AGM batteries - are they better?

[DryCamper11]

Upgrade to an AGM battery. You can safely mount them inside, and upside down, and they will out-perform any flooded battery you ever owned!

Here's a quote from another thread. It's typical of others I've seen. I wonder if anyone here can convince me it's correct. Clearly the AGM has some advantages. Two are seen in that quote - inside and upside down. If you need to mount upside down and can't ventilate, sure, that's an advantage, but I don't need those advantages and don't want to pay extra for something I don't need.

We're left with the rapid charge rate they are reputed to permit. I would love to run my 80A charger at 80A continuously until I reach 100% SOC. Right now my 460AH FLA batteries recharge at 80A from 50% SOC for about 3 hours (some fluctuation in current - slow climb from below 80 to above 80 during the first hour as they warm up then down to 70+ at the third hour), then begin to taper more rapidly during the last hour as the battery voltage approaches the charger voltage.

Does anyone have charge curves for AGM showing the performance (preferably with an 80A charger)? I'd particularly like to see the tail end of the charge cycle. How do AGMs perform? Is it significantly better than FLA batteries? Do AGMs taper the charge rate the way FLAs do, or is the entire advantage in the fact that I could run a bigger charger (100+ A) for my 460AH battery bank?

Are there other advantages that AGMs offer?

[Wayne_Dohnal]

Without providing any of the data or analysis, I'll say that in my RV the way I use it, FLAs make the most sense. In my home PV system, when the grid is up most of the time (which so far it is), AGMs make the most sense. If the grid were to become unreliable, the advantage would flip over to FLAs. I use FLAs in the RV, and AGMs in the home PV system.

[full_mosey]

Gdetrailer;

I want to acknowledge and thank you for your post. I'm thinking!....

HTH;
John

====================================================================
OK, here is my view.

Your analysis claims that AGM cost/benefit claims are insignificant on a monetary basis. Plus, any procedures related only to FLA are also insignificant on a monetary basis. This leave the analysis where an AGM must outlast an FLA by a simple multiplier based on the ratio of their purchase costs.

Since my goal is to maximize the R in RV, I will modify my position to say that I feel that AGMs give me more R with less attention to V. I am confident you feel the same about your RV.

HTH;
John

[MEXICOWANDERER]

All these responses should make it perfectly clear to anyone reading them.

Battery A and Battery B

Have their strong points

Have their weak points.

Reminds me of the "Ugly but sure can cook, baby" analogy.

[Gdetrailer]

Full mosey writes “I am pleased to see you agree with my position on the minimal charge time advantage of AGMs. However, that feature alone should not drive the choice for or against. There are many merits that in the aggregate may influence the choice. Unless wets charge faster, the fact remains and it is a "feature" that AGMs charge faster.

#1 Where do you stand on the claim that AGMs charge cheaper?

#2 Are you saying your GCs are cheaper to own?

#3 Do you get cheaper Watt Hours over their life, or are you only considering the up front AH/purchase cost?

#4 Did you intend to ridicule my request for a fair labor rate? It is my understanding that there are several procedures beyond adding water that are unique to wets to which a labor rate could be considered.

#5 Other than purchase cost, do you see additional factors that steer you away from AGMs?

#6 Perhaps you could post a list of the "features" where wets excel.

HTH;
John"

Added in the numbers in order to address each point..

#1 The claim that AGMs charge cheaper comes from the supposed “higher charge acceptance rate” due to “lower resistance” of the AGM design. This is touted as an advantage by many but in reality at the end of the day it amounts to having to run a generator for couple minutes less PER day.

The “savings” in money (gas and gen wear and tear) is so insignificant it simply amounts to a couple of PENNIES per charge. To even break even, the AGMS would need to last nearly twice as long as a lower cost FLA.

Typically a FLA normal life is 8-10 years WITHOUT ANY “SPECIAL PROCEDURES” (50%-80% dod) (I have had FLA car batteries easily reach 12yrs of usable life) . That would mean a AGM would HAVE to last at least 15 years before you break even BUT AGMs life typically do not do well if you regularly discharge them to 50% dod (some are not recommended to be discharged more than 20% dod). AGMs also do not tolerate and “recover” if you accidently run them 100% dod, do that once and you have an heavy and expensive doorstop (FLAs can tolerate and recover but at a reduced capacity).

Many folk who are on the AGM bandwagon are there because they HATE the noise of even the expensive quiet gens and don’t want to “listen” to a gen for any more time (yes, even a couple of minutes less per day) and are WILLING to pay the extra money on AGMs to get that extra couple of minutes of quiet time.

Personally, if I was in that concerned with generator noise I would be camping in places with electric hookups. After all whats the point of dragging a long a big expensive RV out into the wilderness with a big screen, DVD/Blue ray, surround system, PC, cell phones, game system and any other electronic gadget if you are not willing to put up with a generator for a few hrs per day?

#2 YES, not only in purchase price but due to the fact that FLA GC batts are well designed and with VERY LITTLE care typical life is 8-10 years and well cared for can net 12-15 yrs of usable life.

