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post #1 of 19 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?

Thanks
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post #2 of 19 Old 10-07-2018
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Re: Battery mystery

Something is drawing down the battery, is the chargering alternator actually working on the outboard?
Most problems can be found with a simple multimeter
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post #3 of 19 Old 10-07-2018
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Re: Battery mystery

Bad connection.
Clean and reattach
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post #4 of 19 Old 10-07-2018
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Re: Battery mystery

Battery charge showed fine when home, other systems ran fine with it while some didn't work at all. Sounds to me like a bad connection or worn switch related to some of the non working items in question as Registered alluded to.

For large draw items like a starter even a slightly dirty connection at the battery terminal can cause it to work intermittently or not at all.
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post #5 of 19 Old 10-07-2018
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Re: Battery mystery

You could have a dead cell. Best way to determine this is with a hydrometer. The specific gravity of each cell should be equal and read 1.275. If the cell is shorted, your battery charger would not be able to detect this and indicate that the battery is fully charged, while you may have a shorted cell.

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post #6 of 19 Old 10-07-2018
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Re: Battery mystery

I would give it 95% that it was a bad connection. Removing and replacing batteries might have left something loose or maybe one of the connections somewhere is corroded. Check the ground side as well as the positive.

The fact that the battery showed good charge at home is a pretty good indication the battery is OK.
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post #7 of 19 Old 10-08-2018
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Re: Battery mystery

As I understand it, there is no such animal as Dual Mode. Just marketing BS. Deep cycle is what you want, if itís running your nav/radios and should be just fine to start a small outboard. I think your past experience was coincidental.

It sounds to me that youíve either got a short somewhere or corroded connection.


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post #8 of 19 Old 10-08-2018
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Re: Battery mystery

Sorry to hear you're having such trouble.

I'd trace my connections with a multimeter and see if something's wrong in your connections. It's tedious work but you may find that one wiggly connection is causing your problem. Like others have said, if the battery was new and reading fine at home, it shouldn't be the problem.

Good luck and keep us updated - I'd like to hear what the end result is

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Re: Battery mystery

Quote:
Originally Posted by Rezz View Post
Sorry to hear you're having such trouble.

I'd trace my connections with a multimeter and see if something's wrong in your connections. It's tedious work but you may find that one wiggly connection is causing your problem. Like others have said, if the battery was new and reading fine at home, it shouldn't be the problem.

Good luck and keep us updated - I'd like to hear what the end result is
Checking the circuit with a meter is a good place to start but one warning. A corroded or loose connection may show good voltage with no load on the circuit but as soon as you try to draw power from that circuit the voltage can disappear. If possible watch the voltage when you apply a good load or follow up with a physical inspection of all connections.
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post #10 of 19 Old 10-08-2018
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Re: Battery mystery

No need to exchange the deep cycle battery for a start/deep cycle battery as long as the current battery is not defective. A deep cycle battery will easily start an outboard. In fact it will easily start an inboard diesel.

It definitely sounds like you have something going on with your wiring. With an outboard and single battery, you have a simple system so it should be easy to track down the issue.

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