Up-sizing Batteries - to 6 volt

[gary1burke]

Hi All,

I hope this isn't already out there somewhere, but so far I've been unable to find it exactly. I want to upgrade from my two 12 volts to 2 6 volt Lifeline batteries and get the max size that will fit in my battery box. I understand that Airstream enlarged the size of the box for 2016 to accommodate 6 volt batteries, but I've been thru the specs and cannot seem to find the exact dimensions . It appears to me that 6 volt batteries can vary considerably in height, right? one is almost 16" tall while others are only about 10".
While I'm on the subject, I'm sure there are lots of opinions, but what's the best for the money, Lifeline or Trojan, or ??

Thanks!
gb
ps: Not sure if my profile shows this: 2016 Int Serenity 27 FB.

[mikeinca]

I have no info on whether they are "best", but we did an upgrade to Trojan 6V AGM batteries for our 2017 25' Flying Cloud. They fit perfectly in the battery box, which was designed for Group 24 batteries, with no modifications. The specs for those batteries:

http://www.trojanbattery.com/pdf/dat...ata_Sheets.pdf

[GMFL]

Post #6
http://www.airforums.com/forums/f142...ad-166085.html
And
http://www.airforums.com/forums/f449...ts-165535.html

[gary1burke]

Thanks! That's what I was hoping for. Probably too early to comment on their performance.

[gary1burke]

Oops! Still figuring out this interface. That was to "Mikeinca". Thanks, also, to "GMFL" for the link to the very interesting forums where he posted pics of the mod'd battery box! Nice work! Fortunately I won't need to do that as AS has made the boxes deeper now, apparently. My model also has the front storage area so wouldn't have been able to do that. Think I'll go with the Yrojan flooded for same reasons as "GMFL".

[Glenn T]

I bought 6v batteries this spring and I'm VERY happy with the performance.

In order for them to fit my 2011 FC I bought a battery box extension. The 2" extension would fit Trojan T-105 (golf cart) batteries, but I decided on the Trojan T-105 RE "renewable energy" batteries. They're a little more expensive, and slightly taller. I bought some vinyl framing from Loews, cut it to size, and placed it between the battery box & the extension, and everything fit perfectly.

I just got back from boondocking at Glacier National Park and Waterton NP in Canada, and I'm thrilled with the performance of these batteries. It took 4 days of use for them to drop to 12.5 volts. That's half-charged according Trojan, but ¾ charged according to the Airstream monitor. At that point I used the generator to charge them. Batteries will last longer if you don't take them down lower than halfway.

[SeeMore]

Originally Posted by Glenn T

It took 4 days of use for them to drop to 12.5 volts. That's half-charged according Trojan, but ¾ charged according to the Airstream monitor.

That is an interesting observation as my Trojan deep cycle spec sheet states 6.05 volts per battery (T105 RE model) is 50% depleted which makes 12.1 a 50% reading for a pair as opposed to 12.5v. An individual 6v battery at 6.25 is at 80% per Trojan. You had a great deal more juice available and the Airstream monitor was close to accurate. Most 12v lead acid batteries are at 50% when measuring 12.2v.

[uncle_bob]

Hi

Any time you go from worn out batteries to brand new ones, the new ones *should* seem pretty neat. In the case of typical AGM lead acid batteries, worn out is 50% of new capacity at 4 to 6 years. It will happen a bit sooner with flooded cells.

Compared to group 27's (at 200AH) 6V's at 220AH will give you about 10% more capacity. If you have group 24's (at 160 AH) then the improvement is a bit more. Strangely enough group 27 AGM's are not wildly more expensive than group 24's. Since there are a lot of 6V batteries out there, there are a lot of package sizes. Comparing AGM's (any brand) to flooded (any brand including Trojan) is not quite apples to apples since the AGM's are a different technology with a few advantages.

50% available capacity ( = time to recharge) happens at 12.1V on 12V batteries and at the same point on stacked 6V batteries. There are differences for various Lead Acid plate types so it's never an exact number. The bigger issue is temperature which will move the 50% point by a half volt up or down depending on how hot or cold it is.

Bob

[Skycar]

I have more of a question than an answer for you. Can a person keep the two 24s and add a separate box on top for 2 six volts? I want to maximize, but I'm not sure replacing the 2 24s with 2 six volts alone would be worth it. Thanks.

[uncle_bob]

Originally Posted by Skycar

I have more of a question than an answer for you. Can a person keep the two 24s and add a separate box on top for 2 six volts? I want to maximize, but I'm not sure replacing the 2 24s with 2 six volts alone would be worth it. Thanks.

Hi

You certainly *can* do it. It's just a matter of going over to a welding shop and giving them your credit card. If you do so, putting all the batteries on a single bus is a real bad idea. You would want to have them on separate converters running separate sets of loads. Otherwise the charging process will not balance out very well. One or the other set of batteries will get nuked and die fairly quickly.

If you are going to "build" a big battery out of separate individual batteries, then all need to be same / same. Not just the same make and model. They also need to be the same age and ideally from the same batch. Perfection would involve measuring the cells and matching things up, that's beyond what you would do for an RV, but it's a very common part of building up battery packs.

Also consider that if you are putting in 600 to 800AH of battery, you will want a 150 to 200A converter charger to go with them. To charge things properly, it needs to scale at the same time. There is value in charging lead acid batteries fairly hard ....

Bob