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APC UPS with inverter to out batteriers.

APC UPS with inverter to out batteriers.

(OP)
Not sure if possible and was basically told by APC that they didn't think it could be done but here goes:  We have a big APC Matrix 5000 UPS in out server room and would like to when power goes out for an extended time, plug the UPS into and inverter then into one of our large batteries that we use for our forklifts.  We had tried years ago and go correct inverter to connect to our battery and was able to run normal AC outlets directly from it but when plugged UPS in, it didn't work.  APC said something like it having to do with going from dc to ac and back to dc or something like that, I can't find old notes.  Anyyone have any ideas on this so we can swtich without having to power things off first?  We can do now to a generator but not the best solution.  Thanks, Joe

RE: APC UPS with inverter to out batteriers.

It sounds as though the AC coming out of the inverter that's connected to your forklifts is out of tolerance as far as the APC Matrix 5000 is concerned - either frequency, or voltage (high or low) or the waveform, or it may not be able to supply the amperage necessary. Check the output rating of the inverter - it may not have the capacity to support your 5000VA UPS if the UPS is running near its full load.  Using a generator for extended outages is preferable, but I understand that you want to have an alternative, a way of carrying the load while you refuel the generator. The APC UPS is designed to work from regular sine wave - the power company uses rotating machinery. So does your local generator. You inverter puts out some kind of stepped square wave, and it may be OK for refrigerators, buffers, etc, but the protective circuits in the APC UPS may see it as unsafe for the network equipment you bought it to protect. There are safe ways of getting AC from batteries - we used to have a rotating inverter in our Titan Missile launch center, to provide AC from our battery banks. It was a DC motor and an AC generator on the same shaft, so it produced Sine Wave AC needed for the electronic equipment.

Fred Wagner

  

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