Alternator problem??

[Art]

On the way home yesterday after 5 hours on the water (genset off all day) I started getting an intermittent alarm (aprox. 1 sec alarm every 20 secs) and Stbd "Check Engine" light came on and Stbd voltmeter dropped, when the alarm beeped. Neither the SR System monitor or Smart Craft indicated the nature of the alarm. It was getting dark and still 2 hours from home so I pulled into a close-by marina to assess the situation. When I restarted the engines I realized my NEW (April) batteries were weak. I turned on my Genset for ~30 min (to help recharge the batteries), and then restarted the engines, the alarm had stopped. We decided to spend the night at the marina and in the morning I ran the Genset for 30 minutes before starting the engines and then ran the engines for 30 minutes before departing everything seemed OK. But, 500 yards from the marina I got a steady alarm and returned to the marina. I was not getting the Check Engine light, so I don't know if this is a different but related problem.

I decided to be towed home. Due to wind & dock configuration I had to start the engines and dock the boat. For 15 minutes the engines ran with no alarms, but then I got the intermittent alarm. I immediately turned on my Gen and the alarm stopped. Typically my voltage reads ~ 12.1v on both sides.

When I turned on the shore power the battery charger was putting out 38 amps and after 7 hours is still putting out 12 amps.

The boat is always on shore power when docked and since we are in Fla. the Genset is almost always on when we are out. Could one or both alternators be weak and this unusually long trip without using the Gen surfaced the problem or is something else going on?

Any and all help and advise would be greatly appreciated.

 

[Steve Craig]

You should see a solid 13.5V at the battery terminals with the engine(s) running. Marginally less is still OK but less than about 12.5V I don't think the batteries will fully charge. Confirm the voltage is being generated first. Next borrow/buy/ steal a battery load tester & get an idea what shape the batteries are in. New maybe, healthy sometimes not. Pulling the batteries may be an option & bring them to a shop with a load tester.

 

[Alex F]

The voltmeter gauges on the dash tells you what your alternator is outputting. What readings do you have when the engines are on?

If I unerstand your situation correctly, then it sounds like you could have simply run the generator to keep the batteries constantly charged and move on to your destination.

To fix the issue I would make sure your batteries are able to hold charge and then test your alternators output. It's possible that you have weak battery that was damanding extra juice form the alternator which what makes them work harder and eventually fail. If you have one battery that's weak, change both on the same side. My Cummins Tech advised me to do so when one of my batts got "cooked".

I had to trace alt. failure and it's pretty straightforward process. I got my alts rebuilt and bumped them up to 160amps instead of standard 130amp. You might consider this as well.

Hope this helps a little.

 

[Art]

Guys thanks for the help. After being on the Battery Charger all night both batteries read 13.5 v with my digital VOM and the charger was putting out ~ 0 amps. I then shut-off shore-power and started both engines. Voltage at both batteries read fluctuating between 12.2v to 12.7v. I took voltage reading approx. every 5 minutes and for the first 15 minutes the reading at each battery were fluctuating +/- 0.25v and were tending down after 20 minutes they were reading 11.9v to 12.4v. However, after 30 min running the fluctuating stopped and both sides were reading stable.
Port 12.51v, Stbd 12.48v. Increasing engine RPM from 650 to 1000 did not change voltage.

I then I shut everything down put shore-power back on and let the batteries recharge for an hour and re-ran the same test but this time with my genset running before I started the engines. Initial voltage before starting was 13.2v on both sides. Initial reading after starting engine was stable 13.2v on both sides. After 5 minutes battery charger was fluctuating and pegging to max current. For the next 20 minutes the battery voltages continued to fluctuate similar to the first test with reading running 12.1v to 12.6v. Again after 30 minutes everything stabled. The battery charger and the batteries were at Port 13.1v, Stbd 13.08

I ran the same test with shore-power on instead of genset and got the same results of voltage instability after starting that then became stable after approx. 20 minutes.

Is this short-term instability indicative of battery chemistry, and is it abnormal?

I guess my next step is to locate a battery load tester as you both suggested, since the idea of pulling 2 130lb. 8D batteries out is not appealing. Will the cheap Harbor Freight do the job?
http://www.harborfreight.com/100-amp-6-volt-12-volt-battery-load-tester-90636.html
Thanks, Art

 

[Steve Craig]

Not familiar with load tester construction but for $25.00 I'd buy it. Check the electrolyte levels in the cells & top up as necessary. Do a recheck if any of the fluids were unusually low. I still think you should be seeing +/- 13.5V at the terminals with your engine or generator running.
The load tester will apply a load on the cells & monitor the terminal voltage.

 

[fwebster]

With the engines running and the converter off, you should be seeing ±13.5V at the battery terminals. If you do not, then either your alternators are not delivering adequate voltage or there is a wiring problem on the engine. I'm not sure what a load test will do for you other than confirm good batteries.........you charge over nite and have cells measuring 12.6V+; then you crank up and the voltage at the batteries only drops to 12.2-12.4V. Cranking a 6 cyl diesel is a pretty good load test.

The fact that you get proper voltage from your convertor but cannot on your engine's alternators is a pretty good sign you have bad alternators. This is also a pretty common problem with your engines. Given your location, you should be able to remove the alternators and take them to a decent alternator shop and have them tested and re-built if necessary...but be sure you specify that the alternators will be for marine use.

 

[Alex F]

Guys thanks for the help. After being on the Battery Charger all night both batteries read 13.5 v with my digital VOM and the charger was putting out ~ 0 amps. I then shut-off shore-power and started both engines. Voltage at both batteries read fluctuating between 12.2v to 12.7v. I took voltage reading approx. every 5 minutes and for the first 15 minutes the reading at each battery were fluctuating +/- 0.25v and were tending down after 20 minutes they were reading 11.9v to 12.4v. However, after 30 min running the fluctuating stopped and both sides were reading stable.
Port 12.51v, Stbd 12.48v. Increasing engine RPM from 650 to 1000 did not change voltage....

Art,

IMO, this test indicates that both of your alternators will need to be rebuilt. Take them to your local shop to be checked and then you'll get the final verdict from the pros.

 

[Art]

According to the guy in the Alternator shop both my alternators are fried because boat does not have a Crossover Charge Isolator (CCI) and I have been running my convertor when my engines are running. He claims it is not an uncommon occurrence. Do some of you without a CCI shut your convertor off when you are running your genset?

 

[tbirdvet]

I bought a load tester from harbor freight and it works very well.

 

[Alyssaly]

Wow,I love the pirture upside!So nice!!!!!!!!!:smt038

 

[ardeprint]

According to the guy in the Alternator shop both my alternators are fried because boat does not have a Crossover Charge Isolator (CCI) and I have been running my convertor when my engines are running. He claims it is not an uncommon occurrence. Do some of you without a CCI shut your convertor off when you are running your genset?

I am intrigued with this question... Any answer or comments?