Author Topic: DC/DC Converter That's Efficient?  (Read 8312 times)

0 Members and 1 Guest are viewing this topic.

Offline gerathegTopic starter

  • Regular Contributor
  • *
  • Posts: 102
Re: DC/DC Converter That's Efficient?
« Reply #25 on: January 19, 2015, 12:02:46 am »
Thanks for the link, I actually learned something from it.
Now I know what those diodes inside of the box on the back of the solar panels are.

Given a small budget and the fact that this need not be 100% reliable since this is only a temporary project, I might just settle for something that works. I found this on ebay: http://www.ebay.com/itm/DC-DC-Converter-Voltage-Reducer-Regulator-24V-Step-Down-to-12V-20A-240W-DC-to-DC-/120966517136?pt=US_Power_Inverters_&hash=item1c2a2a9190

I'm thinking of buying 2 of those, 1 for each panel. And then wiring the two converters directly in parallel. I don't know if that's a good or bad thing to do.

What do you think?
« Last Edit: January 19, 2015, 12:05:10 am by geratheg »
 

Online Circlotron

  • Super Contributor
  • ***
  • Posts: 3167
  • Country: au
Re: DC/DC Converter That's Efficient?
« Reply #26 on: January 19, 2015, 10:42:59 am »
Is there a device that can preserve the amount of power after converting the voltage? In other words, lower the voltage but increase the max current.
Yes, it is called a buck converter. -> http://en.wikipedia.org/wiki/Buck_converter
Buy one, 13 bucks   ^-^  -> http://www.dx.com/p/produino-dc-5-32v-to-dc-1-5-32v-converter-buck-adjustable-electronic-power-regulator-module-289944
 

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1938
  • Country: us
Re: DC/DC Converter That's Efficient?
« Reply #27 on: January 19, 2015, 04:15:26 pm »
That would not be a good choice.  Doesn't anyone in the group have any electronic experience?
 

Offline gerathegTopic starter

  • Regular Contributor
  • *
  • Posts: 102
Re: DC/DC Converter That's Efficient?
« Reply #28 on: January 19, 2015, 06:06:21 pm »
That would not be a good choice.  Doesn't anyone in the group have any electronic experience?

I appreciate all the advice you give. I learn something from good electronics practices.
For this project I'm just willing to compromise a little bit to fit the budget.
 

Offline suicidaleggroll

  • Super Contributor
  • ***
  • Posts: 1453
  • Country: us
Re: DC/DC Converter That's Efficient?
« Reply #29 on: January 19, 2015, 06:26:46 pm »
That's not a small compromise, a regular buck converter will not work correctly off of a solar panel.  Please read what I posted earlier again:

Quote
You don't just need a DC/DC converter, you need an MPPT.  Look up the I/V curve for a solar panel.  It's non-linear...at either no load or short circuit they deliver 0 power. Maximum power occurs somewhere in the middle.  Where, exactly, depends entirely on solar irradiance, temperature, etc.  If you just stick a DC/DC converter on a panel's output, as soon as the motor draws more power than the panel can provide (cloud passes by, etc), the DC/DC converter will drop its input impedance to compensate for the voltage drop, and you'll fall off of the edge of the panel's I/V curve and get essentially zero power, indefinitely.

It's not just a matter of losing some efficiency, if you don't use SOME kind of power tracker intended for use with a solar panel, there's a good chance things will work ok for a while, and then just stop.  It'll get stuck in an infinite reset cycle, maybe overheat itself, who knows.  BEST case scenario is that doesn't happen, but you get SIGNIFICANTLY (read: half, third, etc) less power than the panel is capable of providing.

A regular DC/DC converter expects a CV (constant voltage) supply, a solar panel is a CC (constant current) supply.  You can't stick a DC/DC converter that's designed for a CV supply on a CC supply and expect it to work correctly.
« Last Edit: January 19, 2015, 06:30:36 pm by suicidaleggroll »
 

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1938
  • Country: us
Re: DC/DC Converter That's Efficient?
« Reply #30 on: January 19, 2015, 06:38:21 pm »
It is not about being cheap. I have over 1000W of panels that are controlled with a $6 UNO and simple electronics built from a couple old UPS. The world is your oyster, there is so much electronics out there that can be had for free.  It just seems that if a group is going to do a project the members should bring something to the table or at least learn something.  I learned electronics by reading. I had my first job repairing electronic organs at 15.  My brother had to drive me around on service calls.  You have the internet, far more out there than I had.  You want to start with projects and not learn the basics.

Basic buck converters can easily be modified to operate at power point, but you need a little electronic knowledge to do it.  This is a great fun project.  Too bad you don't want to put any effort into it.
« Last Edit: January 19, 2015, 06:44:18 pm by Seekonk »
 

Offline gerathegTopic starter

  • Regular Contributor
  • *
  • Posts: 102
Re: DC/DC Converter That's Efficient?
« Reply #31 on: January 19, 2015, 07:45:58 pm »
Basic buck converters can easily be modified to operate at power point, but you need a little electronic knowledge to do it. This is a great fun project.

That's very intriguing and sure does look fun, just a lot of effort with college work already taking up a lot of my time and I try my best to learn slowly about my hobbies (I actually have many, not just electronics). For this project I'm probably going a little too slow.

Too bad you don't want to put any effort into it.

Okay okay, you win ;)

And certainly, I appreciate all replies to this thread. I've gained some knowledge :-+
Thanks!
« Last Edit: January 19, 2015, 07:47:41 pm by geratheg »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf