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Old 16-07-2021, 08:49   #16
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Re: Running the engine to charge batteries - gear for load or no gear?

Where I sail everywhere I go you anchor. Winds can easily oick up to 25 knotts at night. I routinely put my enine in reverse to 1500 rpm after anchoring to simulate a high wind condition. I rather know it is dragging then than at 2 oclock in the morning. I dont remember the last time I have had to reanchor in the middle of the night.
zi do have 400ft chain with a delta anchor and good holding ground of sand and mud. I tried that on a charter boat in the BVIs and it did not worked as expected..
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Old 16-07-2021, 09:13   #17
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Re: Running the engine to charge batteries - gear for load or no gear?

This is an excellent question, one that has baffled me since I have had a boat with a diesel engine.
What is the best strategy to recharge the batteries at anchor (on a boat that does not have solar panels)?
I actually had the opportunity to ask the question to a certified Yanmar mechanic and to the mechanic who serves my engine.
Both agree that the diesel engines should not be run unloaded for long periods of time ("long" for them = more than a few minutes). They seem to feel strongly about it and had a "technical" explanation (and "good" stories to go with it) that seemed quite convincing to me.
Unfortunately, neither of them seemed to have a good solution to this practical issue, they just said: "run the engine engaged in forward while underway"...
Running in reverse at anchor (but I think it must be engaged, otherwise there is no significant load) may be a reasonable idea after all, but it is still unclear to me how: you would need some decent rpm (1000?), which would put a lot (too much?) of strain on the anchor... I guess you will be paying very close attention to your position as you do it, so if the anchor drags, you'll notice immediately (and use the engine to reset... :-) ).
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Old 16-07-2021, 09:13   #18
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Re: Running the engine to charge batteries - gear for load or no gear?

"In the Yanmar manual it does state to run the engine at wide open throttle for thirty minutes for ever ten or so hours of cruising"

Can you post a copy or give me a link?
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Old 16-07-2021, 09:18   #19
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Re: Running the engine to charge batteries - gear for load or no gear?

I don’t buy into that theory. . Look at the millions of semis idling all night in all the truck stops and rest area around the world. If it was that bad they would find another way to keep ac or heater on.
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Old 16-07-2021, 09:19   #20
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Re: Running the engine to charge batteries - gear for load or no gear?

I have chartered many times and was always advised at check out to run the engine at 1500 every day to charge the batteries. There was no discussion of load but somewhere I picked up the idea that if the engine is under load the oil circulates more efficiently than if idling. So on my boat, load it is.
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Old 16-07-2021, 09:27   #21
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Re: Running the engine to charge batteries - gear for load or no gear?

Honda suitcase genset. Yes, it uses gas, OMG. so do 99% of dinks.

To put finer point on the subject; use LiFP house batteries; they recharge faster. Also, a strong ac to dc charger. At least 40 Amps. But 80 is better.
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Old 16-07-2021, 09:31   #22
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Re: Running the engine to charge batteries - gear for load or no gear?

The 2GM20f in my Sabre was run at idle occasionally by well meaning friends when previous owners suffered health issues for a number of years. With less than 200 hours on the engine the mixing elbow clogged up and had to be replaced. Don't know what running regime was followed but probably start it in neutral and run at idle for short periods of time by the caretakers.

I always run those engines (3GM30f and 2GM20f) in gear, 1500-2000 rpm and allow to warm up completely before shutting down. Have not had any problems with mixing elbow or the engines despite some very long periods between running.

When we were cruising/living aboard years ago without solar, wind or shore power, ran the engine for several hours at 1,500-2,000 rpm in neutral 2-3 times a week to charge the battery for a couple years. The Volvo MD2b lasted for more than 20 years and two cruises to SoPac by us and subsequent owner. Engine finally died on 3rd trip to SoPac.
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Old 16-07-2021, 10:18   #23
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Re: Running the engine to charge batteries - gear for load or no gear?

It is fascinating that there is no clear answer on this. I would have imagined that if there were any potentially well known negative effects - the manufacturers or boat builders would provide a recommendation in order to prevent potential warranty related issues and repair costs.
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Old 16-07-2021, 10:38   #24
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Running the engine to charge batteries - gear for load or no gear?

There is an internet full of advice not to run diesels for long periods at low loads

“Sabb and Lister-Petter are in surprising agreement on the subject, as shown in their operator’s handbooks. In each case the wording is identical: “Long periods of light or no-load running early in the engine’s life may lead to cylinder bore glazing and high lub oil consumption.” Cummins, Perkins and MAN all have issued directives limiting the run time at idle to prevent bore glazing”

The problem is worst when the engine is new. The problem gets worse as the engine gets bigger as it runs cold and incomplete combustion cause bore glazing

The advice to apply a load is so the engine reaches and stays at its working temperature.

As I said the problem is much less prevalent in small diesels.


