Delphi DC/DC Converter
With all the extra electric items I am planning to add to the build like electric power steering, electric door looks, heated seats, etc I began to realize that the Chennic DC/DC converter rated at 800 watts was not going to be enough power. In the electric vehicle there is no alternator to provide 12V DC power to all the accessories when the car is running. A DC/DC converter is used. What the DC/DC converter does is take the high voltage of the battery pack and convert that down to 12V (13.5V actually). Although at 13.5 the current is high, the current from the 400V battery pack is fairly low. The converters are usually about 95% efficient. Another reason I was looking for another DC/DC converter is that I heard of some failures of the Chennic modules. A couple of weeks ago Jack Rickard of EVTV demonstrated a 2.2kW DC/DC converter made by Delphi that was being used by the Chevy Volt and that it was available. The power level of this converter is just what I was looking for. The converter can be controlled and monitored with the CAN bus. The only downside of the converter is that it is water cooled, but that is not an issue for me. I found one of the units on eBay for a really discounted price that was brand new. I think the reason the price was so discounted is that the unit came with a connector on the high voltage side that was a special connector probably just made for Chevy and unattainable for anyone else. It was a Amphenol connector but not available for sale. I looked at the connector and realized that it was on a standard bolt pattern for Amphenol. I looked the bolt pattern up and found a standard 2-pin connector was available. The pins on the connector are 16GA so they are rated to 13 Amps. The connector is also rated to 700VDC so it is perfect for the high voltage input on the converter. I also looked into the alternative connector made by Delphi. A company called New Eagle sells a whole kit with the Delphi connector and an Ampseal connector (used for CAN connection). The problem with the Delphi connector is that it is bigger in diameter and larger in cross-section than the Amphenol so the body of the converter would need to be machined to accommodate the Delphi connector. I did not think that would be a viable alternative because the all the electronics of the converter would need to be disassembled to machine the connector face. Replacing the Amphenol connector with another Amphenol connector seemed to be the best alternative. The replacement turned out to be fairly easy, just removed the case cover, the four screws holding the connector and the 2 screws for the input wires. I used silicon jacket wire rated at 600V for the connections from the Amphenol pins to the screw terminals on the converter. All the screws on the converter where star cross pattern, but not an issue because I have a whole set of screw drivers and socket drivers for star pattern. The next step is to test the DC/DC converter. Watch for an upcoming video on that.
I also tested out my latest version of the BMS and built up a couple of boards, one for Collin Kidder and one for Jack Rickard. The boards performed just as designed, the temperature and voltage were very steady and repeatable. The next step for the software that runs the board is to integrate the CAB300 current measurement. Then the board can be used to calculate and measure the state of charge (SOC) of the battery pack.
A video of the Delphi converter and BMS testing can be found here.
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