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Seeking: ~120V DC 20A supply

D

David Lesher

Jan 1, 1970
0
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

We currently ^H^H^H presently have a 48V 750W supply with remote
sense but would prefer something the charge controller can
directly manage [We now use a D-A to fake the sense input into
giving us our desired output...] as well as being able to charge
the whole string at once.

{Question: If you have 3 EE's is that 6E, or (EE)^3?}
 
J

John S

Jan 1, 1970
0
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

We currently ^H^H^H presently have a 48V 750W supply with remote
sense but would prefer something the charge controller can
directly manage [We now use a D-A to fake the sense input into
giving us our desired output...] as well as being able to charge
the whole string at once.

{Question: If you have 3 EE's is that 6E, or (EE)^3?}

Why do you want an electric car?

That's beside the point. Can you help with the requirement?
 
D

David Lesher

Jan 1, 1970
0
Why do you want an electric car?


We want to *build* an electric car for the same reason people
enter the NYC Marathon, walk on the Serengeti, go to the Moon,
and many other challenges.

There are many people who may buy one; that holds no interest
to us. As engineers who alas seldom get to actually create, we
decided to do just that.
 
J

Joerg

Jan 1, 1970
0
David said:
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.


A good candidate might be a multi-kilowatt VF drive and then hack it.
Sometimes called VFD, other times just "drive". Even big ones have
become quite inexpensive. They come for inputs of 120VAC, 207VAC,
230VAC, 240VAC, 277VAC, and so on. You'd have to remove or disable the
bridge at the oupt so you get DC, and then also hack the control
circuitry so it doesn't scribe a sine.

Another good candidate could be a huge UPS. One of those server room
versions. There are companies that routinely switch them out almost like
the batteries, one of the reasons being (like with VF drives) that the
electrolytics in there have a finite life span. This would also need to
be hacked.


We currently ^H^H^H presently have a 48V 750W supply with remote
sense but would prefer something the charge controller can
directly manage [We now use a D-A to fake the sense input into
giving us our desired output...] as well as being able to charge
the whole string at once.

Afraid there is no market for what you are looking for, so not likely
surplus gear. What's wrong with faking signals for the sense lines? I do
that all the time.

{Question: If you have 3 EE's is that 6E, or (EE)^3?}


For a loner type nerd that would be a crowd :)
 
J

Jamie

Jan 1, 1970
0
David said:
We want to *build* an electric car for the same reason people
enter the NYC Marathon, walk on the Serengeti, go to the Moon,
and many other challenges.

There are many people who may buy one; that holds no interest
to us. As engineers who alas seldom get to actually create, we
decided to do just that.
I think if you are going to work with that level of voltage you should
incorporate some sort of ground fault sensor to terminate the output
immediately if some one comes in contact with it, even if it is floating.

It does not take much to stop the heart.

Jamie
 
M

mike

Jan 1, 1970
0
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

Presumably, you have a high-current variable supply to run
the motor. Can you stick in a relay to flip it around
to take rectified line input and charge the battery?
We currently ^H^H^H presently have a 48V 750W supply with remote
sense but would prefer something the charge controller can
directly manage [We now use a D-A to fake the sense input into
giving us our desired output...] as well as being able to charge
the whole string at once.

{Question: If you have 3 EE's is that 6E, or (EE)^3?}
3 EE's are useless. It's like having three watches.
One watch and you know what time it is. Three and you're never
quite sure. They can't agree on anything.
 
C

Cydrome Leader

Jan 1, 1970
0
In sci.electronics.design David Lesher said:
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

Xantrex and Sorensen (now ametek) made exactly the sort of monster power
supplies you need. I think xantrex dropped out of the power supply
business, but the tiny bench ones were just rebadged units from the TTI,
in the UK.

check test equipment dealers. The really old sorensen stuff will be 1980s
goofy linear power supplies with SCR preregulation. Those will be giant,
and probably stuffed with obsolete parts. The newer ones are real
switching power supplies.
 
T

tm

Jan 1, 1970
0
David Lesher said:
Three of us are working on an electric car conversion. We're
now working on the "home" charger for it. For that, we are
seeking a digitally controllable switcher supply with ~120V
output, at up to 20-30A. At these power levels, 240VAC supply is
more likely.

Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

We currently ^H^H^H presently have a 48V 750W supply with remote
sense but would prefer something the charge controller can
directly manage [We now use a D-A to fake the sense input into
giving us our desired output...] as well as being able to charge
the whole string at once.

