another source for agm batteries

BFL13 wrote:
IMO more attention needs to be paid to this:
...
1.That all means you need to do a serious "recovery" session to get back to full charge (in my case using the Equalize feature on the charger)

Now the crunch is how to do that routine with AGMs? You can blast away on the Wets gassing up a storm.

But "recovery" with AGMs is a very tricky, fussy business. Hard to even find a charger that will do that within AGM specs.

This suggests that AGMs are not the best choice at all for the first case, but only would be suitable with solar where you are sure to get back to full every day (not possible in some seasons in some places)

2. Glad to see mention of good old "progressive capacity loss" too. I bet those with some solar who operate like the first case and have AGMs are losing battery capacity at a good clip, but don't know it.

I am not experiencing the issues you raise. I have numbered your statements to facilitate comments.

1. What recovery? First, charging the AGM is easy, not fussy. Charge until the rate is below 1%C, then float. Periodically do shore power overnight. What part is tricky or fussy?

Second, I don't use any high Volt equalization charging. That is a tricky wet only business.

2. Try telling us AGMers with our 5yo and 7yo AGMs that they are not performing to capacity. Didn't we recently have a post about charging AGMs with a dumb 13.8V converter/charger for 7yrs? Is that a special charger? Start reading here. Which type has the special charging requirements now?

So we have, AGMs:

1. charge faster/cheaper with lower volts,
2. no equalizing.

HTH;
John

IMO more attention needs to be paid to this:

Mex says, "A maintenance charge profile for a battery that gets discharged over a period of a week, stays discharged for four days then goes and gets connected to a charger, is absolutely different than a battery that cycles to 50-60% off capacity every day then gets promptly recharged. How the profile must differ is to offset impending loss of capacity with the first example"

The fist case is how it goes with solar where it is used to delay the time between gen recharging (like I do it usually) It also applies to those who have large banks and no solar and wait till they get home before a recharge.

That all means you need to do a serious "recovery" session to get back to full charge (in my case using the Equalize feature on the charger)

Now the crunch is how to do that routine with AGMs? You can blast away on the Wets gassing up a storm. But "recovery" with AGMs is a very tricky, fussy business. Hard to even find a charger that will do that within AGM specs.

This suggests that AGMs are not the best choice at all for the first case, but only would be suitable with solar where you are sure to get back to full every day (not possible in some seasons in some places)

Glad to see mention of good old "progressive capacity loss" too. I bet those with some solar who operate like the first case and have AGMs are losing battery capacity at a good clip, but don't know it.

It does tell you something about the integrity of this battery. Most AGMs can charge at C, this one only at 0.25C.

But with 800AH, you would be hard pressed to charge at 0.1C. You need a significant solar addition. You're only as strong as the weakest link.

Sal

pianotuna wrote:
Any truth to AGM's REQUIRING high charge rates to survive?

I was looking through the technical sheets of the Genesis AGM battery made by Enersys (I use three of them) and it has some charts about what Mex was referencing as to charge profiles. It probably doesn't apply directly to all AGM batteries but there's some good stuff in there.

It was also cool to note that there is no charge amperage limit. If I had the right converter with an adequate generator, the batteries could be recharged to 90% in an hour. :E :B

Hi Mex,

Definitely makes sense. And is humorous too *grin*.

IT "DEPENDS"



When specifications wander all over the board, I believe it prudent to keep in mind an AGM battery is an AGM battery. There is actually very little room to maneuver the technology and the science behind it. An AGM with fewer thinner plates requires the same voltage diet as a heavier AGM.

Therefore say a Deka will not vary all that much from a Lifeline. I tend to consider comments and remarks from the "Big Boys" as carrying a lot more weight than what some of the smaller companies sales force is spouting.

The problem is this...how does a company approach the customer's pervasive belief that everything these days MUST BE plug-and-play. How do you reconcile charge profiles with different levels of discharge, temperatures, and indeed INEVITABLE abuse?

A maintenance charge profile for a battery that gets discharged over a period of a week, stays discharged for four days then goes and gets connected to a charger, is absolutely different than a battery that cycles to 50-60% off capacity every day then gets promptly recharged. How the profile must differ is to offset impending loss of capacity with the first example. Astute owners who tinker with charge profiles negate aggregate degradation of the capacity in ampere hours. But few AGM owners are willing to tinker. So "what" recharge profile is "best"?

