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Source for 48 volt Alternator?

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Posted by Ulysses on June 6, 2007, 4:10 pm
 


Hi.

Being very unhappy with using the built-in chargers in my new Outback
inverters I'm considering using a small engine to run a 48 volt alternator
for charging my battery bank but I can't seem to find any.  Are these
standard equipment on some kind of industrial machines such as fork lifts or
tractors or whatever?  Anyone have any links?  I'm thinking 40-50 amps would
probably be about right.

I'm also considering various chargers that could be ran from a generator.
It turns out that if a 2:1 step-down transformer was used 1/2 of 115 volts
just happens to be almost exactly the right voltage for bulk charging a 48
volt bank.  After rectifying this will probably change but I'm thinking it
might be possible to adjust the voltage by simply changing the engine speed
a little.  Equalization might also be possible.

I looked at 48 volt battery chargers and Iota with the IQ4 seems to be the
best choice (that's affordable anyway) but their 48 volt charger is only 15
amps unless you get two 24 volt chargers and connect them in series and then
it starts getting pricy again.  Building a power supply to feed into the
MX60 charge controller does not seem to be an option but if it could be done
then the 3-stage charging and equalization would all be figured out already.

I turned my first Honda eu2000 into a belt-drive generator head but I can't
seem to find the DC output going to the inverter.  I don't know the voltage
that it uses but I figured it was worth a look on the off-chance it might be
in the right range.

Thanks.




Posted by Neon John on June 6, 2007, 8:23 pm
 




I'm not aware of an off-the-shelf alternator but any car or preferably heavy duty
truck alternator will go to 48 volts with at most, a change in diode pack to a
higher
voltage one and the proper regulator.  On my current version of my Cordless
Battery
Charger (TM)
http://www.neon-john.com/Generator/CBC/CBC_home.htm  (these are of an early
prototype
but you get the idea), voltage of 12,24,48 or 72 are available at the turn of a
rotary switch.


If your generator has an externally excited field with slip rings then you'd
want to
change the field voltage instead of engine speed.  Ripple from rectified 60 hz is
considered harmful for batteries and the lower frequency, higher amplitude ripple
from a slowed generator would be worse.


You might also take a look at Progressive Dynamics.  I know they offer a 48 volt
version of their Intellipower that is quite reasonably priced.


I didn't quite follow that.  Did you remove the engine from the generator head
and
belt drive it or use the engine to belt drive another generator.

An EU with bad electronics is still valuable.  Toss the inverter electronics and
rewind the 3 phase PM alternator to produce the voltage that you want and the
RPM you
want to run at.  Optionally, add a controller to the throttle to throttle down
the
engine to reduce the output voltage for float charge.

Rewinding the star-shaped stator is trivially easy and can be done sitting in
your
easy chair in just a few hours.  I've done one of these for a friend and the
results
were spectacular.  From an EU1000 came 14 volts at 60 amps at full throttle, all
in a
nice hand-held package.

John
---
John De Armond
See my website for my current email address
http://www.neon-john.com
Cleveland, Occupied TN
If we aren't supposed to eat animals, why are they made with meat?


Posted by Ulysses on June 7, 2007, 12:44 am
 


wrote:

alternator

heavy duty

to a higher

Is that something I should be able to get from an auto parts store?  Every
time I go in one asking for something that's not for a specific vehicle I
get blank stares...

 On my current version of my Cordless Battery

prototype

If it's the same one you had posted a couple of years ago I didn't realize
that it was switchable for different voltages.  I seem to remember you had a
3-stage charge in it.  I'll take another look now....



you'd want to

60 hz is

It's a brushless generator head so does that still apply?



already.

48 volt

OK, thanks.



voltage

head and

The engine was wore out and to repair it would cost about $00 in parts so I
removed the piston, cam, belt, governor gear etc, greased the crankshaft
bearings, and attached a pulley to the flywheel.  I'm running it with a
Honda GC135 with a belt (of course).  The spacing on the carburator holes is
different on the two engines so I don't have Eco-Throttle--yet.  If I'm
running a steady load such as a pump I just turn down the throttle til it
sounds about right and turn it up almost all the way to run power tools etc.
So far it works great but makes a funny, cyclic sound every few seconds.  It
makes the same sound with oil in the ex-engine.


electronics and

the RPM you

down the

Do you happen to know which wires are the output?  I could not managed to
get a DC reading from any combination I tried.


in your

the results

throttle, all in a

I've read many instances of people rewinding alternators and making wind
generator alternators and such from scratch and it bothers me that I don't
know how to do it.  Is there some sort of Idiots Guide to rewinding
alternators?



