Safety Issues

While at EVCCON, I spent a good deal of time looking at and admiring all the conversion, and trying to get ideas for how I might improve the Z3.  Among the things that made an impression on me was the fact that the constructors of virtually all the EVs had made a great deal of effort to make the car's motor bays "touch safe."  The Illuminati team mentioned that during the X-Prize contest, they were required to shows that all the compartments that held batteries and electronics were also "wrench safe."  Meaning that you could throw a wrench into any compartment or area in the car and there was no danger of a short or explosion. 

It became clear to me that I'd fallen short in this area.  I never really considered putting much effort into making the z3 "touch safe" or "wrench safe" figuring I was the only one in that area, and I know what's safe and what isn't so why does it matter?  But as I watched all these people milling around my car, I found myself with an unusually high level of anxiety worrying about someone hurting them self.  Several times people leaned over the motor and battery compartment to get a close look at something, only to have their EVCCON lanyard drag across the top of the cells.  In fact a local boy came in to look at the neat cars.  I explained to him not to touch anything for safety reasons, but then watched him like a hawk to be sure he was safe. 

I realized at that time that not only would making the whole motor compartment touch safe be a good idea, it was essential.  Here's the thing...  I never anticipated that the car would draw as much attention as it does.  I never envisioned that I'd be taking it to car shows and there would be strange people so interested in it and getting so close to it to inspect it.  Imagine what the news media (especially Fox News) would say if some hapless person were accidentally injured, or worse, by an electric car at some car show.  In one fell swoop, I'd be responsible for not only injuring or perhaps killing some poor soul, but the EV movement as well! 

At the public car show the last day of the conference, one of the attendees, David Hrivnak, made a point of pulling me aside and asking me what I intended to do about the safety issues.  Not "are you thinking about doing something?", but "what are you going to do?"  David clearly recognized the risks I was exposed to and the implications, and had the courage to bring it to me.  By that time I had already got it.  I was absolutely on the same page as David.  I understood what was at stake and the imperative to resolve the safety concerns he, and by that time, I had.  Thanks again David, I'm very grateful.

I had been looking at the other cars to see which ideas of theirs I could steal.  What I saw was basically two ways of covering the batteries,  terminal and high voltage connections, if they were in an area where they were exposed.  Either they were sealed in a custom built box, or they were simply covered with plastic.  For anyone who's seen the Z3 or the pictures of it, you know there is no room to redo things in order to incorporate battery boxes.  That meant I was going to need to figure out how to simply cover the terminals of the batteries.  In addition, I needed to figure out how to cover the electrics bay where the controller and contactor are.  That bay is the only placed where the positive terminal is exposed that has full pack voltage. 

After a little research I learned that the best material was probably Lexan, so I purchased some from the local hardware store and started measuring and cutting.  Cutting Lexan is not too difficult.  There are special blades available to cut it, or you can cut it with a thin blade, fine toothed saw.  When you cut it with a blade, you simply score the same line 15 or 20 times and then bend the plastic to kind of tear it through the rest of the way. 

I knew the front batteries were going to be the most difficult to cover.  It looks easy enough, but the clearance between the front corner of the batteries and the hood is as little as 1/2".  So to place a piece of Lexan on top of the terminals and run it straight to the edge of the batteries would certainly be hit by the hood once it was shut.  It would require careful cutting and measuring to make it fit.  Since you can't actually see the space once the hood is closed, I used Play Dough to figure out the clearances.  I simply shaped a chunk of it to the size I needed and laid it on the area where I thought the battery cover and the hood touch. Then I shut and opened the hood and inspected the Play Dough.  You can easily see where it's been crushed too thin, or even pierced.  That's where I needed to trim and do some more fitting.

Ultimately I found I needed to bend the front edges of the cover to clear the hood.  I found a piece of scrap Lexan, and sicked my heat gun on it.  I used the low setting thinking that I didn't want to heat it too fast and potentially over melt or set the piece on fire.  It worked pretty well but I found that when I tried to bend a longer edge, the plastic started to show bubbles inside by the time it finally started to wilt.  I tried the higher temperature and that turned out to work much better.  First, it was faster, but second since the plastic was exposed to the heat for a much shorter period of time, so there was no time for those bubbles to appear.  So, higher heat yielded a much cleaner looking bend.

In the detail shot you can see what I mean about the plastic bubbling under the heat gun.  Structurally, it seems fine, but cosmetically it's kind of ugly.  You can also see the slots that I cut into the plastic and the clips I'm using to hold the piece in place.  These clips are an assembly of two channel clips used to hold a mirror up to a wall.  This works fine, but admittedly it's ugly.  I'd love to have come up with a better way to hold this cover down, but this was the best thing I could think of.  I also drilled little 3/32" holes in the Lexan next to each of the positive terminals.  This way I can stick the probe of my multi-meter through the plastic to measure any one or group of batteries I want.

