How many amp hours do I need?

[MilesAndSmiles]

We just brought home our "new to us" 2004 Southwind 37A, and the house batteries won't hold a charge. No surprise. So, I'm shopping for batteries.  Batteries+ has several different 6v Deep Cycle Duracell batteries: 230AH for $102, 235AH for $130, and 255 for $195. 

We do expect to boondock, but I don't know how to figure if the higher price-point is worth it for the greater amp hours.

I'm a complete newbie... so any advice will be greatly appreciated. My battery compartment can hold two, which I'll wire in series.

Jeff

[GaPete]

You need to do some research on how to hook up batteries before installing new ones. To connect in series, they must be 6V If you are getting 12V they need to be in parallel.

[dartmouth01]

It would be best if you can take an energy audit of your normal daily routine.  One way to do this would be to use an energy meter like the Kill-a-watt plugged between the shore power and your rig.  From there, you'll get an understanding of how much you'll use on a daily basis, and what capacity you'll need (which will be different if you have solar, plan to run the genny each day, etc).  For us, we have 2 6V Costco batteries which I think are equivalent to the cheapest Batteries+ version.  We have 200W of solar, and if we use battery in the evening, we'll generally be around 85% battery (depends on if we run the propane heater at night) by the morning, and the 200W of solar will recharge the batteries to 100%, IF we leave the rig during the day and do things.  If we are working in the RV on our computers and monitors and such, we basically make enough power through solar to just power everything we are using.  So, we aren't charging the battery, so I need to run the genny for a few hours to get back to 100% on days like this.

[MrSeas]

Check the space available for the batteries....height, width, and depth and get the battery that best fits the space and your pocket book.

[MilesAndSmiles]

42 minutes ago, dartmouth01 said:

 For us, we have 2 6V Costco batteries which I think are equivalent to the cheapest Batteries+ version.  

I just went to our local Costco and they no longer carry 6v batteries. They even checked with all of the other local stores. Thanks for sharing your experience... that helps me get a sense of at least one couple and your real world energy usage. Very helpful.

[dartmouth01]

Bummer that Costco is not carrying the 6V Everstarts.  They were a steal at $85 each.  Try Sams Club, maybe worth buying a membership to get them if you don't have one already.  I think they carry Duracell branded one, though brand names don't mean alot, all golf cart batteries are only made by a couple manufacturers I've heard.  

We aren't shy about using power even when boondocking (2 laptops, 1 monitor which sucks alot of juice, multiple hotspots, cell boosters, etc, wife likes a warm rig, etc), but we also try to be efficient.  LED lights are the best upgrade if you don't have them already, a single bulb replacement can save you 5A per hour.  We have a Trimetric meter, which reads how much power we are using from the batteries (or putting back in), and what the state of charge of the battery is, even under load.  It is worth its weight in gold when trying to boondock.

 

[Chad Heiser]

If you only have room for two batteries in your rig and you plan to do any type of boon docking, I would go with the highest amp hour rated batteries you can fit in your battery compartment.  When it comes to battery capacity and boondocking, in most cases, more is better (especially when limited to two physical batteries).  Adding solar down the road will assist in recharging the batteries and lessen generator run time.  Additionally, if you do not already have one, a good battery monitor like a Trimetric (as suggested above) is highly recommended.  This way you can know exactly what the state of your batteries is at any given time.  Other upgrades, like LED lights, will also really help reduce battery consumption.

[Yarome]

7 hours ago, Chad Heiser said:

Additionally, if you do not already have one, a good battery monitor like a Trimetric (as suggested above) is highly recommended.

X2. If you plan on doing a bit of dry camping a decent battery monitor is almost a must have. You "can" get by with a voltmeter, but most folks aren't likely to drag it out to check their batteries as often as they really should. As for the kill-a-watt meter... I would really hesitate to plug that in to your shore power. It's only rated for  1850v's (~15amps) so even with a 30amp rig you might get more than you bargained for. It's great for checking individual 120v loads, but it wasn't intended for that heavy of a load. Without a dedicated battery monitor, checking your batteries with a voltmeter would be preferrable.

When sizing your battery bank remember that for wet cells, you don't want to discharge them beyond 50% to keep them healthy. Lower discharge rates are preferrable, but even with a 250ah bank, only 125amps are "available". Unless I was strapped for room, had weight concerns or was too long between charges the 255ah batteries you mentioned would be more than I would want to spend for the relatively small gain in available juice. It's not terribly difficult to live within your "budget" if you don't stay unhooked for more than a couple of days... or have a generator on board to refill your battery bank. Obviously.. you wouldn't be able to run your microwave or a space heater for long, but it's not a great hardship.

Costo and Sam's.. that's a regional issue. Not all markets will carry 6v deep cycles. For that matter... buying a 6v GC in one Costo/Sam's doesn't necessarily mean you are buying the same same battery in another geographical location.

