Battery / Solar Question

[luthj]

Removing sulfation is a purely electrochemical process. Preventing sulfation is a matter of charging a battery completely between cycles, and keeping time spent discharged to a minimum.

Shedding the lead sulfate from the plates permanently removes capacity from the battery, as does crystallized lead sulfate that will not revert. The lead in the lead sulfate is active material that would otherwise be part of the opposite plate.

 

[DaveInDenver]

I have yet to see any objective report from a source I trust showing that "battery desulfators" are anything but snake oil.

"Sulfation" has to be defined, which is usually narrowed to mean recrystallization of the lead sulfate. This, as as you mention, is understood electrochemically and I so assume you're referring to the "desulfators" such as @dwh uses, that pulse?

Equalization and good charging practices can slow it, that's always the best approach. But the concept of pulsing to reverse it has been considered likely since at least 1995 when the "Pulsed-current charging of lead/acid batteries" paper was published. The professors (Dr. Bob Erickson and Dr. Bill Romish at Univ of Colorado) I had for power systems classes referred to pulsing as a matter of fact. Dr. Erickson still appears to mention it in his lectures.

For example, from the notes for ECEN 4517/5517, Power Electronics and Photovoltaic Power Systems Laboratory, at CU-Boulder.

https://ecee.colorado.edu/ecen4517/materials/Battery.pdf

Battery charge management to extend life of battery:

• Limit depth of discharge
• When charged but not used, employ “float” mode to prevent leakage currents from discharging battery
• Pulsing to break up chunks of lead sulfate
• Trickle charging to equalize charges of series-connected cells

I attached the PDF to which I'm referring.

"Pulsed-current charging of lead/acid batteries - a possible means for overcoming premature capacity loss?" by L.T. Lam *, et al
Journal of Power Sources 53 (1995)

This paper will show up cited in most subsequent papers on the subject.

 

[dwh]

I can see a majority of batteries just sit around like in a solar array or vechicles that don't move very often and can see a desulphation function is important.

It's not just about vibration. It's about the right kind of vibration.

First of all, sulfation happens constantly. It happens faster if the battery is less than fully charged.

It's very similar to rust, except that rust is iron and oxygen binding to create iron-oxide, and in a lead-acid battery it's lead and sulphur binding to create lead-sulphate.

There is a major difference though - in a lead-acid battery, most of the lead-sulphate gets dissolved into the acid when the battery is charged, and the lead ends up back on the plates.

But that only happens IF you recharge soon enough - before the lead-sulphate hardens into a crystallized form. Once the stuff crystallizes, simply charging the battery won't dissolve it.

Equalizing can help some. Mostly it just makes some of the sulphation break up to a more or less equal amount on the different cells and stirs the electrolyte to eliminate stratification. Equalizing equalizes the specific gravity of the electrolyte, which doesn't really have much to do with sulphation.

Desulphators suck a bit of juice from the battery into a capacitor, then pulse it back into the battery as a high-frequency vibration. Some manufacturers claim this freq or that freq works best. Battery MINDer uses what they call "full sweep"...probably like dialing the knob on a tone generator back and forth.

I read that AGM batteries it is not recommended to equalize.

Any lead-acid battery can be equalized - if you know the top-secret lab specs and have the equipment to do it. Doing it to a sealed lead-acid battery (VRLA) without blowing the popoff valve and losing water that can't be replaced is tricky. Using an EQ procedure for a flooded open cell battery on a VRLA is a bad idea. It used to be that all AGM manufacturers said "do not EQ", but with a lot more programmable smart chargers out there, some now publish the specs to do it.

Would you say that a battery in a vechile traveling say down a washboard road while the alternator is charging, would this vibration act as a desulphation function enough to limit the growth on the plates?

No.

In a flooded battery the sloshing/vibration can help to counteract stratification, so it does part of what equalizing does, but nothing in regards to sulphation.

In an AGM, the electrolyte is absorbed into a fiberglass fabric between the plates, so I doubt that bouncing around does anything to prevent or reverse stratification.

I guess only if the vehicle was regularly driven with enough vibration would replace a desulphation function on a charger system?

Totally wrong.

 

[john61ct]

I was the same. I searched and searched...nothing but anecdotal reports and manufacturer claims.
…
It topped out there and never went any higher, but nevertheless, for a battery that old and used up, it was enough to finally convince me that desulphation is worth doing.

Which brings us to the fact that out of hundreds of such devices marketed over the years, none seem to "pulsate" at the same frequency or amplitude.

So even if someone proved a worthwhile long-term benefit for a particular model A, does not translate to validating model B.

My reco is take care of the bank as per mfg specs, use it until SoH falls to ~70%, maybe 80% for mission-critical use in primitive locations.

Then replace.

A good quality bank treated well can last 12+ years that way, no desulfator in sight.

 

[dwh]

Which brings us to the fact that out of hundreds of such devices marketed over the years, none seem to "pulsate" at the same frequency or amplitude.

Personally, I doubt that freq makes all that much difference as long as it's high enough. Hitting the perfect freq just right might make it go a little faster...but it still takes weeks or months.

