Alternator questions

[zigzag930]

Alternator questions 5 Amp regulator?

We are learning a lot about our new 58LRC, including some things that are not working. No surprise on a used boat, but it is frustrating that some of these tings were missed by the "engine" surveyor, despite my specifically asking for these items to be checked.

One issue I discovered is a 24V alternator on the port engine which charges the house bank is not functional. Interestingly, it is a Leece Neville 24V, 175amp unit (dual pulley), however the voltage regulator is not correct. The installed voltage regulator is a 5amp Leece Neville, which according to Prestolite documentation (online) is not even close to the correct VR for this alternator.

I'm wondering why in the world anyone would put a 5amp VR in this alternator? I didn't even think there was such a thing as a 5amp VR. The currently installed part #8RL3007 for verification, but should be a 8RL3024S.

Next, issue with the alternator is that the "excite" or "ignition" wire is not wired to a switched ignition source. It is jumpered from the + battery terminal. I'd think that might be a problem and would be causing the coils in the alternator to stay energized all the time.

Any thoughts?

 

[kelpy]

It should go to a N.O. pressure switch operated by either fuel or oil pressure. Turns the alternator on when the engine is running.

 

[zigzag930]

That makes sense to me.

I guess it would need to be a 24v sender (switch) and I think all the engine sensors are 32v. May need to add another switch somewhere on the engine and run the wire to it from the alternator + and back to "ignition" terminal

 

[Glory]

It is possible the PO installed a alternator with an internal regulator, it may be self excited also.

I do not have any external regulators, and all alternators are self excited and brushless.

My 2 cents.

Good luck withe the LRC, I admire that boat.

 

[Boatsb]

If it is an external regulated alternator get a balmar 624. Its a smart regulator and will allow charging options.

I just installed 2 on a 43 Hayden for the house bank.

They're not that expensive and I use 2 with a center fielder to charge from 2 engines to a LiFePo house bank and inverter.

 

[RichardM]

That makes sense to me. I guess it would need to be a 24v sender (switch) and I think all the engine sensors are 32v. May need to add another switch somewhere on the engine and run the wire to it from the alternator + and back to "ignition" terminal

You could also use a 32v relay energized from your 32v fuel pressure switch to activate your 24v coil on the alternator. Might be simpler that installing another pressure switch.

 

[zigzag930]

Just as a follow-up to this thread...

I decided to replace the existing 175amp (24v) Leece Neville with a 140amp unit. Here is my reasoning:

1) found the brand new unit for $200.00 (regular price is about $600)
2) new unit was self exciting, eliminating the need for a 24v switched power line to the "ignition" terminal
3) probably the most important reason - I measured the pulleys on the engine and alternator and determined that my charge rate (according to the published curves) was almost zero ams on the old alternator until the engine RPM's were well over 1000 RPMS. As I typically run at about 1400 RPM's, the new alternator gives me almost 120 amps at that speed and full output at 1600 rpms. The old alternator never reached 100AMP output (not to mention the rated 175 amps), even at 1800RPM's so this should be a much better choice for charging output.

Not sure who installed that 175amp unit, but I learned a good lesson about not just bolting on a high amp alternator, expecting hight output results. Actual alternator RPM (not engine RPM) must be calculated and mapped to the performance curve of the alternator in order to determine what actual output can be expected.