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Old 10-07-2010, 11:29 PM   #15
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I run 4 12V group 27 (115 AH) deep cycles from Wal-Mart and exclusively boondock. My 200 watt solar panel is all I need, though my wind gen does some work sometimes if I'm deep out in the desert.

They work great and as long as you keep them conditioned well, maintain the water, and don't let them fall below 50% too often. If you are going to run down batteries alot, I find it's better to invest in more capacity than you need on average.

The reason is this...the life expectancy goes down EXPONENTIALLY with the % of discharge. So if I can keep them above 70% regularly, they will last 5-7 years. Compare this with say, two batteries, that I would regularly discharge to 40%. I would be replacing them within a year. Price-wise, over the long term, it's better to have a larger bank, then discharge it less.
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Old 10-11-2010, 10:53 PM   #16
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Deep Cycle batteries are engineered differently that a starting battery as their use and purpose is different. The starting battery is designed to give a high current for a short period - CCA where as a deep cycle is designed to deliver a small current over a long period of time measured in amp hours. To do this they are designed differently to produce the desired chemical reactions that are required.

If you choose 6v you need pairs but if you use 12v you can use odd numbers. I use 3 J-185H's at 215 AH each for a total of 645 AH. I use 45 to 60 AH per day and usually go 5 days without starting the generator. They each weigh 115#'s.

I've been very pleased with them so far.
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Old 10-11-2010, 11:48 PM   #17
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re: "Deep Cycle batteries are engineered differently that a starting battery" -- don't fall for this.

It is not a fruitful model for aiding battery choice in a typical RV situation. Instead, look at measures the manufacturer and retailer will stand behind, not labels and marketing hype.

All lead acid batteries will suffer reduced life if subject to deep cycles as a routine thing. All lead acid batteries will provide available energy that depends upon current draw and most are very close in how they do so with Peukert coefficients that are used to describe the effect near 1.2.

When you look at the batteries you are going to find in common use in RV's the differences are more a matter of degree than of kind. That matter of degree is not much more than the variance you can get in batteries from such things as temperature, cycle to cycle variance, age, and use profile.

Look at the specifications, cost and warranty! Don't get caught believing things from someone who won't give you your money back if it doesn't work as they say.
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Old 10-12-2010, 12:24 PM   #18
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Bryan L and I have discussed this matter before and I do not believe he is a chemist as I am.

Believe who you wish but to chemistry to deliver a fast initial current is different from the chemistry required to deliver a low current over a longer period of time. Batteries are not "fruity". A started battery has more surface area than a deep cycle battery which is why they can deliver a high short burst of current. This is why the specifications are different from a starter battery to a deep cycle battery.

For any non believers buy an excellent quality starter battery and put it in Bank 1, buy a excellent quality deep cycle battery and put it in Bank 2. See which battery bank functions and then functions the longest. Or go to your nearest solar power home, or to many of them and see if you can find any starter batteries, bet you can't.
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Old 10-12-2010, 01:09 PM   #19
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I'd rather avoid appeals to authority and other such logical fallacies (including the ad hominem).

Instead, and I repeat, go by the measures. I'll also offer the caveat, again, that I am talking in the context of those batteries commonly available for use in RV's.

Talking about "believers" and other such truck is inappropriate IMHO. Instead let's talk about measurements and things that can actually be observed.

A part of making good measure is understanding the accuracy and the limitations of your measurements. When it comes to batteries, that means understanding the inherent variabilities from such things as how it is used and stored and how it changes between cycles and over time as well as the influence of variables such as temperature.

As for the 'surface area' thing, if you take a battery apart you'll find that they are all faure type plate construction with minor differences in thickness (0.1" plus or minus if you believe Az WindSun).

It always amazes me how much resistance there is to actually using measure and specification when it comes to batteries.

In regard to the suggested 'experiment' - that provides a good case study of how to get to invalid conclusions. First, the sample size is way too small. Second, there is no objective definition of the involved variables such as "excellent quality" or "deep cycle battery" or "starter battery" or "functions" - most of these are just labels just pasted on batteries by manufacturers or retailers indicating intended use.

Then there's the 'bet' which is another logical fallacy. The bet also has difficulties. One is that this is an RV community and not a solar residence community and the use requirements are significantly different between the two. Another relates to what is called selection bias.

At any rate, the primary point is that one should go for objective criteria and appropriate measure and be very careful of labels, logical fallacies, blanket assertions, terms that don't have clear definition, or measures that are out of context or lacking significance for the desired need.
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Old 10-12-2010, 01:47 PM   #20
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AGM Batteries...

