Thoughts on 230v DC dynamo

[stokelister]

I've been doing a lot of reading and thinking since I joined and would appreciate some opinions. I have an original startomatic 5/1 engine dating from 1935 direct coupled to a 230V DC dynamo, complete with original switchboard (unlike any other switchboard I've seen by the way). I've had the engine for 12 months or so, I bought it in almost fully restored condition - everything runs like a dream except  for the startomatic side of things isn't working - yet. My initial thought was to replace the dynamo with a modern AC alternator to give me a useable source of AC power but I felt it wasn't so nice to separate the engine and dynamo after 80 plus years. I'm slowly building an off grid system comprising of solar, wind and hopefully the lister but my stumbling block has been the 230v DC as opposed to AC. My solution at the moment is a product by a company called Victron called a Centaur charger, this will accept a DC input between 90 and 400 volts and output 12 volts at up to 50 amps. This will hopefully let me charge up my battery bank on days with little or no solar/wind power coming in and carry on powering all my normal appliances via an inverter. Has anybody been in a similar situation with a DC dynamo vs an AC alternator and found an easier way to use the power? I'm quite happy building a solar / wind system but know next to nothing about incorporating the lister into the equation. Have I missed something vital or does this sound like a workable solution. Thanks for your ideas guys.

[dieselgman]

Can the Centaur be configured for 24vdc or 48vdc? These voltages would provide a much more robust battery/inverter based system. Other than that detail I can readily mention, there is vast experience here and on the micro-cogen site for such systems and practical knowledge of what seems to work out best.

dieselgman

[BruceM]

I've been off grid for 7+ years now.  I have my own custom system with a 120vdc battery bank which has an individual battery balancing system typical of EV systems.  I have a linear charger which can handle 12A at 148v or 1776 watts.  My operation mode is to fill up the batteries every day, and on very dark days in the winter that typically means about 1.5 hrs of charging, with PV handling the last 10%.  It lets me get 4.5 years of service out of cheap marine batteries.

My thought about your proposed system is that 12V for a battery bank is something no one today would recommend for a new system except for a minimalist cabin type system.  The very high currents needed for a 12V system cause a great deal of inefficiency.  50 amps of "12 volt" being charged at say 14.6 V would be only 730 watts. OK for a minimalist system but otherwise a bit anemic, and not much of a load for the generator.

 If you're still at the planning stage I would seriously think about a 48V system unless your power needs are quite small.  In the future, 48v will likely be the 'lowest voltage you'll see for typical inverter battery banks.

That said, I do also have a small 12VDC only system, which I find very handy and use for DC circ pumps, motorized ball valves, electronic controls, etc.  I use a single 12V AGM battery, 110AH for that system on a 120 watt PV panel fixed for optimum winter performance and get 7+ years service.  I use a linear, temperature compensated regulator of my own design for that system as well.  



 

[LowGear]

Have you considered an inverter.  That's pretty close to a Sunnyboy grid tie unit.

Casey

[carlb23]

Have you considered an inverter.  That's pretty close to a Sunnyboy grid tie unit.

Casey

He is off grid so the sunny boy won't work

[stokelister]

Thanks for the info already guys. Just a few more details to paint a clearer picture - currently on grid but slowly building and experimenting with what will be a totally off grid system eventually. I'm in the UK and everything I'm working on here is a prototype for what will ultimately be disassembled and shipped to a hobby farm I own in Slovakia, the aim is to be off grid and provide several separate self-contained holiday lets which will also be independently off grid. Each holiday unit will have it's own solar powered system and the lister will be there to augment the fairly minimal power needs of the farmhouse itself. Water heating and cooking is wood fired in winter and solar-thermal/wood in the summer. The current on-grid electric supply is not that reliable and has already taught us to be very frugal with power usage. I definitely agree BruceM that I've aimed too low with a 12v system, the centaur charger was too good a price to miss but that's not to say it won't be replaced in the near future. Unfortunately it's set at 12v and can't be altered. The one good thing is it provides 3 separate outputs that are all capable of charging at 50A each if I were to have some sort of central charging system for multiple battery banks.

[carlb23]

Sorry low gear i was looking at Bruce's post lol.

[LowGear]

Whewwwwwwwwwwww,

I thought I was out of step with carb23.  I guess there may be a first time but thankfully just not now.  carb23's solar hybrid system in New Jersey (somewhere up there in the North East US) is nothing short of enviable.

The SMA suggestion was made with an understanding that this is an off-grid installation.  Sunnyboy will work off grid with the support of a Sunny Island but they are not cheap.  My question has been how much of a sine way does a Sunnyboy need to sync up with?  There are many inverters that have different "grid" requirements and some will establish their own grid (I think). 

Is this where I post my rant against the stupid new anti solar program enacted by the Public Utilities Commission in the State of Hawaii?  At ease team-solar, I remember my oath to stay on topic.  It just seems a shame to mess around with machinery that is well made and has some standing in the classical world of generators.

Casey

[buickanddeere]

Since the input of a VFD is rectified to DC . What would happen if the 230 DC was applied to the VFD and AC uses from the output terminals ?

[starfire]

Buy an  inverter type stick welder, these are called caddy welders over  here. These will happily run off 240 volts DC and convert down to 50 odd volts DC at up to nearly 200 amps.
They can be wound down to whatever current your batteries are happy with, the minimum generally around 40. The welding current output is simply connected directly to the batteries, watching the polarity of course. This is a very cost effective way to obtain a high current battery charger. The only thing is to watch the duty cycle at high current, although most are very well protected against temperature excursions. The digital current display is fairly accurate too, These welders effectively dont much care what the battery bank voltage is, 12 to 48 volt banks will act the same, the welder is designed as a constant current output even though the voltage can vary considerably, as is does when used as a welder.... changing arc length etc.