House Battery

[joelc]

I am looking for a battery for my fifth wheel. I guess it is called a "house battery". For the purpose of running my 12V system in the event power fails or for not being connected to a post. My primary question is what battery group do you have, and my other question is what brand of battery do you have. I will have a single 12V deep cycle battery. One store recommended a group 24 and another tore recommended a group 31 battery.

[joelc]

These are all 12V Deep Cycle Batteries, not Marine STARTING Batteries. The Group 27 battery I found at O'Reilly's and the Group 31 at NAPA.

[wa8yxm]

Skibane wrote:

wa8yxm wrote:

joelc wrote:
I am thinking of getting 2 Group 27 battery, instead of 1 group 31. Does that make sense?

NO Two Group 27 is about 200 amp horus and perhaps 50 usable

If you're only getting 50 AH out of a 200 AH battery bank, you're doing something seriously wrong.

The life expectancy of a decent Group 27 deep-cycle battery doesn't really start falling off until you're regularly discharging it beyond 80 percent.

This includes good-quality trolling motor batteries.

For a 90 AH Group 27 battery, an 80 percent discharge would yield 72 AH - or 144 AH for a pair of them.

Compare that to a single 115 AH Group 31 deep-cycle battery - which would supply 92 AH when discharged 80 percent.

144 AH is more than 92 AH.

While your math is good your assumption is not
You do not discharge MARINE/deep cycle to 80% discharge
You want them 75-80% FULL. this gives you only at most 25% of the capacity to use.... With full Starting batteries the minimum is 80% State of CHARGE or 20% of capacity and you really should not go that low

DEEP CYCLE like Golf Car batteries can go to 50% and LI to about 5% (or less) but most of your 12 volt GROUP XX types should be kept to 75% or more STATE OF CHARGE. not discharge but CHARGE.

The other thing is with Lead Acids voltage reduces with state of charge. With LI types... not so much...(I have a small LI I use for a radio. it hangs in there till it is gone and that radio really likes over 13 volts (does not work well on 12.6)

[Skibane]

wa8yxm wrote:

joelc wrote:
I am thinking of getting 2 Group 27 battery, instead of 1 group 31. Does that make sense?

NO Two Group 27 is about 200 amp horus and perhaps 50 usable

If you're only getting 50 AH out of a 200 AH battery bank, you're doing something seriously wrong.

The life expectancy of a decent Group 27 deep-cycle battery doesn't really start falling off until you're regularly discharging it beyond 80 percent.

This includes good-quality trolling motor batteries.

For a 90 AH Group 27 battery, an 80 percent discharge would yield 72 AH - or 144 AH for a pair of them.

Compare that to a single 115 AH Group 31 deep-cycle battery - which would supply 92 AH when discharged 80 percent.

144 AH is more than 92 AH.

[wa8yxm]

joelc wrote:
I am thinking of getting 2 Group 27 battery, instead of 1 group 31. Does that make sense?

NO Two Group 27 is about 200 amp horus and perhaps 50 usable
Two GC-2 is 210-230 amp hours. a bit taller but not as wide and you can use fully half of that power without seriously harming the batteries. Nearly twice the power.. but less price.. Only you do need to add distilled water from time to time.

That is,,,, unless you can find TRUE DEEP CYCLE Group 27s. (they do exist but hard to find and often expensive)

GC-2's are a bit taller. you might need a different battery box but that's one time. Consider them..

Another thing. battery weight = Capacity that is the heavier the more power it holds.. Battery TYPE (Starting, MARINE/deep cycle or True DEEP CYCLE) how much of that power you can use (MARINE/Deep cycle Sometimes called RV/deep cycle or MARINE/RV are really starting batteries first and deep cycle.. not so much) True Deep cycle you can use half the stored power before rapid aging sets in and .... What's more... they stand a better chance of recovery from an OH C**P level discharge (So long as you don't leave 'em there for days on end)

Starting batteries general do not recover from that kind of thing

[joelc]

I am thinking of getting 2 Group 27 battery, instead of 1 group 31. Does that make sense?

[Ray_IN]

Consider being without power all night during cold weather. A gp 31 12v deep cycle battery probably will last one night just running the furnace, nothing else. When you lose power put the fridge and water heater on propane immediately to save the single battery for keeping warm.

[joelc]

Thank you all for your input. All was very helpful. I will review several times and go on from there. We are Full-timers who have our 5er on our own lot and are stationary most of the time. Occasionally, we go out to volunteer. Thanks again.

[pianotuna]

Remember you don't need the complications of an Li battery. Just buy a drop in an SiO2.

[theoldwizard1]

pianotuna wrote:
Hi,

If you plan to boondock without shore power then buy the biggest meanest deep cycle battery that will fit.

Remember, dual purpose Marine/RV batteries are a COMPROMISE !

Golf cart batteries or LiFePO4 are true deep discharge.

[pianotuna]

Hi,

If you plan to boondock without shore power then buy the biggest meanest deep cycle battery that will fit.

If you are always on shore power, any battery will "fill the bill".