Such ambiguities serve as fodder in "meetings". What do you tell the customer? If a company committed itself to an in-depth explanation of how charge profiles must vary (which is absolutely the best method as far as the battery is concerned), it would scare prospective customer "Joe Smudge" to death. So ash trays get filled and gallons of water get consumed as engineers go head to head with salesmen.

CHARGE "JUST RIGHT" TO MINIMIZE
A) Loss of capacity
B) Excess positive plate erosion
C) Live up to the AGM mantra CHARGES FASTER
d) The possibility of Smudge abandoning ship and going with a company that lies like 600 year old persian rug.

I've capacity tested numerous AGM batteries that customers absolutely swear are like "Brand New" yet render 40% of design amp hour capacity. And a similar number of "junk" AGM batteries that had near OEM design specification capacity.

And some salesman is going to say their company has the perfect pair of pants to fit either Laurel or Hardy?

Go with the charging recommendation commonality you find in the information as supplied by the major manufacturers.

Learn how to "Condition" an absorbed glass mat battery if you suspect the battery has been losing amp amp capacity.

Does this make sense to you?

Salvo wrote:
The Deltran AGM info gives charging at 0.4C. That's more like it for an AGM battery. Fast charging is one of the main attributes for AGM.

Excellent charger BTW. I still have it from when I was charging 2x D31T Optima.

pianotuna wrote:

1. Any truth to AGM's REQUIRING high charge rates to survive?

2. There are some Universal's here that work out to $1.76 per amp-hour http://www.batterystuff.com/batteries/rv/#a8830

1. No,.. maybe? See 2.

2. Here is your grp 24 battery at $1.73USD per AH.

http://www.batterystuff.com/batteries/upc-telecom/UB12750-45821.html and,

The mfgr/dealer/distributor http://upgi.com/Themes/leanandgreen/images/UPG/ProductDownloads/45821.pdf.

It shows a spec of:
Control of 14.5 - 14.9V and,
Float of 13.6 - 13.80.

I have no idea what control is or what happens in the gap between 13.8 and 14.5. At the bottom they say cycle use they say almost the same with 2.4-2.5V/Cell of 14.4-15V. Also no mention of temp comp.

I know you run a 2500W inverter. Take a look at the Constant Power Discharge Characteristics Unit Watts (25°C, 77°F) table. You can convert inverter minutes into bank size. E.g., if your inverter has an 11.1V LVD, you could run a 1749W microwave for 10Min.

HTH;
John

PT,

Plugging that UB12900 part number leads to this spec sheet

http://www.apeximg.com/images/NB12-100.PDF

Pics show a different battery, but zoom in on the battery diagram where it says

CHARGING INSTRUCTION
Floating use: 13.5 ~ 13.8V
Cycle use: 14.4 ~ 15.0V
Initial current: less than 30A

30 amps max into an 90 a/h AGM, Does not Odyssey say a ~90 AH battery can take safely take nearly 300 amps initially or some such silly number.


Looking at the Vmax battery spec sheets says charging current to 30 amps on a similar size battery.

Vmax might just be a nice new sticker pasted onto the Asian UB agms

Salvo wrote:
Very strange charging spec. It's more like a lead acid battery.

Recommended charge rate: 0.1C
Max charge rate: 0.25C

The Deltran AGM info gives charging at 0.4C. That's more like it for an AGM battery. Fast charging is one of the main attributes for AGM.


SLR100-8 Specs:
VOLTS 12V
AMP HOURS 100AH
WEIGHT 68LB
SIZE : L=12.1" W=6.7" H=8.2"
MAX. CHARGING CURRENT: 25A
MAX. CHARGING VOLTAGE: 14.7V
RECOMMENDED: 10A, 14.5V

The time in bulk is about 1.75 hours at 20amps = 35AH. ( 35/50=70% SOC start taper, which is about right IMO) But then it does 1.5 times the 1.75 or 2.63 hrs in Absorption at average 9.5 amps =25AH and 35 + 25 = 60AH on a 50AH battery. Then it is supposed to be somewhere just over 95% so it keeps charging for longer.

Since AGMs don't gas like a Wet where did the extra 20% AH or so go?