tag:blogger.com,1999:blog-65711982710269825182024-02-07T11:08:46.976-08:00KermitTheCarA car looks at 40 and a change of life.Unknownnoreply@blogger.comBlogger47125tag:blogger.com,1999:blog-6571198271026982518.post-2470300869548416262009-04-05T20:05:00.001-07:002009-04-05T22:03:58.031-07:00Inverter overhaulToday I did most of the overhaul of my motor drive. I got a surplus enclosure and am repackaging all of the guts of the drive to be more compact and more weather resistant. Here is the power stage in the new enclosure, with a pen for scale:<br /><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjiHFA45UHkIf_Zek1scbzVgNZ4mMpcBnsc9WVp1aQOES8fFaOLkYCReoMtZam3ngg7-AjeCs2ioJDtyGJREAW-LVCpmKojF7GtpQzOlmpkq7plmIQ-L2JRecTD3BhnUcNu7ZbFYFG7xD6J/s1600-h/IMG_0011.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjiHFA45UHkIf_Zek1scbzVgNZ4mMpcBnsc9WVp1aQOES8fFaOLkYCReoMtZam3ngg7-AjeCs2ioJDtyGJREAW-LVCpmKojF7GtpQzOlmpkq7plmIQ-L2JRecTD3BhnUcNu7ZbFYFG7xD6J/s400/IMG_0011.JPG" alt="" id="BLOGGER_PHOTO_ID_5321409881013095618" border="0" /></a><br />I made a crimp tool from a pair of bolt cutters for crimping the lugs onto the 4 gauge wire. It cost $20 rather than the $200 that crimp tools this size normally cost. Obviously, less engineering went into this one, but it seems to work fine.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ3fJ3ehaFvuIXuTkTmq-H-D4pJbx5d_DcsdKrIN-8dum3O3BacFNuifFiiLdCOLLFEbPq4VSFa5WhxBtlR69UK4e-Xe1vMXU5N7yQ2DXWvnRbuW7D5YmysdSlGIE9TBsl5rBX-KxcBTON/s1600-h/IMG_0015.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ3fJ3ehaFvuIXuTkTmq-H-D4pJbx5d_DcsdKrIN-8dum3O3BacFNuifFiiLdCOLLFEbPq4VSFa5WhxBtlR69UK4e-Xe1vMXU5N7yQ2DXWvnRbuW7D5YmysdSlGIE9TBsl5rBX-KxcBTON/s400/IMG_0015.JPG" alt="" id="BLOGGER_PHOTO_ID_5321409894435790946" border="0" /></a><br />Here's the drive with the gate drive circuitry in place:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV-k8SNOZpEgpDOWA6v6a9T5cBdANWppsNLDRhryD3Lzp36xwx5pG3ZPshXAmZTG7VcWQJHi-_6ppWfSkFGNql-AajlFlRfWAxgWVSi3fSkObHVzE4059vDshfRGm6C4TZcrlhELh0iwc_/s1600-h/IMG_0012.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV-k8SNOZpEgpDOWA6v6a9T5cBdANWppsNLDRhryD3Lzp36xwx5pG3ZPshXAmZTG7VcWQJHi-_6ppWfSkFGNql-AajlFlRfWAxgWVSi3fSkObHVzE4059vDshfRGm6C4TZcrlhELh0iwc_/s400/IMG_0012.JPG" alt="" id="BLOGGER_PHOTO_ID_5321409884391530978" border="0" /></a>and here it is with the control board in:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsc-T5th2jib23csL1kS0dBn1ruZ57rKVCb5F0Qwwp2Lhax7m-1yYRvVLZFdfVJbHMWuDwQvsR0B7U9xeVvdbWeGBZ9-ZRToJalHTfHSjPeahXEfzr4JW02FDkAi-0iXi5U_X1iCB5514I/s1600-h/IMG_0013.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsc-T5th2jib23csL1kS0dBn1ruZ57rKVCb5F0Qwwp2Lhax7m-1yYRvVLZFdfVJbHMWuDwQvsR0B7U9xeVvdbWeGBZ9-ZRToJalHTfHSjPeahXEfzr4JW02FDkAi-0iXi5U_X1iCB5514I/s400/IMG_0013.JPG" alt="" id="BLOGGER_PHOTO_ID_5321409883732499138" border="0" /></a>and here I've added the main DC link capacitor. I still need to wire it up.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipXju_m1ovz7rH4-ylx0M4MhVeygx9jjX4Y1tlpqGDCVAkGg4ZJ8RO95x8RD-wUUf3fwSJD-KMj6_mIk7ktsXDLhh4i8E2n1jnXC5k9-HnG63mTgK5NoMm0hN805lo11Vo0JpiDWTDCK60/s1600-h/IMG_0017.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipXju_m1ovz7rH4-ylx0M4MhVeygx9jjX4Y1tlpqGDCVAkGg4ZJ8RO95x8RD-wUUf3fwSJD-KMj6_mIk7ktsXDLhh4i8E2n1jnXC5k9-HnG63mTgK5NoMm0hN805lo11Vo0JpiDWTDCK60/s400/IMG_0017.JPG" alt="" id="BLOGGER_PHOTO_ID_5321438722394817362" border="0" /></a><br />and, finally, here is the buttoned-up box. The heat sink fins stick out the bottom. I will set the whole works on rubberized standoffs on top of the motor subframe. I also need to mount the cooling fans.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK39t-t8lhgMeBagZEzEW5EvW8kZVkJB43lY-QJBy8PnbJ65j5cbX7N-ZidbqKUtq6LGTR2_nHo9YhCKuheWKrMitYxIvrKovSIxXS3wlukaCy1SNTU8h3nx8F4S5lZAIlc5_dRXWc8_RP/s1600-h/IMG_0014.