It's not a replacement for proper care and maintainance. It's a slight edge to slow down loss of capacity due to sulphation, or to recover some lost capacity from poorly maintained batteries.



(And...12+ years...my aching ********. Data center power backup roomfuls of batteries don't last that long, and pretty much nobody takes better care of their batteries.)

 

[luthj]

Lead suflate is not very soluble in sulfuric acid solutions, which is part of the reason that charging lead acid gets slower at higher SOC, where the acid concentration is highest.

I have not seen any experiments where frequency (AC current, or pulsed DC) was a marked improvement over a constant current of the appropriate voltage. For lead sulfate at room temperature, this needs to be over 14.7-14.8V, up to 16V or higher is better. The problem of course is that voltages that high heat the batteries, and accelerate grid breakdown, and rapidly deplete the water. In AGMs this can destroy the battery, as water cannot be added. On some more robust AGMs, they have higher pressure cases, and more catalyst, so they can tolerate 15-16V for a period of time. Lifeline for example recommends a 4-5 hour equalize every month for batteries that are cycled continually between 50-95% SOC (note you need to contact them directly for this info).

Many desulfators avoid the corrosion and water loss issues by pulsing the high voltage. Each pulse of around 16V dissolves a little of the crystal (in theory). Over months this can recover some of the lost capacity. Note that cycling the battery much tends to counteract the desulfator during this process, as you are piling more amorphous lead sulfate onto the crystals. The crystals then may tend to grow, as some the sulfate molecules will align with the crystal lattice.

The only immediately effective approach I have seen is the distilled water fill/charge I mentioned above. I have seen this work on big forklift batteries that would not achieve full specific gravity when charged. This can be risky with older batteries, as the debris at the bottom of the battery can be disturbed and sometimes cause shorted cells.

 

[john61ct]

Any lead-acid battery can be equalized - if you know the top-secret lab specs and have the equipment to do it.

Actually you can easily contact qualified tech support for advice at any decent maker of deep cycle batteries, all of whom make such details readily available. I would not advise buying product by those that don't.

> It used to be that all AGM manufacturers said "do not EQ", but with a lot more programmable smart chargers out there, some now publish the specs to do it.

Other way around. Ten years ago they were all saying go for it. Then Enersys, inventor of both TPPL and spiral tech that brought AGM into the deep cycling mainstream, discovered the high voltages were hurting longevity. I think it was Bruce Essig himself put the word out.

Lifeline is now the *only* maker of quality AGM still recommending high voltage equalization.

Odyssey / Enersys and Northstar, also Full River I believe, have "conditioning" protocols that keep voltage within their normal Absorption specs.

I don't think any other sealed LA batts are worth buying for deep cycling use in the NA market.

 

[john61ct]

Some industries set a much more stringent EoL cutoff than others.

It is true that many yacht owners getting over a decade from their Rolls / Surrette bank have pushed past my 70% SoH guideline.

But that level of build quality probably justifies such recklessness; it is very rare to hear of "unexpected destructive failures" in that arena, at least not when they're properly coddled.

 

[DaveInDenver]

Odyssey... have "conditioning" protocols that keep voltage within their normal Absorption specs.

Indeed, Odyssey recommends discharging to 10.0 V for conditioning and then a strict maximum of 15.0 V and conditioning current minimum of 0.4*C10. Then their normal charging profile voltages of 14.7 and 13.6 V as targets.

 

[dwh]

Odyssey's "conditioning charge" is a fairly recent development. As I recall their most recent technical manual (2014) doesn't even mention it.

http://www.odysseybattery.com/documents/US-ODY-TM-002_1214.pdf


It's not an EQ procedure. It's a response to a lot of their batteries not holding their full resting voltage after a few years.

That discharge to 10v then recharge at 40a per 100a capacity - is strange. I haven't seen anywhere where they've explained exactly what the point of that procedure is. My best guess is de-stratification of their "starved electrolyte".

 

[john61ct]

If you contact their tech support you may well get an intelligent discussion on the topic.

The standard protocols for "commission charging" a new set of batteries during the breaking in period, and the process of conducting a 20-hour load test, are similar, and often a substantial boost in apparent SoH is the result.

 

[DaveInDenver]

The Odyssey procedure is dated March 2016. The Technical manual I have from them is dated September 2016. For completeness, also attached the procedure to recover a deeply discharged battery they emailed me along with the conditioning one.

The reason for getting the documents is one of my PC1400 is apparently weaker than the other (resting voltage 12.65 V vs. 12.8 V), so this is what they thought would help.

 

[PV Hiker]

Thank you dwh for answering my questions. A lot to learn and asorb in this posting. Interesting....

 

[Alloy]

And wears out sooner and costs more. That "can't freeze" is nonsense - AGMs use acid/water electrolyte like all lead-acid batteries.

And yes, Trojan makes great batteries.

. . . . ... when there is an issuse with AGM there is no way to test the spec. gravity of the cells.

Crown are another good choice.

 

[Alloy]

Each manufactuer lists the charging parameters.

If the life of the battery is important don't take specs from one type/brand and use the specs. on another.