Power to this unit is AC/DC and polarity does not need to be observed on the input. When the relay is ON, current draw is 21ma. All other times the current draw is under ma at 12VDC. They state battery life is 3 years. Assume that is the total time the machine is not powered. The time the machine is on will be counted. The cover can snap off. Unlikely the battery can be replaced without soldering and then it will likely be an oddball type and not worth the effort. I found the instructions were hard to follow and lacking step by step procedures. That made a lot of wasted time just experimenting with the functions. It first appeared that if a change in program is desired you must start from the beginning and repeat anything. I later found that pressing the C/R button four times would allow setting the clock and programs individually. C will erase absolutely everything.The C button should be pressed first time to reset the timer before you do anything. This totally clears memory.To set the clock, press C and then press D+ to set the day, then H+ to set the hour (it is 24 hour format) and then M+ to set the minutes. Be fast because it will exit after 15 seconds or press clock again. If you forget setting the day of the week and have done entering program, The process has to be done all over. Everything will be lost. It is easy to goof up. Write all steps down before starting. Take time to look something up and the program may lock, forcing a start from the beginning. Use only C/R for future changes.From setting clock, you can enter into programming mode. Otherwise, press C/R four times and then P to view or change settings.To program time on or off, press P. You will be in program 1 and the ON time. H+ and M+ to set the on time. All the days will be displayed for same time every day. Press D+ only for selected days. Press P again to set OFF time, it will still be in program 1. You need not do anything further for the same program every day. There are alternating day routines besides individual days.D+ will bring you to another day when programming by day. Then repeat the sequence.Just don't lose the manual and make notes on the other side of instructions. Procedures are not intuitive and it is unlikely steps will be remembered.Entering the manual mode switching output on and off requires entering a secret code of pressing the C/R button four times. Then pressing MANUAL will cycle thru OFF, AUTO and ON. That can be inconvenient in testing because it reverts out of manual in 15 seconds.It is a powerful timer. I just wish the instructions were better with some step by step examples provided. The use of C/R is not fully explained. It was very frustrating learning to use this timer because of the poor instructions. Hopefully, these comments will make things easier for you. Sorry, I'm just not good enough with this timer to do a video without more than a dozen retakes. Manual states there are 20 settings. I found there were actually 28.

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I ordered the 12V version. I thought it was designed for a 12VDC circuit. This doesn't seem to the the case. It looks like it's triggered by 12V, but it controls a 120-240VAC circuit. But I don't really know. It's very confusing, and I generally can figure this kind of stuff out.

This is the third vendor I've aquired this type of timer switch from. They all look the same, the menu is the same (even if buttons are labled differently, function is the same). So I assume they'r all the same.Programming is frustrating until I accepted that I'm not going to get back into the programming mode to change a program. The option is: reset it, then reprogram it from scratch. That I can do reliably. Anything else is an exercise in frustration.I'm using these to control a DC water pump connected to a LiFeP04 battery, solar panel, and charge controller that irrigates some trees we planted at the hunting property.The first unit (from another vendor) seemed fine with the original DC pump (12v, 2a after breakin). It lasted most of a season until I decided I needed a bigger pump (12v 10a during breakin, 6 amp after breakin). That quickly ruined the timer. Extinguishing a DC arc is more difficult than extinguishing an AC arc, so I'm skeptical of cheap devices that claim to be rated for AC and DC.I replaced the timer with another from another vendor (with the same higher draw pump) and again it failed pretty quickly.Now I got this 2 pack. I assume they're not up to the DC amperage ratiing either. I'll not be running the pump directly from the relay in the timer, even though the timer is supposedly rated for it. Instead, I've ordered a separate (larger, higher rated) relay. So the timer is now just kicking power to the coil in the second relay, which only takes around 0.1 amps. With this setup, I'm expecting it to work.So why not a harsh rating? These are cheap little devices. I thought I was abusing it to start with, and now I can confirm that. My advice is you shouldn't trust the DC amperage rating. If you stick to somethig more plausible, I suspect you'll be fine.