Slitherine

quote:

ORIGINAL: Schr75

Hi BDukes

This is correct. Modern subs are diesel/electric, not diesel or electric, meaning that they are powered only by an electric engine,
The diesel is only used to charge the batteries, not directly powering the sub.
When you are traveling at full speed, the electric engine uses more power than the diesel generator can supply, so your batteries are discharging, although at a slower rate than if the diesel generator wasn´t running.

Søren

quote:

ORIGINAL: stww2

LOL I think BDukes just outed himself as Captain Krueger from "Voyage to the Bottom of the Sea!"

But seriously, as someone whose main familiarity with submarines prior to CMO came from the Silent Hunter series, this has caused confusion for me in the past too.

quote:

ORIGINAL: thewood1

Does charge rate exceed discharge?

Thats exactly it. At full speed, the diesels can't recharge fast enough. The diesels on modern diesels electric aren't part of the power train. They are only to recharge the batteries, from my limited knowledge. There have been several threads over the years on this and thats been the answer each time.

quote:

ORIGINAL: thewood1

I don't think its a battle to pick either way. I'm sure there is some combination of search terms that will bring up one of the multiple threads on it from both the CMNAO and CMO days.

quote:

btw, German XXI boats had diesel generators that had less shp than the electric motor. They were called Elektro boats because the shaft was connected only to the electric drive. I have found the key to figuring out the drive design is if the diesel is listed as a generator vs an engine (btw, that's anecdotal...just looked like a pattern).

quote:

ORIGINAL: Randomizer

Except that there are several examples (see Blair's Silent Service) of WW2 Fleet Boats running for prolonged stretches at "Four-Engine Speed", presumably flank, ~20 knots and yet no mention of flat batteries at the end of the run. In fact, long surface runs at fleet speed, 21-knots, was a design requirement for the fleet boats before the War. If it is the case than did this characteristic extend to the GUPPY conversions? Anecdotally I questioned a friend who served as a stoker on the GUPPY HMCS Rainbow and as he recalls, once the batteries were fully charged, the boat could run at full speed for days, as long as the diesel fuel held out. He did mention that on high-speed runs they would run the fifth, small "donkey" engine a couple of hours a day just to keep the batteries fully charged.

The battery drain at speed also happens with the German Type VII, IX and XXI boats in the CWDB and yet these all had the diesels drive the prop shafts directly and so one would think capable of maximum speed without affecting the battery charge. It seems probable that the Soviet Type XXI derivatives also used direct drives at least as far as the Foxtrots if the anecdotes in Peter Hutchhausen's October Fury are to be believed. I suspect that the battery characteristic in CMO may be more a function of modern boats, which are not intended to operate on the surface for long transits at all.

I suspect that there is wiggle room to finesse this aspect of the CMO diesel-electric submarine modelling and am not sure that propulsion differentiation would be worth the actual developmental efforts necessary to change the current situation. It may be as simple as adding a drain-batteries yes/no flag to the DB's but then everything becomes simple if you don't actually have to do it. Certainly scenarios like The Enemy Below from the Silent Service DLC become easier if the Player's boat can run at speed on the surface.

-C