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Keyair · 01-10-2012, 05:57 PM

Almost ready for my Battery replacement/upgrade plan.
I have a Costco Store Credit, so I can only get what they sell, so please lets keep on track!
My Motorhome had 2 X group 27 Marine Batteries... one died already.
Its a Motorhome, and the battery tray is rotten already, so will be modding the drawer depth.

I was in at Costco today, and trying to get my head around what I am about to do and need some sage advice...

The Batteries Costco sell are called GC2.
The only other spec I could glean is that they have "100 mins Capacity" but the guy had no other info.
I was planning to get 2 now and another 2 in a few weeks

I tried to compare that to the Group 27DC that Costco sells, but its spec is 750CA, 600CCA, and a reserve of 160 mins...

Can someone enlighten me?

HiHoAgRV · 01-10-2012, 06:26 PM

Big Wide Strokes here...

GC2's have 220 -230 Amp Hours...(at 6V)
Group 27's have 90-110 amp hours...(at 12V)

From what I've seen, the cheap GC2's have the same capacity as the $$$$ group 27's...

I'm using 2XGC2's in my Overlander build...

pbearsailor · 01-10-2012, 06:29 PM

I have two of the Costco golf cart batteries in my trailer.

They are ok as golf cart batteries go. Trojan T-105's tend to be the ones that most think are the best and I have four of them in the boat. Generally 180 to 225 amp hours are what the various golf cart batteries are rated--I like dealing in amp hours much more than the cold cranking amps figures that just don't apply to the way we use them.

Anyway, they're 6 volt as you know, so it takes two in series to get the 200 or so amp hours at twelve volts. I think the Costco batteries are fine, cost is probably half of the Trojans and they surely won't last as long, but so far for me they've been fine.

The argument against golf cart batteries is that if you lose one cell, you've lost your whole system if you only have two. That's true, but I've used them in the boat for 23 years and it hasn't been an issue. Less likely to be a problem with an RV, since you can usually source a replacement fairly easily.

Others will disagree, just my 2 cents.

cheers,
steve

Keyair · 01-10-2012, 06:30 PM

After I started this thread, it occured to me that the GC2 100min spec would be per battery... so would that mean that 2 of them would have 200mins, therefore better than the G27 160 min?
I am getting confused because I cant compare eggs with eggs!

The plan is to have at least 4 so 2 x pair...
I think I could squeeze 6 in the space I have, I think it would be overkill and getting near the drawer slide weight limit!

Another question...
I am planning a better charger, as the fitted 45A Fortron is as dumb as a rock...
A Intelli-Power with the Charge Wiz is on my list, but with 4 x GC2's would a 45A be marginal, or should I plan a 60A or even an 80A?

lewster · 01-10-2012, 06:44 PM

Actually, that's not the way it figures.

When you combine 2 batteries in series (like a pair of 6VDC golf cart batteries), the voltage is the sum of the two batteries (they MUST be identical for series connections) while the amperage remains the same. Following this logic, you will get a 12VDC battery bank at the amp/hour rating of one of the batteries.

Conversely, in a parallel connection, you sum the amperage while the voltage remains the same: a pair of 12VDC group 27s connected in parallel would stay at 12VDC but increase the amperage as the sum of both, or about 200 amp/hours.

Most golf cart batteries have a 6VDC rating and a 200-220 amp/hour capacity rating, so I don't know where they are getting the 100 minute rating, which is essentially meaningless as batteries are classified by voltage and amp hour capacity rated at specific hourly rate, like the standard 20 hour rating that most battery manufacturers use.

Class dismissed!

lewster · 01-10-2012, 06:50 PM

I would not wait to get the 4 batteries, as any good battery bank should have all of the batteries installed at the same time, preferably from the same lot with the same manufacture date. This assures even charging across all of the batteries in the bank.

