Re: (ET) 36 to 14 volt DC-DC converter (was Today's lessons with heavy snow)

[Charlie <medievalist gmail com>]

You're going to laugh, but what I want is a bolt-in, solid-state
replacement for the "toaster" that can handle 500 Amps at 36VDC.

According to the circuit designers I've consulted, it's actually
theoretically possible to make a high-current device that throttles
the juice (rather than just blowing off a portion of it as heat) but
it's really not at all cost effective when you consider the price of
electricity and the immense durability of the stock toaster.

Yeah, I said you'd laugh, now didn't I?

--Charlie

On Sat, Dec 22, 2012 at 5:18 PM, Darryl McMahon <darryl econogics com> 
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.
>>
>
> _______________________________________________
> Elec-trak mailing list
> Elec-trak cosmos phy tufts edu
> https://cosmos.phy.tufts.edu/mailman/listinfo.cgi/elec-trak