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[DPRG] Voltage Conversion

Subject: [DPRG] Voltage Conversion
From: Paul Bouchier bouchier at classicnet.net
Date: Sat Nov 28 18:40:55 CST 2009

Kip - you responded with the right answer to the wrong question. Clearly,
wanting that amount of power means Charles is driving motors, and it makes
no sense to regulate 48V @ 5A down to a nice smooth 12V @ 20A only to PWM it
to motors. 20A is harder to deal with than 5A. Better to use a motor PWM
module that accepts 48V and designed to drive 5A average. The only thing
that might make that problematic is if he was hoping to use an
already-installed motor controller that runs off 12V; but really, if you
need to run off 48V, ditch the 12V module & get a high-voltage module. Jose
might be able to steer you in some good directions.

A separate, professionally-built regulator to power the electronics makes
total sense - all kinds of protection built in.


> -----Original Message-----
> From: dprglist-bounces at dprg.org 
> [mailto:dprglist-bounces at dprg.org] On Behalf Of Kipton Moravec
> Sent: Friday, November 27, 2009 7:14 AM
> To: Charles Thurston
> Cc: dprglist
> Subject: Re: [DPRG] Voltage Conversion
> On Thu, 2009-11-26 at 00:41 -0500, Charles Thurston wrote:
> > Hello DPRG,
> > 
> >   I am looking to convert 48 VDC into 12VDC at about 20 to 25 amps. 
> > The supply is Wet cell batteries on a golf cart (I need 
> something to 
> > run steering motors, brake motors and my electronics with). 
> > Suggestions on tapping 1 or 2 batteries are out, These are 8 volt 
> > batteries. Low power consumption at idle is important.
> > 
> For the steering motors, brake motors use high speed PWM with 
> MOSFETs. Just never go above 25% duty cycle.
> I am not sure what you mean by break motors, but the easiest 
> way to break is to short the motor terminals (after removing 
> power of course). 
> Use an off-the-shelf power supply like Dale recommended for 
> the electronics. You will probably be under 0.5A for electronics.
> Kip
> -- 
> Kipton Moravec AE5IB .- . ..... .. -...
> "Always do right; this will gratify some people and astonish 
> the rest." --Mark Twain
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