…Heat is highly detrimental to a battery because the rate of corrosion, solubility of metal components, and self-discharge all increase with an increase in temperature.
You also should have cleaned the terminal posts with a wire brush, coated them with white grease, and regularly wiped down the top of the battery with a neutralizing solution of baking soda and water. (This not only gets rid of any acid residue, but cleans as well. A trail of dirt can create a circuit between terminals that can eventually drain a battery.) And while the jury is still out on the pluses and minuses of storing them on a concrete floor in your garage or basement versus on wooden slats, the one thing that is sure is that neglect will lead to discharge and damage.
With lead-acid batteries you should keep the electrolyte topped off to within 1/4 to 1/8 inch below the vent/fill holes and check the state of charge with a hydrometer. (When storing, check the electrolyte level monthly; during your operating season, I'd recommend doing it weekly.) A fully charged battery will have an open-circuit charge one read with a voltmeter after no load has been on the battery for several hours-between 12.6 and 12.8 volts and a specific gravity reading on the hydrometer scale ranging from 1.265 to 1.290 per cell at 80°F. (If you're storing your battery for an extended period of time, a trickle charge now and then will maintain this level.) A cell reading below the accepted range is most likely shorted out or damaged beyond repair, and the battery will have to be replaced.
A lead-acid battery should never be allowed to discharge to less than 50 percent of its capacity. The farther past this point the process is allowed to go and the more frequent the discharge cycles, the more long-term damage will be done to the plates. In addition, constant discharging and recharging can also damage the battery.
Sulfation is the problem. As the energy level of the battery decreases, the chemical reactions going on within produce deposits that adhere to the plates. Each time a battery is cycled-that is, discharged charged and recharged--a small amount of sulfate is left on the plates. The more deposits, the less surface area available for energy production. Left to continue, this leads to cell failure and eventually, a dead battery.
State-of-the-art electronic battery chargers can keep things on an even keel. And if you don't have one of these neat gizmos as part of your boat's electrical system, you should look into one. Equipped with fully automatic microprocessors, they will watch over your batteries like a mother hen over her chicks, including monitoring the three stages of charging: bulk, acceptance, and float.
Most of the charge is delivered in the bulk stage. Once this limit is reached, the charger enters the acceptance phase, reducing the voltage. Finally, with the float charge engaged, the charger maintains battery voltage at a lower level appropriate for long-term battery maintenance.
The important factor in charging a battery is making sure it reaches its gassing point, the voltage at which the battery begins to generate significant amounts of oxygen and hydrogen gas when fully charged. Not to do so will mean a battery below a full charge. A charger can take the guesswork out of all this with automatic temperature-compensation sensors.
But no matter how carefully you monitor charging cycles, some sulfate deposits will remain on the plates. Equalizing or conditioning is used to not only remove the residue from lead acid batteries but also restore battery capacity, revive efficiency, and extend operational life. You should not equalize your gel-cells due to their vulnerability to over heating. Instead, check with your battery manufacturer if you feel they should be equalized.
Basically lead-acid equalizing involves a controlled overcharging cycle that raises the voltage of a 12-volt battery to 2.7 volts per cell. Given the voltage requirements, and as this is not an automatic function of the charger, you must take care during this process. In fact, if you've never done this, I strongly advise checking with your battery manufacturer first. Additional battery care involves inspecting cable connections for corrosion and wear, replacing if necessary, and always using distilled water when adding liquid.
A few words concerning gel-cells. A gel-cell is nothing more than a lead-acid battery that is pressurized and sealed using special valves and a gelled electrolyte. Gel-cells are recombinant batteries, meaning the oxygen normally produced on the positive side recombines with the hydrogen at the negative plate. This produces water that was lost during operation. Therefore, they are "maintenance free."
Due to their chemistry and construction, gel-cells present unique problems. First, they recharge inefficiently when deeply discharged. Second, most of the charge current produces heat rather than the chemical reaction necessary for recharging. And when discharged to more than 80 percent of their capacity, they are susceptible to damage from two sources: high temperature and an excessive charge rate. High temperature causes a gel-cel's thinner plates to degrade, and overcharging can destroy the battery by raising the internal temperature during gassing. With nowhere to go, the hydrogen and oxygen gas escape from the release valve, and since you can't add liquid, electrolyte is irretrievably lost. That's why if you're thinking about getting gelcells, you need to make sure you've got them matched with the proper charging unit.
You can keep your batteries healthy and working properly if you take care of them on a regular basis. Doing so will enable you to have years of reliable service and trouble-free starting. It's not so mysterious after all.
Selected paragraphs from POWER & MOTORYACHT, April 2002, Spring Maintenance, By Capt. Ken Kreisler.
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