batteries from big chain stores

mshen11 · September 2009

The big chains (Costco, BJs, Walmarts,...) sell battery. Its been mentioned BJs sell Energizer 6V golf cart batteries that seem to do pretty well (and cheap! - 65c/amphr @12V). what are some other brands for cheap you guys know of?

I was at Costco today and they have Kirkland 12V Dual Purpose Deep Cycle 27DC... 115 amp hrs for $85... thats 60c/amphr. the question is would this be a good battery to buy?

I've seen Walmart deep cycles that are around the same price per amp hr. I've heard they're ok but no experience.

Can people chime in on experiences with batteries at national chains - ie, good price, if the batteries are any good, warranty experiences (do batteries last that long), etc...?

BB. · September 2009

Re: batteries from big chain stores

Problem is that private labeled product can (and does) change manufactures--so even if the last one you buy worked great--the next one years later may not.

For Costco--years ago I had read that their batteries were made by Johnson Controls. Now--don't know. If you call them and get a hold of the buyer--they may tell you.

Also, regarding Costco, they have "Kirkland" AA and AAA batteries. They are "dirt cheap" and--it turns out--some of the best performing alkalines out there. And a few years ago, they changed vendors (old vendor was packed in "bricks" of batteries... New vendor is probably those in blister packs). The old vendor was the one with the great ratings... The new vendor was (according to lore) picked when the old vendor could not improve their batteries to new requirements (or maybe quality/cost requirements--who knows).

-Bill

mike95490 · September 2009

Re: batteries from big chain stores

mshen11 wrote: »

have Kirkland 12V Dual Purpose Deep Cycle 27DC... 115 amp hrs for $85... thats 60c/amphr.

It's not TRUE deep cycle, only part way there. So you can start your boat with it sometimes.

mshen11 · September 2009

Re: batteries from big chain stores

mike90045 wrote: »

It's not TRUE deep cycle, only part way there. So you can start your boat with it sometimes.

the DC in 27DC is not a designation for deep cycle? what about the walmart 27DCs? if you google, some people on other forum says they are deep cycle if it is DC (vs some other designatoin i dont remember).

mike95490 · September 2009

Re: batteries from big chain stores

It's the Dual Purpose. Once they make the mods to enable it as a high current starter battery. it's not Deep Cycle. Maybe they could print XDC on the side, and say it stands for eXtra Deep Cycle 120% - But it would still not be a Deep Cycle. The 2 functions can't cohabit the same house.
If you can find a factory code that matches a known true DC battery, you are a step closer.

Don't get me wrong, I have one in my garage right now, but I also don't pretend it's a full DC battery, just an affordable compromise.

Cariboocoot · September 2009

Re: batteries from big chain stores

There are many batteries labeled "Deep Cycle" which aren't really suitable for Renewable Energy applications. These are usually called "Marine/RV Deep Cycle" or some such. They are a "hybrid" deep cycle. The difference between that and a "true deep cycle" is in the internal design: the hybrid has plates with characteristics of both the SLI (Starting/Lighting/Ignition or automotive battery) and the true deep cycle. Thus it is able to be cycled more and deeper than a standard battery, while retaining the much of the latter's ability to handle sudden high current draw (as in starting an engine). But they are not able to stand up to repeated deep discharge/recharge of the true deep cycle type. Some battery manufacturers even designate certain models as "RE" - meaning they are specifically designed for Renewable Energy usage.

It's not likely the average salesperson at a big box store would know about any particular battery's internal workings. If there's no numbers available for "20hr" A/hrs or rating for cycling it probably isn't for RE. That doesn't mean it won't work, it just means it won't work for as long. It's a trade off between buying cheaper batteries you have to replace more often and buying more expensive ones that will last a long time. If you're just experimenting or starting out and don't have to absolutely depend on the system then you can always buy the cheap ones. Better to "learn and burn" on inexpensive batteries than to boil some very expensive ones dry.

mshen11 · September 2009

Re: batteries from big chain stores

take costco specifically because i spent some time there:

they have a 115amp-hr (@20hr) for $85 + $9 core. it is made by johnson (according to johnson and people on other forums) and the manufacture claims it is a true deep cycle [i dont know how much weight i put on that statement]. however they say their battery will not last as long as a golf cart battery.

on top of that there is a 3 year non-pro rated (FULL) refund warranty.

im thinking this... if i beat the heck out of a set of these battery so that they do die early, ill get a free set. (of course if i did that id be pretty embarrassed lugging around 2, 4, or 6 dead batteries for return; plus my back will wont be too happy either)...

normally to set up a system corrrectly you assume 50% DOD so you get double the amount. if you need 100amphr, then you get 200amphr worth (to 'save' your battery). in this case, why not just get 100amphr with the intention of 99% discharge and killing it early? this is borderline ethics but battery companies know what they are doing, they would not warranty them any later than how long they think their battery will last.

ps: i dont remember the details but johnson said they dont have real stats for 80% DOD only 20% (or some small amount) and 100%... and they extrapolate the 80% based on those test data.

