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Old 02-16-2009, 10:19 AM   #1
JMG
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Changing from 12v to 6v Batteries

I currently have one 12 volt group 24 deep cycle battery.
And I am considering changing to Two 6 Volt golt cart batteries.
What else do I need to do?
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Old 02-16-2009, 10:27 AM   #2
bsmeaton
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You'll need an extra battery cable to tie the positive of one battery to the negative of the other.

Also, you'll need to add a second battery box, or replace the one you have with one that holds two batteries. Just make sure they are vented out the bottom of the rig and out the front (natural draft) so that no hydrogen migrates into the compartment.

Blue Sea makes a great box to secure those batteries, but it is for marine and does not have the vents (marine bilge and engines are mechanically ventilated). I had to cut a hole out the bottom and a new hole out the bottom of the compartment deck and stick a vent tube in there (I used the old tube off the old battery box). I also cut a hole in the lid and used the old battery box vent tube to make a flange to attach the upper hose. I have some pics in my mod section.
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Old 02-16-2009, 10:33 AM   #3
OntMont
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Get a battery box to hold them. The one I have is "Blue Sea" brand, but there are others available. Mine is specifically designed to hold two Trojan T-105 batteries. You will need a short piece of battery cable to join the two batteries in series. I bought a short one at an auto parts store, but I still had to shorten it and add a new connector fitting at one end, but it results in a tidy package without any excess cable. For mine, I bought a battery filler kit from Camping World when they had them on sale. That may be a bit of overkill, but it sure makes topping up the batteries a lot easier, and therefore more likely to get done. My 05 trailer did not come with a cut off switch, so I added one of those as well (Blue Sea brand again)

If you have the Iota Converter, you might want to consider buying the add-on "smart charger" option, your batteries will appreciate it.
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Old 02-16-2009, 10:53 AM   #4
MacDR50
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Just in case someone reads this thread who isn't familiar with batteries. Your hook two 6 volt batteries up this way (+ to -) and then other - to ground and other + to line to get 12 volts. If you do this with two 12 volt batteries you get 24 volts. I have seen it done and it isn't recommended practice. To have two 12 volt batteries hooked up for 12 volts, say to increase storage capacity, you connect + to + and - to - and then either - to ground and either + to line.
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Old 02-19-2009, 08:50 AM   #5
Dave Anderson
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If you really intend to Boondock, You might want to consider 4 6volt batteries. by just doing 2 you are not increasing your Amp. storage,which is what you need for longer term stays 2 in series then parallel the pair to double your amperage storage.
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Old 02-19-2009, 09:18 AM   #6
bsmeaton
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Dave, are you sure - these 6-volt golf cart batteries have an awesome storage capacity.

Deep cycle 12V 24M (Interstate)

Reserve Capacity @ 25A = 140 minutes

6-Volt Golf Cart (Interstate)

Reserve Capacity @ 25A = 474 minutes

Two Golf cart batteries would have a combined reserve capacity of over 948 Minutes @ 25A! Even if cut in half to account for 12V, that is a huge advantage over a single 12V deep cycle battery.