What kind of regulation do you need? Current limiting? 120 volts at 30 amps
is 3600 watts at the load. The input power will be higher, say 20% higher.

That is definitely 240 volt territory. You are looking at inverter welder
technology.
 
Followups set to sci.electronics.components.

In sci.electronics.components David Lesher said:
For that, we are seeking a digitally controllable switcher supply
with ~120V output, at up to 20-30A.

Isolation transformer, Variac, bridge rectifier, stepper motor?
(hides)

The real classic way is a phase angle dimmer made of a a bridge
rectifier followed by an SCR; turn the SCR on sooner in the half-cycle
for more current. Use a microcontroller to pick the turn-on point and
you have a digital input. (You could argue that this is a switching
supply, but it isn't what is normally meant by "switching".)
Obviously new this will be $$$$, but I wonder if anyone knows of
a surplus candidate.

The power supplies I have used in the past with this kind of juice have
been from Sorensen (formerly a tentacle of Raytheon, now owned by
somebody named Ametek) and Zivan (an Italian company with US sales).
The Sorensen ones are general-purpose supplies and are usually available
with both front-panel knobs and remote control. Zivan makes ones that
are specifcially designed to be battery chargers for traction
applications; the controller is already built in. I don't think the
Zivan had any kind of data bus; it did have a few discrete inputs and
outputs for things like start/stop, status, and remote sense. It came
with a temperature sensor you could put somewhere in your pack to both
tailor the charge rate and act as a safety. It also had a blinkenlight
to indicate charge states and problems.

One Sorensen supply I used had to send about 48 V at 10 A down several
hundred feet of wire to some DC-DC converter bricks that output 5 V and
12 V. Something in this setup broke the regulation in the Sorensen; it
would still put out something but it wasn't related to where the knobs
were. At least they fixed it reasonably quickly under warranty, and
the repaired unit seemed to work OK. I think it had a data bus, but in
the prototype stage, the operator just tweaked the front-panel knobs to
get "enough" input voltage at the DC-DC bricks.

The Zivan charger I used did just fine at charging a series string of
twelve 12 V lead-acid batteries (144 V), but for some reason, had a
high leakage to ground on the AC input. It would sometimes pop GFCI
outlets or breakers, even when everything was otherwise sound. Non-GFCI
outlets/breakers were fine. Other people who had used Zivan chargers
reported similar problems. I suspect it may have been designed to a
European standard that allows higher leakage current.

I have seen Sorensen power supplies show up at used and surplus
electronics dealers. A Zivan probably won't show up used in these
places, but a group of electric car home-brewers might be a good place
to look. Both are available new, which might help set an upper bound
on time or money for a home-made solution.

Some other random things that you probably have already thought of:

Put a simple (maybe electromechanical?) timer somewhere to shut off the
charger as a last ditch defense against overcharge... it depends on the
pack size, but if you haven't gotten the battery charged in (say) 8
hours, you're probably not going to. This is more important with a
home-made charger; commercial chargers often have something like this
already.

Give a little thought to interlocking the charger power (AC input must
go away before DC output can be disconnected), or select a charge plug
that can stand being disconnected under load. Also, interlock the
"ignition" of the car and the charger input... the first electric car
charger probably got dragged down the street a few days after the first
electric car was invented. The "ignition" interlock also helps prevent
overloading the charger by trying to run the drive motor while the
charger is connected.
{Question: If you have 3 EE's is that 6E, or (EE)^3?}

A really wide shoe?

Matt Roberds
 
M

My Name Is Tzu How Do You Do

Jan 1, 1970
0
A really wide shoe?

Matt Roberds

One and one half pairs of double Es.

No apostrophe needed where this one is.
 
D

David Lesher

Jan 1, 1970
0
A good candidate might be a multi-kilowatt VF drive and then hack it.
Sometimes called VFD, other times just "drive". Even big ones have
become quite inexpensive. They come for inputs of 120VAC, 207VAC,
230VAC, 240VAC, 277VAC, and so on. You'd have to remove or disable the
bridge at the oupt so you get DC, and then also hack the control
circuitry so it doesn't scribe a sine.

That does not leave much left now, does it?

Another good candidate could be a huge UPS. One of those server room
versions. There are companies that routinely switch them out almost like
the batteries, one of the reasons being (like with VF drives) that the
electrolytics in there have a finite life span. This would also need to
be hacked.