( big semis in the USA are increasingly fitted with an auxiliary engine to run over night loads )

Also road truck diesels tend to be run through a large Rev range during the working day. This “ workout “ tends to break up the glazing deposits so the effects of overnight idling are minimised

Yacht engines generally don’t run enough and tend to operated at a fixed throttle for relatively short periods.

Hence if at all possible have a load on your engine , alternatively intersperse any long period of idling with heavy use of the engine at various power settings including max normal power.
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Old 16-07-2021, 10:44   #25
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Re: Running the engine to charge batteries - gear for load or no gear?

Full time live-aboards in the Caribbean at anchor for 6 years. Ran our Lehman diesel in neutral 1 hr in the morning and 1 hr at night every day to charge batteries and run engine driven refrigeration. No problems.
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Old 16-07-2021, 10:59   #26
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Re: Running the engine to charge batteries - gear for load or no gear?

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Originally Posted by mvmojo View Post
Full time live-aboards in the Caribbean at anchor for 6 years. Ran our Lehman diesel in neutral 1 hr in the morning and 1 hr at night every day to charge batteries and run engine driven refrigeration. No problems.


How do you know you didn’t have problems ??
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Old 16-07-2021, 10:59   #27
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Re: Running the engine to charge batteries - gear for load or no gear?

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I don’t buy into that theory. . Look at the millions of semis idling all night in all the truck stops and rest area around the world. If it was that bad they would find another way to keep ac or heater on.
Semi trucks often are not idling, they may appear to be but they can be running other loads, so I have been told by drivers. Even this though is being minimized due to emission requirements.

I do (UOA) used oil analysis on my engines. Once upon a time, I used to have to drive through a place I called the Valley of Death. I named it this because I would sitting in traffic fro 15-20 minutes, or more depending on traffic and/or accidents. I would have a total drive time of about an hour, most of which was at 55 mph. Certainly not WOT but it would run the engine up to speed and keep it there.

UOA showed I had fuel in my engine oil. It as in the acceptable range but I never had it before having to drive into the Valley of Death. Thankfully, I was able to avoid driving into the Valley of Death, I no longer had lots of idling and the fuel in the oil went away.

I have a tractor with a 48 HP Yanmar engine. Most of the time it was not being run at WOT, which is required for some operations, but said operations are not for many hours. I would pick an RPM that was suitable for the work/load and off we would go. My UOA showed fuel in the engine oil. Again, it was acceptable but who wants fuel in the oil, so I increased the engine RPM a bit and the fuel issue went away.

This is odd, because the LOAD on the engine had not changed just the RPM. I went form 1500-1600 RPM to 1800-2000 which is not a big change but it was enough to remove fuel from the oil. Go Figure.

I see answers to the following questions all over the place and I certainly do not know the correct answer:
  1. What is proper engine loading?
  2. How many HP are needed per power unit, KW, AH, etc?
But I sure has heck would test my engine oil, but that is just me.

Later,
Dan
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Old 16-07-2021, 11:20   #28
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Re: Running the engine to charge batteries - gear for load or no gear?

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Originally Posted by GordMay View Post
FWIW: A 12V alternator will require [load your engine to] about 1 hp per 30 amps of output power.


746 watts per hp!! Does not compute. 14 V x 30 A = 420 watts.
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Old 16-07-2021, 11:23   #29
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Re: Running the engine to charge batteries - gear for load or no gear?

Quote:
Originally Posted by goboatingnow View Post
How do you know you didn’t have problems ??
Tough to prove a negative.... Not to be a smart ass, but I know we didn't have any problems because we didn't have any problems! The engine always started easy, ran great, no change in power noted, oil consumption didn't change over the 6 years, didn't smoke, oil analysis didn't show any concerns, etc., etc., etc. We're talking well over 4,000 hrs of running the engine at 1,200 rpm at anchor for 2 hrs per day for 6 years. After selling the boat, I spoke to the next owner several years later and he said he had never had any problems with the engine. So, while I can't prove that repeatedly running the engine with minimal load for charging didn't do any undue harm to it, there's no evidence that it did.
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Old 16-07-2021, 11:31   #30
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Re: Running the engine to charge batteries - gear for load or no gear?

The subject of alternator load is interesting as I monitor the amps into my batteries when engine is on an my 125 amp alternator is charging. It starts out with a max of around 70 amps and in about 10 minutes it is down around 30. at the 30 minute mark it is 10 amps. We have a Balmar controller for our alternator set up with the specs from our Battery manufacture engineering department. Seems to me that on many boats whether you have a large or small alternator the load is minimal after a short time. We repowered 8 years ago and have under 4000 hours on our engine after full time cruising from 50 degrees north to 2 degrees south. I figure at this rate of use including charging in reverse I will be due for a rebuild in another 12 years when I am 80. I am happy not to have a separate genset on board.
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