How about a closeup of the plug, with an explanation of what part connects to the battery, or battery pack's positive pole? That might save someone some trouble.
Boyd, with mine it's plug-n-play. I make sure that polarity is correct and that the connectors can't be reversed in normal use. I also color code the terminal ends at the battery and the charger with red and black heat shrink tubing. This will be handy if/when battery replacement becomes necessary. That said, I've been using the same battery for I think 5 years, now on my personal units.
I use a female terminal on both the battery. The battery terminal stays on the battery and you simply use a male/male cord to jump from the battery to the scale/dispenser. The charger terminal is also male so that it plugs directly into the battery female terminal. The point of all of this is to make it as near foolproof as possible. The only way to mismatch the hot and ground is if you remove the terminal from the battery and or charger. And like I said, I color code them for ease of service when it finally does need it.
FWIW, the hot wire goes to the center pin on the scale. It's all very simple and neat. Battery power is actually better than the power coming from the factory wall wart that is supplied with the scale. They are designed to work with anywhere from 9-16 volts and the factory wall wart, being unregulated, jumps all over that range. Also, the supplied electricity from our homes has a certain amount of fluctuation. The battery acts as a line conditioner and filters out the fluctuations in both input and supplies smooth and steady output power to the unit.
I may try to do a video, such as the wonderful ones I've seen of yours, when I get time to.
The whole idea is the same whether you use the rechargeable SLA battery such as mine, or a battery pack for d cells, etc. I just like the setup that I use better but both work. I have no idea how long these will last, overall. As I said, my battery is about 5 years old. Run time is weeks, not hours, to keep it powered up. The current draw changes with the speed the motor is running at. I don't recall the specific draws but IIRC, a single charge will run it for like 27 hours. wide open, non-stop.
Replacement batteries are cheaper than D cells if you shop around. OTOH, Batteries Plus is about $30 for the same battery, which is way overpriced.