The wikipedia artical actually states that many switching power supplies can be plugged directly into a DC power source. This happens because the rectifiers turn the AC into DC as the first stage and after that it is all DC anyways.
So the thing is in this mode one would need likely more than 100V DC _or_ the power draw would have to be less than 1/2 of what the supply is rated for _or_ one would have to modify it and double the capacity of the input side by putting two (2) rectifiers in parallel. The problem with 24V is that its so low the amperage the thing will try to draw will overload it (unless the draw is very low). I think in general none of these ideas are practical - I'd just go get an inverter and swap the 24V DC back into AC. Talk to Staples. Any cast out UPS does this. The APC model I have here is 24V internal (I think) and its rated for 450 watts. NOTE. Every UPS I have seen is terribly underpowered on the battery side. Even a deep cycle battery cannot handle more than a few deep discharge cycles or it will die! There are things like battery desulphonators which are little circuits designed to counter the effects of deep discharge and they are reported to bring back dead car batteries as well. I've looked at building some and would be interested to work with a small team because why should each of us re-invent the wheel. --------------- The problem however is that other than in very specialised applications, a battery power source is just not suitable. I'd like to know more about the application. On Fri, Jul 22, 2011 at 08:01:09PM -0600, [email protected] wrote: > Yes > > Excellent. > > This is exactly the stuff he is looking for. Then he pulls the 120/240v > switching power supply and installs DC-DC. THe likely won't fit in his case. > > Next if he has maybe of the external enclosues which come with a wall wart > then he is more than 1/2 way there. He needs to match the power output of > the wall wart and that should be going into some sort of DC-DC regulator to > power his equipment. > > I would think its right off the shelf because many need mobile offices which > need to run in cars and campers. > > Any of the big RV stores should be able to help. A couple years ago I spoke > with Novak RV and they said they have solutions. But I think they might be > running inverters - which in this case likely make no sense. > > Still the way the DC-DC transformer might work would be just a switching > power supply to chop the incomming DC current same as the AC power supplies > chop the incomming AC current. Then at very high frequencies its easy to get > the right voltage and smooth it back out. > > http://www.hardwaresecrets.com/article/327 > > > http://en.wikipedia.org/wiki/Switched-mode_power_supply > > > Note his 24V power is "nominal" 24V. It can be anything from 0-24V if the > battry is undervolt (going flat because he is discharging it to run his > gadgets) to a normal 26.4 volts to over 28 volts if there is a charger on it. > > So his power supply must clean this up. > > He should make sure he has the MOV's in the circuit as well but I'm not sure > about them in a DC application. He can still get spikes! > > > On Fri, Jul 22, 2011 at 03:07:52PM -0600, Hendrik Schaink wrote: > > Do you mean DC-DC type pwer supplies? Take a look here: > > > > http://www.mini-box.com/DC-DC > > > > Hendrik > > > > > I am in the market for a harddisk storage device of some sort (like > > > Drobo Qnap FreeNAS) > > > that takes 24V dc in (max) no 110V available. > > > > > > Has to have 500GB or 1TB storage and an ethernet connection so I can > > > give it an IP address. > > > (Pref linux based) > > > > > > Like a freeNAS type of thing ... > > > > > > I could take probably one of those mini-itx ones and shove 2 disks in it > > > and install freeNAS... > > > > > > But wonder if something exists off-hte-shelve ... > > > > > > > > > _______________________________________________ > > clug-talk mailing list > > [email protected] > > http://clug.ca/mailman/listinfo/clug-talk_clug.ca > > Mailing List Guidelines (http://clug.ca/ml_guidelines.php) > > **Please remove these lines when replying > > _______________________________________________ > clug-talk mailing list > [email protected] > http://clug.ca/mailman/listinfo/clug-talk_clug.ca > Mailing List Guidelines (http://clug.ca/ml_guidelines.php) > **Please remove these lines when replying _______________________________________________ clug-talk mailing list [email protected] http://clug.ca/mailman/listinfo/clug-talk_clug.ca Mailing List Guidelines (http://clug.ca/ml_guidelines.php) **Please remove these lines when replying
