Sharks! (?)

I received an email a few days back from some regular readers of my blog, Scott and Cindy Stolnitz, of the 51’ sailing catamaran “Beach House” ( They were arriving today in Cabo, from Mazatlan, and invited me to stop by their boat to say hi.


Almost the first thing that Scott said when I boarded their boat was “It’s a sailing catamaran, but we really use it like a trawler.” He went on to say that they could run under power as much as 1,600 miles, and that they had hardly sailed the last few months. It struck me a little funny, in that I thought that perhaps he was wanting me to feel at home, like I might not feel comfortable on a sailboat. Perhaps it’s just my imagination, but there always seems to be a bit of a culture gap between power boaters and sailors. One way or the other, it was a beautiful boat and there was much to be admired.


Even though I knew it was a waste of time I once wasted an entire day trying to compute the size sail I’d need to move my boat through the water. It takes very little horsepower to move my boat; as little as 100hp can easily give me 5 or more knots. I searched everywhere for a formula that would convert square feet of sail to horsepower, and did actually find one. I forget the math, but remember that the size sail to move my boat was only slightly bigger than the state of Rhode Island.


Scott and Cindy said that their primary passion is diving. They are only in Cabo for a day or two, before heading to Socorro, a small group of islands 200 miles south of Cabo. Socorro is Mexico’s version of the Galapagos Islands, and a paradise for divers.


Check out these photos:


Roberta and I tried to visit Socorro last year, but couldn’t get the permits. Scott says that the process has been greatly simplified, and that now, Mexico is actually encouraging visitation by non-fishing visitors. He said that there is a small office in Cabo where you can go to get a permit, and normally receive permission within a week. He said he posted all the info on the “Southbound Net”, but I’m not sure what that is, or where to find it, and forgot to ask him.


I asked how long they’d be staying in Socorro and thought they had a perfect cruiser response: “As long as we are having fun!” When asked for further clarification, they said “It could be as long as a month. However long it takes the food to run out.” After Socorro they mentioned going south to Panama, then out to the Galapagos, over to Polynesia, up to Hawaii, continuing to Tonga and New Guinea, and then, perhaps back to Polynesia. I was ready to sign on as crew if they’d have me!


When Scott mentioned they had a dive compressor, I asked to see it. As it turns out, they have the same compressor I’m trying to find room for on my boat (the Bauer Jr.) It was packed into the bottom of a locker, and seemed smaller than I expected. Great news! They also said that it wasn’t very noisy.


We then started talking about sharks. I wasn’t completely disappointed when our trip to Socorro fell through. I have seen many photos of sharks at Socorro, and would be nervous about diving. Scott’s eyes lit up proudly at my comment. He went below and returned a minute later with something that I thought at first was a dive regulator.


He described it as a Shark Shield. I’d never heard such devices existed. [Note .. if you’ve never seen these, watch the video. It’s very interesting.]


The Shark Shield is basically a long ¾” thick flexible whip that straps to your ankle. It shocks you if you touch it, and allegedly provides an impenetrable shield from shark attack. Scott and Cindy were passionate about it, and when I left their boat, I planned on ordering at least one for mine (they run around $600 each).


Tonight, surfing the net, I found a few articles questioning how well they work, including an article saying that one was eaten by a great white, and another article referring to a fatal attack on someone protected by the shark shield. So, my euphoria over the discovery has dimmed a bit. I need to do a bit more research to decide if they really do something or not.


And… on a different topic…


Jeff, the project manager doing all the work on my boat sent an email tonight recommending that I go with lead cell batteries. At first I was convinced to make the change, but then after doing all the research, I decided to buy new AGM batteries (the same as I have now, except in a different size, so that I can cram them in better).



Jeff’s email:


Ken: I have checked out the batteries and fisheries has 9 in stock and I can order more they are $379.00 a piece. I agree these are designed more for what you are using them for. No gassing, But if you were asking me to design and build a bullet proof system this would not be my choice. I got involved with a huge project to run a inverter on a 119 Foot vessel that had huge batteries, and did a lot of research because I was leaning towards a Gel Cell battery. The owner paid me to provide him with all my data. He switched and went with the Lead acid. I installed these huge batteries and with the exception of having to fill them with distilled water they are still working. He runs his inverter every night with huge loads. I am not trying to challenge you but you hire me to make the right decisions and I have to a least give you my opinion. But I think this change is in the right direction.


