Double Conversion UPS Update

Old School Tech has released an update in the double-conversion UPS series. The latest article describes detailed test results with two different loads, one load more than twice the nominal rating of the batteries, and the other much less than the nominal rating. What emerges from this latest article is a rule of thumb to adjust expectations for available battery array energy by 2% for each 10% increase from the nominal load. For example: double the load, decrease the energy rating by 20%. This is a useful rule for self-sufficiency enthusiasts to use when planning their own battery arrays. As a reminder, a double-conversion UPS can keep critical loads running for many hours in a power outage, giving you time to drive the AC charger from a generator, or to deploy a solar array and its charger instead. Even better, the double conversion UPS concept can swallow bad power from marginal generators, within reason, increasing the options for backup power. Rather than seeing bad power from the generator, picky loads such as freezers and refrigerators consistently see the cleaner power from the inverter.

These test results also confirm our ground solar experience from the aftermath of Hurricane Matthew. During that exercise, we discovered that we needed to derate our battery array by 30% or more during actual operation, with a load that was about three times the nominal rating for the batteries. For new readers just joining us, links to those Old School Tech hurricane solar articles are listed below:

Ground Solar, Part I
Ground Solar, Part II, The Combiner
Ground Solar, Part III, The Charger
Ground Solar, Part IV, The Inverter
Ground Solar, Part V, The Batteries
Ground Solar, Part VI, Wiring, Connectors and Tools

Old School Tech has also previously posted supporting articles about solar panel and battery principles. Here are links to our abstracts, containing additional information about these topics for self-sufficiency purposes:

Solar Panel Principles
Off-Grid Lead Acid Battery Principles

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