DIY Electric Car Forums banner

C-Rex: Notailpipe's Honda CRX Build

119K views 251 replies 32 participants last post by  notailpipe 
#1 ·
Well, with three and a half estimated months left to finish my build, it’s about time I start a build thread, complete with pictures for the eye-candy addicts. :)

Here’s my car, a 1990 Honda CRX. Ain’t he a gem? Yes, I said he. As my wife always says, he is a stick shift. I got him last summer, and we named him C-Rex.



When we got him, he had 3” lowering springs on him and it would bottom out on every bump in the road. I replaced those with a 1 ½” lowering, with increased spring stiffness performance coils for better handling (and anticipating a slightly heavier endcar, even with lithiums). I also found a nice set of Enkei rims that are just a touch scuffed up – when the conversion’s finished I plan to repaint them pearl silver. The rest of the car will also be receiving a paint job after the electric conversion is finished, new windshield, new rubber moldings, etc. What, you don’t like cancerous sunspots on the top of your roof?

Although this is a build thread and not a blog, people often ask me why I am bothering with all this, so I thought I’d say it once. I’m converting my car because I want the U.S. to be less reliant on foreign oil. Will my car make a difference? I don’t kid myself. But slowly the country is turning its eyes to electric and I hope to be one of the early users. Additionally, I was born and raised in the Motor City, and cars are a huge part of my life. Being an electrical engineer as well, it’s the perfect blend of interests to make a great (and expensive) hobby. My goal for the car is to be fast, fun to drive, practical range, and intuitive to use. I want any of my friends to be able to borrow the car and not have to explain “well, just click that lever three times to prime the pump… and you can’t use the heat while you’re using valet mode…” or whatever. The car HAS to have an intuitive OEM look and feel or the American public will never want one.

But they will want a C-Rex…
 
See less See more
1
#222 ·
More on the build...

I worked on the switch for my heater for a little bit. Basically a huge sinkhole of time. I used a solid-state relay (SSR) from eBay that looked rated for my application. 250VDC loads, up to 40A. Measurements had previously shown my ceramic heater to use about 15A at 144VDC. So it should've worked fine.



Wired it all up and it worked for about ten seconds before dying. I have spent the last four weeks trying to get my money back from these dishonest chinese guys and to no avail. They strung me along for a week asking for my circuit diagram as a prerequisite for getting a refund (when used in an as-speced system, I don't think I owe anybody any of my IP of any sort when their product fails :mad:) Anyway, then they suckered me into mailing it to them before they'd refund it. So I'm probably out even more money... so lesson is don't waste your time with this cheap chinese junk...

I next got involved with a thread here on DIYev.com about what is really involved to switch these ceramic heating elements. Turns out that being such a heavy DC current is extremely difficult to break the current and you need something designed just for that. Some even use a Kilovac just for the heater. Here's the thread if you want to read more detail, but since everyone was just speculating, I did a simple test with a light switch from the hardware store and the result was crackles, smoke, fire, and a racing heartbeat.



After that, dtbaker recommended the switching kit that KTA-ev sells. It's a little bit pricey, but not too bad. I wish I could get my time/money wasted back from that POS SSR and buy something right in the first place. So I've ordered that and it should arrive this weekend, so I can finally button up this particular step.
 
#223 ·
The next step was to soundproof and insulate the hole in the floor. For those that forgot, I cut a hole where a normal car rear seat would go (CRX's only had two seats and a little storage pocket there). The goal for this step was largely just to reduce road noise coming into the cabin, but a secondary goal was to protect the batteries from any road mist/slush/etc.

The first thing I did was coat the sides of the batteries with this stuff I got at Lowes called Peel 'n Seal. It is made for fixing roofing problems, but I got the idea from many car audio forums that suggest it as a cheap alternative to more expensive sound proofing, as it has good sound dampening properties. I've heard that "Quick Roof" is basically the same thing but tends to be only at Home Depot.



Anyway, sticking it around the battery box would be the first line of defense at blocking road sound. In the process of doing this I learned there is basically sound deadening, which means the sound waves are turned into heat by the medium, and then there's sound absorption, more like foam materials, that just creates lots of obstructions for the sound to get through. Deadening can block much sound in a small thickness but the best overall was recommended to do some of both.

The one downside to this stuff is I read on a hot day it will give off asphalt fumes that will take several days to air out of your car. I figured I can get around this problem by putting it on the outside of the car, like underneath, so that the fumes are never inside the car. My sound absorption material I think will block most of the smell too. So, when summer comes, we'll see. :cool:

Step one was wrapping the outside perimeter of the battery box with the Peel 'n Seal, as well as the bottom surface of the sheet metal floor of the car.



