48 volts = not kiss

[Lloyd]

This is a link to another ee forum http://forum.servomagazine.com/viewtopic.php?f=1&t=15191 This is def not kiss but it's wired.

If we are not supposed to point to other forum let me know and I will delete this topic. I couldn't find any rules against.

Enjoy...or not.

Lloyd

[mobile_bob]

i am trying to figure out why he needs 4 alternators to charge 4 twelve volt batteries that will be connected in series, when
the max charge rate is 20amps per alternator and battery???

looks like they have made that job vastly more complicated than it needs to be, in light of the fact a single alternator driven and controlled
to charge the whole string at 48volts nominal, (55-57.6volts) at 20amps max controlled by a single regulator would be so much easier
in so many different ways.

it is interesting though to see another group working on 48volt charging systems, as i suspect there are many out there.

when it comes down to it, any system that will effectively charge a 48 volt bank is better than no system.

bob g

[Lloyd]

Bob,

you're up late..

i was very keen on the help that the moderator was willing to extend to that guy. I haven't looked at the rest of the board, but I did find this little tid bit, which I haven't fully read yet http://www-personal.engin.umd.umich.edu/~fmeral/ELECTRONICS%20I/0300%20Linear%20Volt-Reg/0300%20Linear%20Volt-Reg.pdf

but I sure like to see crowd sourcing work.

just another channel to consume more time, but certainly may be of assistance to those whom like to glue semi conductors together.

Lloyd

[BruceM]

That was an amazingly tactful response, Bob.  Congratulations! 

[mobile_bob]

upon reflection, i can't imagine what the rationale is for that sort of system

the overall efficiency would certainly be in the single digits, and with the use of 4 non digital analog style
regulators, 4 drive pulley losses, 4 sets of copper and iron losses, 4 windage losses

i could calculate the overall efficiency and probably be very close, but it isn't worth the time in my opinion

i would be shocked if the overall efficiency exceeded 10-15%

now if they guy was trying to get 200amps per battery for a total of 200amps at 48volt nominal, then it would start to
make some sense in a rube goldberg sort of way.

he is looking for 240watts per alternator, give or take max?  and maybe as low as 50watts per alternator?
his field losses would be close to that, the analog regulator would dissipate an equal amount per unit

odd they are going that direction, perhaps there is another reason that would be apparent if i were to take the time to read
more of their forum? 

from what i have seen in that thread, i see no real need to do so.

bob g

[Lloyd]

What I found the most interesting was the help the guy was getting, with the semi-conductor design.

If the guy wants to run his 4 alts...that's his prog.

I do know a guy running a 24 volt sys using 2 isolated alts to charge each 12 v bank sep, then he runs all of his 12 v mid bank loads, simultaneous to the 24 v loads from the same bank. The guy is a dedicated offgrider and has had the sys in play for over 5 years on the same bat bank. He also has his pv charger running same as the alts.

When I asked why, he said it met his needs, he balances his 12v loads between the 2 12v banks, while still having the 24v for some of his needs.

Lloyd

[mobile_bob]

Lloyd:

i have no doubt it could be done, but
one should be very aware of the issues involved and be ready to address them effectively.

what i am warning about is someone with a 24 or 48volt bank, just attaching a 12volt load and not realizing
what the end results will be until he has a system that is not working like it should and he finds he has
one or more batteries very overcharged and others very undercharged resulting is a large loss of capacity that
will forever more render the string problematic.

most folks don't want to babysit a problem string for a few days much less over the whole life of the bank.

that was my only point in posting, on a related topic.

as for the 4 alternators, yes it is his choice to do so, and i would imagine he will get it to work to a fashion
acceptable for his use, maybe, but

i betcha a dollar to a dog turd he will become very frustrated with the setup, and i question those that would advise him
on such a path, and those that would help to develop a linear regulator to control each alternator.

he might as well go find 4 electromechanical regulators, at least they can be adjusted with a screwdriver and likely
are no less efficient than the designs they are working with.

my opinion of course 

ymmv

anyway, not to rain on anyones parade, i do appreciate the link, because there is always something to be learned
if for no other reason but to reinforce what not to do.

thanks for the link, later tonight when i can't sleep, i will go read up on their projects

bob g

[Lloyd]

Bob,

You get no argument from me.

The guy running the 4 alts didn't say if he was trying to make a useful gen/power source or just a test bed.

As far as mid string ties, I agree that, that is a sure way to dump a good bat bank.

My friend with the 12/24 sys is a qualified EE, so I know he's ok. He used to work for a big parts house. He went off grid in the Seattle city limits 10 years ago. Many of his sys were what was available on the market at that time...lots of things have changed since then.

