12v to 6v house battery conversion

[pasdad1]

Originally Posted by sknight

I have a question. I keep reading that two 6V in series doesn't multiply the ah, just the volts..

Maybe this helps.... In simple terminology....

Amp hours is not a unit of "work"

Amps x volts = watts Watts is a unit of how much "work" can be done with the electricity.

Double the volts, and you double the watts.

220 amps x 6 volts = 1320 watts
220 amps x 12 volts = 2640 watts

So the two 6 volt batteries still have the combined ability to produce 220 amps for a duration of one hour....... ( not exactly accurate, but good enough for this discussion)
It's when you double the voltage that you can produce more watts from this amperage.

Make more sense now

[Dr4Film]

Originally Posted by sknight

I have a question. I keep reading that two 6V in series doesn't multiply the ah, just the volts.

How is this?

Can anyone explain to me how this halving of available ah happens? Between it not seeming logical to me plus the reports of people experiencing far greater practical capacity I'm thinking that there's something getting lost in translation.

The formula you are missing is WATTS = AMPS X VOLTS.

This is a measure of power. It works for 6 VDC, 12 VDC, 24 VDC, 36 VDC , 120 VAC and 240 VAC.

So, when you take two 6 VDC batteries to make one 12 VDC battery, since VOLTS in the formula has now changed, WATTS and AMPS have to remain the same.

2700 = 12 X 225 with one 12 VDC Battery

2700 = (6 + 6) X 225 with two 6 VDC Batteries

If you had a 6 VDC coach system then wiring them in parallel would increase the AH's for each battery BUT your coach is NOT a 6 VDC system.

I hope this helps.

Dr4Film ----- Richard

[sknight]

Originally Posted by pasdad1

220 amps x 6 volts = 1320 watts
220 amps x 12 volts = 2640 watts

Now it does.

I had worked the math on watts, but was still stuck on ah. This in writing, plus my taking it further down to watts per cell (1320/3=440 watts per cell) then multiplying back up showed that it actually intersects mathematically at each step voltage wise.

Thanks!

[charles tuit]

I altered my slide out tray to accommodate 4 each golf cart 6V batteries. Measure, measure, measure to assure you have enough clearance on sides, width, and height. On my Journey I had to increase the width 1" to have enough room for the 4 golf carts. Using a air powered cut off tool from Harbor Fr. I slit the slide out tray in half. I then bolted 2 each, 1 in front, 1 in back of 1/4 X 3/4" steel stock (the black bars in pics). Had to slot the square chassis to tray carriage bolt holes to line up with the additional width. I had just enough flange on the slide to bolt the carriage bolts back on to the chassis.

If you have any further questions PM me for additional info.

[az bound]

Originally Posted by DonKarstedt

chboone is right, if the battery has "marine" in the name, avoid it. It's not a real deep cycle.

--DonK

Not true !!
There are "true" marine deep cycle batteries, been using them for over 20 years in my boat.
There are marine deep cycle/ starting batteries which are a hybrid, which are used to start the engine and run small trolling motors or electronics.
Examples; Trojans SCS series is deep cycle. BCI series is deep cycle/starting.

[Sherpatt]

We have a new to us 2008 Four Winds Majestic 28a. I want to modify the coach battery storage to a sliding tray capable of holding up to 4 6v batteries. The current tray holds one 12v class 31 battery lengthwise across the MH beam. I have measured and there is up to 28" in width, 17" depth, and more than adequate height. Has anyone done a similar mod to this specific MH? Which sliding tray will fit and support the weight? How did you attach the new fabricated support system that holds the sliding tray? Where did you install the inverter? Thanks for the help!

[pasdad1]

Originally Posted by az bound

Not true !!
There are "true" marine deep cycle batteries, been using them for over 20 years in my boat.
There are marine deep cycle/ starting batteries which are a hybrid, which are used to start the engine and run small trolling motors or electronics.
Examples; Trojans SCS series is deep cycle. BCI series is deep cycle/starting.

The goal was to make it easier for less "techie" people to make the right choice.


Look at the battery itself...... The SCS150 does not have the word "marine" on it.
so the advice is still sound.

Batteries which have the word "marine" clearly on the battery case, are 99% not the
true deep cycle design. The wording is a marketing trick to make the battery appeal
to a broader audience IMHO

[az bound]

Not to start an argument here, but I have never seen a Trojan battery that has RV it on either.
The point was there is a difference between a deep cycle and a deepcycle/starting battery. Thats all.

[pasdad1]

Originally Posted by az bound

Not to start an argument here, but I have never seen a Trojan battery that has RV it on either.
The point was there is a difference between a deep cycle and a deepcycle/starting battery. Thats all.

The simple "rule of thumb" was .....if the battery said the word "marine" on it
then avoid that one.

See...? simple for non-techie people to understand.

