Friday, March 12, 2010

Some Tests

Though I haven't heard back from the distributor of the batteries yet about the discharge capacity, I feel safe in saying that my original belief was true. These batteries are capable of putting out the current I'm asking them to dump. A kind reader of the blog pointed me to a great page at EV Works that detailed some tests they performed on the Sky Energy and Thunder Sky batteries. The tests reveal many things, but key among them is the discharge potential. So at this point, I feel safe saying the batteries are not the issue.

I took some measurements on the HEPI pedal yesterday. There are 6 wires coming from the pedal. One is a 5 volt power (Red), one is ground (Black), and the others are signal wires. The voltage on the signal wires changes as the pedal is depressed. Here's what I found.

In the up, or "not depressed" position
Red - 4.94 V
Green - 1.58 V
White - 4.94 V
Orange - .792 V

Fully depressed position
Red - 4.94 V
Green - 4.83 V
White - 4.94 V
Orange - 4.33 V

It would seem that the White wire is also just providing power. Truthfully, I don't know if the differences in these readings has any significance, but I find it interesting that neither the Green nor Orange wire come up to the full 4.94 Volts when depressed. But even more interesting is the fact that the Green and Orange wire don't match. My understanding is that the pedal has two sensors in it for redundancy. I would think that would mean the voltage they put out should match, but that's just an assumption. I'll be sending this data off to the distributor I bought the pedal from to ask for help and assistance.

The Zilla controller has the ability to put out a stream of data for diagnostic acquisition or DAQ. All the data is displayed in Hex format, at the rate of 10 lines per second. I connected my MacBook to the Zilla, set everything up and then captured some data during a full, pedal to the floor, acceleration. Once I had the data, I imported it into a spread sheet and converted all the Hex to decimal. What I found backed up what I was experiencing. Under full acceleration the current across the motor's armature peaked at 150 amps.

So, what did we learn from all this? I think all I really learned was that the Zilla is indeed sending a fraction of the current to the motor that it's capable of. And it re-enforces my previous beliefs that it's either the pedal, or the Zilla. Now that I have some data, it's time to get the manufacturers and distributors involved.

By the way, thanks to all that have been offering help and advice! It's truly appreciated.

2 comments:

htfiles said...

See: http://www.ngcontrols.com/PDFs/HEPA_Installation.pdf

Looks like the second hall sensor may not come up to full voltage by design.

Can you pull the pins on the 2nd hall to isolate and test operation on the first hall sensor to verify that it's working properly?

If your hairball is only reading the second hall, perhaps you're only getting ~50% of full throttle input.

If the Zilla will operate on one hall signal, that might be worth a try.

Jack Rickard said...

No, normally the two sensors provide DIFFERENT voltages. This is to allow a microprocessor to do a SANITY CHECK on accelerator pedal. In the event of shorts or loss of ground. Both voltages will change, but they will always be different. In this way, you can detect problems such as loss of ground (both voltages at supply voltage) or shorts (the two outputs shorted together). This is a safety feature. We don't have a good way of taking advantage of it with our controllers. You could do some sort of sanity check with an Arduino or something. But in an electric car, they are unlikely to runaway. You can always turn the key off or hit your emergency shutoff.

Bottom line, your HEPA pedal is working perfectly.