High Voltage Concern

[exsailor]

On our 85 ED with 871's, just had new Rolls batteries installed with all things seeming normal with the charger on until leaving the dock. In general the Port set of (4) are for all house power, Thruster (24V) and the Port engine. The STB are for the Generator (24V) and STB engine. The pilot house SBD volt meter (still in the green) is showing 41V when under way. The Port shows around 36. I have checked tightness of connections at all batteries and making sure all cells are filled to the bottom of the tubes. I am having a Tech on board next Tuesday. What should we be looking at?

Thanks for input since the Batts were not cheap!!!

[Nonchalant1]

What voltage batteries are they? If they are 8 volt, they should be reading around 35V for the bank, but then how do you get 24V for the thruster, genny, etc? Do you always run the genny when underway? Are you running an inverter underway? At 41 volts, it's almost impossible for this to be a battery problem, but we need more info.

The first thing I'd do is to turn off the charger at the dock and get voltage readings. That will be your battery bank voltage reading with no charging system running. If fully charged, it should read around 36V for both banks. Take a separate reading at the batteries with a simple digital voltage meter. Make sure that the meters agree so you know that it's not a voltage meter problem.

Next, start up only the port engine and read the voltages. It should still be unchanged at around 35V for the SB side and around 35 to 38 on the port side depending on the alternator. If the voltage jumped up to 41V on the SB side when you started the port engine, there's something strange in your wiring, because normally the port engine won't affect the SB batt bank.

Next, start up the SB engine and read the voltages. If the SB reading jumped to 41V, the problem is your SB engine's alternator is putting out 41V charging current. The battery bank may be just fine, but the alternator is giving you the high voltage. Check you alternator specifications to see what the max charging voltage should be.

If it still reads OK and you normally run the genny when cruising, start the genny and check again. If it jumps up now, it's the charger running off the genny or the combination of the charger and engine alternator.

None of the above problems are the batteries. Let us know what you find and maybe we can help.

Good luck,

Doug Shuman

[CapetaniosG]

From your description the batteries, while underway, are being charged by the engine alternator and not the battery charger. If that's the case have you checked the voltage regulator of your alternator to see if it properly works? If the voltage regulator is not funtioning properly it coud result in the high voltage (41v) you are seeing at the volt meter.

With the engines shut down and the engine key in the ON position what is the voltage the engine volt meters show? With fully charged batteries the voltage for a 32v system should be around 36v + or- a volt or two. Now with the engines running ie. alternator gharging the batteries (and battery charger OFF) measure the voltage with a hand held volt meter at the back of the engine volt meter and see if the voltage of the hand held volt meter agrees with the voltage shown by the engine v-meter. This test will tell you if your engine volt meter is accurate. If it is, but it still shows 41v then you may indeed have a defective voltage regulator. You can check that with your hand held volt meter. If it is, replace the voltage regulator.

CapetaniosG

[Brian Degulis]

Are you tapping into a 32V battery bank to get 24V for your gen and thruster? If you are this could be your problem when you tap into a 32V bank to get a lower voltage you end up depleting the cells you have taped into but not the others. What this will do is cause the bank voltage to drop and tell the charger or alternator to put out. So you end up charging cells that are already up (the ones not taped into) in order to bring up the bank voltage. This will result in some cells over charged and some under charged.

Brian

[exsailor]

Thanks for feedback.

Some numbers
With Chrgr and Engines off P34 & S35
With only Chrgr on P38 & S38
With Chrgr and engines on P36 & S38 (500-600RPM) and inc to 41V by 1200RPM
With only Engines on P35 & S ...... same as above.

I sure do not recall the high numbers prior to the yard installing new Batts. Anything they could have screwed up? Also Batterry source says 38.9 should be tops and that I should "dial down" the regulator. Possible??

I will have mech on Tues check some of these with a meter, however I have gotten similar numbers at both helms and PH panel.

[exsailor]

As was suggested, the voltage regulator of the alternator was at fault.
Delphi alternator/regulator was removed Tuesday, rebuilt and repalced today. Never thought 35 - 36 Volts would ever look so good.

Thanks all.

[Nonchalant1]

Byron,

Glad you got it. Now maybe time to worry about how you're getting 24V out of a 32V bank. Running a wire from the 3rd batt. is not a good idea.

Regards,

Doug