For pickup: VAX-11/750 and RK07

Chuck Guzis cclist at
Sat Jun 6 15:45:15 CDT 2009

On 6 Jun 2009 at 15:59, Patrick Finnegan wrote:

> 1) Newer models seem to have a charging circuit that's smart enough
> not to overcharge nearly-dead batteries to the point at which they
> expand and blow their seals.  Cleaning batteries that have done this
> out of a UPS runs somewhere from "difficult" to "a complete mess". 
> And, I've had to clean this up several times out of UPSes I've
> received; the only good thing is that it usually makes the UPS much
> less expensive to acquire. :)

I think the LM317(mumble-mumble-high-voltage-suffix) is limited to 
about 1.5A output current anyway.  And the batteries I'm using are 
basically garden-tractor batteries, not gel-cells, which seem to have 
a rather short (3-4 years) in UPS.  I replace the batteries (in their 
own box)  in mine about every 6 years--and I check the electrolyte 
level every 6 monts.
> 2) Higher-efficiency inverters mean more runtime out of the same
> batteries, and usually at the same time, a lighter UPS.  Considering
> how often I seem to move stuff around, lighter is definately a plus.

No argument there, except that many cheap inverters deliver only an 
approximation to a sinewave output.

> 3) Better monitoring.  I really like the amount of information that I
> can get out of SNMP on a modern UPS's network card.

This one has some sort of RS-232 output, but I haven't the faintest 
what it indicates, other than "your power just failed".  I've got the 
software for it somewhere, but have never run it.

... and can be more useful for hacking up to do different
> things (like mashing three of them into being a 3-phase inverter,
> which is somewhere on my project list, to power stuff like my IBM
> 3420, and Liebert System/3).

They also make great sources of big power transformers for linear 
power supplies.  Some have multiple high-voltage windings, so they 
can also serve as isolation transformers.


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