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Yanmar 4JH57 - Alternator AMPs & Temp

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Manyata View Drop Down
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    Posted: 07 July 2021 at 16:14
Hi All

Can anyone help me...

Any 458 owners out there - with the 57HP engine with the standard Alternator fitted - still with factory fitted batteries out there - with a battery monitor fitted ??

I would like to know - with the batteries discharged (ish) and the engine running - how many Amps the standard alternator is pushing in to the batteries ? Also, have any owners clocked the temperature of the alternator (with maybe a laser temp gun) when engine is in idle and pumping max Amps out ?

Thanks 

Tim
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H8jer View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote H8jer Quote  Post ReplyReply Direct Link To This Post Posted: 07 July 2021 at 21:30
Hey Tim

Not able to fullfill your specific requests, but I learned alot about alternators when going for lifepo4 batteries.
Maybe you could get a bearing by reading my saga about the changes that was needed...
Scroll through it quickly and you will find that the stock setup almost don't charge your batteries. The belt might be loose and it never charges in idle...


Edited by H8jer - 07 July 2021 at 21:33
Hanse 370#487 30HP 3-cabin
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S&J View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S&J Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2021 at 23:40
I just completed my first multi-day passage so have current experience of this.
I have the 57hp with standard 125A alternator and standard batteries plus one additional, so 3x160 rather than 2x160.

I also have a Victorian Smartshunt and currently nothing else (solar to be added asap).

Overnight our SOC dropped to about 75% with a typical load from lights, instruments, fridge and autopilot of 10A. Running the engine (1,200 revs with alternator current of 13.7A) at this point showed input current of about 50A on the Smartshunt monitor.  I'm assuming the total alternator output would be this 50A plus the normal system load of 10A.

I have a watt meter fitted to the fridge which shows it uses about 1A (12W) per hour.

I am very interested in understanding best way to manage the batteries and get the most out of charging sources available.
H458 #159 Primal Mediterranean cruising
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Manyata View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Manyata Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2021 at 06:26
Thanks S&J  - really appreciate you sharing your numbers. 

If your house loads are about 10a - and you were seeing 50a going in to the batteries at the shunt - yes your logic is good - the alternator would be generating about 60a. However, the big engine bay fan pulls about 10a - so your alternator is probably doing closer to 70a - if you are seeing 50a at the shunt. 

Be interesting to see if your fan is doing same as mine. If you look at the shunt with engine off... see what is being drawn from house loads, then turn power on to engine but do not start the actual engine, you will hear the fan running in the engine bay, then have a look at what is being drawn at the shunt.  I suspect your loads will increase by about 10a. Any chance you could do this test and let me know ? 

I was really surprised to see this on mine. Not just surprised by the large load of the fan. But also surprised to see the fan is wired to the house batteries - not the starter battery.

Last big ask... don’t suppose you have a cheap laser temperature sensor gun on board ? Would be really interested to know what temp the alternator gets to after she has been pumping 70a out for a while. 

Thanks again for your help S&J. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote S&J Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2021 at 12:45
As requested I ran the engine fans which appears to add 9.5A to the load.

I don't have anything to measure alternator temperature.
H458 #159 Primal Mediterranean cruising
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Manyata View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Manyata Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2021 at 13:20
Many thanks S&J - much appreciated.
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