[Shop-talk] Boosting a UPS?

[Peter J. Thomas]

On 7/27/2014 4:08 PM, Mark J Bradakis wrote:
> It is hot here in Salt Lake. I got a small fan for my office to help 
> keep me cool.
> I plugged it into one of the non-backup outlets on the UPS that powers 
> the Team.Net
> server. Now when I turn the little fan off or on, the UPS beeps a few 
> times. Interesting.
>
> It could be a sign that I need to replace the UPS soon. Maybe time for 
> a mini fund drive?
> I have also heard that one can increase the capacity by wiring normal 
> 12 volt car, motorcycle,
> lawn tractor, etc. batteries into the circuit. Anyone have any 
> experience doing so?
You want a deep cycle battery, like a golf cart battery.  Auto batteries 
that provide a short burst of very high amperage to turn a starter.  
They are not designed for continuous high amperage draw and will fail 
when used for backup power.  The plates in a starter battery are thinner 
than a deep cycle battery and more of them. This is too provide a larger 
surface area for chemical reaction. The heat build up from continuous 
higher amperage draw can warp the plates and cause shorts.
>
> mjb.
>
> ps: About the only thing I remember from all the electrical 
> engineering classes I took
>     in college is that given enough current, any circuit element can 
> be modeled as a fuse.
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