When all of it was applied, I went over the whole layer with my heat gun and got it pretty hot. This melted the asphalt/sticky-rubber surface to ensure that it oozed into cracks and really was stuck on there good. That stuff ain't goin nowhere.



Here you can see the view from inside the car. I stuck the PNS between the sheet metal of the car and the side of the batteries. This helps contain the sound but also gives me a backing for the second line of road noise defense, sound absorber.



Finally, just in case I didn't do an underbelly plastic cover under the car (I eventually did), I didn't want drivers behind me to see a glaring shiny foil box under the car. So all the PNS and any uncovered slivers of battery get blasted with black paint.

 
#224 ·
Next step was my sound absorber. I used "Great Stuff" expanding foam to fill any gaps that I didn't get with PNS. This stuff is also a great sound absorber, they use it in door cracks in houses to keep out noise (as well as heat).



I next bolted down a sheet of plexiglass cut to fit over the top of the battery box. I've got rubber weatherstripping around the bottom of the plastic which forms a tight fit against the box. I figured the only part of the batteries that sound could still come through was up through the vertical channels between batteries, since I didn't PNS the box bottom. So any sound that works its way into the battery terminal area is further dampened by the plexiglass top and weatherstipping sides. Lastly, on top of the plexiglass, before the rear seat cover goes down, I put down a layer of carpet padding which further absorbs sound.

Note the cool warning stickers from eBay again. :)



After carpet padding is put down and then the seat cover, it looks OEM again (but can be lifted to check BMS indicator lights). Batteries? What batteries! ;)



We took a ride in the car later and it was very quiet. Mission accomplished!
 
#226 ·
Thanks. Yeah, that was the main reason for the low ground clearance, but the Integra springs gave me the clearance I needed. Actually, I forget if I wrote about that but I put some aftermarket Tein springs for a DC Integra (94-01) on there because they have a higher spring rate, it boosted me about 2" in the back. :cool:

That wood was a spacer to hold up the rear trunk floor so I can still put groceries or my puppy back there. :) I got rid of the spare tire.

Soon that wood spacer will go away because I'm going to mount my vacuum pump in a sealed enclosure back there. I'll use the box to also hold up the floor instead. I'm also going to put a travel kit of like useful tools back there in case I need to diagnose anything on the road (screwdriver, multimeter, Zilla error code list and diagnostic palmpilot, etc.)
 
#227 ·
Many thanks for the excellent update and pictures of your Honda EV and congratulations on making it before the deadline.
I wish that the Icelandic authorities would introduce some similar tax refund programs for EV conversions. Considering that we have abundance of clean electric power from hydroelectric and geothermal power stations this should be a no brainer.
Agust
 
#228 ·
Yeah, that's a bummer. I've read a lot about your country's power generation. Usually I think of tax credits/subsidies as something the government has to nudge in the direction it wants. Since cheap clean power is so prevalent in Iceland, maybe they figure it doesn't need any help and market forces will steer it there on its own?
 
#230 ·
I've seen Rex's at crxcommunity.com with 17's and bigger... not my style. Plus has a killer effect on watt-hours/mile at high speeds due to the extra rotating mass. I think 15s/16s look good, but got a good deal on the 15s I found on CL so that kinda settled the issue for me. :cool:

In other news, that seller who sold me that crappy SSR off eBay not only wasted my time and money with his cheap POS product but also duped me into sending it back to him (on my own dime) to get the refund. Now eBay says it's past the time I can file a claim... :mad: arrrrggghh! I am done trying to save a buck on the junk coming out of that country. SSR was junk, throttle box was junk, only the batteries have been good so far... you get what you pay for.
 
#231 ·
I've seen Rex's at crxcommunity.com with 17's and bigger... not my style. Plus has a killer effect on watt-hours/mile at high speeds due to the extra rotating mass. I think 15s/16s look good, but got a good deal on the 15s I found on CL so that kinda settled the issue for me. :cool:

In other news, that seller who sold me that crappy SSR off eBay not only wasted my time and money with his cheap POS product but also duped me into sending it back to him (on my own dime) to get the refund. Now eBay says it's past the time I can file a claim... :mad: arrrrggghh! I am done trying to save a buck on the junk coming out of that country. SSR was junk, throttle box was junk, only the batteries have been good so far... you get what you pay for.
Did you use vise through paypal? You can tell visa and if you claim is good enough they will get your money back. I had a guy take my money for a tranny and I had to get visa to get my money back when he never shipped it! Paypal just said "we tried to get your money back but there was nothign in his account" lol.
 
