Stacking UPS (was How long does a PWRDWNSYS restart(*no) actually take?)

> But it might pay for you too look at the
> option of chaining 2-3 small UPS units together and thus extend the
> duration of the batteries.

*DO* *NOT* *DO* *THIS*

This is a horrible, terrible, as well as a very bad idea. Chaining UPS is NEVER recommended and the smaller they are the worse the idea is. You WILL set yourself up for failure here.

IF all the UPSs are charged when you connect them it may appear to work initially. Power fails and UPS 1 takes load. UPS 2 may or may not accept that input because with small UPSs they cannot lock into anything that is not SPOT ON 60 cycles. (This is why smaller units are often NOT generator rated and simply remain on Battery if connected to a generator.)

Assume it DOES run for a while then dies and UPS 3 takes load. Eventually it too dies. This is best case but now it gets interesting.

Power Returns.

ALL THREE UPS now have dead batteries and of course your equipment will also be connected.
UPS3 has to charge and run the load.
UPS2 has to charge and run the load including charging UPS3.
UPS1 has to charge and run the load including charging UPS2 and 3.

Very likely UPS1 now is overloaded and either flat shuts down or at least drops it's output. This may repeat automatically and this is bad. In an extreme case we have seen UPS1 release the magic smoke inviting the red trucks and the guys with the backward hats.

You are FAR FAR Better off obtaining a UPS which accepts external battery packs to extend run-time. THIS is a better idea in every way.

- Larry "DrFranken" Bolhuis

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - Commercial IBM i Cloud Hosting.

On 7/28/2017 1:02 PM, Nathan Andelin wrote: