AGM vs Flooded Bulk Times

My observations on my Northstar AGM-27 battery, indicate that how many amps the battery can accept depends on how many cycles it has gone without a full charge, or without a high amp recharge.

Lots of low and slow recharges until 92% and then if 40 amps are then applied( to a 90Ah battery) amps will start tapering much faster than if the day before had a high amp recharge until 100% was achieved.

I don't really have the data to compare to a flooded battery, not in any scientific manner anyway, but the screwy31 ( 130AH)had no issues accepting 40 amps for quite a while when depleted.

At which point in the SOC that amps started tapering at 14.X volts, compared to the AGM is not data I have on Hand.

And as i do ot ever use a generator, how I recharge is not as important as to someone doing successive 50 to 80%. I Aim for no less than 95% and 100% every 5 cycles.

So how much partial state of charge cycling has been going on, in my opinion, will have huge impacts on when amps begin to taper when held at absorption voltage, and this makes direct comparisions of the AGM vs Flooded in the bulk phase, unwise.

No doubt a test could be set up that would be valid, for that particular AGM brand vs that Flooded brand in X type of use/ charging regimen, but a flat out statement that AGM always charge faster given the same amperage charger as it takes longer to reach absorption voltage, has dozens of qualifiers for it to actually be true anrf repeatable.

But just the fact that when new and healthy an AGM has less resistance, means it will be able to charge faster, if the amperage is there to do so. If the charging source cannot instantly achieve absorption voltage is not there, amps will likely start tapering a bit later on the AGM, and perhaps one could shut off their generator sooner than the guy with flooded jars of the equal state of health and the same number of PSOC cycles accumulated.

MrWizard wrote:
I want to apologize to the OP
For stomping on this thread and his test
But thank him for starting it and stiring up everybody's
Thought process during these lazy holidays

Mr Wizard, thank you for posting that, but no worries-- I did not see it that way, so no apology necessary IMO.

And yes, I think it is a good discussion. I had not thought of some of these things before, so it is good to "peer test" new- to- me ideas.

Mex, I figured from the start in this thread you were talking about something else from what I was talking about, and still are somewhat, sort of, but that doesn't matter because we get more good info from your posts anyway. Nothing is wasted.

I see all this battery stuff in terms of my ugly graph, which I built from tests I did after reading Barre's book.

I didn't think the AGM chemistry itself was in question at all, but I must not have been clear on that! Oh well. I just wanted to see how it would play out when actually charging a battery in the same ugly graph approach, which was what I thought PT was asking about.

Mr Wizard appropriate negative commentary cannot be viewed as "stomping" or can it? Einstein once remarked the definition of insanity was to "Do something over and over exactly the same way, and expect a different result".

Technical questions should be sought the answer...

First by noting relevant remarks made in answer.

Then pursue those answers by whatever research means available. In this day and age this means the internet. The only quest is to differentiate comment from fact. Multiple agreement from several reputable sources should satisfy questions about batteries. 90% of what I repeat endlessly here about PbSO4 characteristics can be found these days on internet websites.

Someone with better access can research for a 15 minute video (You Tube?) Made by Concorde about the construction of their AGM. excellent manuals are available FREE download from Rolls & Surette and Concorde Lifeline.

BFL13 sir, with respect, have you downloaded and read one or both manuals? Been to the batteryuniversity.com site? There is an incredible amount of valid information waiting at the touch of a button.

I prefer to deal with the subtle idiosyncratic moods of the electrochemical spectrum. It does indeed frustrate me when I prove incapable of giving forth of basic battery rote. My lack.

I want to apologize to the OP
For stomping on this thread and his test
But thank him for starting it and stiring up everybody's
Thought process during these lazy holidays

Hmm
High CCA
High capacity
High cyclablity

Wait! I forgot one...

High cost

Concorde Lifeline

Or is it (?) Wealth cannot buy happiness - just ask the bodyguards and alarm companies.