#237 ·
I'm seeing a theoretical range of about 70miles, though I haven't figured out a good way to test this without getting stranded. Theoretically I can drive down to Denver and charge overnight. :)

I need to post updates, I spent about 6 months building my EV, then 6 month hiatus from working on it/posting. I guess I did get a little burnt out...

Time to get back to it!
 
#238 ·
I'm seeing a theoretical range of about 70miles, though I haven't figured out a good way to test this without getting stranded.

you REALLY don't want to drive the pack down to its knees if you can avoid it for the long healthy life of the pack.... what I would suggest is driving 'normally' till your ah counter shows exactly 50% DOD based on your cell size, and doubling that to figure 100% ;)

i.e. what I did with 100ah cells was drive around till my CycleAnalyst showed 50ah consumed. I did this a couple times, and it came out pretty consistently between 25 and 27 miles at 50ah in my case. So I use 50 miles as a theoretical max range..... at least until the cells get old and start losing capacity.

THAT is a whole 'nother topic, and I think the only way we'll know when cells start losing capacity is when we start seeing some sag or lack of recovery with fewer miles driven.
 
#239 ·
That's precisely what I've done, is that I get roughly 35 miles down to 50%.

Now, I agree you don't want to go to ZERO-zero, but I'm using the EV Display as a SOC meter and I've got 20% charge left set as my "E" level. So if I went 70 miles, theoretically I'd still have 20% charge left at that point. Some people go lower/higher than this, but 20% is the consensus I came up with through reading.

I guess you have to determine what you're comfortable with and then use as is. For example, I designed it to make an occasional trip to Denver, but that would be its max range. I'd rather make that trip and shorten my battery life a tiny bit than think of my car as an expensive, over-engineered, grocery-getter. I'd rather it felt a little more utilitarian at the cost of lifetime.
 
#240 ·
Took the day off work and one goal for today and this weekend is to post a few updates about the car.

Update #1 is someone asked if I could send them my wiring diagram. I redrew it because I made a few edits to the old one. Figured I'd just post it here in case it benefits anyone else. Comments below the pic.



  • Attempted liberal application of fuses
  • You'll notice my DC/DC is wired to always-on. I used to have this wired off and then when I turned the key to ON it would use power from the backup battery to energize the relay for the DC/DC. I discovered that my 7.2Ah AUX battery wasn't big enough (at least for this) so if I left my car undriven for a few days, there wouldn't be enough juice to turn on the relay and the car would be unstartable. I thought about using a momentary switch to temporarily "jumpstart" the DC/DC, and get 12V going, but it was a bit ghetto since I'd have to pop the hood (true, I could put it in the car). But I learned the MTBF for these DC/DCs are like 16 years of always-on operation, so I'm just leaving mine on all the time. Sometimes I think it'd be nice to revisit this, but I might just leave it. The root problem is the DC/DC itself actually drains a few mA from the AUX battery, as well as a few leaks inside the car (clock, etc.)
  • The Kilovac contactor is obviously N.O., but I forgot to mark that.
 
#241 · (Edited)
Someone else asked about how I wired up my brake system and basically trying to understand the vacuum switches in general. I thought now's a good time to finally write up my vacuum box in more detail as well as how to adjust Square-D switches. A lot of people have these switches but there isn't much out there on how to set the hysteresis.

Everything you will need: MDF for the box, tube, pump, vacuum switch, vacuum gauge, check valve, muffler, lots of $ worth of pipe fittings and clamps from your local ACE hardware, NPT die set, pipe thread teflon paste, and some ABS pipe if you are building a reservoir (recommended, I can pump my brakes 2, sometimes 3 times before the pump kicks on again). Note I was redoing my brake system so I already had a previous reservoir built (will rebuild here).


If anyone with the same equipment wants to build the same exact box, this fits perfectly in a CRX spare tire well. :) Here's my cut list:


Build the box, glue with wood glue, brad nails are extra credit.


While that was drying, I took apart my old reservoir and found the culprit for my inability to hold a vacuum. Don't buy this crappy AutoZone "universal" check valve. In my scan of the system below, I give the part name for a good valve.


