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House Batteries 6V VS 12V

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After 11 years, my 4 - 6V Interstate house batteries finally died (i'm one of those strange ducks that takes care of his batteries). Found a heck of a deal on four new 12V Interstate Marine/RV deep cycles. They will fit as they are almost the same exact size as were my 6V's. I realize I can hook them in parallel and still have 12V, but will increase the amps, which is my concern. Will my Xantrex Invertor need to be reprogrammed or will it handle the amps as is? I would not even conside this, but the deal I got on the 4 Interstates was too good to pass up

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Couple of points:

You might verify that indeed these 12 VDC batteries are DEEP CYCLE batteries, as most "marine" batteries are start/deep cycle batteries (read that compromise of the two) with thinner plates not really meant for extended deep cycle work.

Yes, your inverter/charger always needs to be re-programmed if battery technology, bank size (amp-hrs) or temperature changes (unless you have the remote, optional temperature sensor). An easy job from most Xantrex remote panels.

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Thanks Wolfe 10. Yes they are the start/deep cycle Interstates, But you'd be shocked at the price I paid for them; it was 1/4 of what I would have paid for 6V Interstates; they were a going out of business sale. So, I will install them, and if they last two - three years it's OK with me. So, to continue your comments, I will have to reprogram my Xantrex to be handle the increase amps? BTW, I do have the temperature sensor attached to one of the current 6V's.

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If they are wet cell, as were the old ones (i.e. same technology) then no reprogramming for that part is needed.

If total amp-hrs @ 12 VDC is the same or close to the same, no reprogramming for that part is needed. 

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Read my Xentra manual and I should reset the RC amperage. Each battery is 140 RC X 4 = 560 amps. The setting levels are 500 and 1000; nothing in between so I plan on calling Xantrex Monday and ask which one I should use. According to the manual the inverter will adjust automatically after several charges/discharges, but they recommended it's best to reset it close manually. My one question I am trying to find the answer to is in order to hook the bank in parallel, do all four batteries attach in a "complete circle" For example: Positive posts, 1 to 2 to 3 to 4 and back to 1 (or stop at the four and not go back to 1)? I know that sounds like a dumb question, but want to be sure.

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Positive of house to positive of battery #1 to positive of battery #2 to positive of battery #3 to positive of battery #4.

House ground to negative of battery #4 to negative of battery #3 to negative of battery #2 to negative of battery #1.

 

Yes, there are some more complex configurations, but this is the basically accepted way to wire 4 batteries in parallel.

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IMHO RC is always given in minutes and is the number of minutes you will see a specific discharge. Minutes X 4 does not give you amps. On one chart that I looked at for a 24 series battery gives 140 minutes @ 25amps. that suggests an 80 ah battery at a 20 hour rate. If that is correct, you are looking at a 360 ah battery pack.

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In fishing boats you have two types of batteries.  Start battery and trolling motor batteries.  The start battery has higher cold cranking amps. The trolling motor battery is a deep cycle battery like the deep cycle golf cart batteries. 

Some of the newer golf carts are coming with 3 or 4 12volt deep cycle batteries depending on if you need 36 or 48 volts. 

Herman 

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You will never get the service life from the 12v "marine" batteries you enjoyed from the 6v's.  They are not made to discharge deeply and recover as the 6v's.

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Since the OP has already made the decision/bought the marine batteries, probably no need for us to make recommendations as to the viability of the two types.

Just make sure they are wired properly and his inverter/charger is programmed properly for them.

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True.  Sometimes we chose to save a dime, for the wrong reason! Don't ask me how I know.:rolleyes: I wish him the best.

Carl

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I think the OP is going to be OK. He knows going in they might not last as long as the 6V batteries. On the other hand we have 4 fingers and a thumb, new 12V deep cycle batteries are far better than they were 30 years ago. B)

Bill

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They will work however the useable power in terms of time of discharge will be somewhat shorter because of the construction of the battery.  Marine batteries are generally structurally stronger because of the beating they have to withstand in rough seas.  They are not true deep cycle.