My rationale for wanting AGM batteries is three-fold: 1) The lead acid batteries put out gas during charging. This gas needs proper venting or it can be an explosion risk. And, 2) Lead-acid batteries require more maintenance than AGMs. And, lastly 3) AGM batteries can accept much higher charging rates.


We haven’t yet tested my current AGM bank, but I’m confident we will find the batteries are ruined. When I first took delivery of my boat, the Atlas international shore power system had major problems. We solved the problems, but before we did, the batteries were fully discharged several times. I don’t think the batteries died, I think we killed them. The Atlas, now that we have it fixed, has been rock-solid. I am not worried about this new set of batteries being mistreated.


So many decisions… Jeff’s a bright guy, and usually right. I suspect I’m going to go with the Gel-Cells, but it will be a tough decision.


-Ken W


13 Responses

  1. Ed: After my initial posting, I was quickly “educated” by readers of my blog as to the differences between gel cell and AGM batteries.

    After some research, I settled on 6 volt AGM Lifeline batteries. They aren’t specifically golf cart batteries, but essentially the same as near as I can determine.

    http://www.lifelinebatterie (

    These are essentially the same batteries as I have now, but their sizing will allow me to use less space in the lazarette, and improve access. (I hope!)

    Thank you,
    -Ken W

  2. Hi Ken:
    I have been following your adventures since before the Atlantic crossing. I have owned 22 Boats the biggest a 34′ CHB Trawler. The AGM batteries are the only way to go, however they are not gel cells, they are Absorbed Glass Mat (much better). My boats have all had 12volt systems and I always used golf cart batteries that will take much more abuse and will last about 7 years. I don’t know what type batteries you are using, but if they are 12 volt, the 6 volt golf cart batteries will give you much more capacity.

  3. Patrick: That’s a great acronym! (RTFM) .. I need to remember that one.

    I need to get smarter at knowing what sharks are in the water before diving. In Costa Rica, we were swimming in water that seemed tame, but then had large sharks patrolling the back of the boat during the evening. I haven’t studied sharks enough to know which are dangerous and which aren’t. They all look mean to me.

    As you said, for $600 I’ll certainly get a couple to have on board for diving, and will definitely RTFM!

    -Ken W

  4. Hi Ken,

    I also did a bit of research on the sharksheild device a while ago and I thought I would offer my opinion on the device. I don’t see it extremely feasible for fast moving objects, and for objects not totally submerged. So the reports about a surfboard getting eaten aren’t too surprising, especially since the company reported the unit was faulty. Also, you have to follow the instructions exactly and since a lot of people don’t RTFM I wouldn’t discount it off hand as a total device failure. I would test it first around non-aggressive small sharks first though to make sure the unit is sound.

    Usually a shark pushed close enough to the shore to attack a surfer (more than a single bite is it a ‘seal?’ taste test) is either desperate or hyper-aggressive, and just like any animal in that state it really would take something with deadly stopping power to make you “safe”. Unless you have your own dolphin! 😉

    So I would say if diving is something you do or want to do and you have the money, $600 is worth the chance that it might save you! That said, it is best to know the type of sharks in your diving area and if you have any feeling they are agitated move as little as possible and get out of the water as soon as possible. In other words don’t act like food!


  5. From: (

    This URL has good info and fully describes “traction” batteries.

    “A newer type of sealed battery uses “Absorbed Glass Mats”, or AGM between the plates. This is a very fine fiber Boron-Silicate glass mat. These type of batteries have all the advantages of gelled, but can take much more abuse. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. These are also called “starved electrolyte”, as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken.
    AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:

    Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

    Nearly all AGM batteries are “recombinant” – what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

    The charging voltages are the same as for any standard battery – no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.

    AGM’s have a very low self-discharge – from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged.

    AGM’s do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM’s are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

    Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM’s will cost 2 to 3 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don’t have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.”

  6. Ron: Yes. Jeff has a couple of complaints about the AGM Lifeline batteries.

    1) Jeff believes they are finnicky, and that it is easy to shorten their life.
    2) They are more difficult to test than lead-acid batteries.

