Testing AGM batteries?

[Naio]

When I got my last set of batteries (150aH AGM, used), they had been tested on a high-amp car tester. But my friend who knows batteries pretty well said that was not a proper test, that what we should do was put a 25 amp load on, and see how long the battery took to get down to 11v or so.

This method caused us to reject several batteries that had tested fine on the high amp tester. And the batteries I got have been good.

This same friend, though, told me it was important to cycle batteries in long term storage (not just float them). Doing that, with the 25 amp load, one got away from me, suddenly dropped to 10.5v or so, and that killed it.

I have also killed numerous 33aH batteries by putting a 100amp brief load on them, before I figured out that was not cool.

So. How should I test these used AGMs I am looking at now? Should I rely on the sellers 150aH 15-second test? Should I do a smaller load for longer? What do you all do?

[MrWizard]

Same ones,
But seems like the 20 hour rate should be higher than that

[pianotuna]

Hi,

If these are the ones Naio purchased the 20 hour rate is 135 amp-hours.

[MrWizard]

A little note on specs

Camping world sells exide
The Edge agm dual purpose sells for $199 and are spected at 120 minutes RC at 25 amps

The 12flx500 batteries I bought
Spec at 48 amps for 120 minutes
And
22 amps for 300 minutes
15 amps for 480 minutes that's 8 hours

An 8 hour capacity of 119 amp hrs , 8 hours discharge not 20 hours
The 20 Hr capacity will be much higher, anyone know how to calculate/extrapolate that from this info

Float voltage is 13.62 at 77°F
Charge voltage and amps is 'undeclared'

Hoping to get these installed today

[Naio]

Oh, that's great, Mr Wizard :).

[westend]

....... I have a beer budget with champagne tastes. I need my batteries to last a long long time.

I hear that!:C

[pianotuna]

Hi,

If possible on a vrla you do not wish to charge passed the gassing voltage by much, or for very long. Surplus acid AGM's are a different beast than what you have, so probably different guide lines would be best. I am a neophyte as well, and I have a beer budget with champagne tastes. I need my batteries to last a long long time.

westend wrote:
Hey Don,
I'm rather a neophyte with VRLA construction but I would think the recombinant gas mechanism would reduce the need for a lot of gassing, irrespective of SG. I might be totally wrong about that?

The Genesis EP AGM's I'm using describe a "reconditioning" process should the batteries lose capacity. IIRC, the voltage is set at 16V for a period of time and there is no admonition about temperature. That's not a real healthy diet IMO. as boiling out any electrolyte would be bad AFAIK.

FWIW, my 6 V bank has the temp compensation connected from the solar controller and that pair is fairing very well. I just recently added water to the cells after a year of nearly constant charging. My controller is set to go into 14.6 bulk for a short period and then floats for the rest of the day if voltages stay above 13.5 V. The SG remains at a baseline 1.30 while in storage.

[MrWizard]

I bought 4 of these for the house side to replace my 5 yrs old set
Everyone i bought checked at 13+ volts
I grabbed one of my picks , put my 500 amp carbon pile tester on it
And it tested at 300 amps load

I think i will be just as happy with these as with my CD technologies set

[westend]

Hey Don,
I'm rather a neophyte with VRLA construction but I would think the recombinant gas mechanism would reduce the need for a lot of gassing, irrespective of SG. I might be totally wrong about that?

The Genesis EP AGM's I'm using describe a "reconditioning" process should the batteries lose capacity. IIRC, the voltage is set at 16V for a period of time and there is no admonition about temperature. That's not a real healthy diet IMO. as boiling out any electrolyte would be bad AFAIK.

FWIW, my 6 V bank has the temp compensation connected from the solar controller and that pair is fairing very well. I just recently added water to the cells after a year of nearly constant charging. My controller is set to go into 14.6 bulk for a short period and then floats for the rest of the day if voltages stay above 13.5 V. The SG remains at a baseline 1.30 while in storage.

[pianotuna]

Hi,

The reason I asked is because my surplus acid agm telcom jars have a specific gravity of 1.30 when fully charged.

I know that tropicalized electrolyte is of a lower specific gravity and winterized electrolyte is a higher specific gravity. I don't know the actual numbers.

Now that I think about it--clearly the temperatures for gassing need to be lower with the higher specific gravity. That is kind of important with any VRLA jar.

[westend]

pianotuna wrote:
Does anyone know if a higher specific gravity increases temperature for charging rates?

Example:

1.275 vs 1.30 can temperature be higher for the 2nd number when charging?

Good question and could get quite theoretical/technical in answering. One unknown is: Are both of the specific gravity densities you listed at the full SOC measured density?

Off hand, I'd say no, it doesn't matter because there is a gain in density while charging and all other things being equal, the rise in density range may be the same for both examples, hence temperature would be monitored alike.

[EsoxLucius]

MEXICOWANDERER wrote:
Naio, download and read this PDF manual. You can trust the information.


https://www.tayna.co.uk/docs/datasheets/lifeline/lifeline-manual.pdf

I particularly like the title, "TECHNICAL MANUAL For Lifeline Batteries". It doesn't say "TECHNICAL MANUAL For AGM Batteries".

[pianotuna]

Does anyone know if a higher specific gravity increases temperature for charging rates?

Example:

1.275 vs 1.30 can temperature be higher for the 2nd number when charging?

[pianotuna]

Hi Land,

That is why I keep recommending temperature compensated charging.

[landyacht318]

Curiosity+ data from actual instruments, somewhat accurate, is so much more revealing than a2 +b2 =c2 book learning.

My battery temperature is swinging much more widely than I imagined before I had battery temperature actual data.

Short read,. it gets hotter, faster than expected, and holds it through absorption and maintains it well after during discharge which can also alter the apparent capacity during discharge, as it basically maintains temperature during discharge during falling ambient temps.

77f, is easily exceeded in 65F ambients in Absv, or VAbs, if BFL13 decides it is time to come back.

A thermocouple in the battery case, has been extremely enlightening to me.

I wish I had better ability to log the data I can now collect.

My battery temperature data, so far, has slapped me upside the head, with only a semi closed fist. My ears are still a ringing, as my expectations were very far off of actual.