12 Little Volts

Twelve volts doesn’t sound like much, but when your boat needs them, it gets pretty quiet without them.

The twelve volts come from the boat’s batteries. These are pretty much like your car battery, but a little larger. A typical car battery is referred to as a Group 24, and weighs about 45-50 pounds. The batteries in the boat are referred to as 8D’s and they weigh about 160-170 pounds each.

I had a battery charger on the boat, and this little tale started when I began to wonder if that 20 year old battery charger was doing a good job of keeping the batteries charged. Because of its age, I was reluctant to leave the battery charger running when I was away from the boat, but I was nervous about leaving it off too. See, if any water starts coming into the boat, from a leak above or below the waterline, the bilge pumps will turn on to try to return the water to the outside of the hull. That’s a really good idea, and as long as the bilge pumps have power from the batteries, everything goes according to plan.

But…if the charger is off, and the bilge pumps come on, they start to run the batteries down. Sort of like leaving your lights on in the car. If the bilge pumps continue to run, for instance if a hose springs a small leak and the pumps keep running to push the water back outside, eventually, the batteries will “die”. At that point, if the water is still coming in, the boat will soon become an artificial reef.

One weekend, as I got ready to leave, I decided to leave the charger on to see what would happen. When I returned the following Friday, I could tell that the batteries were being seriously overcharged. That will kill a battery pretty quick, so I got right on the internet and found a nice shiny new charger. I had it shipped, and planned to install it as soon as possible so my batteries didn’t get ruined.

As it turned out, “as soon as possible” wasn’t soon enough. Next trip to the boat, I found both batteries were dead. Not low,… dead. I tried to bring them back to life, but they were, unfortunately, as dead as batteries can get. They were totally shot.

This wasn’t what I wanted to happen, but I wasn’t totally heartbroken either. Ever since I’d seen the batteries for the first time during our initial visit to the boat a year ago, I wanted to do something about the “creative” wiring arrangement. This is what they looked like when we bought the boat.

That rat’s nest of criss-crossing hot and negative wires looked to me, to be an electrical fire waiting to happen.

So, I installed my new battery charger, and carted the old one to my marine surplus storage area (my garage). With the new battery charger in place, and a set of very deceased batteries, the next order of business was to get rid of the old batteries, and then do a little wiring rehab.

First step was to get the old batteries out. Horsing 320 pounds of batteries up out of the bilge, up six steps to the salon,then back down six steps to the cockpit was interesting. Brian and I both were grunting like a couple of plow horses, but after a bit of sweating and the liberal application of some choice swear words, we got them both onto the dock and then into the back of my truck.

What was even more interesting was what we found when the batteries were out. The floor of the battery box had rotted completely away over the years due to the acid leaking from the batteries.

We decided that the floor of the battery box would need to come out, and I enlisted the help of my son Brian as official battery-box-floor-taker-outer.

That hole he’s digging around in is where the batteries were, and he’s in the process of cutting out the rotten part of the battery compartment floor. Once he got it all cut out, this is what we had to work with.

I fabricated a new floor using some 3/4″ plywood, and covered it with three coats of West System epoxy to seal it.

Now it was time to put batteries back in the boat. Replacing them with the same type of batteries just wasn’t an option for a couple reasons. The old batteries are called “wet-cell” types because they have a liquid electrolyte inside them. The electrolyte solution is what allows electricity to flow, but it is an acid solution, it’s highly corrosive, they need periodic refilling with distilled water, and there is a remote, but very real risk of an explosion from the hydrogen gas that is produced during recharging.

None of that was very appealing, so I decided that the new batteries would be a more costly, but much more user-friendly type known as absorbed glass mat (AGM). There’s still an electrolyte solution involved, but an AGM battery is sealed so that the electrolyte can’t leak. No refilling is ever needed, and there is virtually no possibility of producing flammable hydrogen gas. There are several brands of AGM batteries out there, and I settled on the Lifeline brand. These are made by folks who first made batteries for military aircraft, so they are very well made and should last me for several years.

Here are my two new babies in their new home.

The wiring is a lot neater now, and the whole battery area is cleaner and easier to maintain. Those of you who notice such things will see that the positive terminal on the battery on the left is covered by a black insulating “boot”. (Positive terminal boots should be red, like the one on the right) I’m well aware of that, and will replace it with a red one in the next few days.

Now my engines will start, the 12 volt lights will come on, and I can feel safe leaving the charger on during the week to keep the bilge pumps happy. There are plenty of chores left, but at least this is one more I can cross off the to-do list.


About TwoCaptains

The TwoCaptains are Jim and Janet, both US Coast Guard licensed boat captains home-ported in Daytona Beach. We recently sold our 1990 Ocean Yachts 56' CPMY "Magic Carpet", and now we're in the hunt for a replacement.
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One Response to 12 Little Volts

  1. Kirk says:

    Hi Jim, love reading your blog. Is the Toyota ad paying for any of the boat repairs? Wish we were fishing this Thanksgiving. I like red fish better than turkey. Looking forward to seeing you and Janet at Christmas. I guess a boat is like an onion. You find a problem and start pealing back the layers of the onion. Then you through the onion out and but a more expensive shallot.

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