    -Ken W

  7. It just dawned on me why Jeff preferred a lead-acid solution. You cannot manage AGMs as well as you can lead-acid. With lead-acid batteries you can measure specific gravity and find bad cells. Outside of their performance, my 3 AGM 8D’s condition is a relative mystery to me. I monitor their performance via a Link 2000 which also controls my inverter and its charger. This is on a Willard 40 liveaboard trawler.

  8. I have just reread Dashew’s piece and he doesn’t name the batteries because as I remember it they were imported. He makes the point that you must build a place if you intend to house these heavy, lead acid, traction batteries. They are also referred to as industrial batteries. Of course, he has a venting system for his battery compartment. Ken wants to save space and he won’t be able to with those monsters. There used to be two companies competing with Balmar. Both still exist in a reduced form. One used to sell 2V batteries made of heavy polyethelene construction. They were slim and tall. You made them up into an appropriate voltage using copper buss bars. A friend outfitted his 50 foot sailboat with their filling the space over his keel. A vessel designed to take these could swap out bad cells.

    Ken, my only point is that you used the word “gel” in a previous email instead of AGM. For some reason, Jeffery is recommending gel cells after lead-acid. Is it possible he means AGM? I would ask him to explain his preference. It is hard to dismiss the views of a project manager at Delta.

  9. Ken,

    Sorry to add to the confusion. On another part of Steve’s site, he mentions here ( Trojan Batteries 1500 with 80% discharge.

    He talks more about them here ( but mentions no names

    He seems to know is stuff though and has a ridiculous amount of hours and experience using them…

    Good luck Ken

  10. I’m totally confused.

    My current batteries are AGM Lifelines. The batteries Jeff is recommending are lead-cell batteries from ( . I’m leaning towards the AGM Lifeline batteries. The batteries I’ve selected are 6v, and because of their shape I can fit 2/3rds the amp hours of what I have now into 1/2 the space.

    I read what the Dashews have on their site about Traction batteries, and then tried to google them. Amazingly, the first batteries to appear are the AGM Lifelines, which claim to be traction batteries. Is this correct? What’s a good brand of traction battery I should look at? (that is easily available in the US?)

    -Ken W

  11. Ken,

    AGMs are not Gel cells. As I related earlier, I found Gel cells harder to keep happy. Both types can be fully discharged and recover. It is my *impression* that Gel technology preceded AGM technology. The newer batteries like Energy 1 are AGM batteries of increased density. I think that this was pioneered by Hawker Sidley. However, that was a British firm and reminds me of Lucas “The Prince Of Darkness.”


  12. Hi Ken

    Interesting that you should meet and mention Scott Stolnitz as he was a member of my yacht club ( ( ) until retiring and setting forth in September of 2007. More directly, he was also the SYSOP of the CYC Winlink HF Email station until I took over in June of 2007. You may already be aware of Winlink (and its commercial brethren, Sailmail) but it is a system that allows email, attachments, and a litany of weather products and other information and bulletins to be sent and received free via Amateur Radio around the world. All you need is a HF SSB radio (most boaters use the Icom 802), a SCS Pactor modem, and a computer. Many sail boaters use it as their primary or secondary means of email communication, weather products and position reporting (Winlink can automatically update your position on a map so that friends can see where you are and where you have been at any time, and can also report your position to such services as YachtReps). At our Winlink station in Marina Del Rey, we routinely have sailors 4,000 miles out in the South Pacific using our service. Due to the nature of the Pactor digital signal, it can get through when no other mode of HF communications can, down to a -18 db signal to noise ratio.

    Since all you would likely need with your setup is the modem, you might want to consider it as yet another means of communication and backup.

    Tom K6TGT
    CYC RAG Chair and Winlink Sysop

Leave a Reply

Your email address will not be published. Required fields are marked *

Be the first to know when

the game releases!

Plus, receive special insider, behind the scenes, sneak peeks and interviews as the game is being made. Don’t worry. We will not spam you, and we will not flood your box with too many emails.
 — Ken Williams

Credits     |     Video produced by: Rock Steady Media     |     Teletype photo: Arnold Reinhold     |     PDP-11 photo: Trammell Hudson