Hi Matthew,
"48v DC is also 'Telco Voltage' and there will be a lot of kit around for it." That what you would think. When I did my research, I found very little that was small, light, or cheap and nothing that was all three. Most Telco equipment is based on 120VAC to 48VDC and the best DC generators that I found are the Polar Power equipment that I already mentioned.
Like you, I use an air-cooled portable 120VAC Yamaha 2kW generator (yours is red, mine is blue). I can drive my Elcon charger from the generator, and like you, I have never had to use it "in anger". As such, my DC output to my batteries is limited to about 1500W. Balancing a larger generator to to a larger charger gets complicated and the system cost, weight and volume starts to get out of control.
I found some information published by Polar Power concering cost of AC and DC generators. See pages 17 and 18 in the following link. My Yamaha generator fits everything that Polar says about AC units.
Why are AC generators lower in cost than DC generators?
• AC generators less than 10 kW are aimed at either construction work or standby use. And these applications require low cost and do not need long operational life.
• AC generators are not designed for the demands of the Telecommunication sites, especially in rural locations.
• AC generators from the major manufacturers are not bundled with hardware and software for automatic and remote control operation.
• AC generators have no magnets, they are not as efficient.
Why do Polar's DC generator have a higher cost the AC generators?
• Polar generators are designed for long operational life and very low maintenance.
• Rare Earth Magnets for high efficiency and low fuel consumption.
• Fully automatic start / stop operation with remote control.
• Polar DC Generators combine the functions of a generator and battery charger. There is the software and hardware to function as a high performance battery charger.
• Military grade electronics with extensive use of circular C type and other sealed connectors.
• Polar generators are designed specifically for meeting all the the needs of telecommunications.
http://www.hybrid.ie/docs/Polar_Power_Telco_2.pdf
I know that many people here are trying to do their conversions as cost effectively (cheap) as possible (aren't we all?). So I'm going to put this back out as a challenge. After anyone has built and operated an effective HV DC generator, please post your description and costs. So far, Propulsion Marine seems to be leading the way with a stand alone unit that costs about half of what the bigger companies are selling, though I do not believe that the PM unit has auto start/stop capabilities. It does seem to meet the rest of the Polar Power's DC benefits. That said, it's way more than what my boat currently needs, so I don't see one in my boat's future.
Considering the start/stop stuff, my battery bank is large enough to operate the boat normally for hours in silent mode. Even with a somewhat larger boat with a use case that might need daily charging, as a sailing auxilary, my generator need would be limited enough to be able to start and stop the generator manually, the charging controller would protect the batteries.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Matthew Geier <matthew@...> wrote:
>
> On 10/04/12 07:04, Eric wrote:
> >
> > Unfortunately, regardless of random member's analysis of why these units should be cheaper, I'm going to guess that any reliable marine DC generator in the 48V-144V range will be more expensive than an AC generator, primarily due to the limited demand and low production numbers. So I would expect that a Panda, Onan or Kohler AC genset of an equivalent kW output will be cheaper than what you'll find in DC or even what you'll be able to cobble together yourself.
> >
> > That's just my opinion, but I'm aiming to set realistic expectations. And think of how awesome it would be for all of us if you can prove me wrong...
> >
>
> 48v DC is also 'Telco Voltage' and there will be a lot of kit around
> for it. But Telco's expect and are prepared to pay for, very high
> availablity - these gen sets are back up power that just 'has to work'.
> So between 'it just has to work' level of engineering AND the 'it's for
> a telco mark up', such kit is expensive. It will be absolutely bullet
> proof, but expensive.
>
> A DIY really should be cheaper - as you are targeting and entirely
> lower level of engineering rigour.
>
> Now you could argue that a marine system should be even tougher than a
> Telco spec one - as lives might depend on that system reliably starting
> and kicking in, but that's a whole other argument :-)
>
> Now I use a Honda eu20 as backup on my boat - which by any marine
> engineering standard is unsuitable for the job - between fumes and fuel
> spill potential, but it works for me. (I've never had to use it 'in
> anger' fortunately.) I'm aware of the risks and act accordingly. (Like
> NOT starting it in the enclosed areas of the boat for starters)
>
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