I would agree 4 would be better for boondocking, but so would 6, or even 8. As I understand it, 2 6-volt golf cart batteries outperform even 2 12-volt deep cycle batteries. Am I reading that wrong?
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Old 02-24-2009, 07:06 AM   #7
Dave Anderson
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Brad ;As I understand it,If a 12vlt Batt. has 220 amps of storage,and you replace it with 2 6vlt batts. you must put them in series to get 12vlts. you will still only have the storage capacity of what the single batt. has. I believe there are some new batts. out there with more storage,but VERY expensive...Dave
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Old 02-24-2009, 07:53 AM   #8
bsmeaton
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Dave, I agree with what you are saying, but clearly the 6-volt out performs the 12-volt 3 to 1 using your formula. If you are saying there is no advantage to installing (2) 6-volt batteries to replace (1) 12-volt deep cycle battery, I would have to disagree with you.
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Old 02-25-2009, 04:26 AM   #9
Dave Anderson
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No,no I have 6volt batts. and I think its the ONLY way to go, unfortunatly they are quite heavy, I have 4 that give me 440 amps. which is plenty with my solar panels recharging daily. We had one MOC member Steve at Q that had 6 that gave him 900amps!! but Very heavy and VERY expensive...........Dave
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Old 02-25-2009, 05:56 AM   #10
bsmeaton
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Dave, how do you determine your amps? Mine only give a reserve capacity based on the rate of draw. Also curious, what do your solar panels put out. (wondering what your rate of recovery is - thinking about putting a system together).
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Old 02-25-2009, 10:43 AM   #11
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Brad/Dave:
I hope you two keep this conversation going as I to would be interested in going with solar panels. I agree with you Brad on the 2 - 6 volts for extended life. I have tried both and am presently with 2 deep cycle 12's. In my old camper of S.O.B., I had 2 - 6's together and it was almost as good as the 2 - 12's. I am just waiting on these bat's to go bad and then I will probably switch unless I'm in a big hurry. I have an onboard charger if I pull in where there is an electrical hook-up. Going down the road they charge off of the truck. I also have a couple of Honda 2000's on board if needed.... JB
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Old 02-25-2009, 11:03 AM   #12
bsmeaton
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Deadeye,

Check out Simonsrf's picture of his roof in the "Boondocking w/extreme view thread!" He has quite a setup.
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Old 02-25-2009, 11:13 AM   #13
deadeye
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Looks nice - don't it...Thanks..JB
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Old 02-25-2009, 11:15 AM   #14
bsmeaton
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Sure does. Nice install. I'm going to PM him and ask him the output.
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Old 03-08-2009, 11:19 AM   #15
Dave Anderson
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JB; sounds like your really set for boondocking,generator style that is.
Brad; I don't know the terminology for this measurement of Amp capacity,All I know is my 6vt Trojans have 220 amp storage capacity put 2 in series and I now have a 12vt with 220 cap. Put another set of 6's together , then put both pair in parallel,I now have 440 amps of storage. My 4 solar panels provide me with 420 watts of energy ,when run through my controller,will provide me with 21-22 amps on a really brite day. The batts.,of course, are wired to my 3500 watt inverter that I have going to dedicated circuits..........Dave
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Old 03-28-2009, 01:44 PM   #16
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If anyone is interested there is a book out (available at camping world) called Understanding 12 Volts. The book is extremly helpful and very easy to understand. After reading the book I set up my rid the same as Dave only using 2 - 130 watt solar panels and even though I usually run my batteries down below 50% each night on a sunny day they are fully charged. I keep a Honda 2k handy just in case of clouds or rain.
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Old 03-28-2009, 03:56 PM   #17
chas
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I boondocked at slab city - where everyone uses a solar system and checked out their set ups , The most popular was 4 - 6 volt golf cart batteries and 4 solar pannels with at least 110 watts each .
I found out that the inverter shuts down all 110 volt power when the batteries reach 10 volts -- so u only have 2 volts to drop and then the system wont work .. The inverters can only make 110 from batteries that are between 14 volts and 10 volts = below this the voltage would drop to levels that would burn up many electrical devices ,a good rule of thumb is 1 pannel of at least 110 watts for each battery - or they wont fully charge and slowly drain and shut down = also get an inverter of at least 2000 watts - with this set up you can use a deepfrier during the day and still have a small amount of charge to the batteries - no you cant run it all day
you have to budget , u can run a microwave but do the cooking during the day and just the tv and nessary lights at night
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Old 10-02-2009, 02:18 PM   #18
pbahlin
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A few points about batteries...