Cariboocoot · September 2009

Re: batteries from big chain stores

One thing about Depth Of Discharge: few batteries can take deeper than 80% even once. So drawing cheap batteries down to 'dead' will probably leave them there.

But if you discharge them only 25% - you could get years out of them. Ideally, 'abuse' them just short of 3 years worth and keep getting free batteries ... Highly unethical and largely impractical so I don't recommend it.

mshen11 · September 2009

Re: batteries from big chain stores

Cariboocoot wrote: »

One thing about Depth Of Discharge: few batteries can take deeper than 80% even once. So drawing cheap batteries down to 'dead' will probably leave them there.

But if you discharge them only 25% - you could get years out of them. Ideally, 'abuse' them just short of 3 years worth and keep getting free batteries ... Highly unethical and largely impractical so I don't recommend it.

so if that is true (25% DOD)... then logically speaking, costco's battery should suffice under normal care for RE.

niel · September 2009

Re: batteries from big chain stores

it will work, but don't expect the lifespan of the battery to be much more than around 3 years or so.

mshen11 · September 2009

Re: batteries from big chain stores

niel wrote: »

it will work, but don't expect the lifespan of the battery to be much more than around 3 years or so.

as opposed to... trojans @ $1.42 (225 amphr, 6v, $160/battery) that will last 6 years(?). note $1.42 vs $0.60

in one of the basic battery thread, it says buy the smallest se of battery you need. because if you buy 4 lasting 4 years; if you buy 8 it should last 8 years. if that is the case... wouldnt it be more logical to get a costco battery... from a $ perspective but also it will pretty much last the same duration as a trojan if you normalize the cost?

im just trying to figure out what is the most cost effect battery, factoring in duration, wear, etc...

BB. · September 2009

Re: batteries from big chain stores

Yea, I am the guy that came to the conclusion that battery costs vs life time seem to be pretty closely related (spend 2x for batteries and they last 2.2x longer).

Part of the problem is how do you use your batteries. And do you occasionally really deep cycle them. The more expensive batteries will probably last longer--unless something really bad happens--then you are left with a more expensive pile of junk.

Talk with people (and vendors) one what they find lasts well for them (and their customers).

If you end up with a set that last 3 years, for example, and the next power failure at 2.9 years--the batteries run for 15 minutes then die--that could be an indication that getting a set of batteries that last 10 years will leave in you the lurch 1/3 or 1/4 as often as an "economy" bank would...

Good batteries that have been well taken care of will last a long time (10 years or more)... The fact that you only have one change out in 10+ years vs 3+ change outs with less expensive/fewer batteries may be worth it to you (or not).

Obviously, I don't know the answers either. That is why I purchased a small/fuel efficient 2kW genset and 20 gallons of gas cans--figured that would take me through our next big emergency (assumed to be an earthquake that happens once every 100 years)... But I don't have the numbers or length of outages like you do.

-Bill

mshen11 · September 2009

Re: batteries from big chain stores

BB. wrote: »

Good batteries that have been well taken care of will last a long time (10 years or more)... The fact that you only have one change out in 10+ years vs 3+ change outs with less expensive/fewer batteries may be worth it to you (or not).

Obviously, I don't know the answers either. That is why I purchased a small/fuel efficient 2kW genset and 20 gallons of gas cans--figured that would take me through our next big emergency (assumed to be an earthquake that happens once every 100 years)... But I don't have the numbers or length of outages like you do.

-Bill

well assuming you dont mind changing batteries more often than not, and you take good care of the batteries, and you are price sensitive, you have come to the conclusion that its better to get 4 batteries for 4 years than 8 batteries than 8 years [both scenerio is the same BEFORE throwing in price sensitive, price sensitive makes you get less battery]. is there a collorary to it like...

get cheaper battery, even though you switch them out more often than good batteries, you edge out ahead price wise (price difference is DOUBLE, but i dont think lifetime duration is double?). and then the money you save, you goes to your medical insurance for bad back.

off topic question. HOW do you *really* figure out in a scientific but not wasteful (like draining the battery to calculate load) way that a battery is no good. from what it sounds like, a battery monitor doesnt quite do it?

