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Comparing Marine Battery Technologies

(Gel, Absorbed Glass Mat (AGM), Flooded Lead Acid, and Nickel-Cadmium)

While I was on a month long assignment in Washington DC in 1999, I read an article on battery management in the 1999 Ocean Navigator "Annual" issue that I thought was deeply flawed. The contributor, Chuck Husick, illustrated how he thought one should maintain and configure a marine battery system. Some of his key recommendations ran counter to accepted industry policies and physical laws that I had read about in Nigel Calders excellent Boatowners Mechanical and Electrical Manual, as well as web-resources like the Ample Power web-site and their line of books.

The research I conducted for my letters to the editor led to this collection of web pages. For my purposes, Lifeline Absorbed Glass Mat (AGM) batteries are the best choice, but every battery technology has its strengths and weaknesses. Naturally, I have no commercial affiliation with any battery or charge system manufacturer. I suggest you start off with my Lead-Acid Battery Glossary Page to familiarize yourself with all the terms that will be used throughout this site.

Learn more about the different types of marine lead-acid batteries currently on the market with my page on lead-acid battery technology (Flooded, Gel, and AGM). I discuss the features of traditional flooded lead-acid batteries commonly found in cars and most boats versus Valve-Regulated Lead Acid (VRLA) batteries like Gel and AGM. Each battery technology has its virtues and its downsides, so it is important to understand them and then make the decision which best suits one's own needs.

Next, I researched what sensible people have written about how to size your battery capacity. The industry consensus is usually 4x your daily energy needs, although it depends on the type of battery your have on board, as well as your charging system, available space, weight considerations, and usage profile. However, starting off with at least 4x allows you some breathing room later when/if you add more electric circuits.

On another page, I have assembled a number of arguments why the average marine user would only want two battery banks on board (house + starter) and how such a bank configuration leads to better battery performance, longer battery life, and higher safety. Basically, the less you discharge a battery, the better. Fast discharges are also harmful and lower available battery capacity (see Peukerts law).

Chuck Husick made a number of assertions in his responses about battery costs, so I looked into those as well. A cost model later, I had a number of startling results. Namely, that AGMs worked out to be less-expensive for my marine application, despite having a high initial cost, due to their superior features. Over the life of the AGMs we would save a lot more on lower maintenance costs, fuel consumption, etc. than the premium we spent initially (when such a premium exists).

I then go on to explain how my bulk charging model works. This is a rather simple cost model (hey, it's my spare time) but it covers the battery conditions usually found on cruising sailboats ( bulk-charging, i.e. not fully charging the battery banks except on occasion). The model is available for free and runs on Microsoft Excel (see the page for details). A later cost model also looks at replenishing batteries beyond the bulk stage.

I then go to wrap up my marine battery technology findings in the Conclusions page. I detail what battery technology I chose and why.

For those who are interested in the written volleys between myself and Chuck Husick, I have preserved the e-mails for your review. I found the exchange quite amusing and thought-provoking. While his essay made me research this topic enough to make an informed purchase decision, Chuck Husick has yet to convince me and the rest of the battery industry that his ideas are superior. After all, when confronted with contradicting evidence, he decided to "withdraw from the discourse".

Anyway, last but not least, I have assembled some;

Some Great Battery Links:

Introductions to Batteries

Battery Manufacturers / Distributors: 		 

Experiences with AGMs:

Marine electrical Systems:

Other Battery Sizing Recommendations:

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The wonderful world of the DSC  
Do you have a DSC facility on your radio? If you are asking 'What is a DSC?' then you really need to study this article.

Are you confident that you know ALL the side benefits of this technology? If not, then there is much of value to read below.
'DSC Making communication easier, making life at sea safer'    .  
Digital Selective Calling (DSC) distress alerts, which consist of a preformatted distress message, are used to initiate emergency communications with ships and rescue coordination centers. Most marine radios now have a DSC facility, consisting of a simple button, which can be pushed in the case of an emergency.

