Auxiliary batteries upgrade

[Devildog]

I'm going to upgrade my auxiliary battery system and add 2 more, giving me a total of 4. Can I expect to have to order some sort of additional wiring? If so, what? Is there any followup with regard to any systems running off this battery upgrade?
Lastly, what's the best battery to work with the factory batteries, for this upgrade?

[gentilebrian]

Originally Posted by Devildog

I'm going to upgrade my auxiliary battery system and add 2 more, giving me a total of 4. Can I expect to have to order some sort of additional wiring? If so, what? Is there any followup with regard to any systems running off this battery upgrade?
Lastly, what's the best battery to work with the factory batteries, for this upgrade?

Do you currently have two 12v batteries or two 6v batteries?

Also I know with mine it came with a Garbage battery and if you are doing this you may want to just replace them. Mine didn't even make it a year. You don't really want to mix old batteries with new.

[Devildog]

My Thor Challenger has 2 - 6 volt batteries.

[gentilebrian]

Here is a drawing. You will be creating 2 12v battery banks and connecting them.

[lazinskm]

great drawing! what is the advantage to this set-up over 2 12 volt batteries?

[Chance]

Originally Posted by lazinskm

great drawing! what is the advantage to this set-up over 2 12 volt batteries?

With only two 12-Volt batteries, each 12-Volt battery would need to be of 225 Amp-hour capacity to get the same overall bank capacity, making them relatively large and heavy. In many cases, two larger 12-Volt batteries may not fit where four smaller 6-Volt batteries will fit. The smaller 6-Volt batteries should be more common too, making them easier to find and/or replace.

[tinman01]

Originally Posted by Devildog

I'm going to upgrade my auxiliary battery system and add 2 more, giving me a total of 4. Can I expect to have to order some sort of additional wiring? If so, what? Is there any followup with regard to any systems running off this battery upgrade?
Lastly, what's the best battery to work with the factory batteries, for this upgrade?

Hi, I just added two additional batteries to my Challenger. I added two Trojan T105 6 volt 225 amp hour rating. My existing coach batteries are Deka 6 volt 75 amp hour. Both are Flooded cell batteries.
I didn't have room in my battery compartment for them so I used the next storage bin back and put in a sliding tray to make it easier to service and sealed that part of the pass threw compartment and vented to the outside. I made dividers on the tray to hold a total of 6 batteries, for now I only put in two but will be adding 4 more as the budget allows.

If you go to a place like batteries plus they can make you the cables you will need Just lay out your batteries and measure between posts (I used 1 gage, but the bigger the better) you will need one to go positive to negative to make 2 - 6 volt batteries into one 12 volt, then you will hook the "new 12 volt" battery Positive to Positive and Neg to Neg of your existing coach batteries this keeps them 12 volt and increases the amp hours. Keep in mind you should not discharge them below 50% (it greatly decreases the overall life of the battery) so a 225 amp hour battery only has about 110 usable amp hours.

As long as you match the type of batteries you should be ok (Flooded to Flooded). 6 Volt batteries deep cycle are the best to use and will last longer than the 12 volt. Keep in mind that you should balance out the batteries to optimize them.

I hope this helps
Don

[Laco]

Anyone going for AGM batteries, when upgrading?

[gmc]

Originally Posted by gentilebrian

Here is a drawing. You will be creating 2 12v battery banks and connecting them.

One change I would suggest to the drawing - especially if you are separating the batteries by any distance (between bays, etc) - the positive to the RV should come off the first battery (or set of 2 6v) in the parallel arrangement - and the negative to the RV should come off the last... In gentilebrian's drawing - I would move the negative/ground down to the other pair.
Electricity will always take the path of least resistance - wired as drawn it will favor drawing from the first battery (or pair) resulting in that battery getting driven harder in both discharge and charge... Balance and equalization is good for improving the life of the overall bank.

Originally Posted by Laco

Anyone going for AGM batteries, when upgrading?

I use golf cart/wheel chair AGM batteries for another purpose - and would certainly consider when it comes time to replace my current batteries... Be sure your converter can handle AGM - as they do use a different setting on typical multi-chemistry chargers.

Originally Posted by gentilebrian

... You don't really want to mix old batteries with new.

Agree - adding good to bad - new to old - or mismatching capacities - will all lead to shortened life of the overall bank.

[99dart]

Originally Posted by Laco

Anyone going for AGM batteries, when upgrading?

I wanted to go AGM a couple weeks ago when replacing my dead units. But, at $315-350 each I stayed wet cell. I was already upgrading from 2 12v batteries to 2 6v batteries, so we will see how they last. I use Odyssey batteries in a couple of my cars and really like them.

[TyCreek]

Assuming same chemistries:
Unmatched batteries in series is simply bad news for both discharge and charge cycles.
Unmatched batteries in parallel however can "sort of" be ok for discharge to whatever appropriate DOD is for the weakest cell/pack. The issues start to progress when charge cycles are introduced while still in a parallel configuration.

[Laco]

What do AGM batteries require in different charging circuitry from charging flooded cells? I had been told same will work for both. I know lithium is a different animal.

[Chance]

Originally Posted by Laco

Anyone going for AGM batteries, when upgrading?

Just as a source of information, I saw recently that Trojan has a new (as far as I know) line of AGM batteries they are marketing towards solar, and describe them as true deep cycle AGM.

I don't know much about them, and mention it only because in the past some have questioned whether AGMs are as good as flooded for serious deep cycling.

Since solar involves stationary batteries, I would ask Trojan technical if these can withstand shock and vibration of an RV. I suspect cost could be high because I don't see them listed under RV applications.

[TyCreek]

Originally Posted by Laco

What do AGM batteries require in different charging circuitry from charging flooded cells? I had been told same will work for both. I know lithium is a different animal.

Actually a BSM controlled Lithium solution is more drop-in friendly than AGM as its circuitry could handle pretty much any input. AGM can be a drop-in for most automotive uses however in an RV the float mode from the typical stock converters is usually set too high. AGM use in an RV is best by selecting the AGM battery type switches or at least adjusting the float mode down if possible. Swap out the charger if necessary to one that is AGM selectable/adjustable. I did AGM as a drop-in replacement for the coach supply some years back and basically fried them in one season. An expensive lesson!

[Beau388]

Good news is AGM batteries only self-discharge at 1% per month as opposed to flooded batteries self discharge rate is 1% per day. Charging is a problem though -

"AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require "lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive.

AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F).

[Chance]

Some RV chassis/vehicles like Ford Transit vans come with AGM batteries so charging from alternator should already be compatible. In case of Transit, batteries are located under driver's seat, which should help keep them a little cooler.

In case starting battery is AGM, do RV manufacturers supply flooded battery for house, or do they go right to AGM?

[RV Pirate]

Originally Posted by Chance

Just as a source of information, I saw recently that Trojan has a new (as far as I know) line of AGM batteries they are marketing towards solar, and describe them as true deep cycle AGM.

I don't know much about them, and mention it only because in the past some have questioned whether AGMs are as good as flooded for serious deep cycling.

Since solar involves stationary batteries, I would ask Trojan technical if these can withstand shock and vibration of an RV. I suspect cost could be high because I don't see them listed under RV applications.

Not sure about Trojan specifically, but AGM batteries are designed to be more vibration resistant and lighter weight than conventional batteries. They were originally designed for use in aircraft which also allows them to operate in any position.