I find it more useful to think in terms of watts and watt-hours instead of amps or amp hours. Watts measure work, and watt-hours measure power. One amp flowing across a potential of one volt results in 1 watt of work. 1 watt expended for one hour is 1 watt-hour.

When you consume power the common unit of measure is watt-hours. This is why your stick house gets a bill for kilowatt-hours. You're not buying amps or volts. You're buying and consuming power (kilowatt-hours).

This is really important for an RV or boat because one of the important things you want to do is store DC energy at some voltage like 6,12,24, or 48 but your major consumption is likely to be AC at 120 volts. Bottom line, you shouldn't worry (in the planning stages at least) about volts or amps. If you think you will consume 3600 watt-hours in a 24 hour period (of AC) then you need a DC source of 3600 watt-hours in a 24 hour period from your DC storage system. Actually you'll need a bit more due to losses in converting your DC to AC.

So if you are designing a solar system, your first layer of calculations should be in watt-hours. They are the common denominator that lets you provide DC watt-hours that are consumed as AC watt-hours. Here's how that translates to batteries...

The most popular battery is the 6 volt Trojan T105. This battery weighs about 60 lbs. and is rated to deliver 225 amps over a 20 hour period (about a day). The most common rating for deep cycle batteries is their amperage rating over 20 hours. For optimal life out of the battery you never want to discharge (at least too often) below about half of this capacity. For me then, I think of the T105 as a battery capable of storing and supplying 112 amps at 6 volts, essentially forever. TAKE AWAY... The T105 is a (6x112) 672 watt-hour power source. It can deliver it all at once (672 watts for one hour) or it can deliver it a little bit at a time (672/24) 28 watts for 24 hours.

The reasons this battery is so popular are three. It comes from a highly respected manufacturer. It is made in big quantities (for golf carts). It is a mature/stable workhorse.

The reason it is used instead of a 12 volt (or higher) battery is that power storage capability drives weight. More power means more weight. To get a 225 amp rated 12 volt battery requires approximately twice the weight of 225 amps from a 6 volt battery. By putting two 6 volt batteries in series you get 2x672 watt-hours of storage in 2 60 lb packages. The same power can be had from a single 12 volt battery but it will weigh in at an unacceptable 120 lbs or so.

Put this all together and it means that every pair of T105s weighs 120 lbs and stores a usable 1344 watt-hours (daily). Two pairs yields 1688 and three pairs yields 4032. So a practical system might be 6 T105s that can store 4kWH. By way of comparison, my modest stick house uses about 20kWh per day in September.

I'm going with 6 @360 lbs. The Onan specified for my Big Sky is 290 lbs. and 5.5 kW. It can deliver a whopping 132 kWh per day (5.5x24). Of course it can run air conditioner(s)all day and night but my thinking is that if I'm doing that, I'm in the wrong place. I'll burn diesel and climb up to September conditions before I'll burn that much propane with earplugs on.

I've measured all my toys that I plan to run while boondocked and it comes to less than 1800 watt-hours per day. Measure all your toys in terms of their watt-hour consumption. Don't be scared by appliance labels. My biggest instantaneous load is probably a toaster at 1000 watts but it only runs for 5 minutes so its consumption is (1000/12) 83 watt-hours. 1000 watts sounds scary enough but if you keep all of your planning in terms of watt-hours you'll be amazed at how little you really need.

Last but not least... If you read this because you saw the tag line 'a few points about batteries', my sincerest apologies are offered. I have a tendency to run on about things. My DW has been known to go comatose during my usual 'explanations'.
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Old 10-02-2009, 02:36 PM   #19
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I am the said DW and I would have to concur,,,,he does tend to go way to technical for my taste, and I do tend to blackout!!!! I keep telling him it's because he's an engineer....always makes it too complicated for me!

So when I am having trouble getting to sleep I just ask him to explain something and that takes care of the problem! HA!

bahljavascript:insertsmilie('')inout2
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Old 10-02-2009, 02:45 PM   #20
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Great post.
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