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Old 01-06-2021, 10:27 PM   #41
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Originally Posted by woolf View Post
Attached the spec sheet for the APS 55i we installed.

Thanks. I hadn't heard of APS before. It's a bit hard to tell, but they seem a bit like Balmar, packaging up stuff for specific applications. My guess is that like Balmar, they are more or less stock LN alternators. Their 42i sure looks a lot like mine... Nothing wrong with that, just not likely to yield any magic with respect to efficiency.


Interestingly, their "large frame" alternators are 50% efficient, your 55i is listed as 87%, and the 42i is 70%. That's quite a spread. I also expect the efficiency number in the data sheet is best case since it is otherwise unqualified.
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Old 01-07-2021, 03:42 AM   #42
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The APS 55i was installed on Volvo Ocean racers, where efficiency and low weight is paramount. That's how I found them, and they looked like a good fit for our application.
I bought them from Bruce Schwab at OceanPlanet Energy in Bath ME, who is doing some interesting electric installations, mainly on sailboats.
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Old 11-13-2022, 02:50 PM   #43
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Hi there - VERY interested in your setup as I would like to do the same - biggest downside I’ve heard regarding this sort of PTO High amperage DC Alternator output is belt slippage - I must confess I’m not great mechanically I just had the idea - what pulley / belt system did you use to avoid slippage? I am in Muskegon

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Old 11-13-2022, 04:07 PM   #44
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The missing information on most alternator brochures is the actual output in a 120 deg engine room at cruising rpm. 60% is pretty efficient for an alternator, and a 6 kw output alternator is generating 4 kw of heat or 14 KBtu. About the same as a diesel furnace in a package the size of a football. You can let it fry, or temperature limit it with an external regulator that derates on temperature, the inevitable result is you don't get 6 kw output.

Making things worse, if you are running a 1600 rpm cruise and a 2.5:1 belt ratio - just some typical numbers, the alternator cooling fan is running at about half speed.

APS says "at ambient conditions" which I assume might be standard atmospheric, 68 deg F. It will run about 50 deg hotter in a typical engine room, by the time you derate for that your output power will be significantly off.
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