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Re: (ET) Lifts and DC-DC Converters



Those other motors were produced by Prestolite.Those of us that have worked in the automotive service trade recognize them as being VERY similar to windshield wiper motors used on American Motors Corporation products.

RJ


On 12/22/2012 11:09 PM, Christopher Zach wrote:
Ah yes, you're right. Those motors were not converted window winding 
motors,
so we're back to square one.

I'm willing to sacrifice a motor for testing purposes, but what would be 
the
risks of running a series motor at 3 times it's rated voltage? Heat
dispersion could be an issue, one should limit the current (I'll go to a 10
amp fuse or maybe a 7 amp instead of the 20a one in there now).

Any other thoughts?

-----Original Message-----
From: Clean Power Supply [mailto:cleanpower att net]
Sent: Saturday, December 22, 2012 10:40 PM
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) Lifts and DC-DC Converters

  Daryl and All,
  I have a small quantity (5) of DC-DC converters here with an 18-72VDC 
input
and a 13.2VDC output at 5 amps. Not enough for a lift but good enough for
LEDs, etc. I would sell those for WAY less than $150 if anybody is looking
for one.  I also have access to some with outputs  of up to 30 amps. I will
have to get pricing on those, though.
  On running lifts on more than 18 Volts: If Chris Tromley still has the
tractor he used to have it is a New Idea and that lift motor is totally
different than those used on the GE versions. I have run the New Idea lift
motors on 36 volts for years and don't feel it is a problem. I usually run
the GE lift motors on 24 volts and again, seems to work out fine.
  Sincerely,
  Harold Zimmerman
  Clean Power Supply
  Ephrata PA

On December 22, 2012 at 5:18pm -0500, you wrote:
I have looked for a 36-volt nominal input to 14.2 volts regulated and
steady output device for years, which is expected to survive more than
one use and be in the affordable range (under $150 retail).  Never
found one.  I figure there are plenty of automotive 12-volt devices I
would like to run from the whole pack - like winches, lighting, horns, etc.

My son the electronics tech says this is an easy unit to design and
build.  However, he figures if he goes to the trouble of designing and
testing one, we should be looking to make a few to justify the effort.
His question is, what current rating is required(on the output side)?
I have struggled with that one.  Price goes up with power handling.
It's stepwise based on components, so not quite linear (power/cost).
The winch I am using seems to pull about 15 amps.  I would likely
rewire my original lifts to the 14 volts from the sagging 18 to extend
their life.
  Lighting will likely be a pretty small load (thanks to LEDs).

So, is anybody else interested in a 36 nom to 14.2 regulated volts
DC-DC converter (fully isolated - 2 leads in, 2 leads out), and if so,
what current (output) would you consider desirable?  If there is any
response, I will chat over the information provided with him over the
holidays and see what we can come up with.  (I already know he'll say
we don't need any new projects - but my response is that we have been
talking about this for so long it's an old project <smile>.)

Darryl McMahon

On 22/12/2012 4:15 PM, The CZ Unit wrote:
On 12/22/2012 11:30 AM, Chris Tromley wrote:

For the lift, how big a deal is it to just run it on 36V?  If it
only runs for a few seconds at a time and has plenty of cool-off
time, why would it hurt?  If it is a problem, I wonder if you could
use a cheapo off-the-shelf scooter controller?
Honestly? I don't know. It probably would be ok, the problem is the
lift current breaker would probably fuse instantly if it tried to
open due to overload, that would be a problem.

Hm. Actually I have a bunch of apart-lift motors, I'll give it an
honest shot. The question is how do we current-limit it so the
overload can work? Maybe bypass it completely and use a 5 amp circuit
breaker instead of a fuse? What would be a good auto-reset 5-10 amp
circuit breaker?
How common are 36V-to-12V DC/DC converters that would be suitable
for the lights?  Are there any 48V input models that would still
work with a sagging 36V pack?
I used to use a Vicor DC-DC that would put out 12 volts for the um
E-meter and lights. But one morning I came out and found it had
literally blown up, which was odd. Might have been over-voltaged, but
it should have been able to handle up to 50 volts input.

Where I really need to limit current is on the sweeper. The motor on
that is just too darn fast, it beats up the brushes and the grass.
Maybe I could get a much smaller pulley or something.

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