Monday, 18 August 2008

Battery "sulfation": An investigation into rip-off technology

For pretty much all of what I refer to as my self-guided education in science and skeptical thinking, I have been fascinated by medical and biological claims. After all, that's the reason I started - I needed to educate myself so that I could provide educated information to my clients.

Recently, I've looked more closely into climate change. But evolution, medicine and climate have been the most entertaining and interesting avenues of investigation.

Here's a little episode, however, which illustrates that investigative skills, a good grounding in science and common sense, along with a skeptical thinking toolkit which includes conspiracy-theory-spotting techniques, will stand you in good stead in almost any situation. I had originally written this in an email, but I resurrected it, dusted it off, expanded it and produced this for your interest, education and profit:

Almost a year ago now, I was involved (I started it) in a battery thread on a bike forum. The basic outcome was that I ended up knowing more than I used to: vis, that a battery can die sporadically and not all at once, which was the common knowledge around me at the time. However in this thread somebody, having demonstrated that they didn't know how to answer a question and couldn't be trusted to keep track of what's going on, mentioned that people should buy a particular brand of trickle-charger which uses rapidly alternating current to shake free sulfation on the battery plates and extends the life of the battery. I come back to this now because I have just seen similar claims from a motorbike website reviewing a product they didn't understand (by the way, this is called "parroting" not "journalism").

Now, I am not a physical chemist, engineer or anything of the sort. But I remember enough of chemistry and have, I hope, enough common sense knowledge of physics, for alarm bells to have gone off when I read this.

Rule Number One: What are they talking about?

I went off to look at the website for this fancy trickle-charger, and in the FAQs it explained that the build-up of sulfates on the plates kills batteries and that when they are "shaken free" they will dissolve back into solution.


Rule Number Two: Try and understand the science involved.

Point one: Energy can neither be created nor destroyed, only converted. In generators, mechanical energy is converted to electrical energy. In a lead-acid (and any other) "battery", chemical energy is converted into electrical energy. Specifically, you have lead plates with a solution of sulfuric acid surrounding them. This is an unstable situation, and at the negative plate the hydrogen sulfate ions in solution react with the lead to produce lead sulfate, hydrogen, and a couple of spare electrons which, you may gather, is where the electrical current comes from. The positive plate is more complicated, but the summary is that lead oxide on the plate combines with hydrogen sulfate, hydroxide ions and a couple of electrons to produce lead sulfate and water. To charge the battery, force electrons through it backwards and everything is reversed.

You will note that as a result of this, "sulfate" is deposited on both battery plates as a result of the battery working properly and is removed during recharging. Bear this in mind as we read on.

Still on the manufacturer's website, I found this gem in the FAQ: it had "Why haven't I heard about Battery Life Saving technology?" and the answer was "The companies don't want you to know." Whoop! Whoop! Woo-alert! Paranoid conspiracy nut ahead! Abandon ship, abandon ship!

I can't stress this enough: That's not how the world works. Nobody is really competent enough to hide something like this when people are trying to sell you the technology. Physicists and chemists would be using them and recomending them to all their friends, for a start.


Rule Number Three: Look for supporting or rebutting evidence.

I Googled and found the same information repeated ad nauseum by retailers and by people attempting to offer "advice" by regurgitating what they had just read (it is a really, really bad idea to take the word of a manufacturer as gospel). Tellingly, not a lot of actual evidence turned up highly ranked on Google results - just anecdotal reports (which isn't evidence - trust me on this) and endlessly repeating "apparently"'s and "I've heard that" and "They say".

Ah, but also the Battery Performance Research Institute. Now, that name alone is highly worrying. Doesn't sound like an independent, objective body, does it? And no, they're a consultancy firm. But they do explain sulfation as: Large crystals of elad sulfate will grow on the lead plates, which ultimately prevents the chemical reaction necessary for the current by tying up the reactants and preventing the acid reaching the lead.

That's a little more believable. But what to do about it, and why doesn't charging the battery get rid of the crystals? And if it doesn't, what are you trying to do about it?

Rule Number Four: Keep looking

By tacking "evidence" onto the Google search for "battery sulfation" I managed to find a fascinating little thread in a battery newsgroup hosted by a university in the USA, where a poster (this was from 6 years ago, so fuck-off trying to sell "unique, innovative technology") quoted an electro chemist as not just shooting this "sulfation causes battery failure" theory down in flames but comprehensively burying it at a crossroads at midnight with a steak through its heart and its head on display in a a bowl of holy water in the next county. Well, I exaggerate a little.

Essentially, although the formation of large lead sulfate crystals is a worry, it's only number three or four on the list:

"...sulfation is, by definition, irreversible. Once lead sulfate crystalizes and sheds from the plates of a battery, there is no way, electrically, chemically, or otherwise, to return it to the plates. The sulfation represents irretrievably lost capacity in one or more cells."

And to save me time, I will copy and past the information quoted from the chemist, one Nawaz Quershi who, apparently, worked for a couple of different battery companies. At the end is the executive summary from the quoting poster:

-- begin quoted text --

1. Normally, batteries do not fail from sulfation. They fail from the positive grid corrosion, but primarily from the positive plate active material (lead dioxide) shedding. The loss of this material means loss of capacity.

2. The positive plate loses its integrity by cycling: the crystal structure gets destroyed, a little bit at a time, until the particles get so small that they float away from the plate forming the sludge at the bottom of the cell.

3. During charge, when the lead dioxide particles, floating around in the acid, touch the negative plate, they convert (plate out) into lead metal dendrites which grow towards the positive plate, eventually creating a short. This is also called mossing.

4. During discharge both of the electrodes (lead dioxide and spongy lead) convert to lead sulfate, reversing upon re-charge. So lead sulfate formation is a necessary condition for the battery to function.

5. If you let a battery sit for 6 months or more, the self discharge reactions occur very slowly, forming very large lead sulfate crystals. Since lead sulfate is an electronic insulator, they do not convert (recharge) easily. This rather pathological condition is called sulfation. Normal operation of the battery should not and does not cause this condition unless you operate your batteries in significantly undercharged condition (mismatched charger?).

-- end quoted text --

In short, unless you allow your batteries to sit unmaintained for many months at a stretch, or unless your charger's output is much too low, sulfation is not as much of a problem as it's made out to be. (This was news to me too. For many years I believed what I'd read -- that sulfation was the main cause of lost capacity.)

So, in other words:

No battery will last for ever, learn to accept that. On the other hand, not using a battery is bad for it. Don't let it drain too low, don't put the wrong charger on it, keep cycling it. There's not a lot you can do about gradual degradation except (maybe) buy a better quality battery to begin with, and get a charger which can do an "equalisation charge" which gets each individual cell to the same charge and prevents too much stress on any of them. In fact, the evidence is that any good work done by a "desulfater" is through an equalisation charge which is a side-effect of the way they operate.

Rule Number Five: Reality is usually more complicated than that - there are no simple answers.

What you can, therefore, do to keep your automotive batteries happy is to use them. There are chargers which will do equalisation charging and which will maintain battery life by slowly discharging and recharging if you leave them plugged in. Get one of those if you must but, purely on the theory of "don't encourage the bastards", don't buy a desulfater.

References and links:
The chemistry of lead-acid batteries from
The thread on the Tufts Institute of Cosmology, Tufts University mailing lists.
Battery Performance Institute "Desulfation"

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