Boof
Hi all! I really need some help here. Two years ago we replaced what I thought was a good battery with what I thought was another good battery - an Interstate Marine/RV from Costco. Evidently this battery just doesn't pack the punch that our little 176S needs for even a night! OR, I am doing something seriously wrong while storing or running the battery. The numbers on the battery read as follows: CCA: 550. RC: 140.  I have Googled this kind of info but it's all Greek to me, sadly. & I can't seem to retain any battery info.

So earlier this year I do a test run overnight to our local CG. The guy next to me in a 40 ft Monaco is an RV genius & I dote on every word, taking notes. He said my battery is completely inadequate for this RV. I need an AGM battery (Absorbent Glass Mat). I also Googled that. My problem is I have no idea about battery power, RV needs in relationship to that power, or how to store it in winter which always seems to be wrong; keep the RV on shore power, take out the battery & trickle charge it, what? 

So the other info I have received is that I need an RV Converter. My friend has one on her 12' Sunset & her lights are on all the time!
I also Googled that, and again, Boat & RV Accessories website shows me a few hundred! I admit I do not understand nor can I retain info on these kinds of mechanical things. It doesn't sort itself out in my head to be even comprehensible, sadly, but I know I need something better and I very much need to know how to get it through our somewhat mild winters (Anacortes, WA).

Any info would be greatly appreciated. Thank you in advance
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Boof
another question for anyone - where is the converter located? 
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TravelerGuy
Hi Boof,
There's a whole lot to know about batteries, more than on post can cover.  You may have an ordinary car battery, which is ok if the TT is always plugged into 115 vac, but completely inadequate for boondocking.  What it's all about is "amp-hours".  An amp-hour is an amp of current (12 watts at 12 vdc), for one hour.  So if you run a 2 amp fan for 8 hours, you've taken 16 amp-hours out of the battery.  Run a 4 amp water pump for 30 minutes total, that's 2 amp-hours.  Then 5 hours of lights at say, 2 amps, that's 10 amp-hours.  Charging a cellphone, maybe 4 amp-hours?  Run a 50 watt (4 amps) TV for 2 hours, that's 8 amp-hours.  So if I add those all up, you might need 40 amp-hours for a day of camping.  So how much capacity does a battery have?  Depends on the battery.

Ordinary car battery - NO GOOD.  Small ones are 80 amp-hour but you can't take more than half of that without weakening it.

"Marine" deep cycle battery - very common in small TT's as they are cheap and available.  Small one (Group 24) might be 80 amp-hours, large one (Group 29) might be 120 amp-hours.  BUT you can't take more than half out of them (50%) without weakening them and shortening their lifespans.  They say they can do maybe 20 full discharge/charge cycles before they are degraded.  They say "Marine Deep Cycle" on them but they really are not deep cycle batteries.  In fact if a battery specifies a CCA (cold cranking amps) value, it is NOT a deep cycle batteriy.  They are cheap, maybe $80 - $120 at Walmart.

True deep cycle batteries, like golf cart batteries - They are true deep cycle.  They can be discharged safely to 20% of their capacity.  So a small golf cart battery (100 amp-hour) can actually supply 100 x 80% = 80 amp-hours.  They can be charged/discharged maybe hundreds of times.  They may have a lifetime of 3-4 years.  They are heavier and cost more than Marine.  I just bought a Trojan T-1275 battery from a golf cart place for $259..  It is 150 amp-hours, so 150 x 80% means I can get 120 amp-hours out of it before re-charging.  Hopefully that's 2-3 days.

Lithium-Iron-Phosphate LiFePo4 - These are by far the best.  They weigh less than half of a lead-acid battery and are smaller.  They do thousands of charge/discharge cycles, can discharge down to 10-20% with no harm.  They don't self-discharge much.  They don't produce poisionous gas so you can put them inside.  They may last for many years.  So why don't we all use them?  Well, for 100 amp-hour rating, they are from $700 - $1200.  For some people it's worth it, think of it as a long term investment.

