Wednesday, June 25, 2008

Revisiting the Controller System

Things have been changing quickly in the EV world these days. I was looking at the new line of motor controllers from Logisystems. They seem to have similar characteristics of Curtis controllers, but at a much cheaper price.

I've already put down $2250 for the holistic EV system from Belktronix. This system contains pretty much everything you need including controller, charger, contactor, potbox, battery balancer and DC-DC converter.

There are many good things about the Belktronix system:

  • The tech support is excellent
  • The system contains low-voltage protection circuitry to prevent hurting your batteries
  • The potbox is optically based so that there is no resistive potentiometer to wear out
  • Everything is designed to work together holistically so that you don't have compatibility issues between parts
  • The price is excellent for what you get. I can't piece together a cheaper system

There are also a few downsides to the Belktronix system that I've pondered over the past week:
  • There's only one person making these systems which can be problematic if that person wins the lottery and moves to Tahiti (or gets hit by a truck)
  • The battery balancing system is very similar to the regulators put out by Rich Rudman at Manzanita Micro. They work, but they require a lot of wiring and need heavy duty heat-dissipating resistors which may put out 60 watts of heat apiece.
  • Parts of the system are powered off the first two 12V traction batteries, which has generally been frowned upon in the EV community as it tends to lead to battery imbalances.
  • All the pieces aren't really interchangeable with similar pieces available on the market. That is, you can't just replace the controller with a Zilla or change your potbox.
I priced out a system that uses widely available EV parts from several suppliers that includes the following:
  • Logisystems 144V 550 amp controller
  • 12 Soneil 1214S 7amp individual battery chargers (balancing implicit in the process)
  • Albright SW200 contactor
  • PB-6 potbox
  • IOTA DLS-45 DC-DC converter
The above parts come out to $350 more than the Belktronix system. The battery charging system contains less wiring and doesn't have heat-dissipating resistors. The Logisystems controller is a similar form factor to several Curtis and Kelly controllers, making them somewhat interchangeable and upgradeable.

While I'm still sticking with the Belktronix system for this version of the vehicle, there are many things to ponder for the next version as improvements. We'll see what issues come up with the Belktronix system. Next time around, I'll look at how to gain the advantages of the Belktronix system while sill retaining the off-the-shelf components of standard EV parts.


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