[time-nuts] UPS for my time rack

Mark Spencer mark at alignedsolutions.com
Sun Oct 11 16:11:07 EDT 2015

I've also seen inverter systems that are designed for stand by power use in service at commercial sites in third world countries.  Within reason they basically let you run what ever reasonable arrangement of rechargeable lead acid based batteries you want that will supply the required voltage and current.  They handle the conversion of dc to ac and the switch over from commercial to inverter power.   They usually also feature a basic battery charger with settings to charge various types of batteries (ie, gel or conventional lead acid.)

Typically I've seen them used with a number of automotive style batteries.

The users would need to sort out the necessary cables, fuses, batteries, deal with safety considerations etc.

I've never seen these devices in Canada or the U.S.  Sort of a value engineered UPS system for price conscious markets.  Might be a nice starting point for those who want to role their own system and can deal with the safety aspects of this.   I'm not sure what the transfer time from utility to inverter power would be.

In the U.S. and Canada the typical practice seems to be to use packaged UPS systems that include their own batteries.  

Sent from my iPhone

> On Oct 11, 2015, at 10:36 AM, Bob Benward <rbenward at verizon.net> wrote:
> Dave, 
> You could use a 120V relay and switch the high capacity battery from its own
> charger to the battery pack in the UPS.  When power comes back, the relay
> automatically switches the battery out and back to its own charger.
> Bob
>>>> -----Original Message-----
>>>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Dr.
>>>> David Kirkby (Kirkby Microwave Ltd)
>>>> Sent: Saturday, October 10, 2015 6:07 PM
>>>> To: Discussion of precise time and frequency measurement
>>>> Subject: Re: [time-nuts] UPS for my time rack
>>>>> On 10 October 2015 at 14:20, Chris Waldrup <kd4pbj at gmail.com> wrote:
>>>>> Hi,
>>>>> I have decided I'd like to get a UPS to put on the rack containing my
>>>>> Thunderbolt, the laptop that runs Lady Heather, and frequency counter.
>>>> There's one issue with them that I don't see anyone mention.
>>>> I was thinking of doing the same a while back, and intended getting a
>>>> and adding a large external battery pack, so if the mains failed late at
> night, I
>>>> could run the GPS receiver and a few other things overnight, and
> consider
>>>> starting the generator in the morning.  I contacted a dealer on eBay,
> who
>>>> specilaises in UPSs. He told me that the smaller units with built in
> batteries
>>>> will die if you put large external batteries on them.
>>>> Essentially the charging circuits are not designed to run as long as
> needed to
>>>> charge big batteries. Even on ones designed for external batteries,
> there's a
>>>> recommended limit on the size of them. So if you think you might want to
>>>> increase runtime by adding some batteries, buy one designed for that
> service.
>>>> I've had two here which were HP/Compaq 5 kW units. These were different
>>>> to the normal, in that the batteries added up to over 300 V, so could
> produce
>>>> 240 VAC with no need to step it up. Both these blew up on me, for
> reasons I
>>>> never worked out. The load was never anywhere near 5 kW.
>>>> Lots of people mention sine wave. Of course, if you keen enough, you
> could
>>>> make a class A amplifier and sine wave oscillator. The problem is that
> the
>>>> pure sine wave inverters tend to be very inefficient.
>>>> As with most things, there are a lot of things to balance - runtime,
> cost,
>>>> quality of output, audio noise, RFI  etc etc.
>>>> Dave
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