[time-nuts] DC-DC converter

Ed Palmer ed_palmer at sasktel.net
Sat Sep 26 17:12:36 UTC 2009

I know what he was looking for, Jim.  That's why I said 'wade through 
the 48V -> 12V models' - so he could get to the less common 12V -> 48V 
models that he wanted.  I should have made that clear.  :-)

Telecom equipment is always spec'ed for ~54 volts.  The battery strings 
consist of 24 (occasionally 25!) cells.  To keep them healthy over their 
20 - 25 year warranty period (!), they are occasionally given an 
equalize charge which can push the voltage up to ~56 volts.  Of course, 
during an extended AC power failure, the voltage can drop well below 48V 
so the equipment has to function under those conditions as well.


Lux, Jim (337C) wrote:
> On 9/25/09 11:23 PM, "Ed Palmer" <ed_palmer at sasktel.net> wrote:
>> Have you checked our favorite auction site?  I saw some there by
>> searching for '12v 48v converter'.  Wade through the ones that are 48V
>> -> 12V and there are a few that look interesting.  One in particular
>> from Vicor looked quite attractive.
>> Ed
> I think he was looking for 12V to 48V, which is substantially less common.
> 48V to whatever is quite common, since 48V is a standard DC bus voltage.
> Of course, another problem is that the Z3801A doesn't use 48V. It takes more
> voltage, from K8CU's site: The Z3801A is specified by HP (depending upon
> model) as  either a nominal minus 54 or plus 27 volt device. The best bet
> is to keep the voltage at the nominal value specified by HP.  This way any
> out of specification internal DC to DC converters  are satisfied, and the
> units will perform normally. Reports  from other users confirm this.
> Mouser and Digikey both have a ton of DC/DC bricks with isolated inputs and
> outputs. You can series the outputs (make sure you've got load resistors on
> each one, and perhaps some diodes)

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