Sunday, January 27, 2008

DC-DC Overcurrent Malfunction

It's good to get the extra transmissions out of my garage. I guess it's poetic justice that the guy who bought my side shifter from the original car is going to give it to Jeff at Rothsport systems for a rebuild, the same guy who didn't work on it for 2 1/2 months when I gave it to him.... The buyer of the tail shifter transmission is also in the process of doing an electric vehicle conversion, so he asked a bunch of questions about my project.

I've been noticing that my auxiliary battery seems to drop in voltage significantly as I commute to work. After some experimentation today, I found that under a moderate load of 8 amps or so, the DC-DC eventually stops working and fails to charge the 12V battery. I was misled a few times because when I turn off the key for awhile and turn it back on, the DC-DC starts working again for about 30 seconds before stopping.

At light loads the DC-DC keeps working, so I can charge the 12V battery if I just turn on the key (to close the DC-DC relay), but don't turn on any accessories or start driving (thereby pulling current from the motor controller). For the moment, I charge the main pack at work and turn on the key for about an hour before I have to drive home to recharge the 12V battery.

Here are some current values I measured coming from the 12V battery (without the DC-DC in operation) from various accessory loads:

  • key off - 10 mA
  • key on (motor controller idle) - 700 mA
  • parking brake flashing light - pulses of 300 mA
  • parking lights - 3.7 amps
  • parking lights and headlights - 9.4 amps
  • parking, headlights and fog lights - 17.3 amps
  • left and right turn signals - pulses of 3.3 amps
  • backup lights - 3.1 amps
  • parking, headlights and backup lights - 12.3 amps
  • brake lights - 3.3 amps
  • CD player - 1.0 amps
  • climate control fan (low) - 2.8 amps
  • climate control fan (med) - 4.5 amps
  • climate control fan (high) - 6.7 amps
  • defroster (hair dryer) relay - 200 mA
As you might suspect, I'm irked by the DC-DC still not working, but it's probably my own doing given the modifications I made to the controller. I guess it's back to taking the thing apart and adding an increasing load to see when it fails. Argh.
Posted by at

1 comment:

Frank said...

I'm not sure what you DC/DC is designed for, but mine started out life as an RV auxiliary power supply.

So I came up with a clever scheme (yet to be implemented) that would use the Zivan's "all done charging" output to flip a DPDT relay over from the traction pack to 120 VAC from the charge cord. I.e. when the traction pack is done charging it tops up the auxiliary battery.

January 28, 2008 at 6:37 PM

Post a Comment

Subscribe to: Post Comments (Atom)