We also went with AGM batteries as part of the purchase agreement for the coach. Joe
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Old 10-12-2010, 02:09 PM   #21
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Based on real #s there is really very little differences between 12 volt vs 6 volt batteries. I go with 6 volt batteries. I did so simply based on cost. I bought my golf cart batteries from a golf cart supplier, and as such, the GC batteries were quite low at 40$ each. The comparable 12 volt cost of a battery was more... not a lot, but about 20$ more per inexpensive battery.
One thing not mentioned so far in this discussion is the size wire needed to connect batteries together. When I bought my first 5er the dealer asked whether I wanted 6 volt batteries or 12 volt batteries. I said I wanted 6 volt batteries. He installed two golf cat batteries and then delivered the trailer with a 8 size wire between the batteries. I looked at that and laughed and pointed that out to the service manager. He simply said that was the largest wire they carry. I said that if he puts in 6 volt batteries then the connector between them has to be capable of handeling current of say 150 amps constant load especially if you plan on using an inverter. I asked him what wire is used to connect 2 12 volts and he had 2 pieces 1/0 cable about 2 feet long. I asked him to use one of those connectors instead.

After all that I went out on my own and bought about 60 feet of 4/0 cable and crimp on heavy duty lugs and proceeded to make all the wire I needed to connect batteries to each other, negative to ground wires, and inverter leads all from 4/0 marine grade wire. Folks, no matter what batteries you buy, the power from those batteries still has to flow and if you have an inverter that's rated at 4000 watts, that's nearly 400 amps of current from battery string to inverter. The leads between batteries and from batteries to inverter have to be large and robust enough to carry 400 amps of current without a significant voltage drop. A # 8 wire would just fry at that load. Always oversize your wiring from batteries to ground and from battery to battery and also battery bank to battery bank. Even if you have 20 6 volt batteries but are using 18 guage wire you'll never realize the battery potential because voltage drop will be so large. Use the largest ( and shortest) wire run you can get and use heavy duty rated all copper lugs.

Heavy wire is hard to use and is heavy. 60 feet of 4/0 welding cable is also quite expensive comming in at anywhere between 6 and 12 dollars per foot depending on where you buy it. 60 feet will probably weigh in at 130lbs. Copper is way up this year and high quality welding wire will not be cheap. My experience is that few really understand how batteries need to be adequately wired. When an inverter is pulling max rated power you will easily hit 300 amps draw from your battery banks. Unless the leads between batteries is just as robust as the inverter leads, you will never get the amps at the voltage you want no matter how many batteries you have or how much is spent on them.
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Old 10-12-2010, 07:13 PM   #22
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I have an '02 Winnebago Brave, It came with two BCI 24 Deep cycle batteries for the coach, and one BCI 65-750 for the chassis. I still have the chassis battery it came with, works great. I removed the two 24's, and put in a 8D starting battery, when I bought the coach.
I then added another 8D starting battery, in front of the rear tire, pass side.
I never really did any major boondocking, but felt that there was just never enough power to last. I added Solar in '09 and changed batteries again in '10 this time using 8D Deep cycle Deka Batteries. I have been to a few places this year, that had no hookups, and I was using the solar and some generator to keep them up, but I had a problem the last time I was out, as the generator did not start, during the stay. so, only the solar was doing the charging, and not much at that due to shade issues. I went three nights, with heat, tv for some time, day and night, microwave at times, and coffee in the A.M., on just the batteries and a little solar.
I do think the deep cycle's did make a difference. Even when the starting 8D's were new, I could never get that kind of duration, granted there was solar, but it was slight, 2-4 amps was the best I saw.
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Old 10-13-2010, 12:02 AM   #23
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As I mentioned we have had this conversation before. Temperature, weight,, time and amps can be measured rather accurately. If you see a CCA rating you are probably looking at a starter battery. If you see a 20 AH rating and no CCA then you are probably looking at a Deep Cycle battery. If it is big and heavy even better. The deep cycle batteries are commonly available for RV's just ask Trojan, they sell them for RV's. good battery too.

The quick energy needed to start an engine is referred to a CCA and can be explained by an increase in the surface area of lead to the acid. High AH ratings, found in deep cycle batteries have less surface area and thicker plates yielding a slower reaction. CCA's from 450 to 650+ are starter batteries. In a 12v 20 hours AH ratings of 200 or so will be a Deep Cycle and no CCA will be given. Kinda simple.

Bryan L does not believe in the existence of Deep Cycle Batteries yet he won't try a simple experiment claiming insufficient sample size, so increase it do it a hundred times. He won't go into a solar power system because it is not a Motor Home but I think the reason is he won't see starter batteries but he will see Deep Cycle batteries, big ones. Yes Byron L real deep cycle batteries do exist. A 200 AH deep cycle isn't probably going to start that big diesel you might have either. So buy a 100 big diesels and 100 200 AH deep cycle batteries and try it. Make sure each engine is different and each battery is different and just think of the degrees of freedom you will have to play with.