Okay, here's what we're building:


The "left end" hooks to the brake booster where your old ICE used to supply vacuum. Note that my vacuum settings are pretty low, this is because I live at high altitude and after leaving my pump on for like a minute determined the highest it could hit was about 17.5" Hg, with time to reach that exponentially higher after 16.5", so that's where I set my high limit. Low limit was at about 11.5", the lower this goes the longer you can go without the pump going on after a brake, but you don't want to go too low or sacrifice brake performance. :eek: So I just found a good tradeoff in that the pump can pull it back to high level in a few seconds of pumping, and 11.5" Hg felt still pretty strong at the pedal. You'll pretty much never use the gauge for anything but setting it, since it's mounted in the box. You can always do a clear lid if you want, or mount the gauge outside the box, but I figured if I'm having brake issues, it's just a few screws to open the box and I like everything being contained in there and so I know nothing in the trunk can mess with the brake system. I listed the McMaster-Carr part numbers for the muffler, gauge, and valve on the schematic. Also note that you point the valve in the direction the pump will suck. It will be labeled, but you can always check it by sucking on one end of it (don't blow, some valves don't reliably work the other way to pressure vs. vacuum, I've found). The outlet of the pump has to come out of the box so the air has somewhere to go, so this is the part I put outside the box (since the box must be sealed). Then I ran that tube through a hole in the trunk, into a little nook behind my batteries and attached the muffler, then rolled that up in carpet padding to silence it more.

It's actually decently quiet. You can hear it when you sit in the garage and start the car - this is the most common time you hear it cause nothing else is on and there's (hopefully) not traffic in your garage. Also, the pump will always have leaked out by the time you get to it. I find the vacuum leaks so slowly I can sit for 15 minutes without hitting the brakes before it hits the low trip point and kicks on the pump. When you are driving or have the radio on slightly, you can't hear the pump. It's funny though, cause my wife and I were still shocked by how loud it *seems* but really it's because it's intermediate. For example, we make my pump go off, then started her Lexus to compare the noise and it's like her car was deafening. But we've been trained to think that's normal for a car to be that loud - so of course my car seems louder just cause the pump's not on all the time and you don't get used to it. Posting so I don't lose all this... :)
 
#242 ·
Back to the system...

Build the reservoir out of 4" ABS from a big box store. Very strong, light, cheap, and when you buy the little black ABS "glue" it's completely airtight. Drill and then tap NPT threads for barbs. Another thing I learned from my first version: never use the ABS glue compound to glue in barb threads! For one, it may not actually make a great bond with metal. For two, you'll never get it out again without breaking something. For three, you don't need it, and that's what they invented teflon paste for! You just put a little on the threads and it will (over a long time, like days/months) gel more and more. It seals well right away and the advantage of this is that when you turn on the system, any leaks will pull the teflon paste in to the holes and kinda self-heal any minor leaks. Also you run less chance of dripping ABS glue clogging a hole (had that happen too). So just use the paste. :)


Rough placement of where the parts will go in the box (as drawn in schematic):


Now I take a brief aside and mention how to adjust these Square-D vacuum switches. My exact model is a GAW9016. Others should be similar, but make sure it's a vacuum switch, not a pressure switch! I know some people have figured out how to turn a pressure switch into vacuum... power to them, but I didn't do that.

First remove the cover of the little box part. There will be a dust gasket under the cover but things in here aren't actually under vacuum. The bottom right are the N.C./N.O. switch connections, either can be made. I forget which one I used, I guess it depends on what the switch makers considered "normal." ;) Bottom left is where you adjust hysteresis. Top right ring with grooves is where we'll adjust the top vacuum point.


But first we have to hook it all up...

Here is everything connected and after I mounted the parts and lined the box with carpet padding for sound absorption. Just following the schematic I posted in the previous post. As for wiring, it's pretty simple. You have +12V coming from the Ignition signal. This wire needs to be able to carry a few (8-10) amps. Not shown but outside my box on the red wire I have an inline fuse carrier with this fuse in it. That you do want outside the box, so if it blows you can quickly check it. The other end of the pump goes to chassis ground. Anywhere in series in the circuit you insert the vacuum switch connections to break the circuit. For this part, you want to find connections on the switch that are closed, because you haven't hooked anything up and shouldn't have a vacuum yet, you want essentially the pump to be on right now. That closed connection should open when the vacuum hits the high point, which shuts off the pump. Once your circuit is hooked up you can test it with the current hysteresis points. Note that your high point may be so high your pump can't achieve it. If this happens your pump will run forever which it isn't designed to do, so if it runs more than a minute, disconnect the fuse. If it is able to achieve the level, you should see it pump up, watching the gauge climb, and then stop at some point. Then you should *not* be able to see a leak on the gauge, if there is one it should be so slow it lasts 5-10 minutes without pumping. Then sit in the car and hit the brakes a few times and it should kick on again. When this is working we can adjust it.
 
#243 ·
Once you are ready to adjust, you twist this ring with a screwdriver to set the high point. Try not to damage it too much, it can be hard to twist. I don't think you want to lubricate it though because you don't want road vibration to adjust your settings.



