Best battery for our needs?

[DavidJ]

We are heading down south this winter for 3 months. Sometimes we will boondock but I am afraid my 12 volt battery is weak. 4 years old.

What is the best battery to buy for our use? A budget of $150 or less?

My research tells me the RC (Reserve Charge) is the most important rating for an RV. The number of minutes a fully charged battery will discharge 25 amps until the battery drops below 10.5 volts.

It should not need much for CCA (Cold cranking amps), it just needs to last long on a charge.

I have found the Interstate SRM-31 to have an RC of 210, for around $140.

Any other recommendations are should I be paying attention to other ratings of the battery?

Thanks

[TitanMike]

if you are conservative in your use of electricity when boondocking this battery will serve you well. You will need a means of recharging it if you plan on more then one or two nights in warm weather where the furnace doesn't have to run regularly through the night.

I've used a similar battery in the past and it lasted me as long as a week but all it did was keep the refrigerator control board powered, some use of the water pump, and a light or two at night just before bedtime.

FWIW, you can do better on price at O'Reilly Auto Parts stores. The same battery with different name is only $96. Their 31 DCMJ is a Deep Cycle marine (not starting) battery made by Johnson Controls. Same mfr as Interstate's.

[Theo]

I suspect you'll get a lot of recommendations against a battery which may be designed for an automobile. Most folks look for "deep-cycle" flooded lead acid (FLA) batteries.

I'd look for a 12V or (2) 6v batteries that are designed for deep cycle use (RV or golf cart). I went with (2) 6V Duracell 6V batteries from Batteries Plus and paid just over $200 for 215 Ah of capacity.

Remember, with FLA batteries, you risk battery damage if you draw down more that 50% of battery capacity. The Interstate SRM-31 has a rated capacity of 98 Ah. Therefore, you only have 49 Ah of capacity that can be used without damaging the battery. For most 12V FLA batteries, the 50% level of capacity will read roughly about 12.1V. Dropping the battery to 10.5V is asking for trouble.

[TitanMike]

Originally Posted by Theo

I suspect you'll get a lot of recommendations against a battery which may be designed for an automobile. Most folks look for "deep-cycle" flooded lead acid (FLA) batteries.

I'd look for a 12V or (2) 6v batteries that are designed for deep cycle use (RV or golf cart). I went with (2) 6V Duracell 6V batteries from Batteries Plus and paid just over $200 for 215 Ah of capacity.

Remember, with FLA batteries, you risk battery damage if you draw down more that 50% of battery capacity. The Interstate SRM-31 has a rated capacity of 98 Ah. Therefore, you only have 49 Ah of capacity that can be used without damaging the battery. For most 12V FLA batteries, the 50% level of capacity will read roughly about 12.1V. Dropping the battery to 10.5V is asking for trouble.

All of what you say is true however two points in the OP's post.

#1 ----- Budget $150 or less.

#2 ------ His original battery which was probably smaller than the one he's considering as a replacement has lasted 4 years. This would indicate that his needs are a lot less than those of a hard core boondocker.

A note on the "50% rule". Yes, discharging below 50% will reduce the number of cycles the battery will last. A battery only discharged to this depth will give a good balance between usable power and number of cycles but just discharging below 50% will not "Destroy" the battery. If it's recharged as soon as possible you may be looking at the difference between 500 cycles and 300 cycles (varies greatly among battery types, sizes, and mfrs).

Like I mentioned earlier, the OP's battery lasted 4 years. Not bad for a single battery.

[Theo]

Noted, TMike!

He is not putting much demand on the battery. And, I know his budget is <= $150, but for another $50, he could get (2) 6V (if the space is available) and more than double his Ah.

FWIW - My opinion is that reducing available cycles by 40% IS “damaging” the battery. Just my 2 cents.

[RMWSierra]

Originally Posted by Theo

Noted, TMike!

