2020 Alternator Issues

[2in2out]

Step A: Test the battery with lowest charge first. Ensure battery switch is off. This will be your baseline voltage. If less than 11.7 vDC, charge battery for several hours with a smart charger. Retest voltage.

Step B: Next turn the battery switch to the lowest battery. Measure and record voltage. This will ID parasitic drain voltage.

Step C: Turn on ignition and let systems fully boot up, approx. 30 sec. ensure audio, lights, pump systems, blower, are all turned off. Record voltage.

Step D: Turn ignition off and select power off on control system. Wait 10 sec, then turn ignition back on and let system boot up, blower run. Audio, lights, pumps should be off. This is your pre-start voltage. Measure and record. If low battery is below 11.7 vDC, battery should be replaced.

Step E: start engine and record voltage input. At idle, voltage should be 13.7-14.4vDC. If not, check alternator connections to battery switch/bus bar. If no issue, and voltage is 12.9 vDC or less, have voltage regulator on alternator tested, and assess for engine / fuel system shorts and bad connections, then move on to next step. Goal is to have idle voltage between 13.7-14.4.

Step F: at idle, engage pumps for 5 min. Record voltage. If voltage at battery drops below 11.7 vDC and remains after pumps are shut off and engine at idle, there is a short in the pump system. If voltage returns to 12.9 or better, system is ok, but not performing optimally. Isolate and assess any parasitic drains. Clean/replace/tighten connections.

Step G: at idle, run audio system for 10 minutes at volume you would usually float with. If voltage drops below 11.7 vDC and remains after audio is shut off and engine at idle, there is a short in the audio system. If voltage returns to 12.9 or better, system is ok, but not performing optimally. Isolate and assess any parasitic drains. Clean/replace/tighten connections.

Repeat with Bat2.

Idle voltage 12.9 or less suggests poorly performing alternator, voltage regulator, or circuits. Cycle all breakers and ensure no partial disconnects that may be causing resistance. Check belt condition and tension, pulley tightness, etc.

Unequal idle voltage between battery banks may indicate failure in charge circuit or battery switch / bus bar. Repeat test with Bat1 or Bat2 physically disconnected. If voltage returns to 13.7-14.4 replace disconnected battery as a cell may have collapsed.

If none of this results in diagnosis or solution, the gremlins may be deep. Seek professional help and good alcohol to absolve your frustrations.


Currently boatless

[gedakbx]

What was the voltage at the alternator?

[Hayden]

What was the voltage at the alternator?

12.5V


RE: 2in2out's posts, I have lots to work on there. Did you get that from a website? If yes, have a link?

I could have a less efficient battery now according to those points. It tested ok at mechanic shop. Still not sure how there could be such a big descrepancy between the two if I've always been running them shared.

Appreciate the suggestions. Thanks.

[2in2out]

12.5V


RE: 2in2out's posts, I have lots to work on there. Did you get that from a website? If yes, have a link?

I could have a less efficient battery now according to those points. It tested ok at mechanic shop. Still not sure how there could be such a big descrepancy between the two if I've always been running them shared.

Appreciate the suggestions. Thanks.

12.5v at the alternator indicates a malfunctioning alternator or regulator. 12.9v is a minimum input voltage to keep a battery topped off and provide systems voltage for critical engine components. For accessories, more voltage needs to be supplied by the alternator, hence the 13.7-14.4 range. A weak battery can put a lot of load on the alternator causing premature failure.

Given the materials and worker shortages I can see vendors cutting corners and a lot of system components failing. This should be a warranty issue and I hope it can be resolved quickly.

Batteries can fail for multiple reasons. Discharge rates, temperature, and manufacturing issues. If you shock a battery hard enough you can collapse a cell, decreasing output and battery life. This can happen when it’s being loaded on a pallet for shipping, etc. Lead acid batteries are weak, cheap, and prone to failure. AGM batteries are more expensive, have better service time, but require a lot of care in the charge/discharge cycles.

As far as a website for this info, I did a lot of research on RV solar systems and went down a van conversion rabbit hole. I learned a lot about integration of different battery systems into vehicular charging systems from electrical engineer blogs. I left lithium batteries out of the discussion as they aren’t practical cost wise, or system wise, but they would handle better as “house” batteries.


Currently boatless

[Hayden]

So now I'm thinking the one battery may be compromised because I ran it down to 9V trying to get back to the dock and deballast.

[2in2out]

So now I'm thinking the one battery may be compromised because I ran it down to 9V trying to get back to the dock and deballast.

I would still have the alternator bench tested, but replacing that battery is probably a wise choice.


Currently boatless

[Hayden]

I sent my testing videos to my dealer and then took the boat in to have it checked out. It was 100% a faulty alternator and dealer was saying that with the (Indmar) boats they've sold in the last year, 1 in 6 came back in for faulty alternator this spring/summer. It's running 14.7V when above 2000 rpm now.

[mjb929rr]

My 20 sl450 did this last season several times. Usually when we had all the lights on at night. My batteries were never low though. Dealer looked at it last fall and couldn’t find any issues. I’ve had a several times this summer where I get the voltage below 11, maintain rpms above 1500 warning still. At this point I’ve just disregarded it as a glitch in the system. You would think there would be some kind of problem but dealer couldn’t find anything and it hasn’t caused any issues.

[HFarr]

I sent my testing videos to my dealer and then took the boat in to have it checked out. It was 100% a faulty alternator and dealer was saying that with the (Indmar) boats they've sold in the last year, 1 in 6 came back in for faulty alternator this spring/summer. It's running 14.7V when above 2000 rpm now.

That's a good find!

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