Dewalt battery holder or adapter. You could use this just as a mountable holder or if you insert a .7 inch strip of .032 brass you can connect to the battery. A small compartment is made for a fuse, reverse voltage protection or what you might like to add.
DON'T CONNECT TO THE BATTERY IF YOU DON'T UNDERSTAND THE HAZARDS.
IF YOU INTEND TO READ ON. Li-ion batterys can be easily ruined by discharging below 3 volts per cell. Murphy's law states that you will forget. If you make use of the battery power then make sure the device will disconnect when the battery voltage gets below 3 volts per cell. Don't use this as a connector to charge the battery intentionally or by accident. It can cause the battery to explode and or burst into flames. This disables all the charge, discharge protections that or provided in the Dewalt tools and the connection to the extra pins are not provided.
I'm using this because I shut my device down when the battery voltage gets low and I always use the appropriate Dewalt battery charger when charging. This provides a safe battery for my projects that is well protected when handling and provides an inexpensive charger. I've only used this on 20V battery's but it was modeled off the charger so 12V should also mount.