Not what we have in mind. We need a switcher supply.
 
D

David Lesher

Jan 1, 1970
0
Presumably, you have a high-current variable supply to run
the motor. Can you stick in a relay to flip it around
to take rectified line input and charge the battery?

Hardly, the motor controller deals in hundreds of amps, more at
peak. Further, we'd have to run its cooling pump. And a relay
to switch the output? Huge.
 
D

David Lesher

Jan 1, 1970
0
What kind of regulation do you need? Current limiting? 120 volts at 30 amps
is 3600 watts at the load. The input power will be higher, say 20% higher.

Yes, current limit. But that term basically describes the
control input; power supplies limit output, and the consequence
reduces both voltage and current furnished to the load.
 
D

David Lesher

Jan 1, 1970
0
Isolation transformer, Variac, bridge rectifier, stepper motor?
(hides)

As you should. You should have said "Selenium bridge rectifier..."`

The power supplies I have used in the past with this kind of juice have
been from Sorensen (formerly a tentacle of Raytheon, now owned by
somebody named Ametek) and Zivan (an Italian company with US sales).

It sounds like no one has seen what we need; and/or the 750W 48V max
supplies are not that bad after all.
Some other random things that you probably have already thought of:
Put a simple (maybe electromechanical?) timer somewhere to shut off the
charger as a last ditch defense against overcharge...

There is a separate charging controller processor. It has lots
of AD inputs and measures every cell while charging. If any cell
gets too high in voltage, or too warm; charging terminates with
an error report. At $135/cell, you do not want to cook any.
Give a little thought to interlocking the charger power (AC input must
go away before DC output can be disconnected), or select a charge plug
that can stand being disconnected under load.

There are numerous interlocks, both hardware & software.....
 
P

P E Schoen

Jan 1, 1970
0
"David Lesher" wrote in message
Yes, current limit. But that term basically describes the
control input; power supplies limit output, and the consequence
reduces both voltage and current furnished to the load.

You might want to read this thread, and I have several posts as PStechPaul:
http://www.diyelectriccar.com/forums/showthread.php/10kw-60a-diy-charger-open-source-59210.html

It is an open source design so you might be able to scale it down for your
smaller needs. There have been many suggestions and ideas thrown around. If
you are not too concerned about power factor, a simple full wave bridge
might be OK, and if you need a higher voltage, a doubler circuit may be the
way to go. If you do not mind having high ripple content, you could dispense
with a capacitor filter (which causes poor power factor), and use the raw
rectified output. Then you can make a simple buck converter that will
regulate the portion of the waveform above the battery voltage for charging.

Good luck on your electric car. All we need is a major advance in battery
technology or some other small efficient means of converting or storing
energy, and they will be very cost effective and "environmentally friendly".

Paul
www.muttleydog.com
 
J

Joerg

Jan 1, 1970
0
Hal said:
Are the electrolytics running too hot, or is there another wear-out
mechanism that I don't know about (yet)?

I assume temperature is the #1 culprit. It gets quite toasty in those
boxes and they save every penny because the market is so tough since
China entered it.

Then there is always the question what quality grade of capacitor they
have put in.
 
J

Joerg

Jan 1, 1970
0
David said:
That does not leave much left now, does it?

Sure it does. You have a big fat switcher that can be precisely
controlled and you don't have to stack several telco switchers. Stacking
switchers is always a white-knuckle scenario.

The control circuitry is easy, what's difficult are the ferrite
transformer, the big semiconductors and the layout (for good EMC). The
latter are all done. I don't think you will find the perfect solution
with your desired control gear on a silver platter for this job.
Not what we have in mind. We need a switcher supply.


UPS and VFDs _are_ switching supplies. For the UPS kind you just have to
make sure that it is a true power conditioner type and can work sans
battery.
 
D

David Lesher

Jan 1, 1970
0
You might want to read this thread, and I have several posts as =
PStechPaul:
http://www.diyelectriccar.com/forums/showthread.php/10kw-60a-diy-charger- =
open-source-59210.html
It is an open source design so you might be able to scale it down

Looking at the http://www.emotorwerks.com/ page, I've not found
the circuit description or schematics.

From reading mentions of GFCI's, it sounds like this design is
not isolated. We have debated that issue, and for now at least,
we want isolation.

I don't know if the other 2 folks have seen the thread, but I
will point it out to them.
 
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