Can't have it all so enjoy what's on the plate

Monday Metaphorama

Hi,

I have the same surplus acid AGM battery type as Mr. Wizard--and they are limited to a lower charging rate than most starved acid AGM's. In my particular case that works out to 19 amps per 100 amp-hours of battery bank or very close to c/5. That is a perfect fit for me as I'd prefer solar charging to other methods.

BFL13, I would suggest that house AGM's be cycled from 50 to 95%, and that 100% would be even better. I'd base the stop generator charging on the solar harvest. If you have enough solar, stop at 85% just as if they were flooded jars. If you don't then go for 90% or 95%.

MrWizard wrote:
Niner
my AGMs are high output AGMs, they won't last 10yrs
but if they make 5yrs like my last set, I will more than happy , with money well spent

batteries in an RV are like engine oil, a job to do , but in the end ,, a consumable product with a finite life, i can budget that use, just like fuel

Showing my age with battery impedance testing. Getting obsolete. Thankfully chemistry cannot change - merely assume disguises. I really should get a resistance comparator. For one or two years (?) Hmmm. Really tempting to simply assume exit stage left condition and start reducing numbers of feasible projects. Blow $500 on a vibrating recliner and $400 on a six inch memory foam mattress.

Now I am wondering about the whole concept of 50-80s, for AGMs which was invented for Wet cells to take advantage of their higher acceptance rates in the low SOCs zone.

An AGM's zone will be higher in SOC, not sure how much higher in general, but might even be 65-95? Same AH spread.

This could matter for those who use a generator first while the low batts will accept the high amps and then go solar the rest of the day. That makes good sense with Wets because the low amp solar more fits the low acceptance rate of Wets in the high SOCs.

With AGMs, it could be that it would make more sense to run the gen to a higher SOC with its high amps and have less of a job for the solar to do that day. It could maybe work out that the generator gas money would not be much more than the "old way" and you could save money (or hassle) by not needing so much solar.

It would take some bean-counting to figure out, but there might be an "AGM advantage" in there somewhere. Not quite a game-changer perhaps, but sort of?

Niner
my AGMs are high output AGMs, they won't last 10yrs
but if they make 5yrs like my last set, I will more than happy , with money well spent

batteries in an RV are like engine oil, a job to do , but in the end ,, a consumable product with a finite life, i can budget that use, just like fuel

its those d-a-m-n expensive diesel engine problems, that i hate the most

MrWizard wrote:
As extended full timers
Generator time and fuel costs can over run the any savings gain in battery life
This is where a larger solar array is a big long run cost saver
I'm definitely thinking about adding more panels

Mr Wizard is correct in choosing AGMs as we have seen, where he operates daily in the 75-95? SOC zone and sometimes goes to 100.

It is now clear why that is the correct choice over Wets for his situation. (For me doing some 50-90s a year, not a full-timer, Wets work better over-all in the various factors in play.)

On solar, if a MH has two rows of panels laid flat, you can swap from amorphous to poly and make a gain in panel area to increase the amps, plus you can tilt them for quite a good gain.

But that means parking E-W to have the panels tilted facing S. The "front" panels will shade the "back" panels if the fronts are tilted, so that means only tilting the back row. Even so that will make for a significant gain. It might be a huge PITA to arrange all that though.

So if the usual plan is to do some gen from 75-85 and the rest with solar, you could make up for having less solar just by running the gen a little longer at high amps charging, taking advantage of the AGMs being able to accept those high amps to a higher SOC.

Some juggling of the bean-counting will reveal the "optimum" combo and operating procedure. Which will be good until you change locations in a couple of days and the weather changes :)

But in every way, Mr Wizard is getting the best bang for his buck with AGMs the way he RVs. That doesn't mean everyone else would of course.

The thing this thread has shown IMO as I have learned from it, is just exactly how to exploit the AGM advantage and when there is and is not an advantage.

This gives you some factors to play with when planning or adapting your set-up.