[az bound]

Originally Posted by pasdad1

The simple "rule of thumb" was .....if the battery said the word "marine" on it
then avoid that one.

See...? simple for non-techie people to understand.

Why?

[pasdad1]

Originally Posted by az bound

Why?

Because it is most likely a hybrid deep-cycle starting battery

Or a low quality battery being marketed as "deep cycle" but
without the quality internal construction that gives it high cycle life.

[wa8yxm]

Originally Posted by bamaboy473

for those of us that follow threads just to gain knowledge, what benefit is served by going from 12V to 6V?

More "Bang for your buck" the most common six volt pair is 220-230 amp hours, The batteries compare in price to Group 24 12 volt which woudl be 150 amp hours for two, So you can see a big benefit there.. PLUS the Golf Car batteries are DEEP CYCLE, designed to go to half full (if promptly recharged) often where as the most common 12 volt RV battery is a Marine/Deep cycle, 50 percent state of charge is something that will do much more damage to them than to a DEEP CYCLE so they end up lasting longer in many cases. So it is Maximum Bang for Buck.

NOTE: you can get 12 volt DEEP CYCLE (no marine) but $$$$$

6V golf cart batteries weigh a ton, so they must be even stouter than deep cycle marine batteries.

Yes they do but the pounds per amp hour is nearly identical for VERY Lead Acid battery, Starting, Marine/Deep cycle, DEEP CYCLE, Flooded wet, Maintenance free and AGM, all the same. or very close to it, so the heavier the battery,, The more amp hours.

I'm thinking that our house batteries ought to be deep cycle instead of starting batteries, so is the conversion just ramping up that concept to the max...or something else?

Yes, that is correct. Golf car are DEEP CYCLE, MARINE/deep cycle are.. not (note the case as I typed it.

[DonKarstedt]

A "Marine" battery is a hybrid of a deep cycle and a starting battery. They were original designed for boats, which need high cranking amps to start the boat, but also long continuous power for lights and trolling motors. Since they try to do two very different jobs at the same time, they do neither one extremely well.

--DonK

[doorguy]

tebethurm, I swapped my 3 12V's for 4 Coscto Golf Cart Batteries which were about $89 ea. I believe. A good post to view on this subject is from FIREUP who did the same thing and documented it well with write up and pics. I copied his installation.

Our son lives in Visalia, nice town, we visit quite often.

[doorguy]

Not sure my post went thru just now, so will try again. tbethurum, I swapped my 3 12V for 4 Costco 6V Golf Cart batteries at about $89 a pop. Look up the post by FIREUP on this subject, he did an excellent job with description and pics.

Our son lives in Visalia, nice town, we visit often.

[sknight]

Well, just got back from eight awesome days boondocking and will say this. I use a cpap machine at night, plus was a little happy with the inverter a couple of rainy nights watching a movie on the TV.

I have four 6V ACDelco golf cart batteries, series/parallel of course, going through a two way switch so I could split the pairs if that need ever arose (One battery failed, I kill one set flat and don't want to work my truck alternator that hard, etc.) with polished connections.

The display panel showed 2/3 battery state, which was around 12.31V, every morning. That was simply great, worked better than expected actually.

I had my generator with me and tried to adhere to the two hour max run time, I'd fire it at about 10:00AM, let it run until lunch time or so and shut it down. Six+ hours later when most of the top up charge had dissipated they would show 12.65V to 12.70V, right at 100%. Again, much better than expected, they recovered very quickly on a charge.

My converter (65 amp) worked great with them. To bring them fully back in two hours was really impressive.

So I'd call it a complete success and I highly recommend it. I've been in somewhat similar situations with three 12V batteries and didn't have that kind of success, no where close. Frankly, by mid week, it made me a little lazy and if I wanted to watch a movie with dinner, I'd watch a movie knowing I'd be fine.

I'm very happy with this and frankly can't see me ever going back. If I get the reported service life I'll be even happier!

[Dr4Film]

Now there is one very Happy Camper with a success story.

Glad that it worked out for you.

Dr4Film ----- Richard

[Ray,IN]

I've never considered downgrading to 6V batteries. I have 3 Exide 12V batteries, each with 200AH. That gives me 300AH available if I adhere to the 50% rule. I couldn't get the taller 6V batteries in the space anyway.

[pasdad1]

Originally Posted by Ray,IN

I've never considered downgrading to 6V batteries. I have 3 Exide 12V batteries, each with 200AH. That gives me 300AH available if I adhere to the 50% rule. I couldn't get the taller 6V batteries in the space anyway.

Wow, the only 12v batteries I've seen that are 200AH are the 8D size which are HUGE.

[az bound]

I upgraded to 3 8D 12 volt Concord marine deep cycle AGM batteries which are 255 AH each giving me 765 AH total. They are "true deep cycle" batteries.