xEM Access Controller Specs?

I’m hoping to find some specs on the xEM Access Controller. The website lists it as +12v and gives a milli-amp draw (without white wire load). Nothing is said about how much amperage the whilte wire will support.

I’m assuming there’s a voltage range, ie, 10.2-16 volts for input voltage, and a max amperage, (50 milli amps???) for the load on the white wire. That seems reasonable, but it’s just a wild hair guesstimate. While I can certainly work with what I know, it might be helpful in some applications to know where the limits are.

Case in point, it might be convenient for me to run an 18V power pack. Or 24, or 36, depending on what’s available.

I can’t answer your main question, but as far as Operating voltage range goes it is
9V to 15V DC
11mA when idle and 48mA when reading
Sorry, I’m trying to find the switching current on the white wire, I know it’s quite low, just give me some time to track it down…
If you haven’t already, throw on a Diode to the white wire just to protect it and run it to a suitably sized relay coil to operate/ switch a higher current, it adds a bit of bulk to your project but at the end of the day it is a great bit of kit.
xEM wiring Video

I know where I saw the switching current mentioned, but frustratingly at the moment I can’t get myself back to it on the interwebs.
FYI it was on the German manufacturers website

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It was really more of a two part question, and that really helps. I was originally thinking small sealed lead acid battery. But… I’ve got a brand new DeWalt battery pack here for a drill, that the casing got busted on. I’m thinking of liberating the 18650 cells and repurposing them. 3.7v times 4 cells gives me a 14.8 volt battery.

I’ve not set up these types of cells before, and I’m still deciding on whether I need a charging / control circuit or not.

Learning new things is fun. :books::bulb:


Load balancing lithium ion batteries can be challenging. I would definitely use a charge controller, for safety. It might work fine just wiring then together at first, but unless they were EXACTLY the same cell voltage the weakest one is going to degrade over time, and you can’t really tell when it’s tucked away in an enclosure. Lithium fires are no joke.

The terminology they use for charge controllers is a number of cells and a letter for wiring configuration. So in your case you want a “4S” charge controller, for “four cells in series”. Here is one that should work for your purposes from SMAKN, who I’ve ordered power supplies from before.

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Figured out how to repurpose the cells and part of their holder. Found a load balancing charge controller, and I’m going down to 3 cells, that should work out to 11.1 to 12.6 volts. Turns out 4 cells could have gone as high as 16.8V at full charge.

Nice thing about researching how to do this, is I’ve learned how to make my own battery packs to any reasonable scale. Good for many other future uses.

Thanks for the link! Will have to look at SMAKN next time. Got a feeling I’ll be using this again.

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