Thursday, November 2, 2017

The little things

I think it is kind of funny how most of the time I have spent on this is figuring out how I can use what is available (junk yard, on line, make easily, local hardware store, etc.) to do what I want. There used to be a machinist in town who would do small jobs. Even though he was expensive, it was still way cheaper than buying a lathe and milling machine. Plus they came out better with a professional at the helm. But he is no longer in town.


I was surprised how important a parking brake is. Adjusting the parking brake is equally important!
 

Above is a photo of two "barrel adjusters" for bicycle cable brakes and one I made for the parking brake adjust. The brake cable for the parking brake is huge! Even bigger than a motorcycle cable. So I had to make my own barrel adjuster. Between trips to the motorcycle shop, automotive store and hardware store, plus the time to figure out how and what to use out I have to have a few hours into a two dollar part.  All that for what is essentially a slot in a nut and bolt. Perhaps it is time for a home lathe and a milling machine?!

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Monday, October 16, 2017

Q and A



I have had some questions on various parts of the ghost, so I thought I would give some answers.

Relay, Main Contactor:

For some reason these are open air contactors. The new one is sealed. I do not know why they are called contactors when they are just big relays!

These can be completely disassembled with a screwdriver. Normally I wouldn't want to take these apart, but I was having problems and had nothing to loose by attempting a fix. What is odd is that the relay still opened and closed. And even at 500 amps it had near zero voltage across the contacts (after I cleaned it up). There may have been a partial short in the coil that was causing an over current fault. I am told this has been known to happen.


Battery Charge Voltage

I am using Lithium Iron Phosphate batteries. These are very similar to Lithium Ion, but are much safer with the trade off of lower cost and slightly lower energy density. Because of the different chemistry, they will have a different charge and discharge profile from LiIon. Over time, the manufacture has learned that for maximum life, the final charge voltage is somewhat less than the 4.2 volts originally specified.

There are all sorts of equations and trade-offs in battery charging.
Charge/Discharge Rate Vs. Battery life and energy per charge
Final charge voltage Vs. Energy per charge
Energy per charge Vs. Lifetime Energy

And I am sure there are more. These are from an outfit in China and the data they have supplied is relatively sparse. As with much of the product from China, buyer beware.

I just found this on AEVA forums:


I have 4 in parallel and 30 in series for roughly 16 kWh of energy. This should be a final charge voltage of 108 volts. That is what I recall measuring a few weeks ago, so it looks good now. I'll have to double check to be sure.

For comparison, a Nissan leaf with a 24 kWh battery pack has 84 miles of range. I was getting over 100 miles range with a smaller battery size of 16 kWh. The aerodynamic improvements of the body should lower the power requirements when cruising. New batteries have higher energy density and will save weight. Plus I have room for a larger battery pack.



Chain Noise and Alternatives

Part of the problem with the chain noise (most or all?) has to do with the regenerative braking (the motor pumps energy back into the batteries when braking). The regen moves the chain tension from the top of the sprocket-chain to the bottom of the sprocket chain. There is a chain tensioner on the bottom for normal driving but when the tension shifts from top to bottom appears to be what causes the noise.

I have a few ideas on how to fix this, but time and money is limited. So for now it is good enough. I am open to ideas, even though I am unlikely to use them any time soon. Could adding a chain tensioner to the top part of the chain help?

Update on progress

Moving slowly. Adding attachment points for panels. Driving around every weekend. So far, so good. Just taking longer than I would like. :-)




Tuesday, September 26, 2017

Ready for the Body

Looks like I am ready to attach the body now!

The batteries appear to be weakening. Perhaps due to age, but the root cause of the weakening seems to have its roots in the fact (OK, more my opinion) that  these batteries are made by a bunch backyard yahoos. Originally they were supposed to be charged to 4.2 volts. Later, evidently after learning this caused reliability problems, they lowered the peak charge voltage. Too late for me. Additionally I have low confidence in the manufacturing standards this company used. In any case, they still work reasonably well, so I have no plans to change them (for now).

I am not 100% happy with the chain noise, but someone once said:
             "do not let the perfect be the enemy of the good" or something close!

The electrical is now flawless! No errors, everything works great! So with a little chain noise, I now have to finish the body panels! (yes, that is a lot of explanation points. I feel like Elaine in an episode of Seinfeld)

more to come.......

Monday, September 18, 2017

Still a little more to do

Cleaning up the master relay (contractor) did not fix the problem. So I wired in a bunch of monitorpoints and ran some more test drives.  The voltage across the relay is very low, and all the drop seems to be coming from the batteries. Nothing looks abnormal, yet the codes persist.
I must have not cleaned the master relay good enough. I was originally afraid to take it completely apart, because it seemed like it would not go back together. But with nothing to loose, I took it down to the bare bones.  It looked like one side of the contactor was still having problems. I cleaned everything up again and, to my surprise, it all went back together with no left over parts! It looked like this was the problem, but a test drive showed the same error codes.
I went through the electrical system again but still nothing was obviously wrong. Everything pointed to the relay, but the relay did turn on and off and looked good. Plus there was almost no drop across the relay even at 500 amps. I thought about buying a new relay, so I gave myself a few days to think about it before spending money on something that might not fix the problem.

I decided on a new sealed relay from a different manufacture. A week later I installed it and ...... no more codes ..... so far!

 I took the Ghost out for a long drive but the battery voltage was falling fast.It fell so fast I had to have Mary come by with the truck and tow me over to a friends house for a quick charge. But the good news is that I think I know why the battery voltage was dropping so fast. It looks like the charger was not set right. So I have reset the charger and reprogrammed the BMS and will test it again this weekend. If this fixes it, the body goes on!

One by one these problems are being fixed!




Monday, August 7, 2017

On the Road Again!

Greetings, Avian Motors Enthusiasts (and random people I subject to my emails),

I took a long drive in the Ghost this weekend. Still working out the bugs before I put the body on. I got two error codes from the motor controller during the trip and had to turn the vehicle off and on to start it back up. What is this, Microsoft? At one point I thought I smelled some electrical. Plus the battery voltage seemed to drop more than expected at high currents under acceleration.

I got it back home and worked through the debug process. The codes had to do with over voltage and the main relay welding. At first it seemed I thought the batteries might be getting old and the series resistance/impedance might be the problem. Then it looked like the main disconnect. But the master relay was hot, very hot. This wasn't right. I took it apart and there was a small nut in the contacts. This failure matches all the symptoms!

I cleaned up the master relay and put everything back together. That was yesterday, Sunday. So I will have to wait until next weekend  will conduct more tests. I am optimistic that I am getting down to the smaller problems now. Hopefully I will have things up to par within a few weeks and can put the body on.

I think what happened is that I dropped the nut while bolting in the main contactor. This is in a box in a very tight place with little room to move your fingers. I suspect I thought the nut dropped on the floor and I just grabbed another nut as a replacement. After rattling around inside the main relay box, it eventually got lodged in the relay. This is a big relay that can handle 500amps.I also changed the way the box mounts to make it easier to get at.

Photos soon!

Sunday, April 23, 2017

I forgot about this blog! If anyone reads this, please let me know.

Quick update:
1) Rev 3 almost complete
2) will be  a retro style with reference to the Rolls Royce Silver Ghost that I always liked.
3) Aluminum airplane style nose, wood/fiberglass body pannels and aluminum tail.

I know this is taking me a long time to finish. Next blog: Mistakes were made!