Great Lakes Singlehanded Society

FROM THE NAV STATION
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When we last left our intrepid super hero, Solosailorman, he was in hot pursuit of the perfect electrical system. He had come up with a list of his electrical needs, found a place where he could install them, and headed off to his discount marine supply store of choice to plunk down his hard earned cash for some electrical peace of mind. Gadzooks, there in aisle four were three types of batteries-AGM (absorbed glass mat), Gel, and flooded! And what's up with these 6-volt batteries-all of the goodies on my boat are 12 volt, right? What's with CCA, MCA, and reserve minutes? And what's the deal on these prices??

Flooded (wet cell) batteries are at the low end of the scale price wise. The initial cost generally won't initiate second mortgages to pay for them, and if properly maintained, can last between a few hundred to over a thousand cycles. They can stand more overcharging than the rest, within reason, as distilled water can be added to replace that which vents out. Therein lies one concern - venting. The gas, which comes off, is explosive, so the compartments or boxes they are in must be well ventilated. They are corrosive if the case is ruptured, discharge more than the others on their own, require periodic off season recharging to prevent sulfation, and need proper care and feeding more so than other types. If you are willing to undertake that aspect in particular, they give a lot of bang for the buck.

Gels are one type of recombinant battery, (AGMs are the other) in that they "make" their own water. That's a bonus because it gets the start-it-and-forget-it boater off the hook when it comes to adding water to them. Gels can be installed on their sides with a little loss of capacity, last a thousand cycles plus, can't spill even with the case cracked, and are nearly bullet proof when it comes to shock, vibration, and over discharge. They are not idiot proof however, and if they are overcharged repeatedly, you now have the heavy part of the second set of ground tackle, holding power good in rocks, poor on other bottoms. Once the electrolyte says "adios" which is what happens when the charging voltage is too high (over 14.2), it cannot be replaced. These batteries are NOT cheap, either!

AGMs are similar to gels in that they will withstand a lot of boater abuse before throwing in the towel. They can be installed at any angle except upside down (it still won't leak, but the valves inside the battery won't work), can be submerged (handy in a capsize) without damage, excellent dual purpose (starting and deep cycle discharge), long cycle life (1000 plus cycles), very low self discharge, and will recharge quite nicely if left in a discharged state for a long period of time. They too dislike constant overcharging, and like the gels are land fill fodder if the electrolyte is destroyed by overcharging. An unregulated charging system is the kiss of death to AGMs, and at $230 per Group 31 battery, to your checking account as well.

One long lasting, very viable option is to take multiple 6-volt golf cart batteries in series to get 12-volts. They will withstand vibration, have a very long life, and are cheap - great for a house bank. They are compact from a footprint standpoint, but are taller than the others, so it may be more difficult to find that perfect mounting location for them. They share the same traits as the 12-volt brethren they are related to, either flooded, or gel, and the largest ones weigh in at a hernia inducing 113 pounds. And don't forget, you need at least two of them....

A few terms you'll see when checking out the battery stable are CCA (cold cranking amps), MCA (marine cranking amps), and reserve minutes. CCA is the number of amps a battery can deliver for 30 seconds, at 0 degrees F without the voltage dropping below 7.2. MCA is the warm weather version (32 degrees F); since batteries will perform better with an increase in temperature, the MCA will be higher than it's CCA comparison. These terms mean the most when a brief but high load is imposed on the battery such as starting, or operating an electric windlass; in the normal DC load use, rated amp hours are a more useful measuring stick. Reserve minutes are handy in that this measurement provides the minutes that a battery will last on a continuous load of 25A until the voltage drops to 10.5 (dead battery). Yet another example of bigger is better!

As expensive as batteries are, there is some reluctance to throwing out all of the old batteries, and starting anew. Why not just replace the one bad flooded battery with a brand new gel or AGM? The quick and dirty answer is that it is bad to mix battery types, as they require different, and specific charging voltages (see above about converting gels and/or AGMs to anchors). It is also not a good idea to put in a new battery into a house bank which may contain multiple older batteries, even of the same type. While it won't damage the new battery directly, the older batteries have the effect of pulling the new one down to their level, and you won't get the efficiency that was expected. As painful as it is, it is best to start from scratch, same type, same age for the maximum performance.

Next issue we'll explore how the intrepid Solosailorman will recharge his newly installed investment, and how to make AC all the way to the island without the 320 mile yellow umbilical cord!

Cheers
Tony Driza

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