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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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  #21  
Old 12-02-2012
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Re: .

Quote:
Originally Posted by floridajaxsailor View Post
rant on about 10 minutes not doing it but I have a very capable digital dual bank battery monitor and it works great- 10 minutes is more than enough
Clearly it is either improperly programmed, faulty, your batteries are heavily sulfated or you're just misreading it. Improper programming of Ah counting battery monitors is quite common and once the counting is off they get out of sync really, really quickly.

If you have reinvented Ohm's law, physics or invented a new technology no one knows about you really should take this to market or let us all in on the secret...

Quote:
Originally Posted by floridajaxsailor View Post
let me ask you this- if your car battery was dead would you leave your vehicle running in the driveway for 45 minutes??
Yes I know we're talking about different styles of batteries
-JD
I have killed my car battery more than I'd like. My daughter seems to want to hit the dome light and then I don't notice it. When the battery dies I charge it with battery charger over night because even 45 minutes won't fully recover the battery. If I am in a hurry I will jump it and run it for a while then when I get home I still throw it on the charger over night.
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  #22  
Old 12-02-2012
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Re: .

Quote:
Originally Posted by floridajaxsailor View Post
rant on about 10 minutes not doing it but I have a very capable digital dual bank battery monitor and it works great- 10 minutes is more than enough

let me ask you this- if your car battery was dead would you leave your vehicle running in the driveway for 45 minutes??
Yes I know we're talking about different styles of batteries
-JD
No ranting here, just easy math. Without you providing your variables such as battery type, amp hours of storage, starting state of charge, finishing state of charge and charging output of your charging device, there really isn't much to discuss. The majority of the folks, myself included, are using generalities and averages for examples. Maine Sail took more time than I did and provided a more complete answer based on his example. As you can see we both used the same math providing the same answers. Maybe you have unobtainum batteries and a 10,000 amp charger and 10 minutes is all you need.
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Old 12-03-2012
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Re: Charging batteries with engine while sailing

Keep your revs up when you are charging.
Don't charge at idle, initially at least.
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Old 12-04-2012
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Re: Charging batteries with engine while sailing

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Originally Posted by jrd22 View Post
tib- most marine engines are OK at normal heel angles of up to about 15 degrees IIRC.
One thing to consider is the fuel pickup location if you are running the engine while sailing, especially if you have two outboard tanks and only one pickup tube. I made the mistake of starting the engine while heeled over to starboard and sucked air out of the port pickup tube because the fuel had drained through the transfer hose to the starboard tank. I have separate pickup tubes and the tanks are not connected now:-))
Good point. I overheated my engine once (lucky no damage done, cooled it down when high temp alarm sounded) when the boat was sailing in high wind and heeled over. The sea water intake was on the high side of the boat hull and out of the water at times due to large waves.
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Old 12-05-2012
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Re: Charging batteries with engine while sailing

The charge off thealternator of a a boat at idle speed is about 40% of alternator capacity with most Balmars while my Electamaxx is closer to 70% capacity. This will not charge much of battry in 10 minutes

Secondly, Yanmars are not supposd to be left in the neutral poition when saling allowing the prop to spin. It can damage the tranmission. Not sure what engine he had by when sailing my engine lever is in reverse.
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Old 12-05-2012
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Re: Charging batteries with engine while sailing

Quote:
Originally Posted by chef2sail View Post
Secondly, Yanmars are not supposed to be left in the neutral position when sailing allowing the prop to spin. It can damage the transmission. Not sure what engine he had by when sailing my engine lever is in reverse.
Actually Yanmar states the transmission should be left in neutral when sailing.
See this Yanmar service bulletin:http://www.catamaransite.com/files/Y...al_Sailing.pdf
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Old 12-05-2012
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Re: Charging batteries with engine while sailing

Brian,

The Yanmar bulliten says that in neutral with the engine not running. The engine would be running to charge the batteries therefore, it should be in forwad.

Advisory Number: MSA08-003:

DATE February 8, 2008 Dealers and OEMs
TO: All Marine Distributors
SUBJECT: Gear in Neutral While Sailing All MODELS:

All Sailboat Engines

Quote:
We continue to get questions regarding the correct gear position while sailing with the engine OFF. This advisory is issued as a reminder; Yanmar requires that if sailing with the engine OFF (not running) the transmission shifter must be in the neutral position or internal damage to the gear or sail-drive will result. This damage will not be covered by Yanmar’s Limited Warranty. Please instruct customers and dealers who deliver the sailboat to the customer, of the correct (Neutral) position for the marine gear while sailing.

