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Posted by on Aug 28, 2011 in Boat Maintenance, Engines, UK, US |

Solar Battery Maintenance: An Ounce of Prevention

If you let your starting battery slowly lose its mojo, it will let you down.

I knew I was pushing my luck with my starting battery back in May. It was the beginning of its fourth season, and even though I’ve had boat batteries last longer than four years, that seems to be about the time they start going squirrely.

Small, cheap, low-output solar panels like this are very helpful in maintaining the charge on wet-cell starting batteries. They do need to be sealed with silicone to withstand rain.

Small, cheap, low-output solar panels like this are very helpful in maintaining the charge of wet-cell starting batteries. They do need to be sealed with silicone to withstand rain.

It’s a Group 24 flooded-cell battery – nothing fancy. I like wet-cell batteries. They definitely have their shortcomings compared to their gel-cell and AGM cousins, but I’ve found that as long as they’re kept charged in the winter, and always topped up with distilled water, and not allowed to discharge too far, and generally treated well, they’re reliable and predictable. And relatively cheap. And easily recyclable.

But I did not treat my starting battery well this summer. I neglected it for much of the season, along with the rest of the boat, because of pressing land-based matters. So when I went to run the engine not long ago, it wouldn’t start. And I can’t blame it. Using only a cold shoulder, I had issued the battery a coup de grace. Maybe I can revive it enough to use it for light duty at home (the marine battery pasture?), but it won’t be strong again.

On my simple boat, none of this is really a problem. I have a house battery that stays fully charged via an 18-watt solar panel with a charge controller, and it’s easy just to swing the dead battery out and the fresh one in. But I was annoyed with myself for ignoring basic battery maintenance. Wet cells discharge at a relatively fast rate if they’re left uncharged, and faster if they’re old. I knew it, did nothing about it, and got what I deserved.

There’s a good battery primer by Peter D’Anjou over at Waterblogged, called Marine Battery Types and Charging Tips. One of the recommendations he makes is to use a solar panel to keep batteries topped up. Agreed — it’s a good solution if you have a wet-cell battery that might not see any charging for weeks (or months) on end. I could easily have avoided my starting problem if I’d gotten around to hooking up the dinky little two-watt solar panel I’d had banging around in the car to the starting battery – the way I meant to back in May. Alligator clips to the terminals, snake the wires out of the engine box, leave the panel where it’ll get a lot of light, and done.

If you decide to get a solar panel to maintain your starting battery, here are three tips:

  • Most panels with outputs of under about five watts come without fuses installed. Even with such small panels it’s good practice to install a proper-sized in-line fuse in the positive wire between the panel and the battery, close to the battery.
  • If you go with a panel with more than about five watts of output, you should also use a charge-controller to avoid overcharging.
  • Most of these battery-maintenance panels are meant to live on car dashboards out of the rain, so run a bead of silicone around the edges of the panel at the frame, and where the wires enter.

– Doug Logan

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