3KW Alternator?

[smokey73]

While passing a Hunter 40.5like mine today on Port Royal Sound near Parris Island I struck up a short conversation on Channel 68. He said he wasn't a part of this Forum so I thought I'd check here about opinions and for some info.

After a short chat he mentioned he had a 3KW alternator on his Yanmar and it would run his AC when he was underway. I'm intrigued by this and just wondered if any one was aware of these and how they work. Obviously seems like way overkill for charging but its so darn hot down here in the summer it would be nice to run the AC without having to fire up the Generator too. Of course the fuel burn rate would go up drastically but probably no worse than running both the engine and the generator at the same time.

So if anyone has one of these or some opinions (Maine - this is where you could really help) would be appreciated. Thanks in advance.

 

[kloudie1]

Sounded wonkey to me but it may not be.. The typical unit might take about 1200 - 1500 watts to run on 120V power.. so if your inverter is big enough to carry the start current for a second or so (around 3000 watts) then it would work with the alternator powering the inverter.. Would be pulling 3-5 horsepower from the propulsion engine.. Would require the system to be designed to do that with BIG wires from the alternator to the inverter, and a big belt drive to transmit the power.
Might be cheaper to use a mechanically driven compressor on the engine, like a car one, and hook it up in parallel with the electrically driven compressor

 

[JamesG161]

Would be pulling 3-5 horsepower from the propulsion engine..

And a BIG belt to drive the alternator. There is normally not a lot of load on and battery charging alternator.
Jim...

 

[Maine Sail]

A 3kW alt is about 250A at 12V and would require a ribbed/serpentine belt. Also it is pretty tough to fit a large frame alt on a typical Yanmar without serious modification. A small case alt in this size does not really exist and would heat up and need to be derated by about 35-40% anyway.

While it can be done, as in the installation below, this is not an inexpensive venture and is normally best served for charging LiFePO4 batteries as opposed to briefly running air con...

 

[JamesG161]

normally best served for charging LiFePO4 batteries

I learn a lot from the side bar discussions.
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery
This now explains the reason for why my new Lithium battery screwdriver manual said...
If you charge it more than 45 minutes, you void the battery warranty.
Jim...

PS: You gotta known which Lithium battery type you are charging.

 

[smokey73]

Thanks all for your perspective. I wasn't seriously considering this as a mod to do since I have a 5.5KW generator and can run the AC off of that easily. I can run it when underway if I need to try and cool things down before we anchor. I just thought it was interesting as I had never heard of a engine mounted 3kw alternator.

 

[JamesG161]

I have a 5.5KW generator

Mine is 9kW, and this weekend on hot humid nights, we start our AC one hour before anchoring, shower and cooking so at evening time , comfy. Plus I get my refrig and battery charge too.
Both engine and genset alternators charge the common starting battery, not house.
Jim...

 

[Maine Sail]

Both engine and genset alternators charge the common starting battery, not house.
Jim...

Why...? You're wasting the capability of both of those alts by feeding a 99% +/- SOC start battery which is typically less than a 1A load... You can be much more efficient by charging the house during bulk with them. An ACR will allow for this and, depending upon your bank, can serve shorten your bulk times....

 

[Gunni]

Surely Jim can feed his AC battery charger with that beast genset and top off the house.

 

[Maine Sail]

Surely Jim can feed his AC battery charger with that beast genset and top off the house.

Unless the I/C, very often an old Freedom 2000 on that model boat, can exceed the max bulk rate the batteries can take then the other two alts are not being used as efficiently as they could be. Even a 100A inverter/charger is only .16C of a 600Ah bank. If those batteries are AGM then .4C can easily be fed to them and that would be 240A and this is not even attainable adding both of those alts....

Even if they are golf cart batteries they can take from .25C to .3C (depends upon brand for .3C) and this is 150A - 180A. A simple ACR can speed up bulk charging quite a bit and make much better use of the alts..

Unless you plan to run the genset for 7+ hours you're not really topping off the bank. The declining acceptance rate and premature float of the I/C determines the time to 100% SOC. Generally only very long motor runs, dockside charging or solar will bring the bank to 100% SOC.......

 

[JamesG161]

Even a 100A inverter/charger is only .16C of a 600Ah bank.

You da man!

I do the working charge of 12 to 13.5 in about 1.5 hours if no other demand on my Freedom 2000 100Amp
That working capacity on a cruise is about 12-14 hours , no frig or inverting. My wet cells 4D are the brand @Maine Sail recommended (which were bought before I knew that). Rated at total of ≈380Ah. but ample for my boat and needs.

Surely Jim can feed his AC battery charger with that beast genset and top off the house.

I do have a set of Auto jumper cables, if genset doesn't work, but only in a pinch.

My Alternators are not connected in any way to my House batteries.
Jim...

 

[JamesG161]

An ACR will allow for this and, depending upon your bank, can serve shorten your bulk times....

Can you recommend one?
Jim...