Cariboocoot · September 2009

Re: batteries from big chain stores

mshen11 wrote: »

off topic question. HOW do you *really* figure out in a scientific but not wasteful (like draining the battery to calculate load) way that a battery is no good. from what it sounds like, a battery monitor doesnt quite do it?

Nothing better than checking the specific gravity with a hydrometer. You can also use a 'load tester' for a fairly good idea (hydrometers won't work on sealed batteries of course). But even then ... mine failed 'secretly' within 30 days due to a collapsed plate.

As for how long they'll last ... It's more like proper maintenance will keep the cheap batteries around for the length of the warranty and the good ones around for double their warranty. I think Tony's got some Trojans that have been doing sterling service for a decade? Anyhow, given identical service/maintenance the cheap ones will fail first. Nigh on impossible to determine if its cost-effective to buy inexpensive batteries, but I will say this: if your electricity is dependent on them, go for the good ones. The Interstates that just 'got' me were a 'bargain'.

bryanl · September 2009

Re: batteries from big chain stores

HOW do you *really* figure out ... that a battery is no good.

Put a load of C/10 or so on the battery and watch the voltage for a few minutes. Fit that curve to the known characteristics of the battery to determine SoC and battery health. Easiest reference is just to monitor the battery this way over time and see how it degrades.

or you can do conductance testing - kinda like using sonar to find things in water...

Brock · September 2009

Re: batteries from big chain stores

Elaborating on what Bill said. If you have an inexpensive 200 amp bank and it is dying, say it acting like a 50 amp bank, how long will it run your critical loads? For example with a 10 amp load on 8 inexpensive batteries

year 1 200ah 20 hours
year 2 150ah 15 hours
year 3 100ah 10 hours
year 4 050ah 5 hours

Now taking that same example and assuming a 225 amp Trojan and 6 years and failing at the same rate, which I don't think they would.

year 1 225ah 22.5 hours
year 2 196ah 19.6 hours
year 3 168ah 16.8 hours
year 4 140ah 14 hours

So after 3 years your inexpensive bank is significantly underperforming compared to the true DC bank. Bottom line if running your loads is important than it only logical to get a better battery. If running your loads for a given amount of time or you have a good genset to back them up anyway, then a cheaper battery set may be the way to go. I started with cheap batteries and in an outage there is little point if you have 6 hours of runtime (when they had 24 hours new).

Photowhit · September 2009

Re: batteries from big chain stores

OK, I'm completely lost in your "same rate", I guess your saying over 6 years vs over 3 or 4 years? I your numbers appear as vaporware (inverted)

I just wanted to post that This weekend I was surprised at the health of my battery bank, 4 - 4 year old Sams club 6volt golf cart batts Energizers, We had a cloudy weekend though I'm sure the batteries were topped off each day. Sunday I came home @ 1:00 (I work security) and popped on the AC to take the humidity out of the air, I set it down to 62 so it would run until I turned it off, it was 72-3 inside and quickly fell asleep.

I woke @8am with the AC running, I'm sure it had cooled the place down to 62, so I don't know how much the compressor ran. I don't have my Trimetric hooked up but @10 I went out and checked the battery voltage and found it at 24.5 volts (with a draw @ a 60 watt draw, inverter and fan (a few tiny ghost loads) running, likely about what the array was producing during the over cast morning!

Maybe they'll make it through another summer!

Another factor, is the DOD rate of a 230 Ah Trojan set vs a 440 Ah generic set. Something I would consider as I would seldom take a 440AH set down to 50% while a 230AH set I would take down to 50% DOD quite often during the summer.

Brock · September 2009

Re: batteries from big chain stores

I am not good at getting my point across. Basically assuming one battery will fail in three years and one in six years given the same use. After two and a half years the "three year" battery will be pretty much useless compared to the six year battery.

I am not saying there isn't a place for golf cart batteries or marine batteries, there is and they are made the way they are for good reason. I am just saying by replacing a battery that is less than 1/2 the cost twice as often can get you in to a situation where the battery doesn't perform as needed towards the end of its life.

