Thread: VOODOO MAGIC?
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Old 02-28-2019, 07:03 AM
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I sold a system like that briefly back in the 1990s. We didn't have the magic permanent magnet alternator, so the actual unit was bigger and we were more like 5 KW or so and 120 volts AC, not 48 volts DC.
It was not really a success for the following reasons:
1. Getting 5 or 9 KW off the front end of a diesel with belts is not easy at all without either ruining the belts and/or ruining the bearings with side load.
2. Once you overcome #1, the end result of running a diesel all night at partial loads could be a carbonned-to-death engine.
3. There is no voodoo involved, if you want 1 KW out on the electrical end at least 1 KW has to go in on the mechanical end. 1 KW = 0.75 HP. The "magic" is probably the permanent magnet alternator, which is smaller and more efficient than the normal kind but much harder to regulate.

Nigel Calder is a smart guy, so I assume they have some good mounts for #1 and it may be modern electronic fuel injection diesels don't carbon up the way the older designs can.
On to the larger issue, 48 volt DC systems IMHO will one day be very common. The savings in copper alone on a large boat would be huge. This has been a common voltage in the telephone and IT industry for well over a century and cars are starting to use 48 volts now as well. Chargers, inverters, solar panels, and DC-DC converters (48>12) are all readily available. I am not too sure about 48 volt alternators, that may be a bit of a DIY operation besides for the one in these articles. If you DIY a voltage divider onto your 12 or 24 volt regulator you probably lose some low RPM charging ability.
* edit - I just remembered I know someone that bought a really big 24 volt alternator (300 amps??) that drives directly off the front of their diesel with no belts. No side loads at all. That is almost 9KW and 24 volt boat stuff is available right now vs. some future date. If you are thinking of doing this for air conditioning, be warned that sailboats are usually poorly set up for this. Besides for the carbon issue, running an engine all night introduces a lot of heat into the cabin. You need a pretty big boat with a well insulated engine room to not end up adding as much heat as you remove and then you end up over in the "Why does that farging icehole run his engine all night" thread

Last edited by joe_db; 02-28-2019 at 07:13 AM.
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