Upgrade to 2 batteries...........

[Canonman]

The converter will see the new set up as a single 12v battery and charge normally. It will charge slower since the batteries are larger but that's about the only change.

[Bamabox]

So no worries about overcharging when constantly hooked to 110 shore power?

[Logan X]

Originally Posted by Bamabox

OK, got my Costco Interstate GC2’s couple days ago, got individual GC2 boxes, everything fit fine on the tongue rack. They are in, and wired. Each battery checked at 6.36V prior to installing. After install and jumpered in series, voltage checked at 12.72V. Love it when math works. After reconnecting the battery breaker, and connecting my 110/15A “shore power” from the barn, batteries were reading 13.41. Here’s the question. While I’m connected to my shore power, is the built in converter/inverter in my 2017 Cougar XLite 21RBS going to maintain a “proper” charge level on these GC2’s? And not OVERCHARGE them?

Unless I’m mistaken, the onboard charger/converter sees your 2 GC2 batteries the same as 1 12v battery. Your battery set up is still flooded lead acid with 12v output. The charging profile is the same.

[JRTJH]

Originally Posted by Bamabox

OK, got my Costco Interstate GC2’s couple days ago, got individual GC2 boxes, everything fit fine on the tongue rack. They are in, and wired. Each battery checked at 6.36V prior to installing. After install and jumpered in series, voltage checked at 12.72V. Love it when math works. After reconnecting the battery breaker, and connecting my 110/15A “shore power” from the barn, batteries were reading 13.41. Here’s the question. While I’m connected to my shore power, is the built in converter/inverter in my 2017 Cougar XLite 21RBS going to maintain a “proper” charge level on these GC2’s? And not OVERCHARGE them?

First, the "built in converter/inverter" is a "converter/charger" and there's no "inverter" that's built in as OEM equipment. CONVERTERS change 120VAC to 12VDC and are used to charge batteries. INVERTERS change 12VDC to 120VAC and are used to discharge batteries...

That said, IF (NOTE THE CAPS and underlined word) your OEM WFCO converter/charger is operating properly and the reverse polarity fuses are intact, then it should reliably charge and maintain your GC2 batteries without any problems. You WILL need to check battery electrolyte level regularly. When I first installed my GC2 system, I checked the batteries weekly until I was sure they weren't leaking or losing electrolyte. After a couple of months, I felt comfortable with them and now (for the past 6 years) I check them monthly when the trailer is in use and store them in the garage during the winter. While in storage, I do not "maintain them on a charger" but rather I connect them monthly to an automatic 12 amp battery charger and leave them connected overnight (usually about 12 hours). Otherwise, my GC2 system has required no maintenance or special handling.

You might want to buy a battery handling strap to lift the batteries in and out of the battery boxes. They are an excellent addition to any golf cart battery system. The first time you "crush a finger" lifting a battery by the sides of the case, you'll appreciate the handling strap. https://www.amazon.com/3G-Golf-Batte...s%2C174&sr=8-3

[Gizmo2]

I have owned multiple RVs and boats with both dual 12v and 6 volt battery configurations. Two 12v batteries in parallel can suffer from loss of capacity as the stronger battery will discharge thru the weaker until they are the same voltage. This isn't much of an issue when they are new but can be as the batteries age. With dual 6 volts in series one weak cell will have a fraction of the effect on the total bank voltage as 12s in parallel.

I also completely agree with what's been posted about the cycle life of 12v vs 6v. To get good cycle life from a 12v you should really consider AGM batteries. They are twice the price or more however.

One issue with golf cart batteries is that they consume water over time and you have to top them up periodically with pure water. I think 6v is worse than 12 because of the way they are vented. I've noticed the 12 v batteries on my boat were low on water after a year of use so the maintenance free claim is just a marketing slogan.

I worked on a project involving a battery powered refrigerated shipping container a couple of years ago. The original system used 4 six volt AGM batteries in series that could keep the system cold for 5 days. I modified it to use LiFePo lithium batteries. It's was amazing what a difference they made. The system had double the capacity at half the weight. I know there are golf carts using this technology along with a few RVs. It will be a game changer if the price ever becomes competitive.

[Ccsluke]

Just do the math!
Two 6v 100ah batteries series’d Together gives you 12v at 100ah. So expect to pay much more for one 12v 100ah battery. You’ll get the same output from the one 12v as two 6v’s. In my research (don’t take my word, do your own), One 12v battery is cheaper than two 6v when you compare total ah output. As an electrical engineer I’ve dealt with all types of batteries in various applications for the past 40 years. IMO I would never put a 6v battery on my RV!

[Canonman]

Depending on the model converter in your Cougar, you should have 3 charge stages. Our Cougar is equipped with the WFCO 8955 converter.
Bulk, 14.4 vdc; Absorption, 13.6vdc and Float, 13.2vdc. The float function is meant to maintain your batteries while the other two are for bringing the batteries up to full charge.
The 8955 is capable of monitoring the battery load and automatically adjusts from absorption to float mode. If there is any load detected while in float mode the converter will switch back to absorption mode.

[Logan X]

Originally Posted by Ccsluke

Just do the math!
Two 6v 100ah batteries series’d Together gives you 12v at 100ah. So expect to pay much more for one 12v 100ah battery. You’ll get the same output from the one 12v as two 6v’s. In my research (don’t take my word, do your own), One 12v battery is cheaper than two 6v when you compare total ah output. As an electrical engineer I’ve dealt with all types of batteries in various applications for the past 40 years. IMO I would never put a 6v battery on my RV!

...except one of my 6v batteries is 240 amp hours. I haven’t seen a single 12v battery that can match that.

