the Otherpower.com Discussion Board || Comments been awhile, checkin in

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Rants & Opinion - Diaries - Our Products

been awhile, checkin in | 17 comments (17 topical, editorial)

Re: been awhile, checkin in (3.00 / 0) (#6)
by boB on Thu Aug 16th, 2007 at 02:54:02 PM MST
(User Info) http://bob.gudgel.org

I see most of your problem, bob. One reason the DC to DC conversion efficiency is
low is because you are using a higher input voltage. It may be lower by just
1 or 2 percent because of that BUT the BIGGIE is that you are outputting such
a LOW output power that the power losses are a BIG percentage of the output power.
For instance, the MX (and any controller) takes some power just to operate
the relay and the DC-DC converter. Also, the higher the voltage at the input
terminals... the higher the "idle" or "tare" losses are. Now, if you measure
your output power vs. the input power, it can be extremely low. Say, you
were putting out ONE (1) amp to the battery... The efficiency will be
extremely low. I'd say 85% is pretty good in your case. If it were a 24V
and even better yet, a 48 V battery system, and the SAME output current,
you would have twice or 4 times the output power you have now, and those
idle losses would be less of a portion of the total output power and the measured
efficiency would come up.

You notice how manufactures never seem to publish efficiency at low output
powers ? Especially inverters. You will notice the efficiency curve dropping
at a very steep slope at the left hand side (lower power side) of the power
vs. efficiency graph.

And SOMEBODY has the wrong information on the MX60 meter ! The MX measures
the OUTPUT, NOT the input current. It's the INPUT current that is calculated,
so the output current should read closer. Maybe it got mis-adjusted somehow ??
The current is averaged in hardware and software so shouldn't make a lot of difference if there is output current ripple or smooth DC current.
Most inverters will cause 120 Hz current ripple on the DC line at higher output powers.

Hope this helps shed some light.

boB

[ Parent ]

been awhile, checkin in | 17 comments (17 topical, 0 editorial)

Menu

· create account
· How to use the board
· FAQs
· search the board
· Google search the board
· Old Otherpower Board

Login

Make a new account

Username:

Password:

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest © 2003 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!