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Engine charging - under load

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mattplowman View Drop Down
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    Posted: 05 December 2020 at 22:29
Well my plan to install solar before the current season was foiled by work. This leaves me doing what we have done for the last few seasons which is running the engine for an hour or so a day to recharge the batteries. I know running it at idle is not good and ideally moving at least once a day to get a proper load on the engine is what we should do. 

My question is , if we run the engine at anchor and leave in neutral and give some decent revs, is that the same from a charging perspective as running the engine under load with gears engaged? 

Thanks
Matt 
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350Bob View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 350Bob Quote  Post ReplyReply Direct Link To This Post Posted: 06 December 2020 at 09:31
From a charging perspective, yes it is, the batteries are only interested in available voltage and current which are dependant on the speed that the alternator is turning (and of course itís ultimate capacity). From an engine perspective it is not, there are those that say running a marine diesel engine under no or a low load is bad for them, as the mixture is lean and hence the combustion temperatures are high, which reduces their life. On the other hand many people say that they have done it for years with no problem.

You make your own choice, personally I try not to do it.

Bob
H350 #205
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Ian Coverdale View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ian Coverdale Quote  Post ReplyReply Direct Link To This Post Posted: 06 December 2020 at 14:23
Hi Matt,

Recently upgraded our batteries to Lithium and in doing so, carried several checks/experiments on our Volvo D2 alternator performance. We have the standard Volvo fitted 115A Mitsubishi alternator.

From cold, the alternator delivers around 105A at 1,800 rpm quickly falling to 85A as the alternator temperature rise; typically to 95C. The alternator reduces output to prevent internal windings burning up. At 1,200 rpm, when alternator's internal fan is less effective, temperature exceeds 105C and output reduces even more. Suggest when your alternator is working hard such as charging a low battery, you don't run the engine at low rpm. Think this is widely known but my tests concur.

Charging at 85A/14.4V is ~1.2kW and with something around 50% alternator efficiency, your alternator is taking 2.4kW from the engine. Our D2 engine is rated at 41kW (55hp) so 2.4kW means running engine purely to charge the battery is using only 6% engine capacity which I suggest is very low and very bad!

The other thing to consider is how quickly you're burning through your engine's life. Hypothetically, if you run the engine for an hour a day on average, just to charge batteries and typical small diesel engine life is say 3,000 before major work/replacement then in a year of you've used 1/10 of the engine life just charging batteries. 

We all do it. I do it! Suggest just beening mindful of the tole it takes and avoid if possible.
My thoughts; hope that helps.

Ian & Andrea
SV Gabrielle (H445)
Portishead, SW England.
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Captain Cook View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Captain Cook Quote  Post ReplyReply Direct Link To This Post Posted: 06 December 2020 at 21:59
Hi Matt
If you look at the top left of this page, you will find "Member Control Panel", which is the place where you can inform other myhansers about which boat you own (well, in some cases, the boat is mostly owned by the bank). Just look at the information from the nice people who answered you.

If you know the mark and model of your alternator, you may find a graph like this on the internet:
Most alternators have the same type of graph as this, but try to find your own.
Try to read the sales talk in the following link from Sterling. (Alternator to battery charger). I may buy one some day.
https://sterling-power.com/products/alternator-to-battery-chargers-up-to-130a

:Kjeld







Edited by Captain Cook - 06 December 2020 at 22:11
Freya Hanse400 #27 from 2006, 40HP Yanmar 3JH4E, Teak deck, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)
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Martin&Rene View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martin&Rene Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2020 at 16:22
Nigel Calder wrote an article in the Yachting Monthly magazine on battery charging at anchor and reckoned that the energy conversion efficiency from diesel to electricity was some where between 2 and 5%. Not good.

I did install a Sterling Regulator unit on my 341 in 2014.  Though in theory the installation is fairly easy, I did have a few issues mainly caused by the fact that the wiring diagrams and alternator information that I had were either or poor or actually incorrect.  On the basis that "forewarned is forearmed" I did a write up to help others and so you should find it on this link.  



Giving very detailed instructions sometimes makes a job look harder than it actually is.

Looking at the notes (I think I understood them) I know that I did make the change described in Sect 5.6 so that the ignition feed is from the run position on the key and that did solve the starting problems.  Having a good crimping tool would have made the job much easier.

Since then I have not had a low voltage problem, though I have also made changes to the fridge installation, cooling of the fridge compressor and replaced the batteries so the Sterling regulator cannot take all the credit.
Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout & shallow keel, normally based in Scotland
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mattplowman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mattplowman Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2020 at 18:36
Thank you all for your replyís , very helpful. We do one long trip of 2-3 weeks over the NZ summer and regular 2-3 day trips. The main draw is the 12v fridge , we have never had an energy issue but I am going solar as hate using the engine to charge if at anchor for the reasons above but also just kills the vibe! We generally move at least once every 2 days on the big trip so has never been an issue. In saying that , when I get time I am going solar.

We have 330ah house and seperate start and so far we have not had an issue but as the batteries get older (currently 5 years ) expect to see some performance impact.

Thanks again
Matt 
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StavrosNZ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StavrosNZ Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2020 at 20:10
Matt, turn your fridge off at night while you are asleep, it will remain cold enough until morning if not opened and you can switch it back on during the day.

Best bang for buck is not solar or other but to upgrade your alternator to high output one by Balmar or electromaxx with serpentine belts and a quality regulator. If you calculate how much solar you need to replace a days consumption its about 4m2, not a great solution.

On my 400 i run a 140 amp electromaxx set-up and have 400 A/H house bank and replace a days usage in approx 20 min motoring. Like most of us island hoping around the Gulf its by far the best solution.


Edited by StavrosNZ - 21 December 2020 at 00:35
Stephen
2010 H400 #691, Auckland, New Zealand
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mattplowman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mattplowman Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2020 at 21:19
Thanks Stephen much appreciated. Who did you get to install the beefed up alternator?
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mattplowman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mattplowman Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2020 at 21:23
Hi Stephen I have found your install post. Tks Matt
H355 , #47
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StavrosNZ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StavrosNZ Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2020 at 21:55
No worries Matt, i did the install myself, its not difficult, feel free to reach out by PM if you need a hand.
Stephen
2010 H400 #691, Auckland, New Zealand
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