Sunday, August 16, 2015

Equalizing Lifeline AGM Batteries
By Michael

A Papeete mural.
“What does Nigel’s book say about this?” Windy asked. Her tone was solemn, I knew she understood the gravity of the situation.

“He doesn’t address it.”

“What else have you read?”

“The majority of folks on the cruising forums warn against it, in all caps. I guess there is a risk of fire and explosion, though they make it sound more like a certainty.”

She raised her eyebrows and upturned her palms, So why are you considering this?

“No worries though, the manual from the battery manufacturer says it’s okay—they actually recommend it, sort of.”

“Sort of?”

“Well, they say we should pump in 5% or less of the battery’s rated amperage at 15.5 volts for 8 hours.”

“And that’s good, yeah?”

“Well, sort of. Our charger will do this, but at 16 volts. I think that half-volt may be significant, but maybe not—I have no idea and haven’t been able to find an answer online. I say we do it—but that variable poses the biggest risk in my mind. I’ll keep an eye on things.”

“What do you mean ‘keep an eye on things,’ how?”

“Well, I’ve read that the temperature of the batteries isn’t supposed to rise above 125 degrees Fahrenheit.”

“How will you measure that?”

“My hand—my folks used to have a Jacuzzi, I think I’ll have a sense…except…”

“Except what?”

“That number is from the Nigel Calder book, it’s for conventional lead-acid batteries, I don’t have any info on AGM batteries.”

Okay, not the most riveting dialogue—unless of course you live on a cruising boat with 600-amp AGM batteries aboard and you’ve recently become increasingly aware of a loss of capacity which has led you to conclude that your batteries are heavily sulfated after four-plus years of both repeated discharges and failing to bring them back up to full charge and now you are considering equalizing them despite the most dire warnings that this might a) cost you money and hassle and then make no difference in the health of the batteries that are so expensive and so difficult to replace where you are and so core to your way of life, b) further damage your damaged batteries, or c) kill you and burn your boat to the waterline. The fact is, after poking around the internet for hours (though at dial-up speeds), I’ve concluded that once published, this post will be the most definitive info out there on one man’s experience equalizing Lifeline AGM batteries. It’s not a lighthearted story. It’s not for the faint of heart. If you’re still with me, keep reading.

The way we use (abuse) lead-acid batteries aboard cruising boats (discharging below 50% though we know we shouldn’t and rarely bringing them back up to a full charge state) causes sulfating to occur. This is a material that forms on and coats the lead plates. It happens unevenly, affecting plates and parts of plates furthest from where the posts are connected. It diminishes a battery’s ability to accept and release current. It can make a partially charged battery appear full, such that it won’t accept more current. The material can turn hard and short out those plates it bridges. It’s bad, and the reason batteries have a lifespan.

But upon noticing the effects of sulfating plates, the common advice is to equalize the batteries—generally described as bringing them up to a near-full charge and then raising the charger output voltage to 16 volts, at which point the batteries will accept a higher current flow and heat up and boil. The effect is supposed to cause the not-yet-hardened sulfates on your battery plates to slough off, either dissolving back into the acid or accumulating as deposits at the bottom of the battery. You’re supposed to leave the charger in this state for 8 hours of dramatic battery heat and sizzle, during which time you’re supposed to constantly monitor acid levels in the cells and keep the plates submerged by adding water. At least this is the prescription for conventional, deep-cycle lead-acid batteries. For AGMs, the only prescription is in the paperwork that came with our Lifeline AGM batteries in 2011—and these instructions are likely unique to Lifeline.

But how did I first realize we had a problem? Upon firing up the engine after the batteries had been heavily discharged, the amount of current—measured in amperes—our batteries were accepting from the alternator was less than the amount of amperes I know our alternator can output—roughly 60. I’ve seen this number diminish very slowly over time and concluded that maybe the efficiency of our alternator was falling with wear. Then I noticed a spike downward in this number, and also realized our batteries were running down faster than I expected. I started reading and I tested our alternator output and I realized we had a battery problem. (Not that we rely on our engine to charge the batteries, but I don’t have the same kind of consistent, high-value numbers to qualify from the output of our 430-watt solar panel array.)

So about now is when you can insert the above dialogue I started with, about halfway between the Tuamotus and Tahiti.

“We need to equalize ASAP, and keep the batteries as fully charged as possible in the meantime, to prevent further damage.”

