Charging antimony-free VRLA batteries without float

[HiTech]

Here is a proposed much lower float current method to charge non-antimony batteries. Supposedly better than traditional float.

Low current float for AGM

[HiTech]

I cannot either. No idea.

But to gauge full charge I am going to hundredths of a volt so a small difference might matter until I really have a good feeling on exact amp hours in/out (or sometimes as a handy short cut). I actually saw different pages on battery university, one said Voc goes up with temp and one said down, and neither how much.

The volts <-> SG thread had a really good link that looks like it goes up with temp (makes more sense to me). If I can quit avoiding chemistry and research how to convert the molar strength of sulphuric acid to specific gravity, that will be a pretty good theoretical formula. But it does not give the temperature function, just a point value at 77 degrees so I'll have to look into that next.

Jim

[mena661]

HiTech wrote:

I actually hit this paper researching to find out the effect of Temperature on a battery's open circuit voltage.

I haven't seen a difference on mine. Or would that difference be pretty small?

[HiTech]

Mex what about this paper? They seem to be on the "some voltage below ideal float" band wagon too?

I'm not a fan of the charge and sit cycles since you skip from one size of the positive plate corrosion curve to the other without much time in the sweet spot in the middle. But there does seem to be a set of researchers thinking the reduction in dry out may be worth some balance above Voc but below Videalfloat.

More research into floating below theoretical ideal float voltage for AGMs

I actually hit this paper researching to find out the effect of Temperature on a battery's open circuit voltage. I can find a few references to the idea that it changes, but no pointer to how much it would change by so far.

Jim

[MEXICOWANDERER]

Now yer talkin'!

By observing trends & tendencies, you can play a battery bank like a pipe organ with one hand tied behind your back while watching a football playoff game (the other hand clutches a brewskie).

There has got to be a reason I get a dozen years out of a set of T-105's, twenty plus on 2-volt cells and a dozen years out of a car battery. I am less a slave to my battery banks than you can imagine. Glance at a meter and if it seems odd, determine within 30 seconds if there is a problem.

I just had a person I was trying to help blow a grand on some L-16's he did not need. I told him to test first, he did not, and now US Battery has his 11 crisp Franklins, he has batteries that can not be paralleled with his old Rolls batteries and is several days south of the border. Sure his home is 200 miles from here, but my testing would have saved him a chunk of change. Such is life. I'd hate to be the person in US Battery that would have to deal with his whining about the no return policy.

Hi-Tech is learning on a pretty steep ramp. When you stop learning, you start dying.

[HiTech]

full_mosey wrote:

HiTech wrote:

Clattertruck wrote:
As a practical matter, my Deka AGM batteries are 5 years old, and they have been on charge 24/7 when we are not on the road. My converter is a Xantrex that puts out a float of 13.6 volts. The batteries seem to be performing fine.

So far so good. 13.6 is barely over the specific float voltage spec I got from Deka, and within the float range they allow, I think.

I need to calibrate my volt meters. They agree with each other to within a few hundredths, but the volt meter in my charger is sometimes many tenths off one way or the other, and not by a constant amount.

Jim

Jim;

There you go Obssessive-Compulsive-Disorder(OCD) on Volts again! 🙂

Set your chargers for 14.4V temp comp and calibrate your Amp meters!

Take a deep breath, let it out slowly while saying Amps, Amps....

How many AGM owners with 5-10yr old batteries it going to take?

MY solar two stage MS SS-10PWM doesn't even have a float stage! It simply holds 14.4V temp comp and tapers Amps so low that the battery reaches stasis. Rinse and repeat every day. This is the system that runs my 12V fridge and freezer. We're talking about my beer and ice cream, man!

Think Amps! 😉

HTH;
John

You know to be really obsessive, you alphabetize it into CDO...

Lol it is true. Amps and amp hours are very low indeed. I need to look at amp hours from more sources than solar and verify.

For non float you do have some flexibility on voltage. For 24x7 float everything I read says volts matter.

Time to measure some amps and amp hours on the chargers over time.

Jim

[HiTech]

full_mosey wrote:

HiTech wrote:
You never want to either. It is an extreme recovery procedure for an otherwise dead battery. Lifeline has one for batteries that have run dead and some other recovery procedure too. I used only as a last resort and it did work, but guaranteed the battery was stressed. It was not valve noise, it was a bubbling/crackling sound inside the battery.

Jim

Ah! That clears things up considerably. Your AGMs were already ruined. I had a grp31 trolling FLA that I ruined and it sizzled and crackled when I tried to recover it with a VEC1093.

It had run dry over Winter because I brought it inside and used it with an APC 1250 UPS without checking or adding water.

HTH;
John

Little 32 amp hour car AGM. But the recovery procedure actually worked and it is back in service. But at the time I ran the procedure, it would not start the car so Ah capacity and CCA were way down.

I have 2 not really in service yet Deka AGMs and 2 older small SLI AGMs.

Jim

[full_mosey]

HiTech wrote:

Clattertruck wrote:
As a practical matter, my Deka AGM batteries are 5 years old, and they have been on charge 24/7 when we are not on the road. My converter is a Xantrex that puts out a float of 13.6 volts. The batteries seem to be performing fine.

