Here are links to pictures of my Worx Battery (18V 1.7Ah) and its accompanying charger unit. The battery is for the Worx 10-inch 18V Cordless Grass Trimmer
You could just use a power resistor, but a light bulb shows you that it has discharged. You can probably find 18 volt bulbs as replacements for the flashlight sold to use 18 volt packs from power tools like yours, or just get 24 volt bulbs sold for trucks or connect two 12 volt bulbs in series.
You could do what a lot of radio control guys do and build yourself a simple bulb dis-charger. I don't know where you can find bulbs that can handle 18 volts. I would think most automotive bulbs would burn out @ 18 volts, but it doesn't hurt to try. You need to remember that the bulbs will get hot. I have seen way better examples of a bulb dis-charger, but this will get you started.