It is the least expensive and the most significant safety improvement that writer Ross Trossbach has seen in over fifty years. Later in the article are the full details for leisure craft on the uses of DSC, but the potential use goes much beyond the uses strictly for emergencies, to other communication advantages, summarised here by Ross:

  1.  The ability to call ships on the high seas using their MMSI obtained from AIS
  2.  The ability to request the position of any unit having an MMSI. 
  3.  The ability to call an individual station and automatically switch him to a working channel
  4.  The ability to call a group of stations and automatically switch them to a working channel
  5.  All positions received can automatically be displayed on most Navigation plotters
  6.  An entirely new Man Overboard alarm and real time position reporting system (VPIRB) uses DSC too.
     

These are all extra facilities, and all you need is a little time and practise. The additional advantage of these facilities is to keep Channel 16 as free as possible. This is vital to safety, and all users of marine radios, even in those countries which have been deregulated, are advised to undertake a radio course.

Here below is the paper on the emergency aspects of DSC produced by the Cruising Club of America, and supplied by Ron Trossbach:

DIGITAL SELECTIVE CALLING
The use of Digital Selective Calling (DSC) in VHF and SSB radios is relatively new and not widely understood. This paper will give the reader a broad view of what DSC is and how it applies to recreational boats. Web site links and references are included for more detailed explanations.

DSC definitely has a place in small boat operations and is simple to install with potentially huge safety benefits. It is no longer necessary to read latitude and longitude numbers over the radio in emergencies or when exchanging position information with another boat. DSC does this automatically in less than one second. The best part is that DSC capability should already be in VHF and SSB radios built/sold in the US after June 17, 1999.

The physical hookup is relatively simple - two wires between any model radio and any model GPS. The registration is FREE, and details of how to do this vary from country to country.

'The Coast Guard urges, in the strongest terms possible, that you take the time to interconnect your GPS and DSC-equipped radios. Doing so may save your life in a distress situation!' See www.navcen.uscg.gov/marcomms/gmdss/dsc.htm

This site also provides the background, history and description of how DSC fits into the Global Marine Distress and Safety System (GMDSS).

A recent CCA publication titled Digital Selective Calling and Search & Rescue Areas has important details and information on Digital Selective Calling, MMSI, AIS and Search and Rescue areas in the Atlantic and Pacific. This is a comprehensive review of how to make the most of your DSC-capable VHF and SSB, and how to use the technology to maximize your chances for a successful rescue at sea. See http://www.cruisingclub.org/pdfs/dl.asp?fn=com_dsc_sar.pdf

Boat U.S. Foundation has an online tutorial on Marine VHF titled 'Can You Hear Me?' which is an interactive run-down of everything a boater wants to know about using a marine VHF radio with Digital Selective Calling (DSC). The headline on this announcement is 'Spending 35 Minutes Online Could Save Your Life'. See www.boatus.com/mmsi

At a bare minimum, responsible boaters should be capable of sending a DSC Distress Call as well as taking the correct action when a DSC alarm sounds on their radio. DSC is in place and operating now, especially in US coastal area where RESCUE 21 is operational. This is a huge safety improvement that all boaters should understand and be prepared to use in case of emergency.

MAKING A DSC DISTRESS/MAYDAY CALL.
This call is only made when personnel and/or property are in immediate danger and immediate assistance is requested. Press the Red Distress Button on your radio and hold it in for five seconds. Listen for a DSC Distress Acknowledgement. After it is received, or if it isn’t acknowledged, shift to the VHF Distress, Safety and Calling Frequency (VHF Ch-16) or a SSB Safety and Hailing Frequency (2182, 4125, 6215, 8291, 12290 or 16420 kHz, USB) and issue a voice MAYDAY, following the format on the Emergency Card on the reverse side of this paper. Persons in distress should use any frequency/means to alert other mariners/persons ashore to their plight.

IF YOU HEAR A DSC DISTRESS CALL.
Shut the radio alarm off by pressing any button on your radio. Write down the MMSI and position information showing on your radio display screen. Wait 3-5 minutes for an authority to answer the call. If no other station replies attempt to verbally relay the MMSI and position information to USCG or Bermuda Radio. Contact the station in distress if no one else does and go to their rescue, if you are able to do so.

IF YOU ACCIDENTALLY MAKE A DSC DISTRESS CALL. Shut the call off. Get on the VHF Distress, Safety and Calling Frequency (VHF Ch-16) or SSB Safety and Hailing Frequency (2182 kHz, USB) and make an all stations announcement to cancel the DSC Distress Call.