Buy in complete sets of the same manufacturer and age rather than adding to your battery bank over time. With a bit of searching average power consumption of various devices is readily available on the internet. It will get you in the ballpark.

Don't forget to allow for approximate 24-36ah's of usage in a 24 hour period for inherent "overhead".. or "phantom draw".

For heavier/more freqent longer term dry camping, a portable inverter generator is a worthwhile investment. Even if you plan on installing solar.. a generator is your best first purchase, IMHO. 

[oldjohnt]

FWIW here's my take. If you consider 230 AH for $102 versus 255 AH for $195, that's like almost double (another $93) for a measly more 25 AH !!!!!!!!!!!!  NOT WORTH IT IN MY MONEY.

This assumes and takes you at your word THERES ONLY ROOM FOR TWO BATTERIES, because if you're gonna do much dry camping at all Id sure consider the use of four taking you up to 460 Amp Hours. I'm talkin flooded lead acid here not AGM etc.

Another consideration, if you were using say the classic Trojan T-105 (225 AH) one advantage is that battery is sooooooooo universal and readily available at soooooooooo many places UNLIKE if you chose their higher AH units which may have to be special ordered and hardly anyone stocks them. In the wet flooded lead acid market I like Trojan and have heard good things about Crown but Interstate or NAPA or Costco or Sams may well be fine, its your money your choice NOT ours

As noted 50% discharge of that 230 AH (115) is the MAX Id advise while I don't like taking them down much over 30%.

I started with two 6 volt golf cart batteries and 200 solar watts and got by fairly well but if you dry camp often you may be bumping that up like I did. A modern so called "Smart" 3/4 stage charger as well as a "Smart" 3/4 stage Solar Charge Controller (if you go solar) can increase the battery life of that expensive battery investment.

John T

  

 

[sandsys]

On 4/19/2017 at 6:46 PM, MrSeas said:

Check the space available for the batteries....height, width, and depth and get the battery that best fits the space and your pocket book.

This. Not all battery compartments are equal.

Linda Sand

[Smitty77_7]

Enjoy your new rig!!!

>Yes to battery monitor addition in the future. (Moderate to heavy boon docking warrants this...)

>On battery capacity. Many, myself included, look at our RV's as a family emergency preparation expense - just as much as a get away and have escape sardine can:)! So for this reason, we added extra capacity to our house battery bank. (May not be important to you, as you and your family may have other preparations in place.). So I endorse the measuring of space available and sizing of the largest AH battery bank that you can fit into it. 

>That being said, you can go all the way from the best bang for the buck wet cells - all the way up to the latest lithium's. And all the way up, also includes a $$$$ higher cost increase along the way to. Even a jump to AGM's may cause a ripple effect of needing to enhanced your rigs charging unit. 

>Doing some reading on say Wet Cell vs AGM's will yield more opinions then you can fit onto a 99 Trillion Terabyte drive:)! But it will give you the Pro's and Con's of each. (We elected to go with AGM's for faster recharge times, no maintenance, and longer DOD Lifecycles then Wet Cells. (If all goes well, the Lifelines we bought will yield two-four years longer life then a Wet Cell, which will recoup some of the higher costs. (And yes, this is always another opportunity for conflicting opinions. As many who take proper care of their Wet Cells, get great battery life out of them too... But, it was the conclusion I came to after my research and our planned usage. And another side note on that longer life, is I double sized our battery bank from what I easily could have got by with. (Our audit showed 400AH's would support us well. I put in 800AH's. So I'm usually at above 70-75% SOC after a night of usage. And battery life is all about finite DOD Lifecycles - AH's out and AH's in:)!)). Doing your own research, and determining what is important to you in relation to life expectancy, power consumption balanced agains budget - is a decision only you can work through.

>Some battery ideas, in no particular order:

-If you have the head room, look at Trojan 125 and 145 wet cells. They cost more, but they also provide higher AH capacity, and are a well respected battery.

-AGM Fullriver are less expensive then Lifelines, and many RV'er's are happy with their performance. 

-Lifelines go up the price ladder, but also have had a longterm track record of good performance and life expectancy. 

====

And OP, as this is a new old rig to you. Go slow, get out and use it some to see what really is important to you. So maybe the easiest thing to do for now, would be to add the mentioned Costco and Same GC2 6V batteries - then go use the coach for awhile. If in a year you decide you want something else. Those batteries with a receipt showing purchase date, could be sold on Craigslists to recoup some of the expense...

Best to you, and enjoy the process,

Smitty

[kayakbob]

 Sams wholesale ?  Got my 4 Duracell there for $85 each , of course you may not want to drive to Florida to save a few bucks ?

[Cedrus]

You might consider using an outside compartment for four more 6v batteries.  Think you should find a dealer or mobile RV guy to install a slide-out tray and do the battery hook up for you.

Did not see what inverter-charger you now have.....