’91 Cummins 6BTA 5.9 M1 – DC Electrical Upgrad

DC Power Distribution–Making Sense of it

James,

I think we have different ideas on what really matters, what really works for the long term (I’m talking 1000’s of hours over just a few years) , what is most important to monitor, and how to compare things..

Battery terminal voltages and understanding it is #1. Your proposal is missing that completely

Knowing what is working, or not working (like your alternators and or AC Battery chargers) in missing in your proposal

Having one engine not affect the other electrically is missing in your proposal.

As to temp, basically zero interest in monitoring alternator temp.. Engine room temp and battery electrolyte / case temp is way more important.. Ever compared the under hood temps in a car idling or going slow vs. engine room temps in a boat?, it’s real common for under hood temps to run at 160F or higher vs 100-120 vessel engine room temps.. Also and important to work into the equation is that automotive coolant temps are just about always close to 200-210F these days vs. marine engine coolant temp closer to 180F.. All that heat adds adds to alternator temps. Do you worry about that ( meaning what ever you drive)?

As to fancy regulators, they have the there place , but until you can really “see” what is happening and understand it all, why?

BTW, basically all decent quality alternators with built-in regulators have temp compensation built into the regulation circuit—stable alternator housing temps in the 80F range vs. a 180-200F alternator temp, I usually see a .5 volt difference. As battery temp rises, battery terminal voltage should drop.

Talking about a continuous duty alternator and large frame alternators—I think you said you wanted a small frame unit that would fit your current mounting arrangement? If you want something “extra” then peek at the attached pics.

Tony

HINT—————————-Look closely at the contact area “number of degrees” on the alternator pulley..

Maybe 210 degrees vs. 140 degrees?

Tony

DC Power Distribution–Re-wiring & common sense

James,

Let me ask you a question..

Why would you want both main engines ( and a gen) dependent on one battery bank as a “default situation”? Plus, the way you have it, you will never have a clue as the what each battery bank is being charged by. Total couch engineering as, IMO, you never want each engine that requires power to run dependent on the other. Why have a twin engined boat? All twin engine boats should be set up to run as TWO single engine boats—Think about it.

This system goes against everything I have learned in the 30+ years of dealing with DC power distribution systems on vessels that run 1000’s on hours per year/and running 200+ days a year at sea…

I’d suggest you study the attached DC power distribution system—Put your generator on the house bank. Each main engine needs the equivalent of 2 x group 24’s ( or a single 31) , and the house as much as you want–The more the better———–Nothing should run off either engine bank other than the engine itself under normal conditions. Parallel switches are OK but stay OFF except in emergency situations and you understand why something needs to be combined

Use DELCO type 19SI’s 3-wire alternators in 105A or 140 A to start…………They can be converted to remote regulator later if you really “see” the need……Upgrade your “belt WRAP”……….. Stay 100% away from “hot-rodded” alternators.

A must have dedicated DVM from each battery bank at the helm station so you always “SEE” what is going on, engine on, or engine off.. Without that, you are driving 100% blind.

Tony

James,

Send me those DC power distribution diagrams in full size (high res) so I can study them a tad before I comment. Or, a link to where they came from.

Tony