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Re: (ET) Lifts and DC-DC Converters
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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