Chuck Husick Replies to My First Letter
My first letter to the editor was truncated on publication, omitting my criticism of the battery household exercise. I would provide a link to the publication, but Ocean Navigator took it off the web. If you have a copy of Ocean Navigator Sept/Oct 1999, you can read it there.
Since reprinting his entire response would go well beyond the boundaries of fair use under copyright law, I am forced to truncate his replies here. Mr. Husicks points are in red and indented.
You can read about VRLAs in my 1998 article (issue 89 of Ocean Voyager)
Assuming he had good information in that article, why didn't he recycle the most relevant points? How much work would it have been?
VRLAs can gas if overcharged. Venting will lead to irreparable cell damage. Flooded cells can be refilled if they have been cooked and the user can limp back into port. Not so with VRLAs.
VRLAs can fail completely if overcharged and cannot be revived. This would be very bad. However, assuming you install a proper charging system, adjust it for use with VRLAs, and supervise it properly, I doubt this happens. Modern charging systems have fail safes... and good batteries should be complemented with a good charging system.
The biggest danger of large banks is individual cells shorting out, causing the bank to discharge into the shorted battery. This in turn will boil the battery and could possibly cause an explosion. However, proper current limiting protection (i.e. fuses) within the bank cures that problem.
VRLAs are 3x more expensive than flooded cells of the same capacity
Chuck Husick elected to compare the cycle life of AGMs to premium flooded cells, while comparing the cost to cheap flooded cells - NOT a valid comparison. A classic case of apples and oranges. You can't just choose attributes from two separate products and compare them "as one" to a third.
VRLAs can be recharged much faster
Flooded cells can have a much longer life than VRLAs
Following the publication in the magazine, I learned that some premium batteries actually have a longer life than AGMs. However, the majority of flooded cells sold into the marine market do not last the 1,000 cycles at 50% DOD like Lifeline AGMs are warranted to.
Mr. Husick pointed to a power plant that elected to use huge traction batteries for critical backup purposes. Surely a power plant would not elect to use the
Flooded cells are "not toxic hazards" as his many years of trouble free experience with them attest.
The electrolyte in lead-acid batteries is actually quite toxic. That is why everyone in government and industry advocates taking serious precautions before handling with batteries. For example, I like the safety guide thatExide Corp. published on their web-site. Given the proper precautions, batteries are indeed unlikely to harm you. But have you worn a face-shield, full-length chemical apron, arm-length gloves and chemical googles every time you handled your batteries?
However, some types of lead-acid batteries contaminate their surroundings more than others. For example, flooded cells vent far more poisonous, corrosive gases than their VRLA counterparts given equivalent charging conditions. Furthermore, it is much more likely in a marine environment for electrolyte from flooded cells than VRLAs to come into contact with salt water, generating deadly Chlorine gas.
Taking away the exposure of the user to poison gases and electrolyte spills (during handling, replenishment, etc.) is a big advantage in my book. Furthermore, the user cannot contaminate a good battery with bad or dirty electrolyte.
Battery banks consisting of different battery types (one VRLA, one flooded) can be recharged by a single source, but it is very inefficient. He recommends only one type of only battery on board.
I agree that having only one battery type manufactured and installed on the same day is an ideal situation. However, like tires on a car, some batteries can fail earlier than the other ones and banks with uneven "ages" can develop.
Yet, charging multiple banks at different voltages from one source does not have to be inefficient. Modern DC-DC power converters can be 95%+ efficient and can be coupled with a 3 step regulator...
I just wanted to illustrate that it can be done, and that the Ample Power solution is a viable one, particularly if you want to ensure that the charging process for the house bank does not overcharge a starter bank (one that is usually paralleled during charging). Overcharges are harmful because they attack plate material, causing it to shed and eventually turn into a short.
While it is true that the higher internal resistance of a presumably full starter bank will ensure that most of the current will go to the house bank, repeated overcharges of the starter bank will lead to inevitable damage. The isolator/eliminator charges the starter bank independently from the house bank. This can also be useful when you want to use a high performance Optima or other VRLA type battery for starting while retaining your heavy duty flooded cell house bank.
Mr. Husick disagreed most strongly with the idea maximizing battery life by having only one house bank on board. Chuck Husick advocates the individual discharge of batteries from a bank, followed by a group charging process. He feels that he gets better warning of abnormal conditions and better performance this way.
His strong disagreement regarding the management of batteries was most curious, especially since he elected to defend his theories on battery management without offering proof that they were superior to accepted policies. See my section on bank charging.
For anyone that understands the implications of Peukerts Equation, the available capacity is always better the larger the battery bank. Furthermore, since larger banks automatically entail a lower depth-of-discharge for a given load, the cycle life of batteries is enhanced as well. Thus, there is no way for individually discharged batteries to have better performance than a bank.
Anyway, Mr. Husicks reply egged me on to research batteries further and prepare a second letter to the editor.