So there's a start in the battery discussion.  Lots of ways to go with batteries.  And I haven't even mentioned solar panels or generators.  My fingers are too tired...
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mikes
Marine/RV batteries are a compromise. They work if you need to start a boat motor and power the lights for a few evening fishing hours. They're not long lasting for RV use, especially if you regularly camp away from an electrical hookup. They're better than an automotive starting battery, but not by much. True deep cycle batteries are rated in amp-hours, not CCA or RC. Marine/RV batteries typically give up the ghost in 2-3 years in an RV if you actually use them. Making it worse is that the cheap WFCO converters they put in don't fully charge them. And, don't believe anyone who says the battery will get charged while driving. You'll pick up some, but not nearly enough. Without a full charge after every use, the batteries will live a nasty, brutish, and short life.

A good replacement converter (Progressive Dynamics is a well respected brand) will do a better job of charging your battery when plugged in. The converter is mounted in the power/fuse panel.

Golf cart batteries are the cheapest solution for long lasting power, but they're not 12 V, so you need space for 2 of them. A Trojan T-1275 is a high quality deep cycle 12 V battery which you should be able to find for <$200 locally. But, it's money wasted unless you have a quality charger/converter. It would give you about 2x the energy of a cheap marine/rv battery, and last much longer if properly charged. It will probably fit, but you'll also need a new battery box, and it's hard to find one which isn't way big.

Here's what I did.

The other thing is, you need to check the battery's water level on a regular basis, and fill with distilled water when needed. It's not difficult, just part of regular maintenance.

If you want to get the most out of what you have, get a decent battery charger and use that to charge when AC power is available. Schumacher makes inexpensive, good ones. You probably have a "Group 24" battery. A "Group 27" replacement would provide a bit more oomph (but might need a bigger box, but they're cheap for that size).
Mike
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Boof
Thank you Traveler Guy!  Do you use only one golf cart battery or do you double up like I hear so many people tell me to do that. I have never seen amp hours on a battery so I better start looking. Golf cart batteries are all 6v, is that correct?  Thank you again for the explaination. I have taken down notes!
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Boof
And thank you Mike! This is very helpful information to me from both of you. The converter that comes with the rv is useless, from what I have been reading, so I am going to look into the Progressive Dynamics brand you mention Mike. I didn't know golf cart batteries were 12v. I hate to put in a new battery without a better charger/converter. That sounds like the only way to charge up the battery after use. How does everyone do it without one? 
I do check the electrolyte level in the cells & yes, distilled water I am aware of that. 
I am going to check out Traveler Guy's golf cart 12v too. right now I'm looking at AGM and gel cell's.
Thanks so much fellas - I feel like I am moving forward.  Boof
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mikes
The most common (GC2) golf cart batteries are 6 V, and that's what I have - 2 of them. There are also 8 and 12 V ones, which are less common. The Trojan I mentioned is a 12 V one.
Mike
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TravelerGuy
Hi Boof,
Golf cart batteries come in 6, 8 or 12 volt versions.  Generally a golf cart will put a bunch of them in series to get maybe 48 volts or something, to run the electric motor.  Lots of TT owners seem to use two x 6 volt batteries in series.  They get maybe 200 amp-hours (or more) that way, vs. the 150 amp-hours that I get.  I chose the one T-1275 (12 volt) because it fits on my trailer tongue better and it weighs less than two 6 volt ones.  For many people, 2 x 6volt is ideal, they can both fit on the tongue.  Sam's Club has the Duracell GC-2 which is 6 volts, for $89.

As for the converter, Mike gives excellent advice (as always!).  My stock WFCO converter works fine to keep everything running while I have shore power, but will not charge a battery to more than 75% or so.  I've measured that. According to the Trojan data sheet, full charge (with charger disconnected for a few minutes), is 12.73 volts.  If I open the converter circuit breaker and wait a bit, then I read 12.4 volts, which is about 75%.  So as Mike suggests, if I'm going to boondock, I'll first open the converter circuit breaker, and then hook up a good stand-alone charger to get the battery up to 100%.  For a long term solution, and for better battery health, I'll be buying a Progressive Dynamics converter as Mike mentioned.  I'll make sure it's a model which is also specified to fully charge LiFePo4 batteries, as I may someday move to  LiFePo4 as they get more affordable.

