Chimo

I see you "cheaped out".

I did a batch of 63.5C eggs and then some 78.4C asparagus tonight and had the Kill-A-Watt (k-a-w) plugged in. The container was a small Coleman cooler with a top opening approx 10"x12". As predicted the start-up draw was about 1050W. Once temperature was reached, the k-a-w readings fluctuated from ~30W to 500W with greatly varying KVA readings as well as the power factor varied as well and dipped to as low as 0.48. The power factor still read low when the k-a-w was drawing a few hundred watts. I would not trust this device to provide an accurate tally of kWH for a cook. As a side note, once the bath reached a steady state temperature, I removed the reflectex lid I had covering the cooler. The k-a-w indicated that the power demand went from ~30W to over 200W to cope with the evaporative losses. Once I replaced the cover, the k-a-w soon settled back down to the lower power demand numbers.

That's correct. I have also seen and built other inverter circuits that have varying output waveforms. Devices with motors are particularly sensitive to UPS output waveform. A corded drill is a handy, if simple, check of how well the output has been smoothed to a sine wave's energy. I noticed that there are a lot of other engineers/techs in this forum. Good to see!

Thanks for the link. There was also some interesting tidbits on the kill-a-watt meter in there. It may not be fully up to the task with respect to getting the steady state power requirements of the SV due to its relatively slow data sampling frequency. During warm up I would expect the SV's heating element to be on at 100% duty cycle. Two key factors in designing a battery-based backup would be the maximum demand (known) as well as the energy required for the desired hold time. As discussed here, that energy requirement will be a function of many variables. Sounds like a fun problem to ball-park!

I have a "Kill-a-Watt" meter that I plugged the Anova into on one of my first cooks. I recall calculating the energy cost of the cook, but I don't recall the numbers. I will try to remember to give it another go this weekend. I do recall being a bit surprised by the steady state power that the circulation motor drew. To comment on the UPS discussion, most consumer models are of the off-line type, meaning the mains provide the power until it is lost and then battery inverter circuit kicks in after a percentage of a cycle. As far as the output waveform, some use a modified square wave, some use pulse width output fed through a smoothing filter to replicate a sine wave. Very few consumer models actually output a pure sine wave.

All this talk about SV hamburgers got me curious about what they would be like. So I made some last night. I made some 5oz (~145gm), 20mm thick burgers. I cooked them at 140°F (60°C) for 65 minutes and then threw them in an ice bath. I did use my chamber vac to seal them individually but I did not draw too strong of a vacuum. Today for supper, I finished them on a cast iron skillet and used a torch for the edges. How did they taste? Awesome. Even using grass-fed, fairly lean beef, they were very moist, flavourful and easy to make consistently. My wife enjoyed hers. I will give this experiment a thumbs up.

Just got my Anova today. Had some excellent eggs for supper! A chamber vac is also on the way.