DSC DISTRESS COMMUNICATION FORM - WRITTEN INSTRUCTIONS FOR USE
Copy and place the form below on a wall close-by each permanently installed radio equipped with DSC
(Fill in Items 5, 6, 11 and 13 prior to getting underway.)

SPEAK SLOWLY – CLEARLY – CALMLY
1. Make certain your radio and GPS are turned on and the radio is on High Power.
2. Send DSC Distress Call – press Red Distress Button for 5 seconds. Wait for a DSC Distress Acknowledgement then shift to VHF Ch 16 or SSB 2182 kHz (USB) for voice instructions.
3. If no DSC Acknowledgement is received Select VHF Ch 16 or SSB 2182 kHz (USB)
4. Press microphone button and say: 'MAYDAY - MAYDAY - MAYDAY'
5. Say: 'This is (Your boat name, MMSI or Call Sign)'
6. Repeat once: 'MAYDAY (Your boat name)'
7. Tell where you are:
a. Latitude and longitude __________________________________________________
b. Navigation Aids or Landmarks nearby __________________________________
c. Direction and distance from a Landmark ________________________________
8. State the nature of your distress and the kind of assistance required:__________________________________
9. Give the number of people aboard and condition of any injured ______________
10. Estimate present seaworthiness of your boat. ________________________________
11. If time allows - Briefly describe your boat:
a. Type – (Sail or Power) _____________________
b. Length in feet- __________________________
c. Hull color- _______________________________
d. Trim color- ______________________________
e. Masts- ___________________________________
f. Other Identifying Info- _____________________________________________________
12. Say: 'I will be listening on Channel 16 or 2182 kHz Upper Sideband '
13. Say: 'This is (Your Boat Name, MMSI or Call Sign) OVER'
14. Release microphone button and Listen for an Answer.
15. Activate 406 MHz EPIRB by following directions on Beacon Body. Ensure EPIRB remains vertical, antenna pointing upward. Take EPIRB to Survival Craft if abandoning ship.
16. If you do not receive an answer Repeat Call beginning at Item 3.
17. If no answer again Check to see if radio is turned on and VHF is on CH 16, high power or shift SSB to 4125 kHz (USB) or higher emergency frequencies for communications with distant shore stations.

by Ron Trossbach/Sail-World Cruising   8:29 AM Mon 23 Mar 2009 GMT

Wireless Anchoring a Winner    

'Anchor safes three elements'   

As every cruising sailor knows, getting the right scope when you are anchoring is vital, and it’s important to count the chain as it goes down. We’ve tried paint and we’ve tried cable ties. Paint wears off after a while, and the cable ties eventually catch on something and tear off. In addition, there are many things to distract the bowman’s attention, so the count can be lost. Chain counters are a great boon, but, depending on your boat setup, there are always disadvantages.

The idea of being able to operate the windlass from anywhere on the boat sounds like Anchoring-Heaven, and that’s just what ‘AnchorSafe’ promises.

The basic system comprises a sensor and a small sealed control panel with display(80mmX80mmX20mm), but for electric or hydraulic windlasses a wireless remote control can be used. It’s easy to use. Alarms can be preset, alerting you when only 5m of chain are left in the locker, for example. .

This is what the gear consists of:

 

Unobtrusive  .
1. The chain counter sensor: This is a very tiny, sophisticated, completely weatherproof and durable unit. In this system only one sensor is used unlike other systems that use multiple sensors to identify the chain direction (up or down). It is easy to install on all types of windlasses, and according to AnchorSafe, should take no more than 40 minutes. The unit is made from UV protected Polycarbonate material including the sun cover.
The sensor is fitted close to the windlass gypsy and is completely wireless so there is NO need to rewire the windlass system. (Usually the hardest part of installing such systems is wiring the sensors from the windlass to the flybridge as in existing chain counters, and the need to make a number of proper and weatherproof connections in this difficult area).


 
Anchor safe  .
2. A control panel made from highly durable and long lasting materials. Any number of these units can be installed. They can be fitted anywhere you choose. These control panels let you wirelessly remote control the following operations: :

A) Precisely measure the amount of chain deployed or rewound.

B ) Automatically operate the windlass. This is very convenient as it now leaves you free to do other tasks.

C) Give an audible warning alarm when the anchor approaches the boom or on deployment when the chain is about to run out.



