12volt vs. 6volt Batteries?

[Wingbl]

What are the pros and cons of installing 6volt batteries in your coach instead of the traditional 12 volt?

[nosticks]

A bank of well maintained wet cell 6v batteries will last for years and take severe deep discharges and bounce back. The typical wet cell 12v will not. Additionally, they provide more amp hours of use. That said, if don't boon dock, there is little benefit to the additional cost of converting to dual 6v batteries.

[wa8yxm]

I second what NoSticks says about last for years, With the addition of the phrase PROPERLY MAINTAINED,,, Mine are six and have been abused, and are suffereing, but many last 10 or more years. Do make sure you check the fluid (Acid) level and add distilled water as needed. Clean often.

MOST 12 volt batteries are "Marine/Deep Cycle" though you can, now, find true deep cycle (no Marine) 12 volt as well. they still cost more per amp hour due to the economy of scale (They make a whole LOT of six volt deep cycle GC-2 batteries,,, Golf courses buy 'em by the pallet load after all)

The Deep Cycle type do tend to bounce back from an "OH @#$!" Better than the Marine Deep Cycle (I should know.... Done the test on several sets myself, Never had a Starting battery live long after an "OH @#$!" and the deep cycles I'm running now have done that at last half a dozen times)

As for the "More amp hours" That kind of depends.

Group 24, 27 and 29. 2 of them have less total amp hours than a pair of GC-2
Group 31 (or larger) that is not the case ONE single 8-D is the equal of a pair of GC-2's both in amp hours and weight... But way more expensive.. You can get 8D in Deep cycle however.

[Ed-Sommers]

Actually, there are really no such thing as 6 volt battery in an RV. What you are doing is buying a 12 volt battery in two parts so as to be able to lift it without help. I suppose one could get a nice hefty forklift 12 volt battery if they really had to have a 12 volt battery in one case.

Ed

[mr300ce]

Quote:

Originally Posted by Ed-Sommers Actually, there are really no such thing as 6 volt battery in an RV. What you are doing is buying a 12 volt battery in two parts so as to be able to lift it without help. I suppose one could get a nice hefty forklift 12 volt battery if they really had to have a 12 volt battery in one case. Ed

Anyway..... Is it proper to 'keep' the coach batts charged all the time, (which is what I do now hooked to shore power)...or should you use them down to a certain voltage, like 10.5v, then charge them back up ???

For example....on my laptop, I ruined the batt because I left it hooked to the charger all the time. With new laptop, I use it daily with battery until the warning of low power signals me to plug it in to charger. I was told by tech that is what I should do to 'excersize' batt and it will last longer.

[Bob/Becky D - VA]

While not a "traditional" 12v, I have gone to AGMs as there is little maintenance, can be mounted in any position, good recovery from multiple discharges, can be charged much faster. The con is that they are expensive.

[450Donn]

Quote:

Originally Posted by mr300ce Anyway..... Is it proper to 'keep' the coach batts charged all the time, (which is what I do now hooked to shore power)...or should you use them down to a certain voltage, like 10.5v, then charge them back up ??? For example....on my laptop, I ruined the batt because I left it hooked to the charger all the time. With new laptop, I use it daily with battery until the warning of low power signals me to plug it in to charger. I was told by tech that is what I should do to 'excersize' batt and it will last longer.

You are far better leaving the batteries connected to the charger. Think of your converter (unless you have a really cheap one) as an automatic battery charger. It will sense when, and how much the batteries need, and maintain that level for you. Unplugged or sitting on the garage floor over the winter, the battery could discharge to a point of no return.

[BryanL]

If you want to look at reality rather than fantasy, the voltage of the batteries in an RV battery bank makes no significant difference in terms of capacity, longevity, or cycle depth capability or the other myth mongering seen above.

The facts are:

+ Battery capacity is simply a matter of weight. All lead acid batteries have about 12 usable watt hours per pound of energy capacity (50% DoD point - see smartgauge.com for the analysis of why).

+ Expected battery life for wet cells is 4 - 7 years (see the NAWS FAQ) if properly used and supported by effective charging and maintenance equipment.

+ All lead acid batteries suffer is discharged too far. Lab tests rate batteries as being able to handle between 200 to 800 discharges to 80% DoD. When you compare that to typical RV usage, you'll see that cycle life is not an issue.

Find batteries that fit the compartment you have and can be wired to provide the proper house voltage. Purchase from a retailer who sells a lot to folks that use batteries like you do and will stand behind what he sells. Then use specifications, cost, and warranty as your guide.

To get best performance, make sure you recharge your batteries promptly with a multiple stage battery charger and then keep them on a battery maintainer that maintains the full charge and applies a sulfation inhibiting technique when they are not in use.