[Ccsluke]

Again, if you compare ah to ah, I can also get two 12v 150 ah batteries for about the same price as two 6v 240 ah batteries. You have to series the 6v’s to get 12v at 240ah. If you parallel the two 12v’s you’ll get 12v at 300ah...and if one of my batteries goes bad, I can just disconnect it and still have 150ah capacity. This is not an opinion, it’s fact. Again, I see absolutely no use for 6v batteries on an RV!

[MarkEHansen]

Originally Posted by Ccsluke

Just do the math!
Two 6v 100ah batteries series’d Together gives you 12v at 100ah. So expect to pay much more for one 12v 100ah battery. You’ll get the same output from the one 12v as two 6v’s. In my research (don’t take my word, do your own), One 12v battery is cheaper than two 6v when you compare total ah output. As an electrical engineer I’ve dealt with all types of batteries in various applications for the past 40 years. IMO I would never put a 6v battery on my RV!

Okay, here's my math. Regarding FLA batteries only, the best Bang-for-the-buck 12V battery I could find was the Trojan SC S225. This can be had for a little over $200 and has a 20-hour capacity of 130AH.

A reasonable 6V battery is the Interstate GC2 which can be had from Costco for around $100. This has a 20-hour rate of 210AH.

Dual 12v batteries means 260AH for around $400.

Dual 6v batteries means 210AH for around $200

In my opinion, the clear winner is the 6v set. Not only better AH per dollar, but you get other benefits from 6V batteries, such as heavier plates, better discharge levels, longer life, etc.

If you're looking for more AH capacity, you can go with the Duracell SLI6V225S 6v battery. It has a 20-hour rating of 250AH but cost around $200. Using two of these, you would get 250AH for around $400. Not quite as good as the Trojan, but you still get all the other 6v benefits.

I still think 6v batteries win, easily.

[Logan X]

Originally Posted by Ccsluke

Again, if you compare ah to ah, I can also get two 12v 150 ah batteries for about the same price as two 6v 240 ah batteries. You have to series the 6v’s to get 12v at 240ah. If you parallel the two 12v’s you’ll get 12v at 300ah...and if one of my batteries goes bad, I can just disconnect it and still have 150ah capacity. This is not an opinion, it’s fact. Again, I see absolutely no use for 6v batteries on an RV!

Could you share a link to the 12v 150 amp hour battery please?

[Bamabox]

Originally Posted by Logan X

Could you share a link to the 12v 150 amp hour battery please?

I might be a bad searcher on the internet, but when I was deciding on the battery upgrade issue, I did a LOT of searching and I don’t recall a 12V true deep cycle (no cold cranking spec) with 150 AH @20 hours.

[Bamabox]

Well, the 6V’s are in. Happy except for the batter straps. Tough to get really tight. Maybe they’re tight enough, but if I have to keep an eye on water level in the batteries I’d like to come up with something better and easier. They fit OK on the tongue rack, but not much room to spare from side to side with the individual boxes. If I had used a single box to hold both, would have needed to reroute the propane line. This was it just went in between the two boxes. Thanks to all for the advise and help.

[Canonman]

A FINE JOB...Finally Done!!

[Ccsluke]

Can’t vouch for your internet search skills one way or another. I provided facts backed up by science. you provided an opinion which you are certainly entitled to! I guess it’s just what you feel the most comfortable with. That’s why I only try to post science based facts and let the readers make up their own minds and form their own opinions.

[JRTJH]

Gil,

Have you considered changing out those battery box straps for cheap 1.5" ratchet cargo straps? You can get them at WalMart for around $5 each. Just thread them up, ratchet them tight and tuck the loose end under the strap. When you need access, loosen the ratchet slightly, slide off the side of the box and open the lid. Easy to keep track of since they don't ever leave the battery tray and "finger tight on the ratchet handle" is all the strength needed to keep them tight.

[Bamabox]

Yes, there are lots of opinions about 6v vs 12v on a trailer. And your facts might be based on hard science. Just provide us with the brand and a link to the 12V 150AH @ 20 hour battery. That would be a fact as well.

[Bamabox]

Originally Posted by JRTJH

Gil,

Have you considered changing out those battery box straps for cheap 1.5" ratchet cargo straps? You can get them at WalMart for around $5 each. Just thread them up, ratchet them tight and tuck the loose end under the strap. When you need access, loosen the ratchet slightly, slide off the side of the box and open the lid. Easy to keep track of since they don't ever leave the battery tray and "finger tight on the ratchet handle" is all the strength needed to keep them tight.

Done. Thanks.

[Logan X]

Originally Posted by Ccsluke

Can’t vouch for your internet search skills one way or another. I provided facts backed up by science. you provided an opinion which you are certainly entitled to! I guess it’s just what you feel the most comfortable with. That’s why I only try to post science based facts and let the readers make up their own minds and form their own opinions.

You said that you could get a 150amp hour 12v battery for the same price as a 240 amp hour 6v battery. Can you provide a link to a specific battery or name the specific battery? I would be interested in that when I need new batteries.

[WestCoastWanderer]

Looks good!

I don't think I could get those 6V batteries into the tray on my 2018 21RBSWE.

I have installed a second battery into the rack. Interstates, because I love the warrantee. Of note, I had to trim the back off of the plastic battery box covers in order for them to fit. It's too tight against the front of the trailer. I get two nights of dry camping without drawing down the batteries too much. By then, I want full hookups, and away I go.

Of note, I drilled several holes into the bottom of the battery boxes to drain any rain/road spray that accumulates (another tip from this forum).