Replacing 12 volt house batt

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The amount of amp-hours is totally dependent on the area of the lead plates in the battery and the voltage is determined by the number of cells (2.1v/cell), so there is no difference in weight between 12v and 2x 6v for the same number of amp-hours.  You can literally buy amp-hours by the lb.
 
OK! Well I really appreciate all info from you guys. But now my head is spinning. After measuring the compartment, it seems that two GC-2's will fit, but it will be tight. The problem will be the door opening not the the compartment size. However once they are in, because of their height, it will be difficult to to connect or service them. I am considering AGM and installing them on their side with the posts facing out. Has anyone ever done that? Or maybe I'll get 12v AGM group 27's  they would fit better. Also, will my converter keep the AGM's charged properly? I believe from the owners manual it has 3 settings that sense the correct voltage. Thanks for all the input.
 
Cuervo1,
For the best specific help to your questions, please tell us what battery size and type of converter charger you have.
 
LTG, the batteries that I have now are : (2) group 27, 12 v Exide  lead acid deep cycle batteries, manufacture date 2013. I cannot recall the brand of my converter, the manual is in the coach. I am not able to get to it because I had knee surgery recently and am not able to get up the stairs.I will ask my wife to get it for me tomorrow. However, I recall that when reading previously, that the converter had 3 modes, indicated by a green light. Steady: indicated high rate of charge; blinking at fast rate indicated lower rate ; blinking at even slower rate indicated normal charge. I really appreciate your help.
 
Cuervo1: those batteries are almost sure what is known as a Marine/RV deep cycle, which is actually a hybrid of a starting battery. To the best of my knowledge, Exide doesn't produce a true 12v deep cycle in the Group 27 size, or any of the common 12v sizes for that matter.  I make that point because at age 5+ a Marine/RV deep cycle is well into advanced age and ought to be replaced (which is no doubt the reason for your inquiry).


Each size 27 Marine/RV 12v produces 105-115 amp-hours (depending on the lead plate content), so a pair of GC2 6v flooded cell deep cycles in series will replace it nicely. The 6v pair will produce between 210 and 230AH, identical to the 12v pair.
 
AGM's require a different charging profile than flooded batteries do, so if your current converter doesn't have a specific setting for AGM you're in the market for a new converter.  So add that to the cost and effort to install AGM's.  Frankly, if you've gotten 5 years out of a set of marine batteries your power requirements are such that you probably wouldn't see much benefit to running AGM's other than avoiding periodic maintenance.  If you are willing to pay for that then fine but from an economy standpoint you'd just replace your marine batteries with another set and check the box.  Sometimes just good is good enough.

Mark B.
Albuquerque, NM
 
My converter is a Intelipower 9200. The owners manual indicates that it has the Charge Wizard controlled charging module built in, with 4 modes. It also has a Remote Pendant for manual override and a mode indicator light. Will this converter charge AGM  batts properly? I do not find any mention of AGM  in the manual
 
Doesn't look like it.  The voltages in the mode description match typical FLA setpoints, and there's one specific reference to gassing and water loss which is not part of AGM use.  Seems a call to the vendor would reveal what if any steps could be taken to accommodate an AGM charge profile.  Guessing they'll refer you to the sales department but it doesn't hurt to ask.

Mark B.
Albuquerque, NM
 
The Progressive Dynamics 9200 Series Converter/Chargers are smart chargers with four stage charging. According to the Progressive Dynamics brochure they are available for Lead-Acid or AGM batteries. However, the brochure is dated in 2018. To be sure, call Progressive Dynamics and ask. They do not appear to be temperature compensated. That means that in hot weather or cold weather the PD9200 will overcharge and undercharge the batteries. In my opinion, while parked in a RV park and on shore power and using 12 volt lights and appliances, that will not make a big difference. However, when in long term storage and on shore power, it will overtime degrade the batteries. For that reason, when in long term storage either (1) turn off the charger and disconnect the batteries or (2) turn off the charger and connect the batteries to an external battery maintainer/charger that has an AGM setting and is temperature compensated.
As for what batteries to purchase, I would recommend Group 27 AGM batteries. Almost all available Group 27 AGM batteries will be a direct replacement for the batteries you now have. 
 
First: Congrats on what I consider to be the BEST converter made.

Second. The Charge Wizard is optimized for Flooded Wet Cells... Now thus it is not the "IDEAL" settings for AGM but.... from others on the forum who have tried it.. Close enough.

My personal experience with AGM was to install them on a seperate loop.. Seperate charger set for AGM.. They were the first batteries to fail and some of the ones which outlasted them were older than the RV.  I'm not sold on AGM at all.

From one battery web site

Type: Absorption Charging Float Charging
SLI/Flooded 14.2V to 14.5V 13.2V to 13.5V
Sealed 14.2V to 14.5V 13.2V to 13.5V
VRLA 14.2V to 14.5V 13.2V to 13.5V
AGM 14.6V to 14.8V 13.2V to 13.8V

The difference is like 0.3 volts  Not much.  and as I recall the Charge wizard is 13.6 Float which is within the AGM range.


 
I believe the Charge Wizard absorption rate is 13.6. The storage rate is 13.2. Charge Wizard calls it's stages Boost, Normal, and Storage. That equates to Bulk, Absorption, and Trickle.
 
.3V may not seem like much but the effects of undercharging are cumulative.  May not appear right away but 1-2 years out.  I had this happen just switching between different brands of FLA.  The specs for the 9200 I think are a bit light even for FLA based on published battery data so I think I'd still be looking for a conclusive SLA solution.

Mark B.
Albuquerque, NM
 
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