Dead Lead-acid Batteries: Desulfation-resurrection opportunities?

Back in November 2023, I told you about how my 2006 Jeep Wrangler Unlimited Rubicon:

had failed (more accurately, not completed) its initial emissions testing the year before (October 2022) because it hadn’t been driven substantively in the prior two years and its onboard diagnostic system therefore hadn’t completed a self-evaluation prior to the emissions test attempt. Thankfully, after driving the vehicle around for a while, aided by mechanics’ insights, online info and data sourced from my OBD-II scanner, the last stubborn self-test (“oxygen sensor heater”) ran and completed successfully, as did my subsequent second emissions test attempt.

The battery, which I’d just replaced two years earlier in September 2020, had been disconnected for the in-between two-year period, not that keeping it connected would have notably affected the complications-rife outcome; even with the onboard diagnostic system powered up, the vehicle still needed to be driven in order for self-evaluation tests to run. This time, I vowed, I’d be better. I’d go down to the outdoor storage lot, where the Jeep was parked, every few weeks and start and drive it some. And purely for convenience reasons, I kept the battery connected this time, so I wouldn’t need to pop the hood both before and after each driving iteration.

I bet you know what happened next, don’t you? How’s that saying go…”the road to hell is paved with good intentions”? Weeks turned into months, months turned into years, and two years later (October 2024) to be exact, I ended up with not only a Jeep whose onboard diagnostics system tests had expired again, but one whose battery looked like this:

Here it is in the cart at Costco, after my removal of it from the engine compartment and right before I replaced it with another brand-new successor:

I immediately replaced it primarily for expediency reasons; it’s somewhat inconvenient to get to the storage lot (therefore why my prior aspirations had been for naught) and given that I already knew I had some driving to do before it’d pass emissions (not to mention that my deadline for passing emissions was drawing near) I didn’t want to waste time messing around with trying to revive this one. But I was nagged afterwards by curiosity; could I have revived it? I decided to do some research, and although in my case the answer was likely still no (given just how drained it was, and for how long it’d been in this degraded condition), I learned a few things that I thought I’d pass along.

First off: what causes a (sealed, in my particular) lead-acid (SLA) battery to fail in the first place? Numerous reasons exist, but for the purposes of this particular post topic, I’m going to focus on just one, sulfation. With as-usual upfront thanks to Wikipedia for the concise but comprehensive summary that follows:

Lead–acid batteries lose the ability to accept a charge when discharged for too long due to sulfation, the crystallization of lead sulfate. They generate electricity through a double sulfate chemical reaction. Lead and lead dioxide, the active materials on the battery’s plates, react with sulfuric acid in the electrolyte to form lead sulfate. The lead sulfate first forms in a finely divided, amorphous state and easily reverts to lead, lead dioxide, and sulfuric acid when the battery recharges. As batteries cycle through numerous discharges and charges, some lead sulfate does not recombine into electrolyte and slowly converts into a stable crystalline form that no longer dissolves on recharging. Thus, not all the lead is returned to the battery plates, and the amount of usable active material necessary for electricity generation declines over time.

And specific to my rarely used vehicle situation:

Sulfation occurs in lead–acid batteries when they are subjected to insufficient charging during normal operation, it also occurs when lead–acid batteries left unused with incomplete charge for an extended time. It impedes recharging; sulfate deposits ultimately expand, cracking the plates and destroying the battery. Eventually, so much of the battery plate area is unable to supply current that the battery capacity is greatly reduced. In addition, the sulfate portion (of the lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large crystals physically block the electrolyte from entering the pores of the plates. A white coating on the plates may be visible in batteries with clear cases or after dismantling the battery. Batteries that are sulfated show a high internal resistance and can deliver only a small fraction of normal discharge current. Sulfation also affects the charging cycle, resulting in longer charging times, less-efficient and incomplete charging, and higher battery temperatures.

Okay, but what if I just kept the battery disconnected, as I’d been doing previously? That should be enough to prevent sulfation-related degradation, since there’d then be no resulting current flow through the battery, right? Nope:

Batteries also have a small amount of internal resistance that will discharge the battery even when it is disconnected. If a battery is left disconnected, any internal charge will drain away slowly and eventually reach the critical point. From then on the film will develop and thicken. This is the reason batteries will be found to charge poorly or not at all if left in storage for a long period of time.

I also found this bit, both on how battery chargers operate and how sulfation adversely affects this process, interesting:

Conventional battery chargers use a one-, two-, or three-stage process to recharge the battery, with a switched-mode power supply including more stages in order to fill the battery more rapidly and completely. Common to almost all chargers, including non-switched models, is the middle stage, normally known as “absorption”. In this mode the charger holds a steady voltage slightly above that of a full battery, in order to push current into the cells. As the battery fills, its internal voltage rises towards the fixed voltage being supplied to it, and the rate of current flow slows. Eventually the charger will turn off when the current drops below a pre-set threshold.

A sulfated battery has higher electrical resistance than an unsulfated battery of identical construction. As related by Ohm’s law, current is the ratio of voltage to resistance, so a sulfated battery will have lower current flow. As the charging process continues, such a battery will reach the charger’s preset cut-off more rapidly, long before it has had time to accept a complete charge. In this case the battery charger indicates the charge cycle is complete, but the battery actually holds very little energy. To the user, it appears that the battery is dying.