It also helped that he was getting parts below, wholesale...lucky dude.

His was the first dc gen that I ever saw, and is what started me on my hunt for the holly grail. He's got an old westerbeke 4 cyl, spinning his machines. He is using it as co-gen, even back then. It has a water cooled exhaust(marine unit), dumping into a storage tank, and recycling. He built a reverse refrigeration cycle(spinning from the WB) to hot water to capture the btu's for water heating, and hydronic heating. The unit maintains the re-circ water after btu capture at about 80-90 degrees going back to the exhaust capture, his loop also captures the waste engine cooling. And it's ultra quiet...so no neighbor complaints, a city lot=very close neighbors.

I like looking at as many solutions that I can, so I can then pick those aps that fit my needs.

Lloyd

[rl71459]

Lloyd

I would love to hear more about how your friend made the 4 banger neighbor quiet!

Have you seen his system?

Rob

[Lloyd]

HiRob,

Yes I have seen and heard the unit run many times.

The wet exhaust dumps into an underground storage tank, it uses silicon rubber hi-temp marine exhaust between the the exhaust outlet, and the tank, which is then insulated with a ceramic blanket from Ballard insulation. The tank has a baffled vent to atmosphere that runs up the side of the house to above roof top, made from fiberglass. He also has a walker air sep on the intake side. He uses a parking lot oil trap/sump to filter the water into the tank. And the refrigeration heatx is mounted into the tank. The atmosphere vent is also insulated, and looks like a regular chimney chase running up the side of the house.

He worked at Heart, and then Zantrex, before he took the parts house job. He now runs his own business outfitting off shore cruisers for on-board power.

Lloyd


By the way here is a pic of the 4 alt setup that I found..it's for his camping lot.
http://www.delanobay.com/DcGenSet

[quinnf]

Wet exhaust is fine, but the idea of recirculating the exhaust water gives me the pip.  I'd be really interested to know what the pH of the water is in that tank.  I expect it's low.  Depending on what he's burning for fuel he could be OK, or he could be makin sulfuric acid.

Old Westerbeke?  4-107 by any chance?

Quinn

[Lloyd]

Quinn,

I don't know the answer to that Q, but the water only goes through a circ pump then back to the injection at the elbow, so none runs through the engine parts.

Next time I talk with him I'll ask, the system has been online for over 10 years now...so me thinks if it had inherent problems, they were either solved, or didn't exist. The tank is a roto-molded tank.

Lloyd

[Lloyd]

Quinn,

I don't know the answer to that Q, but the water only goes through a circ pump then back to the injection at the elbow, so none runs through the engine parts.

Next time I talk with him I'll ask, the system has been online for over 10 years now...so me thinks if it had inherent problems, they were either solved, or didn't exist. The tank is a roto-molded tank.

I believe it is a 4-107(perky badged as a WB) it use to be a AC genset. As for fuel he's running some concoction of heating oil, and vegi-oil that is drawn from separate tanks and mixed just prior to the pump. I don't know the recipe, bc I have never had an interest in vegi until recently...just to many problems to run in an old boat.

Lloyd

[quinnf]

That was a nice old-fashioned pushrod engine.  Perkins badged theirs as the 4-108.  40 hp/3000 rpm.  Pushrods.  Around 500 lbs with gear.  Wish I could remember important things like I can the unimportant ones.  

I was thinking the water-cooled exhaust manifold would be eaten through rather quickly, but if he's not recirculating water through the block he's probably OK.  After writing that I remembered that the raw water circuit dumped into the exhaust elbow; the exhaust manifold, block and head were fresh-water cooled.  Brain fart.  

I'd still be interested in knowing how acidic the exhaust water is.  I presume he has to add make-up water from time to time to replace water lost to evaporation, too.  So mebbe the calcium in the make-up water is reacting with the sulfuric acid created from the oxidation of sulfur in the fuel to make calcium sulfate (gypsum).  Wonder if there's a thick layer of clay-like sludge in the bottom of the tank.   Too many questions . . .

q.

[Lloyd]

Q.

Those old perkys are great and almost bulit proof engines, I'm running 2 64 vintage 6-354's in my boat.

The mani-cooler on that engine is made of alum/bronze, he is using the raw water side, separate of the exhaust. He has belt driven pumps, one for the raw, and one for the exhaust. Any old marine guy is hip to the silicon impellers, they last about ten years, about 6-1 to the stock impeller.

A building I mange has a new 2mil btu boiler, we just chaged from an old 1904 4 mil btu brickyard boiler, so if there is a ph issue, setting up a chemical pump much as is used in boiler feed tanks should be a very easy solution.

Lloyd