So say you can’t count the last year of a batteries life for critical loads, a three year battery would be good for two yours and a six year battery would be good for 5.

Kamala · September 2009

Re: batteries from big chain stores

Trying to cut through.... If batteries are a part of your system, they are probably integral/important to your system. If they are not, why are they there? Use the "best" batteries that you can afford. Can't afford the best batteries? Fine. Go with "cheaper." I steadfastly believe that buying cheap/replacing more often is cost inefficient.

I used to buy hand tools out of the "bargain bin" at the hardware store. (When I had much less money.) Things like chisels and screwdrivers. After I used them less then a dozen times they were ruined. Lesson... you get what you pay for... or you pay (over and over) for what you get.

The tool/battery analogy is not perfect, but I think I made my point.

Craig

Just Me · September 2009

Re: batteries from big chain stores

Hi, new guy here and somewhat new to solar and the characteristics of batteries. I haven't charted my usage and lifespan for my boat, trucks and RV batteries, so I have no actual opinion here, but this sounds like a good Myth Buster episode.

1) Are Deep cycle batteries better than off the shelf auto batteries?
2) Do deep cycle batteries really last longer with the same DOD?
3) Is it better to run 2 - 12V batteries or 2 - 6V batteries?
4) Is there really a difference between marine and other DC batteries?

Cariboocoot · September 2009

Re: batteries from big chain stores

Just Me wrote: »

Hi, new guy here and somewhat new to solar and the characteristics of batteries. I haven't charted my usage and lifespan for my boat, trucks and RV batteries, so I have no actual opinion here, but this sounds like a good Myth Buster episode.

1) Are Deep cycle batteries better than off the shelf auto batteries?
2) Do deep cycle batteries really last longer with the same DOD?
3) Is it better to run 1 - 12V battery or 2 - 6V batteries? (math corrected by 'Coot)
4) Is there really a difference between marine and other DC batteries?

1) Yes. The two designs are not the same. Auto batteries will not stand up to being repeatedly deeply discharged and recharged.

2) Yes. Given the same quality of maintenance as well. True deep cycles are meant for this application.

3) Six of one, half-dozen of the other. The reason why people go "2 sixes" instead of "1 twelve" is that as Amp/hr capacity increases batteries get bigger and heavier. It's simply physically easier to handle 2 225 Amp/hr 6V than one 450 Amp/hr 12V, as it were. Otherwise the twelve has an advantage of fewer wiring connections, which isn't much of an advantage.

4) Yes. Marine/RV "deep cycle" are hybrids; their plate design is something between the porous, sudden high-current design of the "auto" type and the thick, solid long-lasting true deep cycle. They are a compromise between the two functions and don't work as well at either compared to a battery designed specifically for the task.

The original discussion, btw, was over the economic merits of inexpensive deep cycles being replaced often versus more expensive deep cycles having a longer lifespan - other factors being equal. The missing part of the equation is how fast the capacity drops off on the cheaper batteries. The intangible part is how much more prone to sudden failure are the cheap ones and how adversely will that affect your application?

bryanl · September 2009

Re: batteries from big chain stores

sounds like a good Myth Buster episode

but, from what I can tell, there's an awful lot of folks who wouldn't believe what they found out.

For instance, there is no definition of "deep cycle" for a battery that draws a clear line that can be seen in measurable specifications. That doesn't seem to bother anyone, though, as they still assert with vigor that such a distinct difference exists.

You can see some difference in life noted in the FAQ by designated battery type but the source isn't noted and there is no information about the means of measure nor the method used to determine a result. The best measure of life expectancy is warranty near as I can tell. The best path towards long life is in proper use and maintenance.

The series vs parallel debate also easily departs from reason as the many variables, such as battery type and size, bank size, load use profiles, and so on, get shoved aside.

What you can find from looking at line cards is that the basic trade-off is between capacity, cost, and ruggedness. Batteries are designed so that manufacturers can cover the spectrum. When you get to the really, truly, deep cycle (ruggedness) focused batteries, you are likely getting off into the tail of the distribution where the market is rather small. That means that it is difficult to make a profit there and stay in business.

The real kicker is that everyone seems to obsess on single digit percentage differences when the batteries themselves don't support this level of precision. Things like age, cycle to cycle variance, temperature, and so on can make double digit percentage variances. If we can't even agree on what is important, how can we begin to discuss what is better?

BB. · September 2009

Re: batteries from big chain stores

As a start--you can read the deep cycle batter FAQ here...