He is not putting much demand on the battery. And, I know his budget is <= $150, but for another $50, he could get (2) 6V (if the space is available) and more than double his Ah.

FWIW - My opinion is that reducing available cycles by 40% IS “damaging” the battery. Just my 2 cents.

Need to be sure the converter is compatible for charging and maintaining a system with 6 volt batteries.

[PSU Turf]

Originally Posted by rmwmiata

Need to be sure the converter is compatible for charging and maintaining a system with 6 volt batteries.

The charger sees (2) 6 volt batteries, wired in series, as a 12 volt battery.

[bikendan]

My vote is for two 6v golf cart batteries.
The OP's Rockwood has a converter capable of charging two 6v golf cart batteries in series.
It'll cost more than $150 but you'll be be able to dry camp or boondock much easier.

[boondocking]

If you have the room for two 6v go for it and not have to buy batteries again for maybe 10 years. My pair of sixes are 8 years old and still going strong and I boondock 99% of the time so they get a good workout.

[camaraderie]

DavidJ...you should be looking for a TRUE deep cycle battery and a 20hr. amp hour rating...NOT an RC rating.
My suggestion is get the biggest wet cell deep cycle battery you can afford and fit in place. That usual means a group 31...but if you need smaller then a group 27 or group 24 are also viable but with fewer options.
Any advertising on the side of the battery referring to starting or cold cranking amps is a dead giveaway that you are looking at the wrong kind of battery.
FWIW...a Crown Group 27 deep cycle wet cell will run around $140.

[bareftn]

go to a interstate battery disturber and get whats called a blem battery for 40 bucks
a blem battery is one that was on the shelf for 1 year and not sold and they go back to the disturber I get them all the time for all my battery needs from car to boat to tractor
a 5 year batter for 40 bucks not bad and they even have deep cycle and motor cycle batts

[lswartz]

Originally Posted by bareftn

go to a interstate battery disturber and get whats called a blem battery for 40 bucks
a blem battery is one that was on the shelf for 1 year and not sold and they go back to the disturber I get them all the time for all my battery needs from car to boat to tractor
a 5 year batter for 40 bucks not bad and they even have deep cycle and motor cycle batts

Nice advice, I didn’t know about this as an option. Thanks.

I was going to suggest just waiting until you need a new battery. There is always a Sam’s Club or Walmart nearby. A $40 battery is really hard to beat. Think I would try that if a dealer is local.

[DavidJ]

Thanks everyone for all the great answers and opinions.

I will stick with one 12 volt battery. High on the Amp hour and RC side.

People have been noting that I should not run the battery down past 50%. What is a good meet to show me when I am at that level of storage left?

[SlowrideHD]

Originally Posted by DavidJ

Thanks everyone for all the great answers and opinions.

I will stick with one 12 volt battery. High on the Amp hour and RC side.

People have been noting that I should not run the battery down past 50%. What is a good meet to show me when I am at that level of storage left?

Any decent volt meter or multi-meter that you can pick up fairly cheap at any big box store such as Lowes or Home Depot will show accurate enough voltage at your battery.
Ideally, you don't want to pull your voltage level below 12.05-12.1 volts. This is generally accepted as 50% discharged. Repeated cycles below this will tend to shorten useful battery life.

[camaraderie]

The 12.1 or 12.2 recommendation corresponds to 50% discharge level in a battery that has been DISCONNECTED from service or charging for 24 hours.
It does NOT apply to a battery in use.
That said...if you are only going to boondock once in a great while...a reading IN USE down to 11.8 won't do any harm as long as you FULLY recharge the battery to 100% (6 hours!) as soon as possible.
If you are going to boondock more frequently...find another $150 bucks and get a REAL battery monitor like the Victron to measure actual state of charge and many other useful things. Search Victron for numerous threads on this product.

[TitanMike]

Not to discount any of the advice others have given regarding different batteries, multi-meters, and battery monitors, note that the OP has already received 4 years of service from his original battery and only "thinks" it is now going bad.

