DieHard’s Winterizing Program for Marine Batteries

By Captain DieHard


When the cold winds blow, do you think about your boat batteries? You’d better, say the experts at DieHard marine batteries, or your cranking and deep cycle batteries may die premature deaths. When the calendar and cold fronts tell you the worst is yet to come, the operable word is “winterize.” Here is Capt. DieHard’s step-by-step battery winterizing program for marine cranking and deep cycle batteries. Wear old clothes because you’ll be working close to battery acid, which can burn a hole in clothing. Protect your eyes. For safety’s sake, mix a solution of baking soda and water (50-50) and keep it nearby so you can use it to neutralize any acid spills.

  1. Disconnect your marine batteries and remove them from the boat and from the elements.

  2. Inspect the cables and connectors. Repair or replace them now, if necessary, not in the spring when the fish are biting and repair shops are busy.

  3. Clean and brush the cable connectors with a wire brush, removing the crusty, corrosion build-up. Coat the connectors with white grease to help maintain good contact between the connectors and batteries.

  4. Wire brush the battery posts to remove the white, crusty material. Coat the terminals with white grease or Vaseline to help ward off the effects of corrosion.

  5. With a disposable rag, wipe the crud, dirt and grit from the battery cases. Dispose of this rag.

  6. Dip another rag into a neutralizing solution of baking soda and water, half-and-half. Wring out the excess fluid and wipe down the battery cases.

  7. Check the battery acid levels. Add distilled water or de-ionized water, as required, to bring electrolyte levels to within one-eighth of an inch of the bottom of the vent well, or one-fourth of an inch from the bottom if the battery is discharged. Don’t overfill, or sulfuric acid will want to escape out of the vents. Don’t use tap water or well water. They may contain chlorine, iron or salts that will harm the battery.

  8. Recharge your batteries. Wear goggles and old clothes. Do not overcharge. Excessive overcharging causes loss of electrolyte and the interior plates to shed their active material, reducing capacity. Never charge a frozen battery. Always charge in a well-ventilated area.

  9. Cold weather charging requirements make a strong recommendation for the use of a “smart” battery charger such as the DieHard 71320 shelf model. This charger is equipped with a microprocessor capable of recharging each battery according to its own particular needs. On its “automatic” setting, this charger will charge each battery in optimal time then revert to a 2-amp “maintenance” setting, keeping the battery warm and fully-charged.

  10. Store batteries in a cool, dry, and well-ventilated place, far away from the furnace. Make sure they’re out of reach from kids and pets. A temperature of about 50 degrees is ideal. Your garage is fine for storage as long as the temperature inside doesn’t dip below freezing. A frozen battery is a dead battery. Never try to charge a frozen battery.

  11. While your batteries are stored, they’ll slowly lose their charge. Check them monthly. Restore water levels then bring the batteries up to a full charge if needed. A charged battery lasts longer than a battery in a discharged state.

If you have maintenance-free gel cell batteries the winterizing routine is the same except with a sealed case you cannot add more electrolyte. It’s especially important, therefore, that you not overcharge a gel cell battery or charge it too quickly. If you do, the gel in the battery can heat up and will have a tendency to dry out, shrink and pull away from the lead plates.
One of the most asked questions about battery storage is, “Can I store my batteries on cement?” The answer is, “Yes.” Before 1967, storing batteries on cement was a potential problem because battery cases usually were made of hard rubber. Batteries didn’t hold a charge as long back then, and the cold cement often helped freeze the electrolyte. Also, battery sealing was relatively poor. Acid leaks were common in those old batteries, and many cement floors showed the effects of such leaks. In that year DieHard introduced the heat-sealed, polypropylene battery case and cover that have raised battery capacity and reduced the potential for leakage. A word of caution, though: If your vent caps are not tight or if you overfill your cells, liquid acid may work its way out through the vent caps.
If you have any questions at all about what to do with your batteries, stop in at your nearest Sears Auto Center and get some answers, or write me:

Capt. DieHard, Sears, Roebuck and Co.,
Sears Automotive Group
3333 Beverly Road,
BC-103B, Hoffman Estates, IL 60179.
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