On the larger set of batteries I used D-hooks mounted to the aluminum frame and Velcro straps to hold the piece down in place. Again, not the best looking solution.  You can see that the plastic follows the curve of the batteries nicely.  In the detail shot, you can see that I was able to shape the plastic to accommodate the 2/0 cable coming off the pack, and turn the corner down just a bit to make it less lethal.  I used high heat to make these bends; notice the difference in the plastic from the first bends I made.  It looks much better.

The cover over the electrics bay took a lot more fiddling and cutting to get it just right.  It rests nicely in the grove just below the cushy part of the rubber that seals the area from the elements when the hood is closed.  I made a template out of cardboard and then trimmed the plastic to shape.  As it happened, I'd run out of Lexan and the only sheets at the store were either too small or way too big (and expensive).  So I used an acrylic sheet instead.  I can see why people said that Lexan is better.  Acrylic is much more prone to snapping, cracking and chipping.  I was able to get it done, but it would have been way easier with Lexan. 

There is still one more safety concern I need to address, and that's an emergency cut off switch.  You may remember that I had the big red slap switch under the hood, but there were two problems with that.  One, I had no way of actually slapping it in the event of an emergency, that is if I were in the car driving it, and two, it melted.  At some point, enough current went through it that one of the internal contact points melted.  You can see pictures of that from a couple posts ago if you wish.  To replace it, I got this unit:

This needs to be mounted either in the cabin so that the driver can reach it while moving, or I need to rig up some way of actuating it from in the cabin.  I'm thinking that a push/pull cable mounted to the handle should work well.  The questions remaining are, where do I mount the switch and where and how do I mount the cable?  As of now, I have no idea about either.

Apparently Late Night Math is Not My Strong Suit

Lots done today. Let's take a look at some of it.


This is the new location for the shunt. It's at the front right corner of the back battery rack. I had to cut and re-crimp a couple cables to get them the right length, but it worked out well.


Just to the left of that is the emergency breaker, or battery disconnect. I had thought that I'd mount it dead center on the back rack, but the cable for the positive feed to the contactor didn't reach the extra 2 inches. The symmetry in the engine bay will be off, which is kind of too bad.


Here's a shot of the new throttle assembly set up, installed and tested. It's difficult to make out what's what here, so I'll take another once the batteries are in. But you can see the cable anchor in the right side of the picture, and the pedal assembly just to the left of center.


And last we have a shot of the whole assembly mounted in place with the back row of batteries resting in their place as well. There's a bit more tie down work to do, then I can install the front row.

In addition to all that, I also got a few other things done. I re-installed the tray under the motor that holds the fan for the motor as well as the box that contains the new vacuum pump. I ran all the necessary power lines to the items and the vacuum line from the pump to the reservoir. I also installed the new cross brace that stiffens the chassis.

I don't think I mentioned it before, but the fellow that owned the car before me clearly ran it up on a curb or something. There was a bit of damage under the car, mostly cosmetic. However, the original cross brace took most of the abuse, and was a bit twisted. It still fit in place, but was very difficult to bolt in and was under stress once in place. The new one slipped on so easy, it was a pleasure bolting it on the car.

Which brings me to the odd title of this post. You may remember that I had 31 batteries up front in the original configuration. During the rework, I drew up multiple designs trying to get the cleanest install of all the batteries in as tidy a package as I could. Well one night, very late I came up with this design. It is the cleanest by far and I'm very pleased with it. There's just one nagging problem. There are 12 batteries in the front row, and then two rows of 9 in the back rack. In most worlds, that adds up to 30. Apparently for me, in the middle of the night, that sometimes equals 31.

For the life of me, I don't know why I never added them up again, but I didn't. (This is the part where you all laugh at me.) After standing and shaking my head in disbelief, I started laughing at myself. But eventually I started thinking about it objectively. This really was the cleanest design I'd come up with, and it's going to look great. I don't think I want to change it, or would have if I realized it at the time. There is room for one more battery in the trunk box. It will make the end of the box a bit cramped, and I'll have to redo some of the lines in there, but I think it's going to be worth it in the long run.

The worst thing is that it will delay my relaunch by a day or so.

Odds & Ends Part XIII

Lots to report today, but sadly no pictures. You'll just have to imagine how stunning the work is.

I finished the straps and mounting system that will hold the batteries in the rack that will be mounted over the motor. I still need to figure out how I'm going to get some brackets around the batteries to keep them compressed. I had it all worked out in my mind how I'd do it, but once I started working with the rack, I realized what I had in mind just won't work. Funny how that happens, you tend to not see in your mind's eye how different pieces will interfere with each other until you start assembly. Anyway, it shouldn't be to hard to sort it out, I'll just have to come up with something different.

Once I had all that done, I placed the rack in it's space so I could start figuring out how I was going to place some of the elements that have moved. I need to find new locations for the Link-10's shunt, the emergency disconnect, the bracket to hold the traction pack fuse and the anchor for the throttle cable. You may remember in a previous post I built the mount for the throttle pedal, but I hadn't built anything to hold the assembly that anchors the cable.