[Super_Dave]

MFL wrote:
A bigger battery group 31, or 27, likely better choice, than 24, depending on length of time not connected. If just a short term power disruption, a 24 will serve you without issue. I like the Interstate brand, but most brands will do the job, if fresh to start with, and properly maintained.

Jerry

Joel, I believe that Jerry has given you the best advice. It doesn't sound like you plan on boondocking or camping without hookups and just want 12v power when traveling or not connected. If you plan on going with just one battery, I think that I would choose a 27.

[2112]

Not only is a group 31 larger, it's also heavier. It's difficult for me to get my 31 out of the basement. I don't want to do that again.

I've had good luck with a single group 27 Wal-Mart 27DC for $80. I get 5 years out of one with proper maintenance. We will sometimes overnight without power and this has served us well. We can watch satellite TV for hours on a 100W inverter and run the furnace for a few hours if needed.

Your best battery selection really depends on your expectations and how you plan on using it. Do you want it to power your propane fridge and lights for a few days or run your microwave?

Battery maintenance is an important part of how well your battery performs. My WFCO charger will kill my battery if I let it.

[theoldwizard1]

If you have the room, two 6V golf cart batteries, wired in series, is your best bet. The size is GC2.

The best brand is either Trojan or Rolls. These are expensive but top of the line !

Costco sells Interstate and Sam's club sells Duracell. Very good quality at very reasonable price. You can actually buy 2 of them about 50% more than 1 dual purpose/marine/RV battery. Two 6V batteries would store a lot more power than one 12V battery.

[Skibane]

MFL wrote:
A bigger battery group 31, or 27, likely better choice

Yes, assuming those bigger batteries will fit in your particular battery compartment.

Be sure to measure your battery compartment before buying a larger battery.

Here's a link that shows the typical dimensions of various battery group numbers.

(Note that these are TYPICAL sizes - there is some variation among different brands.)

[wa8yxm]

Ok my standard battery post (I need to save it to documents/boiler plate
Batteries come in several differnet types
Most trailers are set up to us a SINGLE 12 volt battery Often a Group 27 or 29
These are about 100 amp hours (Less or more respective) and are usually MARINE/rv or MARINE/deep cycle meaning you can use about 25 of those amp hours (same less/more) Not your best choice. Group 31 is about 130 AH and again you can use about 1/4

Using more than that "Ages" the battery rapidly.

If you can fit them a PAIR of GC2 Golf car batteries (About the same "Footprint" as a group 24 but taller) These are 6 volt which you wire like this -6V+==-^6V+==12 volt to rev (the = is a wire) around 220 amp ours more or less depending on specific version and brand (210-230 is common) and you can use fully half. that's 4 times what a single Group 29 gives you.

Now in addition to the above the batteries come in 3 different types.

True DEEP CYCLE GC-2 Golf Car batteries are often flooded wet cell. This means you add a bit of distilled water from time to time to fill them up to 1/8" or so BELOW the bottom of the filler tube. you also need to frequently clean.> Go with monthly checking of fluid level at first. And quarterly once you find out how often to add. As they age they need more frequent watering.

Maintenance free. or Sealed Valve Regulated Lead Acid. you do not add water or anything else. Most MARINE/rv or MARINE/deep cycle are of these type. they are NOT maintenance free as you need to clean (NOTE Starting batteries not otherwise discussed are also often this type(

AGM.. A sub set of Maintence free "Absorption Glass Mat" is a "Starved electrolytic" Basicaly a moist fiberglass cloth replaces the liquid so if you have to mount 'em upside down or on end or side. No problem. These are also physically rugged and able to take serious abuse

Optima.. A sub set of AGM. spiral plates so only about 60% of the capacity of the same size flat plate battery.

Cost generally increases as you go down the list.

Finally there are some new formulations like LiFePO4 (Lithium Iron Phosphate)

Right now these are most expensive of the list but the price is in free fall. If you go with one I'd recommend either Battler Born or Bioenno power. A well designed LiFePO4 battery has a battery management (Charge controller) Built in
Bioenno (NOTE I may have flubbed the spelling) does not recommend using multiple in parallel (I have one small one) Battle Born does so if you plan on multiple go with them.

Now.. with These you can use over 90% of the battery (Like 99%) and unlike the lead acid the voltage remains near constant during discharge. They do run a bit "hotter" (Higher voltage) Battle Born has a "Deal" with Progressive dynamics to provide a converter matched to their product.

Some modern converters and inverter/chargers (I have one of those) can be "Adjusted" to match the product.

So far I like my LiFePO4.. NOTE: There are muliple Lithium formulations. some tend to "Flame on" (Catch fire due to thermal runaway) LiFePO4 is far less likely and the Battery Management system helps to prevent it. HOWEVER they don't like COLD weather either.. Where as a good Lead Acid can go 10-20-30 or more BELOW zero (F or C don't matter) Lithium's like to be above freezing for proper operation or so I'm told (have not tested, I bring my small one in for charging)

Hope this helps and good luck

Those battery systems sound like a good deal but not a lot of "Juice" in a single battery.



And now it's a boilerplate to save me typing.