Just Me wrote: »

1) Are Deep cycle batteries better than off the shelf auto batteries?

For deep cycling applications--yes, very much so. Automotive batteries are designed to start cars and not cycle below ~15% depth of discharge... Plates are thin and numerous to give high currents to crank the engine for short periods of time.

2) Do deep cycle batteries really last longer with the same DOD?

Yes... plates are thicker so the hold up better with deep(er) cycling.

3) Is it better to run 2 - 12V batteries or 2 - 6V batteries?

Mixed answers on this one... If you have parallel batteries you end up with more cells to water and can have issues with paralleling batteries: Short discussion:

Extra wire adds voltage drop--if the wire/resistance is not balanced, the battery "seeing" the less resistance will do more cycling and wear faster;
also a parallel battery with a shorted cell can prevent the entire bank from properly recharging;
personally I think series bank is easier to quickly see any issues, diagnose and maintain;
some vendors report longer life with parallel strings, others report no issues between well designed parallel/series strings).

4) Is there really a difference between marine and other DC batteries?

Yes--Marine batteries tend to be a compromise between true deep cycle and starting batteries (since they are expected to do both). Marine flooded cell batteries are also (usually?) designed to operate in a boat and not spill.

The bigger range of battery design... There are certainly batteries designed for long life and shallow discharge (such as phone companies). And batteries designed to "float" for long periods with 15 minutes of heavy discharge (such as UPS applications).

And you get into the how much to spend for batteries... Seems like you spend 2x as much and they last 2x as long...

There are other battery constructions to look at too... For Solar RE, the other major choice is AGM (Absorbed Glass Mat/sealed lead acid). Generally, a much better battery for solar than Flooded Cell Lead Acid. But, again, more expensive.

-Bill

Cariboocoot · September 2009

Re: batteries from big chain stores

bryanl has a good point: marketers would stick a label saying "Deep Cycle" on penlight cells if they thought it would sell more.

So how do you tell the difference? For one thing, the true deep cycle will have a "20 hour" Amp/hr rating. If the information given is Cranking Amps or Reserve Capacity then chances are it isn't a true deep cycle. It's particularly good if the manufacturer is willing to give some information about the # of cycles the battery is rated at, recommended maximum depth of discharge, and charging specs such as absorb and equalization Voltage. If they're not too quick with supplying that sort of data, it probably isn't what you want.

Another indication is the battery's intended application. If it's for "electro motive force" like golf carts or fork lifts it may be suitable. Some manufacturers are now defining their batteries as being for Renewable Energy.

In general, look for the information you need to know for a solar power system. If it's not readily available, chances are it's the wrong battery for the job.

RCinFLA · September 2009

Re: batteries from big chain stores

Marine batteries typically have a 20 hour discharge spec, but they are not deep discharge batteries.

There is no right or wrong answer to these questions. There is a right battery for a given application.

Solar off-grid is more inclined to need deep cycle batteries.

Some folks would rather not replace batteries for long period of time and are willing to pay a premium for that end.

Needing high surge current may not be satisfied with deep cycle unless a lot of excess capacity is available.

Cost, ease of purchase, weight, maintanance are some other factors.

There is quality differences between various manufacturers for the same type of battery. I don't think warranty statements are good gauge of quality. Beside marketing hype, there is a definite risk factor on who is the typical end user. Recreational boat batteries, for example, are so abused and neglected, as a battery manufacturer, I would hesitate putting any warranty on them.

I think sometimes we get tangled up in discussions that mixup trying to compare quality of batteries versus a battery type suitable for a given use case. Most individuals have a use case (their's) as a given fixture in their minds which may not be the same use case in the mind of other person the discussion is with.

DeltaFox · September 2009

Re: batteries from big chain stores

There is a battery that is made just for solar panels ,here it is.

http//www.dcbattery.com/rollssurrete_6cs25ps.html

Cariboocoot · September 2009

Re: batteries from big chain stores

There are a number of batteries suitable for Renewable Energy applications.

From our wonderful Host NAWS: *ahem*

http://store.solar-electric.com/batteries.html

Just Me · September 2009

Re: batteries from big chain stores

Sorry, I pretty much knew the answers to those question. I meant those would be the questions I would ask MBs to test.

bryanl · September 2009

Re: batteries from big chain stores

re "Marine batteries typically have a 20 hour discharge spec, but they are not deep discharge batteries."