Posted by Neon John on June 7, 2007, 7:46 am
 



You must be going to AutoZombie :-)  You need to find a locally owned store
where, if
the guy doesn't know, will at least invite you to thumb through the catalog.  The
NAPA store is like that in Cleveland.

I don't know if the diode pack is available or not. MY approach is to order three
case-to-cathode and 3 case-to-anode diodes from Digikey or whatever, along with
some
heat sink, split the heat sink into a positive side and a negative side, mount
the
diodes, hook 'em up to the alternator stator and mount the heat sinks where
they'll
get plenty of air.

On the voltage regulator side, you simply use a standard 12 volt regulator - I
like
the Delco internal regulators from the 70s-80s era.  My reference vehicle is my
old
79 El Camino because I know the alternator had the kind of regulator I want.

I can't seem to easily locate a photo of this regulator by googling so words will
have to do.  It has a couple of screw-down internal connections and a couple of
spade
lug connectors for external wiring.

One of the screw-down terminals is ground and the other goes to one brush.  The
other
brush gets 12 volts.  The regulator controls field current by sinking current to
ground through that brush.

For the outside terminals, there is an "I" terminal or ignition.  This terminal
powers up the regulator.  There is an "S" or "sense" terminal that senses the
system
voltage.  The regulator excites the field to whatever degree necessary to keep
this
sense terminal at 13.8 volts, plus or minus.  There may be another terminal on
some
regulators, the "L" terminal that goes to the charge light.

Those Delco boys were clever.  If there's no connection to the S terminal then
the
regulator will sense the I terminal.  It can also get both its operating voltage
and
sensing from the L terminal, though the regulation is poor because of the idiot
light
in the circuit.

All we have to do to achieve a different voltage is build a simple 2 resistor
voltage
divider.  The two resistors are connected in series.  One end is grounded and the
other goes to the high voltage to be regulated.  The Sense lead goes to the
junction
of the two.  The resistance values are arranged so that when the high voltage
(say,
48 volts) is at the correct voltage, the voltage the Sense lead sees is 13.8.
Viola!
Instant 48 volt regulator.

I mount the regulator external to the alternator to get it out of all that heat.
 It
goes to a small piece of aluminum heatsink.  Only minimal heat sinking is
necessary,
as the regulator doesn't get hot at all.

I set the divider up so that one resistor is fixed and the other leg is a combo
of a
fixed and a variable resistor (pot).   That way I can trim the voltage to what I
want.

Given that GM replacement internal regulators seldom cost more than $0, this is
a
dirt-cheap method of regulation.  Just make sure you get the standard replacement
regulator for say, a 1979 El Camino and not a one-wire or other fancied-up
version.

I haven't updated my site in a LONG time in that area.  My current version uses a
custom digital controller based on a BASIC stamp.  There's a rotary knob that
selects
the desired voltage using a multi-resistor voltage divider just like I described
above.  I took it all the way to 72 volts so I could charge my old CitiCar
(electric
car) batteries.

John

John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Cleveland, Occupied TN
Save the whales, collect the whole set!


Posted by Ulysses on June 16, 2007, 1:42 am
 


wrote:

store where, if

catalog.  The

order three

with some

mount the

where they'll

regulator - I like

is my old

words will

couple of spade

I just took my alternator apart.  I pretty sure it's a Delco (7127?).  The
regulator is as you described except the brushes appear to be an integral
part of the regulator assembly so I don't see how, on this particular unit,
how it could be relocated outside of the case.


The other

current to

terminal

the system

keep this

terminal on some

Mine are marked "F" and "R."  At one time I knew what that meant because I
was using this alternator to charge 12 volt batteries.  In any case it looks
an awful lot like the alternator in my '78 F350 but I'm not certain it's the
same.  Probably very similar to the one in your '79 El Camino.  Anyway,
which one would be "I" and which would be "S?"


then the

voltage and

idiot light

resistor voltage

and the

the junction

voltage (say,

13.8.  Viola!

Are we talking about a few ohms or a lot?  From what you said I was thinking
of connecting, say, a 100K pot and fiddle with it until I got the right
reading and then measure the resistance.  Or do I need a small value of pot?


heat.  It

necessary,

combo of a

this is a

replacement

version.

realize

that selects

described

(electric

generator.

thinking

rectified

amplitude

generator

throttle

sitting


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