Boat Battery Upkeep: Fall And Winter Charging Tips

Our favorite pro football team was playing and being featured on national TV, so when Sunday arrived we packed a portable television and all the fixings for a tailgate party aboard the family pontoon boat. It was a crisp morning following a full week of below-average temperatures, and thin panes of ice lingered in the shadows around the marina’s mostly empty slips as we got an early start.

Fall Boat Launch: Keep Your Battery Charged

Above: Fall boat launching – late-season air temperatures can affect your batteries’ performance. Photo by Dan Armitage for Boat Trader.

‘Start’ being the operative word, for after everyone was aboard and settled in, I turned the ignition key and got just enough juice from the starting battery to turn the 15 hp motor over twice before it groaned and gave up. I knew better than to try again and without a back-up battery we were dead in the water. A close look at the battery’s scratch-off purchase date sticker showed that I had already pushed the cell’s energy envelope by several months over its advertised 24-month life expectancy, so I guess it shouldn’t have been a surprise.

Making the best of the situation we enjoyed a pre-game tailgate party aboard. The TV had optional internal battery power and the party proceeded pretty much as planned, albeit at the dock rather than anchored out or beached at some distant shoreline. As kickoff time arrived, so did the rays of the sun, which by half-time had warmed things up considerably. Jackets and lap blankets were removed and cold beverages became more popular than coffee and hot chocolate among the fans aboard. All was well when I decided to give the key a token turn before the second half, and sure enough: the engine cranked and fired!

Our game day afloat was saved and we enjoyed a combination football and fall color cruise before putting the rig away for the season, but not before leaving a note to myself that I needed to buy a new battery before breaking it out for the start of the next.

Autumn Battery Savvy: Basic Maintenance And Care

Experience and research since that incident have combined to make me a bit more battery savvy. For example, in addition to being past its prime, the reasons my battery failed to start the outboard at the beginning of that brisk autumn morning were threefold: before the sun had a chance to warm things up, the oil in the engine was still thick with the chill, making cranking efforts more difficult. The cold also kept the gasoline from vaporizing – and firing –as easily as the fuel did once conditions warmed up. And, finally, the battery itself was not fully charged from the previous weekend, which had also been frigid and had hampered the cell’s charging efficiency from the outboard. Combined with the cool air temps to start the day, the battery just couldn’t generate the juice needed to get things cranking.

The latter issue changed once the air temperature warmed up. Just as you can “re-charge” common batteries weakened by use in cold conditions by placing them in your armpits (or other warm areas, on your body or elsewhere…) 12v boat batteries benefit from warmer air temperatures. Once the fall sets in, and the colder months are upon you – even if you plan to keep using the boat, it’s important to keep these factors in mind.

Charging A Boat Battery

Above: It’s ok to leave your starting and deep cycle batteries aboard your boat during the off season, even in sub-freezing conditions, as long as you keep it charged on a regular basis. Photo by Dan Armitage for Boat Trader.

5 Proper Off-Season Battery Storage Tips

I’ve also learned that the best way to extend a starting or deep-cycle boat battery’s life expectancy is to offer the proper off-season care. That includes:

  1. Disconnecting terminal connections to eliminate any electrical loads
  2. Cleaning corrosion off the terminals and cable connections
  3. If the battery has removable vent caps, removing and filling each cell to the proper level with the recommended fluid
  4. Fully charging the battery before storing it
  5. Charging the battery at regular intervals during the off-season

For extended periods of non-use, such as winter storage, you can leave a fully charged battery on the boat or move it to an inside location such as a garage or basement for storage; just make sure there is plenty of ventilation and the battery will not be exposed to excessive heat. As long as you keep the battery charged, using a trickle or automatic charger, even sub-freezing temperatures will do it no harm.

Boat Battery Maintenance And Removal

Above: Many boaters prefer to remove their batteries during long periods of storage to make it easier to keep the cells charged back at home. Photo by Dan Armitage for Boat Trader.

I find that keeping the battery in a visible and accessible location in my garage helps remind me – and makes it convenient — to hook it up to a charger and keep it juiced during the off-season so we’re ready to go for those spring baseball tailgates aboard.

Slow and Steady Leads the Charge (Optima image)

Fully discharged 12v boat batteries may not accept a high current re-charge. The depleted cell may be appear to be accepting a charge, but if the current flow is too strong only the surface of the plates may be re-charging and the battery will quickly drain when placed under load. When a battery has been excessively discharged, it’s better to use the low current setting on your charger to bring it back to life. Marine-grade chargers such as digital models from Optima analyze, charge and maintain 12 volt boat batteries.

Boat Battery Terminals

Above: No matter the season, clean terminals and tight connections are critical to getting the most out of your boat battery. Photo by Dan Armitage for Boat Trader.

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