#3 Upfront purchase price (when I bought mine they were $66 per 6V GC batt so I spent $132) for 210Ahrs, at that time to buy AGM would have cost just under $300. Then factor in that I should have no problem achieving at least 8 yrs of use so hands down FLA was cheaper for me.

#4 Not “ridiculing” you.

However there is no need for any special procedures to get at least 8 -10 yrs of usable capacity from FLAs PROVIDED you recharge as soon as possible after discharge, you do not discharge below 50% dod AND you periodically check and add water when needed.

Modern day “converters” with 3 stage charging do nearly all the necessary “work” for you, plug in and let it rip..

Many of these added “special” procedures may help prolong some of the capacity over the life of the battery but to me in my case not worth doing. Not to mention many of these additional procedures are HIGHLY EXPERIMENTAL and some with NO REAL LIFE LONG TERM DATA to backup the touted “benefits”.

There are tens of thousands or more of deep cycle FLA batteries in use for RE (off grid) homes currently in service not to mention Golf carts, forklifts (my work place has multiple forklifts running every day for 10hrs straight then put on overnight charge, they are not "babied" like a lot of the folks on this forum insist that the batteries need, only ONCE in 15yrs I have been working for my company has these batteries been replaced and that was due to scheduled paid for maintenance contract), wheel chairs and so on that NEVER get special treatment and yet most of these WILL give at least 8 yrs of useful life.

If someone could prove without a doubt real hard evidence that their AGMs with constant deep discharges below 50% dod have lasted them 15-20 years then I would consider AGMs.

FLAs get a bad rap for having to periodically clean the terminals, if the terminals are treated correctly at the beginning, this is minimized. Over the years I found using an anti oxidizing grease specifically designed for electrical connections nearly eliminates the need to clean the terminals pretty much over the life of the battery. The type I use is sold as No-Alox which actually is used to interface aluminum service entrance wire to terminals (mast to meter socket and meter socket to breaker panel). I have found many good uses for this grease especially when connected to outdoor electrical connections and even FLA terminals.

FLAs also get a bad rap for needing “watered”, modern day converters with three stage charging goes a long way to reducing the amount of water lost in FLA batteries. In my case I only need to check once a year and add in about 1 oz of water per cell (some folks who use their batteries much harder may need to do this a few times per year but it really takes a minute or so per cell), not very much compared to old single stage converters which required monthly check and add.

Not to mention you can also buy water recovery caps which recover some of the water which would have been lost to the air OR automatic watering system which will do the watering for you. Pretty much turning FLA batteries into nearly “maintenance free”. Yes, they do cost a bit upfront but long term can be reused on the next set of batteries and the set beyond that and so forth.

#5 AGMs can be easily destroyed by accidental full discharge (100% dod).

AGMs can be destroyed by overcharging (to high of a rate too long can build up pressure within the battery and this opens the overpressure valve). When this happens the electrolyte breaks down and releases water vapor into the atmosphere, drying out the electrolyte. Once you lose this water it cannot be replaced, period. This is the same trait as a gel cell.

#6 FLAs have been around well before 1900, the cost of design and manufacture (R&D) is very little.

FLAs are rather robust, can sustain deeper discharges without harm.

FLAs are easily found (although AGMs are making some progress there).

FLAs are made in larger quantities and in some aspects may be easier to make (hence part of the lower cost equation).

Deep cycle FLA like GC batts can be regularly discharged to 80% dod with very little loss in capacity over the life (most AGMs are NOT recommended for discharges of 50% dod or below and SOME are not recommend for more than 20% dod).

FLAs can sustain 100% dod accidental discharge but yet be recovered (although with some capacity loss) provided they are recharged as soon as possible (AGMs do not tolerate this and the result is a doorstop with just ONE time occurrence, this is the same trait as a gel cell).

FLAs can be “recovered” if the electrolyte levels are allowed to go below the plates by adding in water (some capacity loss may occur but the battery will still be usable). Just can’t allow total dry to happen. (AGMs you cannot recover once they have vented).

FLAs have higher Ahr capacity in the same size of container for instance the current FLA GC2 batt which currently Sams has lists 230 Ahr at 20hr rate while the AGM version Sam’s carries lists 190 Ahr at 20hr rate.
HERE

So in a given space you WILL get more Ahr capacity with FLA, for some this can be a very important item especially if they have limited space.

For instance space for qty of 4 6V GC2 batteries with FLA you get 460 Ahr capacity compared to AGM with 380 Ahr (FLA nets you 80 Ahr MORE capacity).

Space for 6 6V GC2 FLA gives you 690 Ahr compared to AGM at 570 Ahr (FLA nets you 120 Ahr MORE capacity). Basically nothing to sneeze at..

Now right about this time someone is going to post about AGMs lower “self-discharge” rate?

