All of the Jeep's exsisting 12 volt systems (lights, wipers, radio, etc..) will continue to be powered by a 12 volt battery. However, like any battery, the 12 volt battery will need to be charged to continue to function. In electric vehicles including the Jeep, a DC/DC converter is utilized to power the 12 volt system and charge the 12 volt battery.
Basically, the DC/DC converter is hooked up to the 160 volts DC traction pack, and it then converts the 160 volts into 12-14 volts DC. The Jeep is using a DC/DC converter which is made by DC power systems (DCP). It outputs around 30 amps max at 12 volts DC.
I chose to mount the DC/DC converter next to the Raptor motor controller in the engine (now motor) compartment. I also decided that one side of the DC/DC would be supported off of the controller mount, and the other side off the driver's side wall of the engine compartment. First thing I did was cut two strips of steel "L" channel the length of the DC/DC converter. For the side that would mount to the controller's mount, I drilled one hole for the mount bolt, and two small holes to match the mounting holes on the DC/DC converter. Next, I drilled two holes in the second piece of "L" channel to match the converter's mounting holes. Then, I drilled two holes in the side of the "L" that would be mounted to the wall of the engine (now motor) compartment. I then marked and drilled corresponding holes into the wall of the engine compartment, and installed two riv-nuts to provide threaded holes for screws to bolt into. When it's all said and done, the converter has two "L" channel pieces which it is mounted onto using four 1/4" bolts.
Update (12/19/2004): Cooling the DC/DC:
After using this DC/DC converter for some time, I've noticed that it tends to get extremely hot. The converter is designed for a 30 amp output. Since the Jeep's electric power steering pump easily pulls 20+ amps at all times, the DC/DC converter is always outputting its maximum power. The problem is that the converter cannot cool itself effectively and ends up cutting back on its output power (to prevent frying itself). When it cuts back on output power, my 12-volt system voltage sags into the 10-11 volt range (as my accessory battery is sort of small). So, I decided that putting a fan on the DC/DC would be a cheap modification that would help the unit live longer and put out more power.
I ended up using a small 12-volt brushless fan (like the kind from computers) on the DC/DC converter. I was able to mount the fan to the DC/DC's heatsink by wedging its mounting screws between the heatsink fins. This proved to be very effective, and luckily it required no permanent modifications to the DC/DC converter. I connected the fan to the switched "IGN" line on the DC/DC converter, so the fan runs anytime the Jeep is turned on. So far, I've noticed the unit stays MUCH cooler, and there seems to be a bit less voltage sag in the 12-volt system.
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