So far so good. 13.6 is barely over the specific float voltage spec I got from Deka, and within the float range they allow, I think.

I need to calibrate my volt meters. They agree with each other to within a few hundredths, but the volt meter in my charger is sometimes many tenths off one way or the other, and not by a constant amount.

Jim

Jim;

There you go Obssessive-Compulsive-Disorder(OCD) on Volts again! 🙂

Set your chargers for 14.4V temp comp and calibrate your Amp meters!

Take a deep breath, let it out slowly while saying Amps, Amps....

How many AGM owners with 5-10yr old batteries it going to take?

MY solar two stage MS SS-10PWM doesn't even have a float stage! It simply holds 14.4V temp comp and tapers Amps so low that the battery reaches stasis. Rinse and repeat every day. This is the system that runs my 12V fridge and freezer. We're talking about my beer and ice cream, man!

Think Amps! 😉

HTH;
John

[MEXICOWANDERER]

At 13.6 what is the current, the amperage aggregate over a day or a month? If you want to fine tune, use an adjustable regulated power supply for constant loads. That and a verified accurate kWh meter is the least expensive way I can think of to establish long term float "precise" reliability.

[full_mosey]

HiTech wrote:
You never want to either. It is an extreme recovery procedure for an otherwise dead battery. Lifeline has one for batteries that have run dead and some other recovery procedure too. I used only as a last resort and it did work, but guaranteed the battery was stressed. It was not valve noise, it was a bubbling/crackling sound inside the battery.

Jim

Ah! That clears things up considerably. Your AGMs were already ruined. I had a grp31 trolling FLA that I ruined and it sizzled and crackled when I tried to recover it with a VEC1093.

It had run dry over Winter because I brought it inside and used it with an APC 1250 UPS without checking or adding water.

HTH;
John

[HiTech]

Clattertruck wrote:
As a practical matter, my Deka AGM batteries are 5 years old, and they have been on charge 24/7 when we are not on the road. My converter is a Xantrex that puts out a float of 13.6 volts. The batteries seem to be performing fine.

So far so good. 13.6 is barely over the specific float voltage spec I got from Deka, and within the float range they allow, I think.

I need to calibrate my volt meters. They agree with each other to within a few hundredths, but the volt meter in my charger is sometimes many tenths off one way or the other, and not by a constant amount.

Jim

[HiTech]

You never want to either. It is an extreme recovery procedure for an otherwise dead battery. Lifeline has one for batteries that have run dead and some other recovery procedure too. I used only as a last resort and it did work, but guaranteed the battery was stressed. It was not valve noise, it was a bubbling/crackling sound inside the battery.

Jim

[Clattertruck]

As a practical matter, my Deka AGM batteries are 5 years old, and they have been on charge 24/7 when we are not on the road. My converter is a Xantrex that puts out a float of 13.6 volts. The batteries seem to be performing fine.

[full_mosey]

I just recently got one of those HF I-R guns. I will be curious to read your experiences in various battery temps.

Maybe I need a stethoscope. I definitely don't want to hear a valve make any noise. Can you explain the bubbling noise more as I have never heard any.

Optima says unlimited Amps but cap the Volts and Temps. My approach is to focus on getting Amps over Volts into my AGMs. That is more aligned with AGM mfgr specs.

Both solar controllers are MS PWM with temp comp and set for 14.4V and 14.35V, the WFCO converter/charger never does more than 13.6V and the portable has an AGM setting and ambient temp comp.

HTH;
John

[HiTech]

Definitely not trying to walk the tight wire or go over voltage. I am trying to validate and feel safe with the OEM float voltage (along with the accuracy of my instruments and power supplies).

When my New AGMs are still just a few percent below fully charged, they can sit for days and days at float at the proper temp, barely, sloooowly, gaining charge.

When they are truly full, just a tenth of a volt high with temps outside in the low-mid 70s seems to develop a stray bubble here of there in less than an hour. It seems at times even just the OEM float voltage will do this. How would anyone not testing for this gas from the valves ever know it is happening? Crazy swags at this level of out gassing and the water it would remove suggest it would be years before that level of gassing would remove many ounces of water. So it may not matter.

I wonder if in the end I may need to run .05 or .1 v less than the recommended float if I really want to float full time.

Next thing I am going to do is run some temp studies at different voltages for float on a full battery. Mex suggested this and I got an IR gun (the one the chemist uses to make his tea on Breaking Bad in fact). Mex told me even one degree of temp increase to too much so I am going to look for that as a sign the energy in is exceeding the self discharge. The exothermic nature of the valves means they heat up even before a bubble of gas escapes, I believe, due to their catalytic purpose of recombining the oxygen and hydrogen back into water. I will check both terminal temp but also the temp of each valve. Hmm thinking about that the temp of each valve under heavy charge may actually show me which cells are stronger, and I could see if the temps settle closer together over time as the string settles in to run as a more balanced set of cells.

One thing this all convinces me of is running AGMs in an untemp-controlled environment without temperature compensation can leave them chronically undercharged, overcharged, or oscillating between states with the weather. It's amazing to me they do as well as they do in starting ignition lighting service. Maybe it is because most starting batteries are chronically undercharged and AGMs handle this better than Flooded batteries. It still kills them, but supposedly they sulphate from it more slowly.

Jim