2001 460 Sundancer Charging System Probs and Q's

[ChillaxinUSVI]

Hello,

I need some help with a 460 DA with Cummins Diesels. My questions are general. I am a very competent mechanic, machinist, fabricator, and electrical tech, just no experience with 24V systems... need general knowledge.:smt100

1. Why do the voltage gauges at the helm read 0-15v?

My questions and problem related to a dead battery and an engine that would not start without the assist switch.

2. What is a "normal" voltage reading on a 24V battery, not connected to shore power, engine not running? My two batteries read 26.5v +/- a few tenths (both now new).

3. What is a normal increase in voltage reading on each battery when the engines are running? (Currently, I get no change whatsoever, even with engine RPM at 1500).

4. Will the alternators create charging current at idle?

5. What RPM should the alternators be producing charging current to the batteries (what RPM should they be tested at)?

6. What is the output voltage from the alternator? Can the main power wire be disconnected, and the alternator voltage output simply be tested between the lug and the engine block?

Is there any other testing methods or advice you can offer? I want to be sure this vessel is seaworthy.

Thanks!!!

 

[Jaws]

I had hoped that someone with more marine electrical knowledge would pitch in.

I'll comment because my boat is similar and the only 24V DC system that I recall on the vessel is the bow thruster system which has two 12V batteries in series. A 120V AC-24V DC converter does the charging.

All other systems as I recall are 12V including the two 8D batteries that each start its dedicated engine unless you engage the emergency switch (a solenoid in the bilge) which then parallels the batteries. A separate 120V AC-12V DC converter handles that side.

What is your battery set-up? I'm curious.

 

[Hampton]

1. I believe that reflects the max output of your engines' alternators.

2. 26.5 seems normal right after charging. 24 is normal. 21 is running low. 1.75 per cell seems to be the low end, and 2.15 per cell the high end (typically). Range is then about 21 - 26. 26.5 doesn't seem out of the norm. http://homepages.which.net/~paul.hills/Circuits/BatteryMonitor/BatteryMonitor.html

3. I don't think you'll see any increase immediately. Increase in voltage is an indication of increase in the charge level of the battery which happens slowly over time. It may depend on where you're getting your reading. It sounds like you may want to test the charger output to ensure it's adequate.

http://www.powerstream.com/SLA.htm Keep in mind that your 24 Volt Batteries have 12 Cells.

4. No. http://rb-kwin.bosch.com/us/pool/usa/pdfs/Technical_Solutions/SG_Alternators_FAQ.pdf#4

5. They create current at all RPMs. There is a minimum amount of current required in order to "Break Even." This current is produced by the alternator and used by ignition systems (not on diesels), chart plotters, radar systems... At idle, it is very possible (likely) that your boat is drawing power from your batteries, depending on how many systems are operating, the RPM of your engines at idle, the output of your alternators at that RPM... From my experience, idle RPM does not compensate for the draw of many systems. At the break even point (maybe 1000 RPM? - seems to be for my truck and my boat), you still don't charge the batteries. Anything above that, you will charge them. I don't know what that point may be for the boat in question. It's a matter of the flow of amps - From Negative to neutral (0) to positive.

6. This may help: http://assets.fluke.com/appnotes/automotive/beatbook.pdf

 

[ChillaxinUSVI]

Everyone bear with me... I am going down to the boat tomorrow and collect a bunch of info, and then give much more detailed up front data for you to help me with.

 

[FireIsland1]

Hello,

I need some help with a 460 DA with Cummins Diesels. My questions are general. I am a very competent mechanic, machinist, fabricator, and electrical tech, just no experience with 24V systems... need general knowledge.:smt100

1. Why do the voltage gauges at the helm read 0-15v?

My questions and problem related to a dead battery and an engine that would not start without the assist switch.

2. What is a "normal" voltage reading on a 24V battery, not connected to shore power, engine not running? My two batteries read 26.5v +/- a few tenths (both now new).

3. What is a normal increase in voltage reading on each battery when the engines are running? (Currently, I get no change whatsoever, even with engine RPM at 1500).

4. Will the alternators create charging current at idle?

5. What RPM should the alternators be producing charging current to the batteries (what RPM should they be tested at)?

6. What is the output voltage from the alternator? Can the main power wire be disconnected, and the alternator voltage output simply be tested between the lug and the engine block?

Is there any other testing methods or advice you can offer? I want to be sure this vessel is seaworthy.

Thanks!!!

1: taking a guess here, your ususable voltage at the helm is 12v to run normal systems. your guage is showing that you have proper voltage.
2: 26v is about the proper reading for 24v fully charged batteries. 12v batteries run about 12.6
3:? what is the battery configuration. 4-6v, or 2 -12v
4: most diesel engines are set to charge at idle because they are often run at low rpm for long times. The rpm of the alternator is not the same as the engine due to the belt configuration.
5: 650 to charge, about 1200 to peek
6: no take the reading while the batteries are in the circuit