Ask the Experts: Batteries

Norris Comer Ask the Expert Features

“Electricity is really just organized lightning.”

-George Carlin

Monkeyfist MarineBatteries. Whether you’re sail or power, just about everything that floats has some kind of battery bank. Most of us are pretty familiar with the old routine with wet, lead-acid batteries. We need to mount them levelly so as not to spill liquid acid everywhere. The water in the cell ports needs replacing every once in a while. The boxy clunkers usually need to be replaced every couple of years and require some huffing and puffing to extract. Some of us shell out a little more for gel batteries, but it’s fundamentally the same technology, just with a little less hassle.

But batteries, like all technology these days, are evolving. AGM (Absorbed Glass Mat) batteries, also called starved electrolyte batteries, are edging in as a new standard as they become more efficient and affordable. Although AGM batteries have been around since the Eighties, the newest iterations of marine-focused AGM battery products are quietly taking up more and more of the marine battery market. Like batteries, chargers have also come a long way, and the new ones are even programmable to maximize your batteries’ lifespan. All this tech piqued our curiosity, so we went on a hunt for knowledge from people who know more about it than we do. To get the inside scoop on the state of the 2017 battery industry, we turn to pros Jim Brown and Dave Stearns of Monkey Fist Marine.

Q: It seems like on land there is a lot of stuff going on when one thinks of Tesla and the like. Are similar developments trickling into the marine world?

Stearns: One way or another. AGM batteries are beginning to replace traditional wet batteries. They are a lot more expensive still, but last a lot longer and have a lot going for them.

Q: Let’s talk about AGM batteries. What exactly are they and what’s the science behind them? What’s the difference?

Stearns: There are more lead plates in an AGM battery, and they are packed very tightly together. The acid is also in a gel form that’s solidified in a fiberglass mat, basically, and is tightly wedged together to be almost vibration-proof. There’s no spilling of liquids, no breakage. It’s a good process that’s evolved a lot over the years.

Brown: The industry is trying to have more capacity and faster recovery. That’s what everybody wants. Lithium batteries are starting to trickle down a bit to the marine industry, but it is still very expensive and being worked out. We find lithium on hybrid-race sailboats that are trying to save a lot of weight, but for the majority of boat owners, AGM is probably the place to achieve that more capacity and faster recovery goal in a more cost-conscious manner. AGM is still more expensive than traditional wet batteries, but far cheaper than going to a lithium battery. If weight is not a huge issue, you can accomplish that by getting more ampere hours out of a battery with a higher charge that can recover more quickly.

Q: When we’re talking about AGM battery charge, what is the difference we’re talking here?

Brown: Probably in the neighborhood of 20% more capacity per battery.

Stearns: It depends on what you’re doing with your boat. The manufacturer is going to generally send you a pair of batteries with your boat, and generally boat owners want an inverter and good charger so they don’t have to run their genset and engine all night on the hook. You make those decisions based on what you want to do with your boat.

Q: Is the emergence of AGM batteries sort of like LED lighting in the marine industry ten years ago where a big transition brought everyone on board?

Stearns: AGM batteries have been in this transition phase longer than LED, but it is similar. AGM batteries have been around for a while now, but they keep getting better and more people are making them. There are AGM batteries from the USA, Europe, and even China these days. I’d say that, for the first time, AGM batteries are becoming a new standard for over 50% or so of the boats we work on.

Brown: It is really transitioning; wet batteries are now more of the exception than the rule. AGM cuts down on a lot of maintenance for the owners.

Q: AGM batteries are maintenance-free, right?

Stearns: Yup. They also have mounting options that lead-acid batteries don’t have. You can mount them standing up, on their side, or what have you because you’re not dealing with wet battery acid.

Brown: We have formats of these [AGM] batteries now where we can have a battery that’s a 240-amp hour battery, which exceeds what a comparable 8D-size battery would be. But the AGM battery takes up half the space of an 8D-size battery, so if you had a wet 8D, you can now put two of these things where you had your old battery, which over doubles the amp hours in that space. That’s beneficial, because even on bigger boats, space is an issue. We can lay two of these on top of each other in a stack, or lay them right beside each other like how the old 8D was oriented.

Q: Is there a giant cost barrier for some folks?

Stearns: Well, they say you can pay me now or pay me later. AGMs last longer and the maintenance cost is really nothing.

Brown: Let’s look at an Odyssey PC1800 AGM battery in a format where it is skinny, same height but half the width of a wet 8D, for example. One of those is about $645 compared to the wet 8D of similar capacity is about $260, so a considerable price difference. But you get longer life, you can double your amp hours, and then the cost comparison starts to level out as boaters can achieve things like more time on the hook where they can invert instead of run the genset. So I guess it becomes a cost of pleasure.

Stearns: Yeah, if it happens to last twice as long as well, you come out ahead.

Q: Let’s talk about longevity. AGM lasts longer, yeah?

Stearns: They’re supposed to. Boaters find all kinds of ways to kill their batteries, but AGM batteries are tough. It’s good technology.

Brown: We have AGMs that are ten years old still kicking around.

Q: Do you have some tips with regards to maximizing battery life?

Brown: Be very conscious of the charger you have aboard. Often times on an older boat when we’re upgrading these batteries, we upgrade the charger as well at the same time. Charging technology has evolved just like batteries, and one thing about AGMs is that they really like a particular charge profile of length of charge, absorption rate, all that. We’ve found over time, and Dave is quite an expert at this, that we’ve managed to set these chargers up with programmable abilities. If you can program those chargers for that sweet spot of charging, it’ll extend the life of your batteries. If you hook up a brand new set of AGM batteries to an old charger that is not a consistent charge, that is not a smart charger, it is likely that you’ll go through those batteries in short order. Some of those chargers that just have a switch use a charge that averages out the battery manufacturers.

For some AGMs that works ok, for others it doesn’t. So if you price compare chargers, often you can find a programmable charger that you can hook your computer up to and set the program and everything for not much more money than the simple-switch version. That’s one of those situations where you get a better life out of your batteries and save money in the long run.

Sterns: Each manufacturer has hopefully done some engineering testing and can provide the absorb voltage flow charge information that’s ideal for the battery.

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Norris Comer

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Norris Comer is the managing editor of Northwest Yachting. He was raised in Portland, Oregon and got his BS in Marine Science at Eckerd College in St. Petersburg, FL where he lived aboard a 1973 Catalina 27 before moving to Washington. He has worked as a commercial fisherman, wandered aimlessly around the world, studied oil spills, and was a contestant on the Norwegian reality TV show, Alt for Norge. He loves living in a state where he can explore the ocean and mountains in the same day.

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