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I thank everyone for your sage advice and comments. It is true the decision has already been made, I bought 4 Marine/RV deep cycle 12V batteries for the price of one 6V deep cycle - it was a going out of business sale, and they are Interstate (I will not buy anything but an Interstate). I have a Bass Boat and both start and trolling batteries are Interstate, and they are eight years old. As I stated earlier, I am one of those strange ducks that akes care of his batteries, thus the reason both my two diesel start 12V's and my four 6V batteries have lasted for 11 years in all sorts of weather. I also attribute their life to my Inverter (Xentra); I check water levels on the first of of every month religiously, and I keep them spotless. I am fully self-contained with an Onan 7.5 Diesel generator; therefore, I rarely use the house batteries via the Inverter. We use the MH less these days than we did years ago (my age, not the MH), and we no longer dry camp except to stay at Cracker Barrel overnight when we are in a hurry to get somewhere, and then I use the generator So, in summary, if these batteries last me for half or less than the four 6V's, I am way ahead. At my age, I probably won't be around in 11 years so I could care less if they don't last that long. LOL

I am somewhat confused over John's comments about RC. The brochure on the batteries states: 

ReserveCapacity-25: 140.00

So, I assume, as John states, that 140 is minutes, not amps, but how did you come up with "that suggests an 80 ah battery at a 20 hour rate. If that is correct, you are looking at a 360 ah battery pack"? I come up with 320 ah for the four battery pack??

 

Again guys, thanks much for helping out an old Marine

Semper Fi, Jim

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Update: Just got off the phone with a very knowledgeable and helpful tech from Xantrex. He looked up my batteries (Interstate SRM 24), and did some calculations. He said my batteries are 70 ah, and my bank is; therefore, 280 amps. He recommended I do not reprogram my inverter, but leave it on auto and after several cycles it will reset the amps on it's own. Also, he said those batteries will work fine as long as I take care of them as I did the others, they will last a long time based on the type of RVing we do today. Again, thanks guys.

S/F, Jim

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Likely the reason your batteries lasted so long is you didn't really use them. Typical deep cycle use is use up all but the last of the current in them then charge them up again the next day use them again the next day etc. A typical electric golf cart in the north with a season from May till October the batteries will last about 2 years but every nice day in the summer months they will be used 2 or even 3 times a day till they are towed back to their charging station to be charged overnite and then repeat. The biggest difference between the 6 volt golf cart and the 12 volt deep cycle is the size of the cells between the two of them the golf carts will last a bunch longer in a draw down situation. for as much as you use your coach without the generator running is minimal so the batteries you purchased should last you just fine and as you said at the price how can you go wrong.  Vic.

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I have a friend with a 2008 American Eagle.  He recently swapped four AGM 6v for two AGM 12v.  He does virtually no dry camping.  Don't think he's been out on a trip yet, we'll see how it goes.  

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5 minutes ago, FIVE said:

I have a friend with a 2008 American Eagle.  He recently swapped four AGM 6v for two AGM 12v.  He does virtually no dry camping.  Don't think he's been out on a trip yet, we'll see how it goes.  

Did he downsize total amp-hrs?  One 8D 12 VDC is very close to the same capacity as two "golf cart" 6 VDC batteries in series.

So, he could have kept the same capacity or he could have downsized.

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Our last coach had one 12v AGM house battery. We dry camped for a weekend here or there and never had a problem, running the furnace also. The interior lighting was mostly LED by then but still did good. I ran the generator in the AM making breakfast for an hour then again around 7PM for an hour.

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On 2/12/2017 at 10:19 AM, wolfe10 said:

Did he downsize total amp-hrs?  One 8D 12 VDC is very close to the same capacity as two "golf cart" 6 VDC batteries in series.

So, he could have kept the same capacity or he could have downsized.

Here's his post:

I have just installed two Trojan 24 AGM 12 volt house batteries replacing my four 8 year old plus 6 volt Trojan GC2 AGM batteries.  My consideration was cost and how much dry camping we do.  The 12 volt batteries have 152 AH rating for two versus 430 AH rating for the four 6 volt.  The only need we have for energy when not connected to shore is when stopped during travel and need to heat something in the microwave, lights occasionally and for our residential fridge.  The cost of the 12 volt was $249.95 each and for the 6 volt was $329 each.  These prices are without sales tax, shipping, etc.  So, for the new setup the battery cost alone was $499.90 and for four 6 volt would have been $1316.

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