In Tahiti, Marina Taina graciously loaned us free of charge their transformer we could use to access the 110V power our charger needs. Med-moored across from the largest megayachts in the world, we got busy doing our laundry on the foredeck while the battery charger did its thing. After about five hours, when the batteries were charged enough that our 600-amp bank was accepting only 9 amperes, I cleared the girls off the boat, tore apart furniture to ventilate the charger and batteries, closed all 12-volt breakers, and pushed the buttons to start the equalizing phase.

Spotted this lionfish while snorkeling in
Lights on the panel flashed, the fan on the charger cycled on, the voltmeter shot up to 16, and a piercing alarm sounded.

Apparently, the carbon monoxide detector in the girls’ room is hardwired to the batteries and didn’t like the increased voltage. I quickly snipped the wires behind the alarm. Everything quiet, I put my hand on the batteries. There was not heat, no boiling, no nothing. The only indications that something was happening were the flashing lights on the charger’s panel, the insane reading on the volt meter, and the 21 amperes the previously full batteries were now drawing.

This was the case for the first three hours. I wondered if anything was indeed happening. Then I noticed the lead ground wire was getting warm to the touch.

Another hour passed and I noticed number of amperes the batteries were accepting was increasing, now to 23. This seemed odd, but then I noticed the batteries were getting warm and I remembered reading that the higher a battery’s temperature, the more current it will accept—four hours to go.

At five hours, the incoming amperage was reading 25 and the batteries were warmer still. I put my ear to them and it sounded like bacon cooking. Was this a huge mistake?

The reason that AGMs are not supposed to be equalized is that they are sealed. There is an emergency valve, but if the battery purges anything, there is no way to replace it. Also, being AGMs, I don’t imagine the plates immersed in a restorative bath of boiling acid, so how will frying these things help? I don’t know. But Lifeline advocates equalizing these batteries, so I am just following instructions, sort of—the voltage held steady at 16.

The last three hours, the batteries—and the entire aft cabin where they’re located—became increasingly warm. The negative battery cable continued heating up. The bacon kept cooking. The incoming amperage topped at 32—slightly above the 5% of the 600-amp capacity limit specified. But it never seemed to get too hot, certainly not 125 degrees, maybe 110.

And then, at the 8-hour mark, the charger fan stopped blowing and the incoming voltage dropped to 13.5 and the amperage in dropped to 2. The batteries were still warm and remained so for about the next 12 hours, cooling gradually. We stayed another night connected to power, so the batteries stayed at 13.5 volts for about 30 hours. At the time I finally unplugged, they were accepting less than half an ampere, the lowest I’ve ever seen.

That was almost a week ago and we’ve been back on the hook, living off the grid, and I’m happy to report that the batteries seem much better than they were. After a day of normal usage, I’m not seeing the voltage drop I’ve become accustomed to. Of course, this week we’ve had plenty of sunshine for the solar panels, so it’s hard to tell. But if things take a turn for the worse, I’ll report back (and I’ll update this post).


Walking through downtown Papeete, Tahiti. For
whatever reason, I never took any pics of Papeete's
wonderful new waterfront. There is a nice malecon
with playgrounds, exercise stations, plazas, and more.

In Moorea, I lopped off Eleanor's hair. She waited
until her Auntie Julie arrived so that Julie could
carry the hair home and mail it off to Locks of
Love, an organization that uses donated hair to
fashion wigs for children who can't grow hair for
medical reasons. That's the girls' cousin, Kat.

Here are the girls in Papeete, heading off for an
introductory SCUBA dive. There was not room
in the boat for Windy or I to join them--oh, they
grow up so fast.

So check out the massive antennas on this Chinese ship that
pulled into Papeete harbor. 

Papeete art. In the Society Islands especially, guys
like this in crafts like this, go past Del Viento all day.

One of two-dozen such stands in the downtown
Papeete market.

Will posting this land me on an ISIS non-terrorist watch list?

Del Viento Med-moored in Maria Taina. See the hand truck
with the transformer mounted to it for us? 

Moorea is a nice place to anchor.



  1. Can't wait for our girls to scuba dive! Awesome!

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  2. Hope this battery fix holds for you! I have aging AGM's as well, so looking forward to hearing your follow up report. Thanks!

  3. I know your fear oh so well. Glad it worked out. And, do you ever get the idea that people writing about technical boat stuff in cruising forums are a completely different population from people who are sailing? And that 80% of what they write (in all caps) is wrong? Or am I letting my prejudices speak for me again?

    Either way, keep enjoying the tropics!

  4. Love the pictures. Who knew you were such a good hair stylist? If word gets out you might have to open up Michael's Salon.


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