Then using a screwdriver, adjust the differential vacuum here. For example, if this was set to 5" Hg and your top end was 22", then it would turn off at 22" and turn back on when it dropped down to 17".



Put some more noise-absorbing carpet pad on the top, and some caulk to seal the top. (Also probably want to line the tire well with padding - these things are loud!



Put the top on and you're done! :D

 
#245 ·
1. Mine was $100, and I'm seeing similar on eBay. $75 used, $150 new. Used is fine, they are very well made.

2. It would be worth even $300 for the reliability (hence safety) plus there is a lot of value to being able to adjust the hysteresis amount. I bought one of the $35 switches you see around here that has 3" Hg of hysteresis. My pump was on/off every 2 seconds, sometimes it was even unstable, flicking on/off at like 10Hz. If you don't want your EV ridiculed, you will want more than 3" of hysteresis. Learn from my mistakes! :cool:
 
#247 ·
It's been a long time since I posted any updates, and I've been thinking about the car a lot lately so I figured it was time. I'll try to keep things short though. I've been driving the car since last December and most of the "updates" I'm posting are still things I did last year to it, just lagging far behind. The car has mostly been done except for a few minor things I'll point out later.

First of all, I wanted to post a picture of this tool that I used frequently toward the end of the conversion. I managed to live without one but once I had one any custom shapes I had to trace were so much easier. Basically you just make a template shape with the tool and then trace the shape onto the piece to cut. Pretty self-explanatory with a picture. Here's me tracing an (old) version of my brake pump solution. This was when I was testing out the Audi/VW brake pumps (loud):



Another thing that's since been added is clear plexiglass covers over all the battery packs to protect people from getting shocked and to protect the batteries from damage due to metal objects dropped on them or from liquids. Here is the rear rack, complete with stickers off eBay:



And similar for the front packs:



I also added an underbelly plastic cover underneath the car to reduce aerodynamic turbulence and drag. I templated it up with cardboard first. The holes go around the rear suspension pivot points and the slits align the underbelly pan to the rear battery box protection angle iron:



The template transferred to coroplast (would get something a little tougher next time around). Extremely slick!

 
#249 ·
Then work began on the body work and paint job. In the end we hired someone professional to do most of the work (repairing door/hail dings, sand, prime, paint) but we did a little prep work ourselves.

Taping off the car to restore the trim to OEM black (instead of sunfade black):


Door trim restored:


This picture represents everything that was wrong with the car cosmetically. Note the hugely cracked, barely intact windshield. It was already cracked several long cracks from highway rocks, but then removing/installing the dash we pressed against it several times, cracking it further. Inside, you can see the ghetto universal seat covers from Walmart. I eventually replaced these with some (expensive!) but nice looking seat covers made by a company right here in Colorado. Not sure if I have any pictures of the new one, but it's custom made by hand to stretch over a CRX seat perfectly (they sell all types of models of cars). In the end that was the way to go as I'd wasted enough time trying to put racing bucket seats or Honda Accord seats in there instead, but the seat rails never aligned and it was going to be a lot of welding. The custom covers were less work. Lastly, you can see the fading paint job, particularly on the roof.


Professional bodywork begins:


He pulled out the sheet metal where someone had backed into my rear fender panel. Unfortunately on the CRX the rear fender is one piece with the main body so you need to pull dents, you can't replace the panel alone. He was able to pull it, smooth it, and fill the rest. You can't even tell it ever happened. Amazing. :cool:






Finally, the aftermarket hood I bought is prepped and painted. This is the last picture I have of the work-in-progress painting.


That's all for tonight, I'll post some pictures soon of the final product!
 
#251 ·
looking really good!

- I used 1/8" ABS for underbelly.... very tough, and is heat-formable as well as heat-weldable and/or gluable.

- what area of eBay did you find the high voltage stickers?

- Questions: what is the name/website of the custom seat cover place? My miata has leather seats with split seams and worn bolster on drivers side. I am contemplating light race seats, but that gets pretty expensive...
 
#252 ·
I would do ABS if I did it again. I think at that time I was grossly overbudget and went for the cheapest thing. It's actually holding up pretty well, it's corrugated as you probably know. Just feels a bit cheap working with it.

Just do a search on the main page of eBay for "high voltage stickers." I just did right now and the ones I got for my battery covers and for the fuse/junction box are both on the front page of search results.

GT Covers made the seat covers. Highly recommended, and I believe they're guaranteed to fit money back for 90 days or something like that. After all the time I wasted trying to get other seats in there, it was less than an hour to just buy the custom seat covers. They're not cheap though, but worth it in time.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top