As for battery boxes, the problem with golf cart batteries is that they are mostly much taller.  The Walmart battery box for Group 27 or 29 is not tall enough.  Fortunately I found one in a local closeout store for $6 which is just tall enough to work for my T-1275.  The lid doesn't click shut, but the big strap will keep it on ok.  For a pair of 6 volt golf cart batteries, I'd suggest hiring Mike to do what he did, or at least copy his work!
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Boof
TravelerGuy - hi! you must be somewhere in the east because I cannot get a Trojan battery here in WA state but I could in Victoria BC! Funny eh? Can’t get across the border tho.
Ok, after inhaling all of this important info from you all I call my rv repair guy to ask about inverters/converters, better battery, etc. He says get a solar panel & plug it in to the outlet on the side of my rig! This is a new ball game. I’m glad to have all this pandemic time to play all innings because I feel like I'm back at first base. So I spent last night reading everything about solar panels. sounds interesting. I would want a portable one I think. Do either of you use these with or w/o an inverter!
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TravelerGuy
Hi Boof,
I'm in Northern Lower Michigan, we have golf courses all over the place.  So there are a lot of golf carts.  Problem with shops stocking big golf cart batteries is that they are so heavy (my T-1275 is 83 lbs.).  If I found one in a distant state, the shipping might be $100 or more.  You might inquire at golf courses nearby to see where they get their batteries.  Or consider an expensive, but lightweight LiFePo4 battery.

My thinking about boondocking is that the first step is to figure out how many days you want to do boondocking and then
either: 
1.  Do a lot of math and figure out how many amp-hours you need for that number of days.  OR
2.  Go boondocking, and discover how many days before your battery voltage goes to 50%.

If you have a battery with enough amp-hours to last, then you just have to be sure to be 100% charged up just before leaving home.  If your battery doesn't have that much capacity then you could do one of the following:
1.  Buy a bigger battery, or use 2x 6 volt ones.
2.  Buy another battery to keep in the bed of the tow vehicle.
3.  Estimate how much solar amp-hours you would need to make up the difference, and buy enough solar panels to supplement the power in the battery.  May be tricky to estimate how many hours of solid sunlight you well get.
4.  Buy a small generator re-charge the battery every other day during mid-day.  If you have the stock WFCO converter, it may take too many hours to fully re-charge that battery.  A better converter or a separate smart charger might fix that problem.

All the above is the same whether you do or don't have an inverter system, but the inverter will probably take a LOT of power if you use it to make coffee or cook things.  You can figure out how many amp-hours the inverter would use if you calculated the wattage drawn x the time running.  Don't forget that the inverter will be no more than 85% efficient so the DC power drawn is at least 18% more than the AC power used. 

For an approximation, I think my 700 watt coffeemaker, running for 9 minutes, would use 10 amp-hours, and draw 66 amps.  And also note that when my battery is supplying 60-70 amps,  I only get 88 amp-hours total, rather than the 150 amp-hours powering small devices.  If you just use a 100 watt inverter to power a laptop, that's just 4 amps DC, not so bad.

There's lots of great info from the great folks on this forum, I'd suggest using the "search" function for "solar panel" or "battery"

Best wishes,
Traveler Guy.
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Boof
Thx again TravelGuy. I feel like I should know everything now! The two golf batteries has been suggested before so after this (short) season Ill talk to my RV repair shop about that. Really appreciate your taking the time to educate me, all of you. This forum is the best thing going for us retro rats. I love being out in my darling little rig! morning coffee with the birds, maybe a river rolling by. My dog! And a battery withPOWER!!!
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TravelerGuy
Yeah, that sounds really great!  Good coffee, birds, river, dog.  We don't have the river or dog, but have a rooster next door...  And 2 miles away is a pretty big lake we can park next to.  Enjoy!
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