The shunt's new home was easy enough. It's going to be roughly in the same location it was, but I had to cut a small piece of angle aluminum to mount it to. Just out of dumb luck one of the new braces used to hold down the batteries was in the perfect spot to anchor the throttle cable. So that's sorted. Last I had to build a small bracket to hold the emergency disconnect switch on the front the new tray. I cut, drilled and had the whole thing mounted, and it looked great. Then I screwed on the big red knob that you slap to break the connection, and realized that I wouldn't be able to slap it down because it ran into the tray. I'm not sure if I'm just working too fast, or why I'm making such silly mistakes. Fortunately, it will be easy to fix that as well.

In addition I reconnected the lines to the reverse switch in the transmission. I really wish I had the proper connector to connect it up. I found the connector online and numerous places that sell it. It's about $4.00 or so, and it's made by Tyco. Would you believe every place that I could find it, it was out of stock, and had a lead time of at least 4 months. Apparently Tyco makes one batch a year and when they're gone, you wait.

I also ran an auxiliary 12 vdc line to the back of the car. This line is switched with the ignition. One of the things I found in the 2 months I was driving the car was that if the car sat idle for 24 hours, the 12 volt system would manage to drain about 1 kWh out of the traction pack. There are only a few things actually drawing power when the car is off, and they are drawing tiny amounts. The one thing that is on, however, are the DC to DC converters. They are providing 13.2 vdc to the car, as well as the SLI battery.

I know that you can leave a trickle charge on a lead acid battery forever, and it will always draw just a bit of power. I don't think they'll draw 1 kWh in 24 hours, but something is. I think it's either the DC to DC converters just using it up because they are inefficient, or the SLI battery is drawing it off. I'm just not sure, so I'm going to run some experiments. I'll disconnect each, one at a time, and watch what happens to the traction pack. When the SLI battery is disconnected, I'll look to see what happens to the traction pack and then I'll disconnect the DC to DC converters and see what happens to the SLI battery. If one of them is the culprit, and there appears to be no adverse affects to disconnecting it when the car is off, I'll use that new 12 vdc line to run a separate contactor that will disconnect the appropriate component when the car isn't running.

Lets see, what else is there to report. Oh, I also cut some plate aluminum to fit over the ends of the batteries in the front tray. This will make it easier to clamp them down and compress them. I still have to build that apparatus though.

Ok, that's it for today. Stay tuned because I'll have lots more to report tomorrow and I'll have some pictures up to show the progress.

Fitting Details

Over the past few days I've come to realize that it's time to solve some of the problems that have been nagging me for months. There was only one way to solve them, and that was through careful planning, measuring and fitting. Boring, maybe; necessary, absolutely.

There are three components to the high voltage lines that I need to find a home for. There's the rather large push button kill switch. If things go horribly wrong, or I need to work on the car and I want the battery pack disengaged, that switch will allow me to take care of that. There's the 500 amp shunt for the instrumentation. It allows the Link 10 meter to monitor the pack without "seeing" the full amperage, which would fry the meter. Last, there's the fuse. And that thing is big. It's about 5 inches long and the diameter of a half dollar coin.

I had originally thought that I'd put each of those in the trunk near the back battery box, but after thinking about it, I realized that would be kind of stupid. All 48 of the batteries will be wired in series, starting at one end (the trunk) and moving to the front. In order to put the disconnect and the shunt in the trunk, I'd have to run a line from the negative terminal up front all the way back to the trunk for those components, and then run it back up to the front again to the controller. A better answer was to find a place up front.

I put all the battery trays and boxes in place, just looking for extra space somewhere around them. While doing that, I remembered that the way the new batteries will be laid out in the two small trays means there will be some space left over on the ends. It had never occurred to me that I might use that space in a tray for something other than a battery, but when I got to looking, I realized it would work just fine for the disconnect switch. Some quick fabrication, and I had it mounted. I still need to locate the shunt, but it's small. The fuse can still go in back because it only needs to be inline on the positive side.

Can't miss that sucker!

On top of that, I found a location for the throttle pedal. The pedal is meant to be a direct replacement for the pedal that came with the car. But Trust me, if you saw the new pedal and the car's pedal assembly, you'd say the same thing I did, "Oh, there's no way..." Well, not without taking the whole assembly out of the car, cutting it up, welding new bits to it at odd angles and refitting it. Well, I realized that extra space in the second box may work out for me, and it did.


Obviously it's not mounted up yet, just propped into place. But you can see that it fits nicely in the space, and you can see the car's existing throttle cable just peeking over the corner of the tray is in perfect alignment to mount to the pedal. Basically what I'll do is lop off the pedal part, and mount a swivel harness to the remaining stump. When I press on the car's accelerator pedal, it will pull that cable and activate the new throttle assembly. How great is that!? Well, it excited me.