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post #1 of Old 10-07-2018 Thread Starter
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Battery mystery

I use one group 24 battery on my Oday 23. A couple of weeks ago, I went to start my engine (8hp Tohatsu 4 stroke, electric start), and got nothing. Nada. A quick check showed that someone had inadvertently flicked a switch to "on" on the breaker panel, probably just before we had left the boat the weekend before. That left some lights on for the week, draining the battery completely.

I took the battery home to try and recharge it, but the message screen on my charger flashed out "Not charging. Service or replace battery" almost immediately. This battery was a good four years old, so I wasn't too upset. It was a "dual mode" battery, combining starting power with deep cycle cells. This was the first time I had bought such a battery; all my previous batteries were standard, deep cycle batteries that I used primarily to start my outboard and run my chart plotter and VHF. I almost never use the nav or cabin lights.

Unfortunately, West Marine didn't have a dual mode battery left (end of the season and all that), so I just bought another deep cycle battery. I installed it, started the engine, ran chart plotter and had a fine sail last weekend.

I went to go sailing yesterday, started the engine with the electric start, no problem. But when I shut off the engine after hoisting the sails, I saw that the chartplotter had shut off. When I tried to turn it back on, I got nothing. I then tried to start the engine with the electric start, and it too was dead.

There was no wind, so I didn't linger long. I started the engine with the pull start and headed back in. The chart plotter started right up (the engine has an alternator), and I had no trouble until I approached the dock and throttled way down to idle. At that point, the chart plotter screen started flickering. I shut it off quickly, docked, and took stock. The electric start on the engine was still not working, and I couldn't get the chart plotter to wake up unless the engine was running. However, the VHF turned on (no low battery light either), and the running lights lit up fine.

I took the battery home and hooked it up to my charger. The needle showed it was almost in the "green" zone, and the voltage measured 14.6. It took no more than a couple of hours to fully charge.

What the heck is going on with this battery? I've used deep cycle batteries for 15 years to start my outboard; granted, it wasn't this outboard (the old engine was a Nissan two stroke, but also an 8 hp), and I've never had this problem before. And I could understand if this battery didn't have the cranking amps to start an engine, but I can't understand how it could have enough juice to run the lights and the vhf, but not the chart plotter.

Thoughts? Comments?

My plan now is to just return this battery to West Marine and get a dual mode battery next spring. Any other ideas?

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