Well, if you are constantly discharging and recharging on a daily schedule (IE USING the battery) then there is NO advantage to AGM over FLA, the self discharge of FLA is so small per day that it would be like attempting to find a fly on the moon using just your eyes. Perhaps adding one second to your recharge time if that…

As far as self-discharge for storage, AGMs have no real advantage unless you are storing for more than 6 months without shore power. I have no problem storing FLA over three months without charging but in my case I have power so I simply leave the converter on with batteries attached.

All told in the big picture even IF you have to replace a FLA every 8 yrs and a AGM lasts say 10 yrs you would have to buy one extra set of FLAs in 40 yrs! Not much of a big deal, no big savings with AGM…

In the end.. ALL batteries should be considered as a CONSUMABLE item, ALL will fail over time and use and they WILL eventually need replaced. Buy cheap up front and use it until the useful life is gone then replace.

Sometimes I think folks just say they like AGMs because it “sounds” cooler to use the latest technology, I am not afraid to say I to use old school FLAs.

[full_mosey]

Wet advantage add:

More tolerant of higher temperatures.

HTH;
John

[beemerphile1]

MEXICOWANDERER wrote:
THE BEST BATTERY IS.......









A FREE BATTERY

Absolutely correct. I get my East Penn/Deka group 24 Gel cells for free. They are rotated out of mobility scooters/wheelchairs at 18 months of age. They would cost me over $200 each to buy them. They are usually good for 2 - 3 years after I get them.

[ken_white]

msiminoff wrote:

ken white wrote:
Flooded Electrolyte Advantages:

Lowest initial cost - True!!

Higher cranking amps so excellent for starting applications - False. In many cases AGM's offer higher CCA than FLA's do

Water can be added when over charged - True

Tolerant of improper recharge voltage - True, as long as electrolyte level is monitored. IMHO, this is the #1 FLA advantage!

Certain designs are good for deep cycle applications - True, but not more so than AGM's

Replacements readily available True, but not more so than AGM's. For example, the DieHard Platinum's are available at hundreds of Sears stores across the country.

Good under extreme cold conditions when fully charged. True, but given the same temp' & SOC, AGM's outperform FLA's

LOL...

There are always exceptions when making comparisons but my comments were based on the general case.

I was just posting advantages since they were asked for.

[msiminoff]

ken white wrote:
Flooded Electrolyte Advantages:

Lowest initial cost - True!!

Higher cranking amps so excellent for starting applications - False. In many cases AGM's offer higher CCA than FLA's do

Water can be added when over charged - True

Tolerant of improper recharge voltage - True, as long as electrolyte level is monitored. IMHO, this is the #1 FLA advantage!

Certain designs are good for deep cycle applications - True, but not more so than AGM's

Replacements readily available True, but not more so than AGM's. For example, the DieHard Platinum's are available at hundreds of Sears stores across the country.

Good under extreme cold conditions when fully charged. True, but given the same temp' & SOC, AGM's outperform FLA's

[mena661]

Flooded advantages
Cheaper
Tolerant of deep discharges
Used in offgrid homes and golf courses
I own them

[ken_white]

full_mosey wrote:
...And the list of wet advantages is.............? LOL!, :), :B

HTH;
John

Flooded Electrolyte Advantages:
Lowest initial cost
Higher cranking amps so excellent for starting applications
Water can be added when over charged
Tolerant of improper recharge voltage
Certain designs are good for deep cycle applications
Replacements readily available
Good under extreme cold conditions when fully charged

[MEXICOWANDERER]

THE BEST BATTERY IS.......









A FREE BATTERY

[full_mosey]

ken white wrote:

mena661 wrote:

timmac wrote:
Wow all these post about is AGM better than WET, I say YES, AGM is better, I never have to add water ever again..

WET's are better, see I can do that too. LOL! 🙂

:B

Every time someone chooses AGMs, an angel gets their wings!

And the list of wet advantages is.............? LOL!, :), :B

HTH;
John

[ken_white]

mena661 wrote:

timmac wrote:
Wow all these post about is AGM better than WET, I say YES, AGM is better, I never have to add water ever again..

WET's are better, see I can do that too. LOL! 🙂

:B

[mena661]

timmac wrote:
Wow all these post about is AGM better than WET, I say YES, AGM is better, I never have to add water ever again..

WET's are better, see I can do that too. LOL! 🙂

full_mosey wrote:

Did you intend to ridicule my request for a fair labor rate? It is my understanding that there are several procedures beyond adding water that are unique to wets to which a labor rate could be considered.

Why are you so stuck on this labor rate? Maybe it takes hours of your day to do proper maintenance but it takes me a few minutes every month max and that time is literally hooking up another charger for top charging. The charger does the work, I go back inside and play Battlefield 3. ONCE a year I check and fill with water, another 15 minutes max. I do this when I have ZERO else to do, I'm just sitting around the house and decide maybe I should do some battery maintenance. So out of an ENTIRE year, I spend maybe 20-25 minutes on battery maintenance. Sorry but that time is negligible and costs nothing. I spend an order of magnitude more time shoveling **** from the horses.

[timmac]

Wow all these post about is AGM better than WET, I say YES, AGM is better, I never have to add water ever again..