Re: AC to DC 65+ volts 60 amp Power Supply Plans?


"Ecnerwal" <LawrenceSMITH@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:LawrenceSMITH-4CA835.09331627092007@xxxxxxxxxxxxxxxxxxx
In article <13flfhioutaoba5@xxxxxxxxxxxxxxxxxx>,
"Ulysses" <eatmyspam@xxxxxxxxxxx/> wrote:

Ah, the upiquitous Ecnerwal ;-) Someone uses your "cats" signature on the
OB forum so I assumed it was you.


I'd be happy to buy a power supply if it's not
too expensive but so far all of my searches have not turned up anything.
Are there any web sites that have high current power supply plans? I
couldn't find any.

Hi Uly,

Knowing a fair bit about why you are trying to do it this way, several
things come to mind. The obvious-but-it-hurts-the-wallet method to get
an off the shelf charger is to drop bucks on another inverter (which
contains a nice high current switched-mode supply, filter capacitors,
charge control smarts so the MX60 can stay put on the solar panels and
not get involved), and set it up such that you are not using the
inverter section (where all that irritating pass-through-the-generator
stuff comes up when feeding the house power). Could be another Outback
(which would give you a spare to move around in case of any issues),
could be a less spendy brand.

I'm using Inverter #2 only to charge the batteries right now. Yes, it was
an expensive battery charger and not all that great (as far as charging
currnet goes) for the money. I just completed my gravity-fed water system
with float switch and I want my other inverter back so I can have my water
on automatic. With only one 3600 watt inverter (OB VFX 3648) no doubt some
bad stuff will happen if someone is using the vacuum cleaner or washing
machine when the well pump comes on. I don't have any solar panels yet
(other dreams of mine have come true) so in the meantime I'm looking for a
better way the charge the batteries. Of all the things I've thought of so
far using the MX60 seems to make the most sense as far as ease of use and
properly charging the batteries. It has all the smart stuff built into it.
OutBack says just get a bigger (12,000 watts or more) generator. Well, like
you said, running the house from a generator stinks unless I spend $4000 on
a 5000 watt inverter generator and I'd still have the "where the hell is all
the power going?" issue. Right now I'm charging my batteries with a $200
2000 watt generator via Inverter #2. That seems to be about as small as I
can get away with. I usually have to run it about 3-4 hours a day (evening)
to get the batteries up to 100%. Sometimes a little longer.

The good news is that since I switched to propane refrigeration and have my
well pump on it's own generator I could probably get by nicely with only six
175 watt panels. Hopefully I could even squeeze in the well pump as I only
run it about 15 minutes a day.



Another off-the-shelf option is to visit the local golf cart dealer, as
48V golf carts need 48V (really 60+V, same as your "48V" bank) chargers,
but I don't know that they pay much attention to efficiency when
designing those.

I found something like what you described but it didn't seem to have a float
or equalize setting. It's in my referece file if all else fails.


The best method for fuel to DC is fuel to DC, not fuel to 60 Hz AC to
DC. In reality, what's commonly available (other than esoteric and
overpriced "48V" DC gensets for the cell tower market) is fuel driven
welders, most of which are doing some form of 3 phase on the way to DC,
though there may be "true" direct DC versions (sounds like a lot of
brush wear issues, though). One with a decent OCV (in the 80 V range)
should work for you, though the main output power is typically intended
to be in the 24V range; but if you get one without too many new-fangled
smarts, it should be possible (perhaps with some taming of the MX60's
MPPT settings) to operate on the higher-voltage part of the curve. Might
take some fiddling with (or at least monitoring) the control
arrangement, I'd think.

Welders eh? I was looking at welders a while back and I don't even remember
why now. They seem to be fairly inexpensive compared to a lot of things, at
least the stuff Harbor Freight sells. I'll take a look.


Another approach is to grab a high-amperage car/truck alternator that
uses an off-board regulator, drive it with a fuel engine, and crank up
the voltage. These are also typically 3-phase AC, with a 6-diode bridge
rectifier. So long as the diodes are not overly low voltage, and you
keep the current within/well below the current rating, they are not
overly picky about what voltage they are putting out. The insulation
should be good for it, and the heat generated is a function of current.

I have a 12 volt 63 amp alternator that I was using to charge a 12 volt
battery bank. A couple of people on the homepower NG told me I could use it
for 48 volt charging if I replace the diode packs with heftier diodes and
heat sinks and somehow modify the voltage regulator. Well, I'm almost smart
enough to do it, but not quite. I tried putting a VR in series with the
field control and managed to get about 30 volts. My understanding is that I
have to remove the voltage regulator and bypass the circuit to get the full
output. Then I have to control the voltage one way or another. Controlling
the field would seem to be the way to go, but I'm not sure. If I could just
find the instructions somewhere I could do it. I've looked at some
permanent magnet alternators and that seems like it would work just fine.
The voltage could be controlled by engine speed and I could probably adjust
it at no load for equalizing too. The problem is that I've only found one
source and a couple of people told me "don't buy anything from them." I
have the booklet that I downloaded from the wind generator guy (can't think
of his name) and building a PMA and driving it directly from a small engine
is yet another option. It's not yet clear to me just what determines how
much current you will get--the voltage part is apparent.

In any case I'm not going to connect anything to my MX60 unless I'm pretty
darn sure it won't hurt it. Some kind of alternator seems like a good
option and could charge the batteries directly, with some futzing.


Perhaps a heavy-duty truck alternator that's already intended for 24V
operation would be a good starting point, but I recall people talking
about ramping 12V units up to 70 volts for various purposes with either
no trouble, or frying low-spec diodes and replacing them with
higher-voltage units when they die. In the case of feeding your MX60,
I'd replace them at the start. 100-200 amp units are rather common, and
should not cost much at the junkyard.

--
Cats, coffee, chocolate...vices to live by


.

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