[Dave78Chief]

Quote:

Originally Posted by mr300ce Anyway..... Is it proper to 'keep' the coach batts charged all the time, (which is what I do now hooked to shore power)...or should you use them down to a certain voltage, like 10.5v, then charge them back up ??? For example....on my laptop, I ruined the batt because I left it hooked to the charger all the time. With new laptop, I use it daily with battery until the warning of low power signals me to plug it in to charger. I was told by tech that is what I should do to 'excersize' batt and it will last longer.

Different type of battery composition (Nickel Cadmium, Nickel Metal Hydride, Lithium Ion). The charging requirements for those dry cell batteries are not the same as a lead acid wet cell battery.

Dave

[mhs4771]

Keep in mind, when using two 6 volt batteries you need to double the voltage (connected in series), thus the reserve capacity is equal to that of one battery (6 volt x 2 in series = 12 volts, reserve cap 210 = still 210). When using two 12 volt batteries you don't need to double the voltage (connected in parallel), thus you double the reserve capacity ( 12 volt x 2 in parallel = 12 volts, reserve cap 105 x 2 = 210) Wet cell batteries are made up of a series of 2 volt cells, thus a 6 volt has 3 cells, where a 12 volt has 6 cells. So for a 6 volt and 12 volt of equal size the plates in the 6 volt will be quite a bit larger generally giving a longer life span. Just some food for thought

[nosticks]

To the above quote, "If you want to look at reality rather than fantasy, the voltage of the batteries in an RV battery bank makes no significant difference in terms of capacity, longevity, or cycle depth capability or the other myth mongering seen above."

I can see that you have seldom, if ever, been without the electrical umbilical cord for any length of time. I have operated cruising boats for over 25 years and the typical use of those boats is to be on the hook, meaning at anchor, no electrical hook ups, and to operate refrigeration, cooling, ice making, lights, water pumps, television, stereo, bilge pumps, and communication equipment for days at a time between charges. Nothing, absolutely nothing, will take the abuse these batteries receive between charges, often to where the low voltage alarms are squealing, meaning less than 10.5 volts remaining on one of the selected dual 6v T-135 golf cart banks. They do this year in and year out and last for several years. It is the nature of the heavy plated golf cart batteries. They are designed to take that type of punishment, and they do. Yes they have multi step smart chargers to bring them back to life, and yes the water level needs constant attention.

The person who boon docks with their RV will operate very similar to the above described cycle. The thin plated sorry excuse for a deep cycle battery (marine 12v), will be toast trying to live a life like that. So as to the myth mongering, this is real life experience mongering.

Like I said originally, if you don't boon dock, don't go the the expense of multiple 6v banks.

[offthewall]

A lot of good information and a bit of bad. There is nothing inherently better about the construction, longevity, plate thickness, etc of a 6v vs. 12v that has anything to do with the voltage. There are deep cycle 12vs made to the same specs as 6v golf cart batteries, they just aren't as common and you'll have to look a little harder for them. That said, there is a distinct advantage of two or more batteries in series to two in parallel. With two 6 volts in series, the total voltage is additive. With 2 12vs in parallel, one low battery will dag the entire bank down to its lower voltage. As an extreme, unlikely example if you had two 6vs and one was at 3 volts, the entire bank would be putting out 9v. If you had two twelve volts and one was putting out 6v, the entire bank would be putting out 6 volts. If you had the room, the ultimate setup would be a bank of 6 2volt batteries in series to make one giant 12 v bank.

Also as others have pointed out, AGM batteries are the best money can buy. They are extremely expensive but require no maintenance, can be mounted in any orientation which often results in being able to cram the max aHs into a given space in your RV. If I had the room, I'd get a bank of six 2v Lifeline AGM's and the converter/charger to handle them.

[jim81147]

OTW , a question for you . Seeing that I know just about nothing about this subject can you explain this to me ? You say ........

As an extreme, unlikely example if you had two 6vs and one was at 3 volts, the entire bank would be putting out 9v. If you had two twelve volts and one was putting out 6v, the entire bank would be putting out 6 volts

While I understand the math , I dont understand what difference it makes. Both examples are putting out less than 12V so are either of these outputs usable? I could see in the 12V example where you could disconnect the bad battery and be back up to 12V , albeit at a less AH rating , but will 12V objects run on either 9 or 6 V ?

I am not sure whats more confusing , batteries or generators

[BryanL]

re: "I can see that you have seldom, if ever, been without the electrical umbilical cord for any length of time."

ad hominem and appeal to authority are both logical fallacies ... how about using relevant measures and taking on the issues raised in an honest fashion, instead?

I provided a set of facts, with references that could be followed to learn where they came from. A response that guesses at my characteristics and spouts authority does not address those facts nor help anyone learn anything on the topic at hand.

re: "I am not sure whats more confusing , batteries or generators " -- neither is really confusing as far as RV needs and uses goes until you get ex-submariners or others citing similar authority for tossing in irrelevant, misleading, or even incorrect information and using inappropriate units for power and energy and whatnot.

Trying to get around the cloud of crud is why I offered what I considered the crucial facts at issue and referred to some places that do a bit better at clarifying rather than obfuscating the issues.