Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Do you have to have batteries while using the AC adapter?  Looking for one without batteries ever needed.
Document: I use this scale to make espresso at home. It runs either off the AC adapter (never shuts off) or off the batteries (auto shut off). It comes with 2 clear plastic tray. One the size of the weigh platform and the other the footprint of the entire scale. The scale can fit inside the trays to protect it for transport. The large tray works well to balance a loaded portafilter hands free for measuring coffee dose.
I use the battery, no AC version of this scale on my coffee bar for years, and the only complaint I had was that the auto-off feature  would occasionally time out -- but always at the worst possible time.This scale is otherwise the same, but with the AC feed, auto-off is disabled. Of course, if you choose you can use it with batteries.The scale can be used with or without either of the trays.
I checked the calibration using nickels and found this scale off by almost 5 grams/100. I asked the seller if I needed to buy a weight to calibrate this and never heard back. I'm using it but not expecting it to be totally accurate.
The product: American Weigh Scales SC-2KG-A Digital Personal Nutrition Scale with AC Adapter, arrived on time and in excellent condition. I haven't really had time to use the scale yet but I tested it out with a nickel and a small bag of unopend pasta and it weighed accurate. I bought this mainly to use for weighing ingredients for making homemade soap. I'm sure it will come in handy for other things as well.
Compact, works on battery or AC wall wart, precise, super easy to use, nice display, couldn't be happier. I use this mostly for weighing out coffee and it is a great scale for that because it's compact and can be used on batteries and so can sit right next to my coffee machine. Also by virtue of being stainless it's super easy to clean up.
Wetness happens. The 2kg capacity of the scale is more than sufficient for all coffee purposesI checked calibration as shipped with 10g, 100g, and 500g reference weights and -- perhaps I was luckier than some here, or perhaps I knew enough to remove the piece of protective cardboard set between tray and scale-body before using the scale -- the scale was accurate to 0.1g.
I had an American Weigh scale already, but it was battery-only, and would turn off before I was done with my weighing and calculating (user, not product, error), so I bought this one. AW scales truly are workhorses - mine sits on my work bench, in dust and grease and grime, but isn't affected and takes accurate measurements, every time.
This is a great little scale that plugs in to save you batteries and to bypass the annoying auto shut off feature. It's just the right size. There's a slight delay when you put something on it and occasionally it will jump from say, .2 grams to .6 grams- so not the most accurate but still pretty good for the price. I recommend it.
it's alright. nothing to write home about. It weighs stuff but dosen't seem to be that accurat at doing so
This is a great scale. Light, small and easy to use.For coffee enthusiasts, it is very functional. Sub gram precision, tare function, different modes and auto-shutoff work great for pour over coffee making.Measured weight can very erracticaly due to temperature changes.I now leave a vessel full of hot water on it for a while to warm it up and stabilize temperature before I use it for making coffee.
Answer: NO batteries needed.  I didn't put batteries in mine when I received it, but I just now opened it up and it had factory-supplied batteries.  So, I took them out, then turned on the scale (AC adapter only), and it worked just fine.