I would use a minimum of 55 amps for your converter and if you plan on a lot of DC use while connected to shore power, as much as 75 amps.

idroba · 01-10-2012, 07:10 PM

I have used two 6 volt golf cart batteries in my Airstreams and Argosys for years. I used to use Trojan T105's but the cost has gone out of sight lately. So, the last pair I got were from Costco. The weight of the battery generally tells you more about capacity than any other spec (flooded cell batteries), and both the T 105's and the Costco's have identical weight. I have not had enough time on the Costco's to give you any other details, but they worked very well last summer season. I have PD intellapower 9245 converter/chargers in all three of my trailers.

If you boondock any, I highly recommend a pair of golf cart type batteries, in series, as your power supply. The only problem in an Airstream is that they do not fit in the original battery box provided, and you have to find another way to locate, mount and vent them.

lewster · 01-10-2012, 07:48 PM

There is a very easy modification for the battery box in newer Airstreams to allow you to mount the golf cart type batteries there. I have a pair of Lifeline GPL-4CT 6VDC golf cart batteries in my '06 19CCD since initial purchase up to the day I sold it 5 years later. They do fit into the box, you just need to add a spacer to the top to allow for the extra height of the GCs.

Keyair · 01-10-2012, 07:51 PM

I have a Motorhome, not a trailer, so the mounting is not an issue for me.

Mexray · 01-10-2012, 08:44 PM

The '100' min rating mentioned above relates the to 'Reserve Capacity' of the battery...

For most 12 volt DC batteries we use in RV's, the Reserve Capacity (RC) rating is the number of MINs you can draw a 25 Amp Load before the voltage drops to 10.5 volts...

Golf Cart 6 volt batteries are in the heavy duty category, used in many high amp load situations, and the RC is rated in MINs at a 75 Amp Load - hence the '100' number stated, which is the typical MINs Rating for a GC batteries in the 200-225 Amp Hr rating...

The equivalent RC rating for these same GC batteries at the 25 Amp Load would be about 450 MINs...

This RC rating isn't really something you can relate to normal RV battery usage, but a higher RC rating would indicate more plates in a given size battery case, etc...

Use the RC rating to compare batteries of the same type and size - the higher the RC rating, the longer you'll be able to run your 12 volt stuff - the same as comparing the Amp Hour rating...higher number, longer running time...

Two 6 volt GC's in SERIES (for a 12 volt system) would have the same RC rating as ONE battery, just like Amp Hours..

If you hooked the two GC's in PARALLEL, you'd still have 6 volts, but the RC rating would be DOUBLE, again just like Amp Hours...

Enjoy...

Jammer · 01-10-2012, 09:10 PM

Quote:

Originally Posted by lewster

There is a very easy modification for the battery box in newer Airstreams to allow you to mount the golf cart type batteries there. I have a pair of Lifeline GPL-4CT 6VDC golf cart batteries in my '06 19CCD since initial purchase up to the day I sold it 5 years later. They do fit into the box, you just need to add a spacer to the top to allow for the extra height of the GCs.

Lewster,

Do you have pictures? I've tried to figure out how to do this and concluded that I can't. My 2010 Classic has the plastic battery boxes and I don't see where there's a place to add a spacer.

Mexray · 01-10-2012, 11:33 PM

Jammer...

I stock this type of battery box for the 6 volt GC batteries:

Quick Cable: 6-Volt Series

As you can see, they come Quick Cable Corp... you might have a dealer nearby that can get them for you...

These GC boxes have much the same 'footprint' as the 10 inch, group-24 type boxes, except they are TALLER to accommodate the inch or so more you need...

However, I thought the 'Classic' AS's still used the two separate battery compartments recessed into the front, with aluminum locking doors??? If so, the GC's won't fit...

Did AS do away with the recessed compartments in the Classics and just mount plastic boxes on the 'A' frame behind the propane tanks, like the Safari's, etc...???

Our old 78 Ambassador has the compartments, and I couldn't 'upgrade' to GC's, but added a third Gr-27 battery mounted in an Alum box http://www.quickcable.com/products.php?pageId=590 behind the propane tanks - this gives me about 300 Amp Hrs of capacity, a bit more than two GC's, but at an added cost of 3 batt's VS 2...works for us...