Or go to your Trojan Dealer and find a battery or batteries that will fit in your vehicles.
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Old 10-13-2010, 12:06 AM   #24
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HotMech and Haller you guys are right on.
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Old 10-13-2010, 01:19 AM   #25
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For any newbies who are still wondering what they should buy after reading all these posts...the correct answer is deep Cycle batteries.

Grandiose verbosity and an inexplicable love affair with the Peukert coefficients notwithstanding, BryanL is just wrong. In terms of total available amp-hours available from an equal group size battery, you will always have more usable power, and much more battery life with a true deep-cycle.

It is true that some el-cheapo mnfctrs call their batteries deep cycle when they really are not...however, if you stick with the tried and true name brands like Trojan, etc. you will get the real thing. I have used both SLA and deep-cycles in everything from electric vehicles, to remote home sites, to RV systems. Starting batteries will simply not hold up to the typical cycling off-the-grid systems experience.

Some people it seems are more in love with their theoretical knowledge than real world experience. But theory doesn't keep the furnace fan running on a cold night. If you are going to boondock like I have been doing for years, get all the deep-cycle batteries you can reasonably stuff into your coach, and wire them appropriately. Then take every opportunity you can to charge them whether by solar/wind, alternator, or gen set.

An over sized bank will cost much less in the long run as each battery will suffer less depth of discharge each night. Their cycling capacity decreases exponentially with every 10% you take out of them...especially past 70%. I personally try not to go below this very often, mainly because I am cheap. the only lead I like to pay for is contained in a copper jacket behind a bunch of gunpowder.These are not theoretical numbers, but measured studies undertaken by reputable manufacturers, U.S. Military & NASA, Electric vehicle manufacturers, not to mention the real world experiences of those of us who use them daily.
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Old 10-18-2010, 03:52 PM   #26
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I just had quite a surprise. Purchased a 2 year old coach where previous owner had installed 3 AGM 55 AH batteries for the "house". Even with what appeared to be a full charge, I was always frustrated in that whenever I tried to use the House battery disconnect switch at the entry door, I would have to hold id down and then wait for a disconnect. (I left one light on so I could tell, plus the chirp of the CO detector) Because they were only 55 AH, and following the disussion about 6 V GC batteries, I decided that next season I would replace them. However, when I took my boat out of the water last week, I took ONE 75 AH deep cycle battery to the coach and connected it, disconnecting all the AGM batteries. My connect/disconnect switch now responds IMMEDIATELY for the first time EVER. I have apparently been limping by with damaged batteries, even though they all would charge and show almost 13 volts when charged. Whoooda thot ! Even if I don't go the GC route, I can't wait to get 3 new 100 AH batteries in place before our next season.
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Old 10-20-2010, 08:50 AM   #27
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Quote:
Originally Posted by JayLodge View Post
I just had quite a surprise. Purchased a 2 year old coach where previous owner had installed 3 AGM 55 AH batteries for the "house". Even with what appeared to be a full charge, I was always frustrated in that whenever I tried to use the House battery disconnect switch at the entry door, I would have to hold id down and then wait for a disconnect. (I left one light on so I could tell, plus the chirp of the CO detector) Because they were only 55 AH, and following the disussion about 6 V GC batteries, I decided that next season I would replace them. However, when I took my boat out of the water last week, I took ONE 75 AH deep cycle battery to the coach and connected it, disconnecting all the AGM batteries. My connect/disconnect switch now responds IMMEDIATELY for the first time EVER. I have apparently been limping by with damaged batteries, even though they all would charge and show almost 13 volts when charged. Whoooda thot ! Even if I don't go the GC route, I can't wait to get 3 new 100 AH batteries in place before our next season.

Yep, Capt....sounds like your AGMs could use some serious re-conditioning. Even then, 165AH total isn't much for a weekend. They probably became sulfated from disuse.

In order to test a battery correctly, one has to put it on a load tester anyway, not just a voltmeter. A battery with just 5% of it's capacity left will still show full voltage, until a load is attached to it. I bet if you put them on a load tester, they'd show up almost dead.

Meehhh...just use them as a core deposit on some nice new group 27 batteries. For a coach as big as yours, I couldn't imagine doing with anything less... unless you are hooked up all the time.
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Old 11-22-2010, 02:30 PM   #28
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Concord AGM battery, 180W solar panel with Moningstar MPPT controller, conservation all LED lights in our grasshopper design teardrop.
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