The 20 hour rate is commonly available for all lead acid batteries, even SLI batteries. RC, an equivalent measure, is also to be expected and both will give you the Peukert coefficient.

The fact is that RE is not a deep cycle application and there are no storage batteries commonly in use that could be considered "true" deep cycle. All lead acid batteries will suffer if subject to deep cycle (e.g. 80% DoD) use as a routine thing. Yes, you can take off into the edges of the distribution like with traction batteries and such but even those are still lead acid batteries with similar behavior. Look at the FAQ and see how little difference there is in life for commonly available batteries intended for either 'marine' or 'deep cycle' use.

The fact is that you need to design your battery bank such that its typical discharge is only 25% to 50% DoD in routine use. Not only do you want to avoid deep cycling because of its impact on battery life but also for its impact on charge needs. A proper and full charge on a deeply discharged battery takes time that a daily cycling (as in RE, especially solar) doesn't allow.

Talking about "deep cycle" in an RE or RV context is deeply misleading. We need, instead, IMHO, to focus on actual RE needs and a good definition of concepts and measures that we can use to design our battery banks and value the parameters that need to be evaluated for our particular needs.

Big chain stores have to feature 'what works' for the major market - the center of the distribution - else their warranty and other costs will make them a 'little' chain store. That means they can provide a good referent for looking elsewhere for different cost versus benefit values.

mshen11 · September 2009

Re: batteries from big chain stores

ive got a philosophical case/argument debate about this and based on what bryanl writes.

so using the same logic - if the big chain mislabels them and misguides the buyer, and the buyer wrongly uses the battery for an application and the battery dies early - that really isnt the buyers fault

let me give you an example:

ive been looking hard at costco batteries. it states 30 month non-prorated warranty for 115amp hr deep cycle. no stick on the manufacture.

it took a long time for me to find out who made it. what did i find out? the battery is actually 90amps over 20hrs. also its not true deep cycle like gof cart (has half the plates). 30-80 cycle full discharge. there is no way i couldve found this information w/out spending more than 1hr probing the manufacturer.

so... a normal user would buy it thinking he bought a 115amp deep cycle battery (it is actually 90amp pseudo deep cycle) - aka solar. he uses it as such even though the manufacturer doesnt recommend it (that is IF you call them up). is it his fault if his battery dies before the 30months and he makes good on the warranty. he was misled into the specs because the big chains want to attract the most to buy their product

having said that - ithink ive done enough analysis on battery for me/my situation. im all about cost cutting and have been comparing costco battery vs something else. i think bj's energizer is a better deal after the latest info i found out about costco. i was leaning heavily towards costco esp w/ the warranty - but the "mislabel on the size is not worth it'

dwh · September 2009

Re: batteries from big chain stores

bryanl wrote: »

The fact is that RE is not a deep cycle application and there are no storage batteries commonly in use that could be considered "true" deep cycle. All lead acid batteries will suffer if subject to deep cycle (e.g. 80% DoD) use as a routine thing. Yes, you can take off into the edges of the distribution like with traction batteries and such but even those are still lead acid batteries with similar behavior. Look at the FAQ and see how little difference there is in life for commonly available batteries intended for either 'marine' or 'deep cycle' use.

The fact is that you need to design your battery bank such that its typical discharge is only 25% to 50% DoD in routine use. Not only do you want to avoid deep cycling because of its impact on battery life but also for its impact on charge needs. A proper and full charge on a deeply discharged battery takes time that a daily cycling (as in RE, especially solar) doesn't allow.

Talking about "deep cycle" in an RE or RV context is deeply misleading.

Excellent point.

Personally, I have spec'ed out a system for my RV which will (hopefully) never go below 25% DoD. Thus, as regards batteries, my priority has been trying to figure out which batteries will endure the maximum number of cycles at that DoD and at what price.

[One reason that I settled on 25% as DoD is because that is about the max I figure I can fit into the vehicle.

2 x 130w PV @12v = 260w (max)
4 x 105ah @12v batteries = 420ah
5 x good sun hours (Southern California)
260w x 5h = 1300wh
1300wh / 12v = 108ah

That's a rough estimate of course, and the harvest assumptions are optimistic. Nevertheless, that's quite okay since the consumption assumptions are pessimistic - it will be a VERY rare day that a full 100ah would be consumed. Most likely the average DoD will be more like 10%-15%, which is right in the sweet spot for such a system.]

batteries from big chain stores

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