My longstanding-use battery charger is a DieHard model 28.71222:

It’s fairly old-school in design, although “modern” enough that it enables the owner to front panel switch-differentiate between conventional SLA and newer absorbed glass mat (AGM) battery technologies from a charging-process standpoint (speaking of which, in the process of researching this piece I also learned that old-school vehicles like mine are also often, albeit not always, able to use both legacy SLA and newer AGM batteries). And it conveniently supports not only 10A charging but also 2A “trickle” (i.e., “maintain”) and 50A “engine start” modes.

That said, we’re storing the Volkswagen Eurovan Camper in the garage nowadays, with my Volvo perpetually parked in the driveway instead (and the Jeep still “down the hill” at the storage lot). I recently did some shopping for a more modern “trickle” charger for the van’s battery, and in the process discovered that newer chargers are not only much more compact than my ancient “beast” but also offer integrated desulfation support (claimed, at least). Before you get too excited, there’s this Wikipedia qualifier to start:

Sulfation can be avoided if the battery is fully recharged immediately after a discharge cycle. There are no known independently-verified ways to reverse sulfation. There are commercial products claiming to achieve desulfation through various techniques such as pulse charging, but there are no peer-reviewed publications verifying their claims. Sulfation prevention remains the best course of action, by periodically fully charging the lead–acid batteries.

With that said, there’s this excerpt from the linked-to ”Battery regenerator” Wikipedia entry:

The lead sulfate layer can be dissolved back into solution by applying much higher voltages. Normally, running high voltage into a battery will cause it to rapidly heat and potentially cause thermal runaway, which may cause it to explode. Some battery conditioners use short pulses of high voltage, too short to cause significant heating, but long enough to reverse the crystallization process. 

Any metal structure, such as a battery, will have some parasitic inductance and some parasitic capacitance. These will resonate with each other, and something the size of a battery will usually resonate at a few megahertz. This process is sometimes called “ringing”. However, the electrochemical processes found in batteries have time constants on the order of seconds and will not be affected by megahertz frequencies. There are some websites which advertise “battery desulfators” running at megahertz frequencies.

Depending on the size of the battery, the desulfation process can take from 48 hours to weeks to complete. During this period the battery is also trickle charged to continue reducing the amount of lead sulfur in solution.

Courtesy of a recent Amazon Prime Big Deal Days promotion, I ended up picking up three different charger models at discounted prices, with the intention of tearing down at least one in the future in comparative contrast to my buzzing DieHard beast. For trickle-only charging purposes, I got two ~$20 1A 6V/12V GENIUS 1s from NOCO, a well-known brand:

Among its feature set bullet points are these:

• Charge dead batteries – Charges batteries as low as 1-volt. Or use the all-new force mode that allows you to take control and manually begin charging dead batteries down to zero volts.
• Restore your battery – An advanced battery repair mode uses slow pulse reconditioner technology to detect battery sulfation and acid stratification to restore lost battery performance for stronger engine starts and extended battery life.

Then there were two from NEXPEAK, a lesser known but still highly rated (on Amazon, at least) brand, the ~$21 6A 12V model NC101:

• [HIGH-EFFICIENCY PULSE REPAIR] battery charger automotive detects battery sulfation and acid stratification, take newest pulse repair function to restore lost battery performance for stronger engine starts and extended battery life. NOTE: can not activate or charging totally dead batteries.

And the also-$21 10A 12V/24V NC201 PRO:

with similarly worded desulfation-support prose:

• [HIGH-EFFICIENCY PULSE REPAIR]Automatically detects battery sulfation and acid stratification, take newest pulse repair function to restore lost battery performance for stronger engine starts and extended battery life. Note: can not activate or charging totally dead batteries.

In fact, with this model and as the front panel graphic shows, the default recharging sequence always begins with a desulfation step.

Do the desulfation claims bear out in real life? Read through the Amazon user comments for the NC101 and NC201 PRO and you’ll likely come away with a mixed conclusion. Cynically speaking, perhaps, the hype is reminiscent of the “peak” cranking amp claims of lithium battery-based battery jump starters. And I also wonder for what percentage of the positive reviewers the battery resurrection ended up being only partial and temporary. That said, I suppose it’s better than nothing, especially considering how cost-effective these chargers are nowadays.

And that said, my ultimate future aspiration is to not need to try to resurrect my Jeep’s battery at all. To wit, given that as previously noted, “I don’t have AC outlet access for [editor note: conventional] trickle chargers” at the outdoor storage facility, I’ve also picked up a portable solar panel with integrated trickle charger for ~$18 during that same promotion (two, actually, in case I end up moving the van back down there, too):

which, next time I’m down there, I intend to mate to a SAE extension cable I also bought:

bungee-strap the solar panel to the Jeep’s windshield (or maybe the hood, depending on vehicle and sun orientations), on top of the car cover intermediary, and route the charging cable from underneath the vehicle to the battery in the engine compartment above. I’ll report back my results in a future post. Until then, I welcome your comments on what I’ve written so far!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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• Energizer’s PowerSource Pro Battery Generator: Not bad, but you can do better

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