Electrical Mystery, Batteries are Good!

I have a bit of a mystery. The only recent work done on boat was the replacement of a starter. We have had a bunch of rain here, and we were running the boat in the rain (with cover), so I'm doubtful there might be a problem with water shorting things out as the boat engine was dry, but am open to ideas. Please note that the batteries are good, so I don't think that is an issue. Here are the symptoms.

Starboard Battery Bank (motor and all systems connected to that bank) are intermittently losing ALL electrical power. I am able to start fine with the emergency crossover. However, when underway, it quit when putting motor into gear at idle. (Again, intermittently). Managed to run and get on plane, but when I hit trim up/down, the motor wanted to quit.

Pulled back into dock, and bumping in and out of gear killed engine and loss of electrical at idle. (Starts fine using Crossover). Had to dock on Port Engine.

Here is the strange part.

When the boat is plugged in to shorepower, starboard motor will start fine without a single hiccup. (Even without the battery charger on)? However, EIM, system view and all starboard electrical will not run unless the charger is on. Generator, which also works on that bank will not turn over.

Then..... everything fixed itself after all of a sudden later this morning.???

Does anyone have any ideas.

1. Lose connection on starter? If this is the case, why would the starter work fine on crossover, and why loss of entire power to all systems from that battery bank.

2. Lose connection at battery. I will double check, but they seem fine with no corrosion.

2. Bad/intermittent batter switch? This seems to be the most reasonable, but wanted to get ideas if these would all of a sudden go bad while underway in the on position. If it did go bad, then I do understand that I might need to replace alternator.

3. Bad alternator? I doubt this too, as motor seemed to have run fine while putting on trailer this morning and the charge was good. Also, the batteries were charging all night on the battery charger, and after turning off the charger this morning, that entire bank was dead. Then 1/2 hour later, everything seemed to come alive.

Please let me know any ideas and possible ways of troubleshooting this. Hopefully this will be a familiar scenario with someone and they can give me an idea.

Mike

Kind of a longshot but it sounds like you got some connections wet and they are shorting out or not making a good connection. Double check the starter connections as well as the battery switch. A can of wd 40 sprayed on the connection can dissapate moisture, see if that helps.

Had a similar issue a couple years back. Had relatively new batteries but one of the four batteries hooked in series developed a shorted cell. That was a difficult issue to isolate. That was one issue. The second issue was a circuit breaker that Searay added to the port electrical set up on my 400DA. It was way up on the port bulk head, not on the scymatics, nothing. Found it by following the wires from the batteries to the starter set up. It was a faulty breaker but it boiled down to a bad connection.

Check your grounds as well.

Agree, sounds like a ground going bad. Check all of them. Corrosion can get inside the sheathing and corrode wires out of plain sight.

Being in fresh water I doubt wet connections would still exist. My guess is a bad battery, they need to be load tested not just put a meter on them.

Found the problem! Battery cell empty and liquid from battery in tray! Replaced and all is good!

MExcelsior said:

Found the problem! Battery cell empty and liquid from battery in tray! Replaced and all is good!

Click to expand...

Man, a cell goes bad, or worse its intermitant, and it throws the whole system out of wack. Bottom line; and best thing to do when anything like this happens is to disconnect each battery and test it independently; double check the connections and grounds. I'm betting that will be a 90% chance of a positive result.