 
Anchor save remote  .
3. The wireless remote control, which releases or rewinds the anchor chain from anywhere on board. (This unit does not need any wiring to the windlass as in ordinary windlass remote control devices). . The effective range of the remote control and the wireless sensor (sender) attached to the gypsy is around 90 metres




For single-handers, deploying or upping-anchor can be done without crew assistance. Even when upping-anchor you can organize the stowage of the chain in the chain locker safe in the knowledge that the re-winding will automatically stop a safe distance from the bow.
If your boat has two windlasses you can have two separate units counting each side separately. If you need a repeater you can install additional units without any connection between them and the repeater will count automatically while the windlasses work

The retail price of the unit is 288.00 Euro per piece including one control unit with the display and control buttons, one sun cover, one internal built-in remote control receiver, one wireless gypsy sensor, and the remote control.

For further information about the system, including how to purchase it online (that's the only way at the moment), refer to their WEBSITE

The Truth about Snubbers

9:51 AM Fri 27 Oct 2006 GMT

'The Simple Snubber'.
No, I don’t mean someone who won’t return your ‘Good Morning’ greeting – I mean the device for protecting the anchor winch from strain in a bucking sea. Here Mike McEvoy from Middle Harbour Yacht Club gives a rundown on the value and method of using this vital yet simple piece of gear:

On a boat that has an anchor winch there are often two parts to the winch assembly. One part is to deal with anchor chain and the other, called the gypsy, deals with a rope rode or anchor line.

Some boats have rope attached to the boat end of the anchor chain so that once all the anchor chain is deployed the rope then holds the boat to the anchor. Many times, when anchoring in shallower water of course, only part of the anchor chain will be required for the anchor to hold the boat.

If the anchor chain is left on the winch drum the winch is taking all the strain of the pull from the anchor with potentially expensive damage to the gearing of the winch.

The solution is the Snubber, being a length of braided nylon rope with a loop in one end, usually spliced back on itself creating an 'eye' to hook on to a deck cleat. The other end has a purpose designed 'hook' (known as a Chain Grab Hook) that fits over the chain. The hook must be the right size for the chain - to purchase take a piece of the anchor chain or measure length and width of a link to get a hook that fits your anchor chain. Ideally the (galvanized or stainless) hook is secured to the end of the snubber rope through a metal thimble to reduce chafe on the rope.
A clevis Grab Hook pin makes it easy to attach the hook through the thimble.
Once the anchor chain has been deployed to the skipper’s satisfaction the hook of the snubber is hooked to the anchor chain just forward of the bow roller with the other looped end over the deck cleat on the deck near the bow. Your boat may have a 'Samson post' i.e. a strong point to which that you normally secure the boat’s mooring.

However, most modern production boats have a cleat on the side deck either side of the bow near the toe rail and that is where the snubber is set.

Having hooked up the snubber, keep some tension on the snubber line while you let out sufficient anchor chain to allow the snubber rope to take the full strain of the anchor. Now the strain is off the anchor winch and onto the snubber rope, which, because it has some give in it, eases the 'snubbing' action as the boat pulls back and forward on the anchor line.

The catenary, which is the dip in the anchor chain below the snubber rope, might only be a few centimeters, but could be much more – say half a metre if the swell conditions warrant it.

The snubber rope should be no more than two metres long and strong enough to
take the weight of the boat in a strong breeze. If the snubber rope breaks, anchor winch remains on the winch drum ready to take the strain if the snubber fails.

A cautious sailor, particularly in a strongly bucking sea and/or a high wind, will add two safety measures. He/she will use a much longer snubber to offer additional stretch (say six metres instead of two), and also put out a second snubber in case the primary snubber fails, to prevent the load coming onto the anchor winch.

Many long-range cruising boats put down a snubber as a matter of habit whenever riding at anchor.

If you can’t splice go to your favorite boatshed and ask them to do the two splices, one for the thimble and the other for the loop, which obviously must be big enough to fit over the strong point on the bow of your boat.

Sail-World Cruising would like to thank the Middle Harbour Yacht Club! for allowing the use of information from Mike McEvoy’s article from their regular magazine Compass Rose.

The diagrams used in this story are courtesy of Bosun Supplies , who manufacture professionally made snubbers and would welcome your custom.


by Mike McEvoy/Sail-World Cruising
 

To join - email The Master at hello.trim@optusnet.com.au