Tuesday, August 16, 2011

Re: [Electric Boats] Re: Valiant 40 purposely under powered hybrid.

 

Like Eric I've only briefly cranked the throttle up on my system even then I did not go to full throttle because the speed scared me so I backed it off. I just was not use to the boat going that fast. As Eric mentions there are a lot of ways to save the boat then always depend on an ICE. There are many stories in the sail mags of engines that failed to start or stopped when they were needed most. Probably because of what I found at the bottom of my diesel fuel tank recently:
This stuff can get stirred up in rough conditions and clog not only filters but, fuel pick up tubes too! Nasty stuff that unless and you have an inspection port to look inside the tank you would never know it was there. I sure did not.
So the prudent mariner has many other tricks when one plan fails. Anchor, sea anchor, drogues or even changing ones plans and direction. A friend of mine in the Caribbean always says he is going toward a destination not to a destination because things happen on the journey. I think that's good advice.
Likewise I plan my trips like I only have a gallon of fuel on board which is about what the battery bank holds in equivalent energy. Even though I have the back up Honda generator (along with solar and a wind generator) and can electro sail for extended distances with it. I consider it part of my backup plans as I consider my boat primarily a sailboat. Though nature does not always cooperate so that's when I move to those back up plans:
For me it's all about preserving as many amps in the battery bank as possible for when I really need it and because I hope extend the life of the battery bank compared to if  I were to deplete it down to 50% or beyond often. For example on the above recent motor/sail I fired up the generator after my battery bank had dropped to 90% on my battery meter. I adjusted my throttle so I had 0 amps coming out of the bank. 37 nautical miles later when I reached my destination I still had 90% of my battery capacity left.  I certainly was not moving along at hull speed but, I moving along nicely at around three knots using only 900 watts of the 1600 availible from the Honda  2000 to move the boat along. That's not to say I did not tap into the battery bank when the current turned against me around some points of land but, after the need lessened I backed off once again.  I could max out the generator with an additional power supply added into the mix but, I have plenty of reserve power and never felt under powered operating this way with what I have now.
 
Capt. Mike


--- On Tue, 8/16/11, Eric <ewdysar@yahoo.com> wrote:

From: Eric <ewdysar@yahoo.com>
Subject: [Electric Boats] Re: Valiant 40 purposely under powered hybrid.
To: electricboats@yahoogroups.com
Date: Tuesday, August 16, 2011, 4:48 AM

 
Apparently, you lost all of your ground tackle too. I'm not sure why anyone would motor into the darkness near dangerous waters with the primary drive near empty, but this scenario is filled with a series of bad decisions. Even a Honda portable generator would get you away from the rocks unless you're in a current that exceeds 3kts.

If you had a diesel as your primary drive, would your first response be to take off at full throttle? As long as we're creating a worst case scenario, we might as well include that you used all of your fuel making microwave popcorn and fresh water for the converted cockpit jacuzzi party, so the geneset won't run anyway.

Seriously, dropping an anchor stops all of this right now. If you're in blue water, in conditions that you would rather not sail in, the traditional responses like lying ahull or deploying a sea anchor are still efffective.

Back to sizing the generator, the capacity of the generator only needs to be enough to power your battery charger, in the case of a 48V charger than can deliver 50A, everything in excess of 4kW is surplus. You could probably get away with the 3.5kW Kubota generator (70 lbs lighter than the 5.5kW, though the 2 cylinder 5.5 is probably smoother) if you pick the right charger and can refrain from excessive house loads during a self-induced emergency. I'm not sure that sizing the generator to drive the motor on the verge of overheating while supplying an additional 18A of 120VAC is a realistic requirement. I can't imagine that anyone would wire the genset starter motor to their traction or house banks instead of a dedicated starting battery, so starting the genset should be unaffected by ignorant use of the traction or house batteries.

On the proposed Valiant 40, I would bet that the genset would rarely be run underway and very rarely for traction energy. Steve, when was the last time you depleted your traction bank completely and then wanted to resort to generator power only to drive the boat? Did you find that you desired to operate the boat at full throttle for a long period right then? On my boat, the only time I've pushed the throttle to the stops is to measure the power consumption and potential speed. I've never done it while sailing. Everyone that has reported using their gensets to supplement their traction bank starts the process long before the primary bank gets below 50% depth of discharge.

If I was going to install a 15kW (20hp) diesel on this boat, I would skip the extra weight, cost and complexity of adding a parallel or serial electric drive and go straight to the prop with diesel power. I would use the weight and money that I saved to upgrade to 35 hp and a 100+A alternator and finish lighter and cheaper. There's a reason that 99% of the blue water cruisers go this route, it works and works well.

OK, I'll step down off my soapbox now. I hope that I haven't offended anyone.

Fair winds,
Eric
Marina del Rey, CA

--- In electricboats@yahoogroups.com, "Steve" <sstuller@...> wrote:
>
> Assuming you are planning on venturing onto the deep blue sea you have to design for the worst case scenario. It is the middle of the night and you have been motoring for far too long because the wind you were counting on never showed up. If you are lucky the batteries are strong enough to start your genset. The panels didn't do much because it has been cloudy for the last couple of days. There is no wind but there is a current pushing you towards the rocks or a bridge or other hard objects. Now the genset has to provide all the power to the 8.5 KW motor. That's the rated output (shaft). The input power would be easily 11 KW because of motor and drive losses. If you want to recharge your batteries at the same time you have to add another 2 KW to 3 KW. We are getting close to a 15 KW genset. This is a hard pill to swallow but you have to be honest with yourself. Thanks. Steve S.
>
> --- In electricboats@yahoogroups.com, "v40beth" <mrkgillis@> wrote:
> >
> > Eric and Steve-
> > Thank you so much for responding. I can make my own plumbing and sew my own sails, but this hybrid stuff is new to me. A number of people are pressuring me to get the Beta genset which is rated at 9.5 KW. Eric, my calculations were along what you did, And I was thinking that on batteries alone I could pretty well do everything I wanted to do, but the genset will be there for extended times on the hook and for those little things that tend to drive the volts down in the batteries. ( I will be using AGM's BTW) As I have read Nigel's study on this, I need a genset sized to the average draw, not the acute draw of a panic move on the motor, or 10 minutes on a stove etc. My battery set needs to be big enough, but if I have the genset just to top it off, or run through slack water (dead calm) in the ocean, why do I need a 500 lbs flesh eating monster? (the smaller genset is 210 lbs)
> > But you guys have been there and done that. I am only speaking theory. I have the bucks to do either, but I do not want to turn my boat into a large party boat where the fun never stops (ie entertainment via electricity)
> >
> >
>

__._,_.___
.

__,_._,___
Posted by at

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)