On Tue, Mar 27, 2007 at 07:35:10PM -0700, Dave Parker wrote: > I guess I was being overly optimistic a bit on the "really easy to > answer" part; two people have recommended that I add some sort of > regulation to the voltage to keep it below 56vDC. > > I'm kind of (not just kind of) out of my league on this, but I've been > thinking then that the circuit described in the "Simple Voltage > Stabilizer" section of this page: > http://en.wikipedia.org/wiki/Voltage_stabiliser might do the trick? My > understanding is that it would "regulate" voltage only in as much as it > would keep it from exceeding a reference voltage, which I would probably > select as 54vDC to be safe.
I don't know any more than you do about what voltage the Soekris can tolerate, but I can tell you that the circuits on that page are all extraordinarily inefficient. They will dissipate the excess power in the form of heat. This might be OK for a line-powered system, but you're talking about battery power, so I suspect you won't want to be wasting power like that. Somebody else mentioned a DC-DC converter, which is in fact a switching power supply, and that will certainly do the job more efficiently. You might find they are a little expensive, though, and not available at your local Radio Shack. DigiKey sells a bewildering array of them. (Emphasis on "bewildering".) You will likely pay $20 or more, depending on how much power you need. You might also see if you can just take a battery or two out of the battery pack. It will have multiple lithium cells connected in series to produce a voltage that high. If you take some cells off the stack, the voltage will be lower. However, the charger is likely designed to charge to a particular voltage, though some chargers are smart can adapt to different voltages. (I suspect that is *not* the case, as it would be added expense in the charger for no benefit in the scooter application.) > > Do people from Soekris read this list periodically? I was kind of hoping > for an "official position" on the topic. Minus that, I guess I'll have > to see if I can build one of those circuits. > > Dave Parker wrote: > > I should mention that the battery bank itself is nominally 48vDC. > > > > Dave Parker wrote: > > > >> Hello > >> > >> I have what I'm guessing is a really easy to answer question: > >> > >> Is 59.2vDC an unacceptably high voltage to send through a POE injector > >> to a net4526? > >> > >> I've salvaged a bank of lithium batteries and charger from an electric > >> scooter, and while I'm suspecting that there are enough amp hours there > >> to run the board for "a very long time" without charging, I'd like to > >> use those amp hours for other things, so I'd like to use the charger > >> while the board is in operation. The charger's logic appears to have > >> voltage top out at around 59.2v, and maintenance is around 56v. The > >> former scares me a bit. Will the board tolerate that? Is there > >> something I should add to the circuit to protect the board while the > >> charger is operating? The cat5 run from the injector to the board is in > >> the 5-8' range. > >> > >> I've tried finding a concise answer to this question with some extensive > >> googling to no avail aside from two documents that mention "absolute > >> maxium voltage = 68vDC. That's not enough to make me feel secure about > >> my magic smoke, hence... I ask :) > >> > >> Thanks in advance, > >> > >> Dave Parker > >> > >> > >> > > > > > > > > _______________________________________________ > Soekris-tech mailing list > [email protected] > http://lists.soekris.com/mailman/listinfo/soekris-tech _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
