My First Letter to Ocean Navigator
My first letter. Written in May 1999. Later corrections and clarifications have been added in [blue].
I am new reader to your magazine and have enjoyed most of the articles so far. However, Chuck Husick's article in the 1999 annual issue warranted some closer attention to detail from your editing staff. I have two objections to the content of the article: the absence of Gel/AGM batteries and some of the technical advice given for the flooded cells.
Chuck Husick cavalierly disregarded non-flooded cell batteries. These alternative battery types deserve more attention, especially in a magazine supposedly written for ocean voyagers. The very weaknesses of flooded cells with should have prodded Chuck Husick to examine alternatives.
Non-flooded battery technology (AGM and Gel in particular) vs. flooded cells:
For example, Chuck Husick goes to great lengths describing how long an engine must be run each day to recharge depleted banks. Gel and AGM batteries allow higher charging rates, resulting in less engine runtime and motor wear. They are also much less toxic on a day-to-day basis than their flooded counterparts. And multihulls aside, the extra battery weight is not a problem. The higher initial cost is not objectionable either, given that some flooded batteries cost even more ([the premium] Rolls [500/CS series] for example).
The biggest stumbling block is the smaller distribution network / availability of / familiarity with non-flooded batteries around the world. Properly maintained, Gel cells and AGM batteries last longer than their [cheap] flooded counterparts. Most after-market regulators now come with pre-set charging patterns for many kinds of batteries, and more marinas are familiarizing themselves with alternatives to flooded cells. Furthermore, it is possible to have different types of battery banks, even with only one alternator and regulator, by using the "isolator-eliminator" manufactured by Ample Power. So much for omitting other battery types.
If that was not enough, the writing in the article on flooded cells is vague enough to cause some headaches. Discharging individual batteries from a bank, as he describes it, is possibly the best way to shorten battery life. Discharging batteries as a bank leads to less internal resistance (and heat losses), lower loads on individual batteries, and a lower average discharge level prior to charging. Ideally, a boat should only have two banks: one for the engine, another for the house loads. Large banks allow the alternator to run at a very high output, minimizing engine/gen-set run-time.
Chuck Husicks battery household exercise is somewhat reminiscent of the antics of a chemistry professor I had in college (who had a habit of creating problems out of the air and then proceeded to muddle through). Who would install a (effectively) 120 Ah battery bank in a boat that consumes 20 (!!!) Amps continuously?
Furthermore, assuming one had the money to install the equipment to draw that much power, why wouldn't one install a dedicated gen-set to run the water maker, recharge the batteries, and cool down the fridge plates? To install a gen-set that is matched to the loads it will encounter, is a much more cost effective solution than ruining a large diesel engine by running it with light loads. Furthermore, to install a alternator in a boat with those energy requirements that has only 100 amps of hot capacity is nothing short of ludicrous.
In short, this article could have been better had Chuck Husick considered more battery types, larger battery capacities, and beefier alternators. By pairing a very large load to a very small bank and charge source, he has left readers wondering what the point of the article was.
Lastly, including references to excellent books on the subject like Nigel Calders "Boatowner's Mechanical and Electrical Manual" or even just a reference to a knowledgeable web site would have put more (and frankly better) resources at your readers fingertips.
Constantin von Wentzel
The letter 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. On the next web page you can read the gist of his response to my letter with my views on them