Here is a dump load I made from an old induction cook top. The frame is 1/2" copper tube and fittings for the conductive parts and 1/2" fibreglass rod (electric fence standard) for the non conducting parts. The coiled wire is nichrome wire cut into similar lengths and held in place with stainless screws.
The cook top elements (x2) I used were rated at 1.2kW each in their normal duty. After trialing a few I found that the wire was rather fragile at this loading/temp and I decided to derate it 50% to give it some extra strength (the wire is well protected normally where as I wanted to hang it outside in the wind) I calculated the appropriate sizing and cut the wire to length.
Here is the load attached directly to two fully charged T-105's (series connected for 12V nominal) pulling 130 odd amps. The T-105's are sitting just above 12 volts under this load. The load should pull arround 150 amps max connected to a shunt regulator set to 14V (that's over 2kW) so it should handle just about any 12V setup. There is a fair amount of heat comming off the wires as you can imagine but it only just glows orange when viewed at night. No visible glow during the day.
Total cost was around $NZ15 ($US9) for the copper T's,stainless screws and the galv brackets to hold it all to the tower. The copper pipe was scrap and we have about a gazillion fibreglass poles lying around. I have epoxied the fibreglass/copper and soldered the coper/coper joins. I'm not sure about mixing the stainless/copper/nichrome but it might be possible to put it to work as a waterheating element?
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