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 > Adding a second battery?

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Tiggs

Pennsylvania

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Posted: 05/21/13 07:03am Link  |  Quote  |  Print  |  Notify Moderator

My new to me TT has a 12V Interstate deep cycle marine/rv battery, spm-24. Looked on line and it offers 140 min. at 25A and it looks like I'm could use as much as 10 amps an hour without the furnace when dry camping, which is what I mostly do. This is probably why my battery is dead in the morning so I want to add a second battery. I would like to add a bigger battery, offering more amp hours but not sure if I have to pair the battery with a similar sized one or if I should replace this battery and convert to a 6V system.

I would like to get to the point where I have enough power at night to run my frig, a light or two, the furnace and the TV for a few hours. Many folks seem to be happier with their 6V power set up over the 12V, but not sure exactly why this is so.

Wonder if I shouldn't go to a 6 Volt system for the general house service and isolate the 12V battery, put it on an inverter and use it only for the TV, thinking if I over did the TV use, I wouldn't compromise my power for the "necessities".

Thoughts?

Carolyn


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EsoxLucius

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Posted: 05/21/13 07:11am Link  |  Quote  |  Print  |  Notify Moderator

You won't convert to a 6 volt system although you can convert to 6 volt batteries. Two 6 volt batteries in series provide 12 volts at the same AmpHour rating as one of the batteries. Two 12 volt batteries in parallel provide 12 volts at double the AmpHour rating of one battery. Four 6 volt batteries in series/parallel provide 12 volts at double the AmpHour rating of one battery. Your TT operates at 12 volts. If you have abused your existing 12 volt battery (the word "dead" indicates abuse) you will have to replace it if you want to add an additional battery, even if it was the same as the one you have now. How much room do you have for batteries? Is that area isolated from the TT interior and vented to the outside?

I would see how much room you have and get a pair of the biggest 6 volt true deep cycle batteries you can find and fit. 220 AH (two 6 volt batteries) should be enough for your described usage, although what do you have or plan for a charging regimen? Four batteries would give you more than enough power for the use you describe.

* This post was edited 05/21/13 07:24am by EsoxLucius *


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korbe

California

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Posted: 05/21/13 07:34am Link  |  Quote  |  Print  |  Notify Moderator

Without any TV or furnace, and in conserve mode, we can enjoy dry camping and use about 25AH per day. That will allow us up to 4 or 5 days with our trojan t-105, 6-volt battery setup.(225 ah capacity)


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Tiggs

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Posted: 05/21/13 08:05am Link  |  Quote  |  Print  |  Notify Moderator

Got it, I understand the basics of batterys wired in series and parallel. I used the term "6 volt system" to specify a system of batteries, not convert to the tt to 6 volts.

I've only drained the battery twice so I don't think has been abused, which is why I am trying to figure out what the benefit is to moving to two 6 volt batteries over adding a second 12V battery and if the benefit to 6V batteries justifies that expense.

The battery sits on the tongue of the TT, behind the propane tanks, and I have room for another battery there.

I have a Honda 2000 that I use during the day for power/charging but sometimes restrictions are placed on overnight generator use, which is why I would like to have enough battery to use for overnight camping, planning to recharge them during the day on generator.

Thanks,

Carolyn

PapPappy

Wilmington, NC

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Posted: 05/21/13 08:09am Link  |  Quote  |  Print  |  Notify Moderator

I think you misunderstand what a 6-volt system is.....it's two 6-volt batteries that are wired in Series, to create 12VDC. Because of the larger size plates and such in the 6-V battery, you will get a longer life from it, but you could also just wire two 12V batteries in Parallel, which would double your service life from them.

Try to keep the batteries about the same size and age....or the smaller, older (weaker) battery will drain down, and be useless.

Depending on the age of the 12V battery you have, and if you could use it for something else, I'd probably go for a pair of 6V batteries in it's place.

But, there are also some folks, who feel that you should stick with 12V batteries, because, if you have a failure of one of those 6V batteries, you are out of business....at least with just one 12V battery, you can still limp home, or stay another day![emoticon]

Read up on how batteries can be wired together....parallel vs. Series, so that you understand the operation before you do anything....or ask a friend who knows these things, to help you.

