned.

 

[osidepunker]

The only problem I see with it is that it would be a triple battery setup and nor a dual battery setup, as mentioned.

lol I see what you did there

 

[M.Bas]

Thanks, that was what I was wanting to hear! So you have one solenoid that charges two batteries in the back. Are those two batteries wired parallel? No problems with them "feeding" off each other? I think its called dual battery syndrome or something like that? I guess thats my main concern.

I'm running 2 start batteries in parallel and 1 aux AGM battery via a Ctek charger. No problems running a setup like that. I'm even thinking about adding a 2nd aux battery to prevent deep cycling when going for multiday hikes and needing to keep the fridge running.

 

[Joe917]

Thanks, that was what I was wanting to hear! So you have one solenoid that charges two batteries in the back. Are those two batteries wired parallel? No problems with them "feeding" off each other? I think its called dual battery syndrome or something like that? I guess thats my main concern.

OK now you have hit the problem with solenoid charging.
When you have two dissimilar batteries in a bank the bad one draws down the good one at rest. Under charge the alternator "sees" the bank as one battery (average voltage). It overcharges the good battery and undercharges the weak battery. The same thing happens with a small charged starter battery and a large depleted house bank. The starter battery will charge quickly but the alternator will keep pushing voltage to it until the house bank approaches full charge. Overcharged starter undercharged bank. With equal sized starter and house banks, that are not worked full time, the effect is small enough to live with since the solenoid system is simple and cheap.
With larger battery banks it is far better to regulate the voltage to the starter battery and house bank independently. This can be done with alternator to battery chargers, battery to battery chargers , two alternators, or a switch that allows charging of each bank independently.
Good info here: http://www.sterling-power.com/products-battbatt-info.htm

 

[osidepunker]

I'm running 2 start batteries in parallel and 1 aux AGM battery via a Ctek charger. No problems running a setup like that. I'm even thinking about adding a 2nd aux battery to prevent deep cycling when going for multiday hikes and needing to keep the fridge running.

Perfect! Im sold. Just gotta pick out a controller and solar panel now

 

[osidepunker]

OK now you have hit the problem with solenoid charging.
When you have two dissimilar batteries in a bank the bad one draws down the good one at rest. Under charge the alternator "sees" the bank as one battery (average voltage). It overcharges the good battery and undercharges the weak battery. The same thing happens with a small charged starter battery and a large depleted house bank. The starter battery will charge quickly but the alternator will keep pushing voltage to it until the house bank approaches full charge. Overcharged starter undercharged bank. With equal sized starter and house banks, that are not worked full time, the effect is small enough to live with since the solenoid system is simple and cheap.
With larger battery banks it is far better to regulate the voltage to the starter battery and house bank independently. This can be done with alternator to battery chargers, battery to battery chargers , two alternators, or a switch that allows charging of each bank independently.
Good info here: http://www.sterling-power.com/products-battbatt-info.htm

Thanks! I am aware of this issue, but I was hoping to mitigate it by using the exact same "house" batteries. I was also looking at the Nation Luna or IBS battery isolators. I figured I would wire everything up just like this:

diagram

Except I would use two identical batteries for the "aux". What do you think?

 

[Joe917]

What I think:
you must keep batteries in the bank the same age, size and type.
When you combine everything with the solenoid you have one big bank.
Starter batteries are crappy deep cycle batteries, deep cycle batteries are crappy starter batteries. What are you going to use in your combined bank? To charge both starter and house with the same voltage (solenoid combined) is inefficient at best damaging batteries at worst.
Solenoid charging systems are cheap inefficient and shorten battery life. I would strongly suggest you look at alternatives first. Check out the Stirling web site.