If the customer desires that the propeller shaft not spin while sailing, either a folding propeller, shaft break, or other suitable device may be used. However, Yanmar accepts no responsibility for the selection, installation, or operation of such devices. Please also refer to Marine service advisory “MSA07-001_Yanmar Sail Drive Propeller Selection” for additional information.

If you have any questions regarding this advisory please contact a Customer Support representative.
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Old 12-05-2012
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Re: Charging batteries with engine while sailing

I apoligize for my mistake...I think the Kanzaki transmissions are ok to run while in neutral when the engine is not running. Its the Hurth zr which is not.

I have always sailed with it in reverse because i dont like it spinning or the rumbling noise and worried about the tyranmission being properly lubed.. Apparently I should only sail with it in neutral.

Live and learn
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Last edited by chef2sail; 12-05-2012 at 04:06 AM.
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  #29  
Old 12-05-2012
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Re: .

Quote:
Originally Posted by Maine Sail View Post
Wow, this tread is a prime example of why people like me replace sooooo many batteries on boats.

10 minutes does squat for charging a house bank of batteries.... This is simple math & physics.. Ten minutes run time won't even burn off start up condensation in the motor. Here in the cold waters of Maine 10 minutes won't even bring most diesels up to operating temp.

Flooded batteries take 10+ hours to charge to full even with a large charge source because of battery acceptance rates as the bank hits absorption voltage.

A 400Ah bank at 50% state of charge needs roughly 240Ah's returned to it to be full due to charge inefficiency.

With a 100A alternator it will really put out about 80A so roughly 1.3Ah per minute at 80A. Easy math shows that 1.3Ah X 10 minutes is about 13.3Ah returned to the battery or just 5.5% of the energy need to charge this bank to full....

5.5% is a long way from a "decent charge", in 10 minutes....10 minutes of run with a 100A alt on a 400Ah bank barely gets you from 50% SOC to 53% SOC when charge inefficiencies are taken into account..

Also keep in mind that just because a "charger" has gone through bulk, absorption and is into float in 2.5 - 3 hours also means little other than the charger is poorly programmed for the bank you are charging. When a charger comes out of bulk quickly all it usually means is that your batteries are already toast and sulfated enough to build a surface charge.
,,,

When charging via alternator it is wishful thinking that you'll ever get anywhere close to full unless you spend 10+ hours running the motor like a trawler would.

This is why experienced cruisers use the "cruisers rule" and cycle the bank between 50% SOC and 80-85% SOC. Trying to charge much above 85% SOC is simply a waste of fuel due to declining battery acceptance...

..
To complete that good explanation one question: Assuming (like you did) a 100A alternator putting out about 80A with a 400Ah bank how much time would the engine have to be running to go from 50% to 80% and 85% charge on the Bank?

About one hour and a half for a 80% charge? And if so it is better to let it fall to 50% before charging an hour and a half or just let it go to 65% and charge it for 45 minutes? What is more efficient regarding charging and what is better for the battery life?

Regards

Paulo

Last edited by PCP; 12-05-2012 at 10:57 AM.
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Old 12-05-2012
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Re: Charging batteries with engine while sailing

Quote:
Originally Posted by hellosailor View Post
...
Then there's the idea of running the engine at low speed to charge the batteries. WRONG! Let's say the engine has an idle speed around 800 rpm and a cruising speed around 2600 rpm. If the alternator was properly matched up (pulley size & output curve) then the alternator will not be putting out signficant power at low rpms. At 1000 rpm it may be putting out 20-25 of the rated power, at 2000 spm it may be closer to 85% of the rated power. (Numbers drawn from a hat but good enough for examples.)

You need to know how the system has been designed, or have an ammeter in circuit to see what the alternator is putting out, because they are usually designed to put out something near rated power at something near typical cruising rpm, and all you are doing at lower rpm is wasting fuel.

Part of this is cheap and sloppy design (who notices?) and part of this is money, because an alternator that can put out full power at low rpms costs more. And an alternator that can put out full power at low rpms while also not burning out at sustained high rpms (i.e. trying to claw off a lee shore for eight hours) is more expensive again.
I had done that in my new set up and the performance of the new alternator and new setup was measured with different RPM. I have not here the list but I found out that probably the most efficient relation between charging and fuel consumption was between 1350 and 1500RPM and that about 2000/2150RPM the max charge was obtained. The cruising speed on my boat is 2400/2600RPM and the engine max RPM are 3600. Of course all systems are different but this can give a general idea. The alternator has 120A and is not a particularly good one but all the rest is maximized, I mean I have a good regulator and a bank charge distributor.

Regards

Paulo

Last edited by PCP; 12-05-2012 at 10:56 AM.
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