DC refer questions

[Ron Hill]

Tony : You are absolutely "Right ON"!!!

As I point out to people that ask about my Honda - I simply say, "Why run that $9000+ thing down below, when I can run this $900 thing up here and get the same recharge". 
They have yet to respond!! 

A thought   

[noworries]

I can think of a few responses...
Carbon Monoxide poisoning if you're not careful
Now you have highly flammable gas onboard
Weight & space to stow it

But you're probably already carrying gas for your dinghy so no big deal there.  I'm still trying to figure out an overprop issue and my boat cruises at 1500-2000 rpm so motoring somewhere isn't that much different than idling in a harbor.

I'll report back on how it lasts.

My catalina doesn't appear to have ever been rigged for a foot pump.  I wish it was though!

[2ndwish]

At great risk of turning this thread into another "head" discussion...

Stu- I should have been more clear- the 1 hour/day rule was for running a typical refrigerator, by far the largest load on most '80s era boats (when I learned the rule 'o thumb). I also agree though, calculating the loads is wise.

Ron-We do not have a battery monitoring system on 2ndWish so I will try your rule of thumb next time out- extremely useful.


Ok now into more controversial territory- First I scoured the M25XPB manual and found nothing about this. They merely provide the idle ranges and cruising RPMs. I contacted Westerbeke to ask about this question and was referred to their west coast distributor. The answer was pretty clear. They consider it unreasonable to expect that boat owners will not charge their batteries using the alternator at anchor. They instruct their customers to not do so at idle, but rather at 1500-1800 RPM. They do not consider carbon buildup from this process to be an issue. It would be if you did it all day.

I suspect that this is all a matter of degree. If you cruise 10-15 days per year, using the engine to charge the batteries probably has a small effect on engine lifetime (our 24 year old engine has less than 1500 hours with 100 hours of use the last year, <10 of those hours charging the battery). With frequent cruising and multiple days at anchor, a generator seems like a worthwhile investment. At 3-4 three day cruises with an occasional 5-10 day cruise, does it really warrant the purchase, maintenance and storage of a generator? As Stu says- Your boat, your choice.

 

[Ron Hill]

2nd : First of all if you have the original engine you have a M25XP not an M25XPB.
 
I hate to inform you that the problem/s that you will be facing will not be from the less than 1500 hours of engine running, but the 24 years of age !

I've written in the Mainsheet tech note and on this form MANY times that any "extended idling" should be done at 1500rpm or slightly over.  Just so you don't load up the engine with carbon and you give the engine some rpm speed to overcome the side load from the alternator. Also a lower rpm tends to shake you teeth and aggravate your 1st Mate - if done for more than 5-10 minutes.

As you mentioned Stu's saying and I completely agree.  You ask for advice and we give you our best! 

[2ndwish]

Ron- I completely agree on all fronts. Thanks
T

[Stu Jackson]

With no battery monitor you'll still need to get an idea of your house bank status.  To do that the battery bank need to be in a steady state - no charge or discharge for about 30 minutes. 

That actually should be 24 HOURS.  See "Electrical 101" and the Ample Power Primer.

[Ron Hill]

Guys : Stu is absolutely correct if you want the most accurate state of charge reading !!

I mention 30 minutes so you all understand that you just can't just turn off everything and then check the voltage  - and get anything even close to an accurate reading !!  
I also didn't believe that anyone out cruising would turn off every item (while they are living on the boat) for 24 hours just to get a battery reading!!

A thought

[Kyle Ewing]

Regarding running the engine at idle to charge batteries, during the recent Mac race I ran the engine at 1800-2000 rpms twice a day while sailing.  This seems to be the sweet spot between alternator output and noise.  I kept a log of how much energy I was using and putting back into the batteries. 

I have a BlueCircle 100 amp alternator with Balmar ARS-4 regulator using PRG-2 (Deep Cycle Flooded Lead Acid) charging four Sam's Club golf cart batteries (in their second season).  The start battery is charged from an EchoCharge.  Data is from the Linklite battery monitor.

Running the engine for 2 hours per day, I returned about 60 Ah/day while averaging usage of 115 Ah/day.  This included use of fridge, cabin lights, instruments, radio (vhf and stereo), auto-pilot, nav lights, etc and is a higher load than at anchor.

This is a good example of the law of diminishing returns when charging from the boat's alternator.  At the end of the race I was down to 60% of capacity. 

When charging I noted the alternator would start putting out 60-70 amps of current for a small amount of time and tail off to closer to 10 amps at the end of the hour.  Based on this I could get 30 Ah in the first hour and 40 Ah or less after 2 hours.

BTW, I also had hot water after charging the batteries.


Date   Start   End   Ah used   Run Time   Ah returned   Ah remaining
15-Jul   0:00   14:00   0   0   0   420
16-Jul   20:21   21:26   98.7   1.1   30.2   354.1
17-Jul   8:55   10:02   66.0   1.1   30.3   322.1
17-Jul   19:17   20:30   44.8   1.2   30.4   310.8
18-Jul   10:50   12:00   62.0   1.2   36.0   294.4
18-Jul   18:30   19:37   32.0   1.1   27.8   294.0
19-Jul   9:19   10:18   77.0   1.0   39.7   254.9