On edit, I guess we were typing at the same time[emoticon]
Anyway, if you have the 6V batteries, you don't have to worry about your inverter...you would just wire it up to the both batteries to get the 12VDC connection from them (with batteries wired in Series).
Hope that helps.

In your current situation, I'd just get another 12V battery that is the same size as what you currently have, and wire it in parallel.[emoticon]

Good Luck[emoticon]


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Matt_Colie

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Posted: 05/21/13 08:26am Link  |  Quote  |  Print  |  Notify Moderator

Carolyn,

What I fear you do not understand (don't feel bad) is that two 12V batteries in parallel will be hard pressed to give you capacity X 2. Even if they came off the assembly line together, they will never be that well matched after the second discharge. Also, real deep cycle 12V batteries are rare and expensive, but 6V (three cap) golf cart batteries are very available and very durable.

There is also a new twist to all this. Theft....
I believe that most often batteries are stolen to be used by the thief. As scrap, they only bring about 5$, but if you can replace you bad car battery, the relative value is much greater.

So, when they rip open your battery box and find batteries that won't fit under the hood of the wreck they are trying to drive, they leave empty handed.

I've been doing boat electrics a very long time.

Matt


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Tiggs

Pennsylvania

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Posted: 05/21/13 09:38am Link  |  Quote  |  Print  |  Notify Moderator

I do understand 12v = two 6 volts wired in series. I do get it. I've already done some wiring to power the 12V exhaust fan I installed in the roof of my conversion van doing just that. I've also run 12 power to various points to power other 12V aux. fans when I must leave the dogs in the van without the motor running. I've also replaced the TV with a microwave and wired the van for 120 amp service to it and 4 plugs so I do understand enough to get by.

What I'm trying to decide is if I would be better off to go with two 12 volts wired in parallel or two 6 volts wired in series. I was hoping for an explanation of why, as Matt has touched on, the 6 volt batteries are a better choice. Economically, it would seem to be adding a second 12V would have been the better choice short term, but long term I think, as Matt suggested, 6 volt golf cart batteries or similiar are the way to go.

Carolyn

CincyGus

Cincinnati

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Posted: 05/21/13 10:15am Link  |  Quote  |  Print  |  Notify Moderator

Carolyn,

The main reason most people that dry camp for extended periods (over a couple days) go with the 6 volt GC batteries are as follows:

Usually, the 6v GC batteries offer higher AH than similarly priced 12v deep cycle batteries.

The 6v batteries are made to take the deep discharge and a higher number of discharge/recharging cycles better and seem to last longer in this type of situation.

So for the 3 day, long weekend dry camper, the 2-12v maybe group 27-29 batteries are generally enough and a cheaper option.

For some that like to stretch that to 5 days or longer, the 6v batteries seem to be more favored.

Your situation, having a genny that you can run for a few hours in the nmorning and a few at night, should allow you to do either. With a good three stage charger, it shouldn't take more than that to bring either solution back to 90%-95% charged.

If you decide to go the 12v route, go at least group 27 or 29 to give you the additional AH bank and buy two new ones together. Keep your 24 to power your TV as you described above, it a good plan. Just make sure it's vented if you have to move it off the tongue of your trailer to an enclosed area.


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mbopp

Henrietta, NY, USA

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Posted: 05/21/13 10:41am Link  |  Quote  |  Print  |  Notify Moderator

FWIW and YMMV:

I had 2-12V G27 batteries on our old HTT that will get mounted on the new TT. And I'm adding the IOTA-55 deck mount converter I have in the front storage compartment because A) it had a better charging circuit than the factory WFCO and B) it's a 3' wire run to the batteries.
The TT's been converted to LED lighting and we rarely use the furnace.

To do over again I'd go with a pair of 6V batteries. But what I have now should do fine considering I have a generator & can run it for a few hours to charge the batteries as needed.


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edbehnke

North America (from Michigan)

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Posted: 05/21/13 11:41am Link  |  Quote  |  Print  |  Notify Moderator

I have 2-12volt batteries but if I did dry camping for more than 3 days I'd have gone to 6volt batteries.
key thing to all of this battery stuff is they have to be wired properly. Use 2 like batteries.
And, a rule on batteries (in series or pallarel)is if you wire a new one with an old one in a few weeks the new one will be just like the old one.


eddie and sandie
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