Silver Goose · 01-10-2012, 11:33 PM

Quote:

Originally Posted by Jammer

Lewster,

Do you have pictures? I've tried to figure out how to do this and concluded that I can't. My 2010 Classic has the plastic battery boxes and I don't see where there's a place to add a spacer.

I would also be interested in the 6V golf cart batteries but I think the battery box arrangement may be different on the Classic from some of the others. Our batteries slide in end first and there isn't much vertical clearance. The golf cart batteries I've seen would be too tall to fit.

Silver Goose · 01-10-2012, 11:48 PM

Quote:

Originally Posted by Mexray

... I thought the 'Classic' AS's still used the two separate battery compartments recessed into the front, with aluminum locking doors??? If so, the GC's won't fit...

Did AS do away with the recessed compartments in the Classics and just mount plastic boxes on the 'A' frame behind the propane tanks, like the Safari's, etc...??? ...

I think we're on the same page here. I have an '08 and have the 2 separate recessed battery compartments with the small doors on the front of the trailer. There is a steel box mounted in the a-frame just behind the tanks but it houses the pump for the disk brakes. I think when AS went back to drum brakes on these models, they kept the box for extra storage. I don't believe the box as is would be large enough for batteries.

lewster · 01-11-2012, 05:55 AM

The battery box on my 19CCD was in the tongue. IIRC the Classics slide in from the front thru 2 doors. Not the same set-up.

On the CCD, I removed the hinged top of the battery box, made a 1.5" aluminum spacer that was painted grey to match top in the same footprint of the top flange, riveted that to the top flange of the battery box and then re-installed the hinged cover to the top of the spacer.

Keyair · 01-11-2012, 07:53 AM

So, with 4 GC2 batteries onboard, can someone suggest an ideal charger?

Also, I wanted to get a basic "Starter" Solar panel to keep the batteries topped off... I dont want to get into the whole charge controller just yet... Maybe a 30W?

tomp1937 · 01-11-2012, 08:29 AM

Another simple way to increase the depth of the box is to again remove the door hinge and then us pressure treated 2x2 wood cut to fit around the top of the box rim. You can screw it down from under the rim. Paint it to match and then screw the door hinge back on top. a simple slot or gouge sawed on the inside of the opposing wood spacer will allow you to lock down the lid.

idroba · 01-11-2012, 11:22 AM

Quote:

Originally Posted by Keyair

So, with 4 GC2 batteries onboard, can someone suggest an ideal charger?

Also, I wanted to get a basic "Starter" Solar panel to keep the batteries topped off... I dont want to get into the whole charge controller just yet... Maybe a 30W?

If I was using 4 GC batteries in two strings, I would consider a Perko type battery switch so you could isolate either string or parallel them when you want to. Cost is about $30 at some RV dealers, most marine dealers, and on line. By putting them in two strings, isolated, you can use them like a propane tank system, run one until it gets low, then switch to the other. It also makes for better charging, one string at a time, rather than two strings in parallel.

I think a lot of the Progressive Dynamics PD 9200 series of converter chargers. Probably a 9260 would be a good one for you to use, but even a 9245 would work, especially if you charge one bank at a time, which I would recommend.

For solar, my opinion is you are just wasting your money if you don't do it right to begin with, but that said, for inexpensive systems, the Harbor Freight 3 panel system is fairly well made, and each panel in the set is 15 watts max, or 45 for all three. Cost, on sale is about $150.

The best (again, my opinion) charge controller for the money is the Xantrex C30 series, which, without fancy monitoring only runs around $100 and is a high quality, well made, well engineered unit. I do volunteer solar work for the Forest Service in my area, and have used them extensively, and never had a single problem.

Keyair · 01-11-2012, 11:30 AM

Good info!
Thanks!

Keyair · 01-11-2012, 10:15 PM

Well.........
I did it!
There are 2 Costco GC2 batteries in my garage.
Both Manufactured 01/12 and $89.99 each.
I marked them A and B.
Tested them, and A was reading 6.37V and B 6.35V.
Linked them and put them on my Battery-Minder Charger at 8A.
They warmed up at 14.25V @ an 8A charge, and after about 4 hours, the charger detected they were good, and dropped off to 13.2V.