Thursday, April 2, 2015

New Charger, New Plan

The new Lear charger arrived from EVTV yesterday, and it's pretty impressive. It's the charger used in a Chevy Volt, and this one appears to be brand new. The part label on the box was partially covered with shipping tape, but the label instructing that the core should be returned in the same box indicates it probably came directly from Mr. Goodwrench.

The two orange wires on the left connect to the battery pack while the orange bundle coiled on the right will go to the J1772 inlet port. It's 12' 10" long so there's a chance it might stretch all the way from the motor bay to the old gas filler on the passenger rear fender. The real magic is in the little black box behind the coil. It essentially contains a small computer that sends CAN bus messages to the charger to set its operating parameters. Mark Weisheimer deciphered the CAN message stream and Jack Rickard programmed the Arduino Due chip set in the black box to spoof the OEM charger into thinking it's getting instructions from the Chevy Volt ECM. It's all very slick and part of the EVTV strategy of making OEM quality parts available to do it yourself converters like me.

On either side of the orange input/output connectors are the liquid cooling ports. The Lear charger is water cooled which allows it to be somewhat smaller than the air cooled TC Charger it replaces.

You'll recall that I learned that my Better Place battery pack really wants to be charged to 4.2 volts per cell (403.2 volts pack total) to get its full capacity. The TC Charger at 389 volts just wasn't going to get me there. Given that the Lear charger is water cooled at a smaller footprint it will go in the motor bay, allowing four more cell modules in the rear battery box in place of the TC Charger. That leaves eight cell modules to put somewhere, maybe in place of the rear seat cushion.

Now we'll be rethinking the motor bay arrangements to accommodate this Lear charger along with the DMOC 645 inverter, cooling system, and precharge/contactor box. That will have to wait until we have the Siemens motor in place and can assess the space available. The project plan now looks like this:

Remaining work items: Pro Automotive
  • Rear battery box
  • Motor to driveshaft coupler
  • Driveshaft tube to motor adapter
  • Front motor mount
  • Inverter mount
  • Charger mount
  • DC/DC converter mount
  • Radiator mount
  • Power steering and air conditioning hoses
  • Front paint and bodywork

After that is all complete, it's coming back to my garage. The ONLY (?!) things left will be all the HV and 12v wiring, instrumentation, and interior work. Our June 30 target date is looming very large indeed.

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