All the "upgrades" are great if one is a hard core boondocker but for one who only needs a battery for the one night here and there they might spend using the battery while enroute to their fhu destination, believe it or not the OE LED battery "monitor" is probably all he needs.

I'm guessing the OP has relied on this for the first four years and it should be enough to let him know when he's reached the 50% point of discharge or as they say, close enough. Key to making it work is to only check battery with no load and it has had some "resting time".

Before battery monitors became readily available I relied on my LED Christmas tree and checked battery first thing in the morning after it had rested overnight. Back then I didn't have to run the furnace at night as I was only able to camp during warmer months. I averaged 6-7 years on a battery and marine deep cycles at that.

As for a Multi-meter? As far as I'm concerned it's an essential tool for any RV. First tool I grab if I have an electrical issue. Don't start working on any electrical device until I've done my basic "power checks" starting with the power source (12 V or 120 VAC). Amazing how much work it saves me when I find that a GFCI has tripped, a fuse has blown, or a wire connection has become loose.

[Dave Lyon]

Originally Posted by DavidJ

Thanks everyone for all the great answers and opinions.

I will stick with one 12 volt battery. High on the Amp hour and RC side.

People have been noting that I should not run the battery down past 50%. What is a good meet to show me when I am at that level of storage left?

As you noted in your first thread Reserve Minutes is king. You will want a true deep cycle, not a marine or dual purpose, but deep cycle. I bought a Deka DC 31 4 years ago and have been happy with it. Its a dual post deep cycle group 31 flooded battery.

my two cents.

[frank4711]

Question while ya'll are helping ... we never boondock ... any need for any upgrade my camper is new 2020 ... Thanks Frank

[SlowrideHD]

Originally Posted by camaraderie

The 12.1 or 12.2 recommendation corresponds to 50% discharge level in a battery that has been DISCONNECTED from service or charging for 24 hours.
It does NOT apply to a battery in use.
That said...if you are only going to boondock once in a great while...a reading IN USE down to 11.8 won't do any harm as long as you FULLY recharge the battery to 100% (6 hours!) as soon as possible.

I don't agree with this statement, having read numerous articles from battery experts that mention not pulling batteries down "in use" below 12.1 volts, or 50%.

Note this reply from "battery stuff tech" that is answering a question from an electric wheel chair user that has had poor performance from battery packs due to excessive rates of discharge.....

quote..BatteryStuff Tech I would definitely not leave the batteries sitting in a discharged state, plus it is never recommended to discharge a battery more than 50% so if your 5 mile run does this then that could be affecting the batteries life. If you are not running them below 50% (12.1 volts) then I would look to the charger... unquote

[dward51]

If you can make them fit, a pair of 6v golf cart batteries is hands down the way to go. Very good reserve capacity and they are made to take a beating and be discharged deeper than a "regular" flooded or wet cell deep cycles.

If size is a problem, then the largest size AGM battery you can fit would be the 2nd choice. Reason is AGM's are less forgiving than flooded/wet cell lead acid batteries for deep discharge. Lead acid is 50% discharge, but AGM's can be taken down to 80% discharge (80% discharge is not 6v, but 80% of the amperage capacity which is a little below 12v). They also are sealed, and you don't have to check or worry about the water level. A group 31 AGM would be right at your price limit or slightly above (Sam's Club sells the Duracell AGM's which are made by East Penn Mfg, the same people who make Deka batteries). Sam's and Walmart had the best price around here, but Cabelas and Bass Pro sometimes run theirs on sale also.

AGM or a pair of golf cart batteries would also charge just fine from most converter/chargers, but check the info for your specific model. The Progressive models do not require any special settings and are perfect if you have one of those already.

One side note, if you have more than one battery currently, AGM's should *NOT* be mixed with other types on the same charging circuit. So if you have 2 batteries, they both need to be the same chemistry (AGM, flooded lead acid, etc...).