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 300px; height: 400px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiK39t-t8lhgMeBagZEzEW5EvW8kZVkJB43lY-QJBy8PnbJ65j5cbX7N-ZidbqKUtq6LGTR2_nHo9YhCKuheWKrMitYxIvrKovSIxXS3wlukaCy1SNTU8h3nx8F4S5lZAIlc5_dRXWc8_RP/s400/IMG_0014.JPG" alt="" id="BLOGGER_PHOTO_ID_5321409889653816226" border="0" /></a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-31871974946808244402009-03-14T10:30:00.000-07:002009-03-14T12:36:17.422-07:00PrechargeAfter learning that we <a href="http://kermitthecar.blogspot.com/2009/01/snubbed.html">do in fact</a> need <a href="http://kermitthecar.blogspot.com/2008/08/we-dont-need-no-stinkin-capacitors.html">capacitors</a>, I bought a nice big 230 uF capacitor made especially for this purpose:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiIqvbNv_RP-JUd4SD5JpO4zrx3BSaiNt-CPurX6gYR4QRhh5zOmhNc02nKuQXsJ7jRGqSTCC5bstZS1Fdj2VY9lK1nljvKdE1v4L06OnmpzvaJCcP7aYcS36YBiStPVcdqq8bIU6SPNU8H/s1600-h/DSC_3194.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 400px; height: 268px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiIqvbNv_RP-JUd4SD5JpO4zrx3BSaiNt-CPurX6gYR4QRhh5zOmhNc02nKuQXsJ7jRGqSTCC5bstZS1Fdj2VY9lK1nljvKdE1v4L06OnmpzvaJCcP7aYcS36YBiStPVcdqq8bIU6SPNU8H/s400/DSC_3194.JPG" alt="" id="BLOGGER_PHOTO_ID_5313127476798210258" border="0" /></a><br /><br />The problem of limiting inrush current still remains- the main contactor wouldn't last very long under the 1kA or so that cap would draw as it's connected across the battery. I ruled out having the cap upstream of the contactor, because that would mean the contactor would need to be in the fron of the car, and the main high voltage cables running underneath the car would have no means of disconnection, other than manually pulling the pack splitting connections in the back. So, I set off to design a precharge circuit. The principle of this is that when the key is turned on, it applies 12 volts to a small relay that charges the main cap through a 1k or so resistor. This takes about 1 second. Meanwhile, another RC timing circuit charges up and turns on the main contactor. I used the free circuit modeling tool <a href="http://www.linear.com/designtools/software/ltspice.jsp">LTSpice</a> to model the timing, and I think it will work nicely. Here's a screen grab of the circuit tool:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggQ6r5iC8gUblTzFIOdNOCDPpLb6GT_uXQ2HViExnXFNb4DB2fKa-jgkosKU2Krg3NdWg8_Zi7EDFzJVNg8si9O9bxK_YD3ce7UAH14fs7xcnL-UkqHhL8pGMlgRr2g1xi9OiMVMuoEmx5/s1600-h/preCharge.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 400px; height: 385px;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggQ6r5iC8gUblTzFIOdNOCDPpLb6GT_uXQ2HViExnXFNb4DB2fKa-jgkosKU2Krg3NdWg8_Zi7EDFzJVNg8si9O9bxK_YD3ce7UAH14fs7xcnL-UkqHhL8pGMlgRr2g1xi9OiMVMuoEmx5/s400/preCharge.jpg" alt="" id="BLOGGER_PHOTO_ID_5313126413308502930" border="0" /></a><br />Note that for modeling purposes, the 12v ground (V1) and the negative terminal of the battery (V2) are connected, while in the car, they are isolated. The main contactor is modeled by the winding resistance, R1, combined with a voltage-controlled switch, S1. As C1 charges through R2, Q1 turns on and draws current through R1 and turns the main contactor on. The main capacitor C2 has been charging through R4 and the small relay S2. The Schottky diode D1 is to make contactor turnoff instantaneous, and D2 is to subtract D1's bias voltage from the gate of Q1. R3 is to bleed off C1's voltage while the system is off.<br /><br />Feel free to copy this design at your own risk!Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-29847745048426639062009-01-22T21:03:00.000-08:002009-01-22T21:14:47.570-08:00Snubbed!Well, it turns out that my assumption that the car failed from overheating was wrong. I dug into the inverter, and discovered that two of the IGBTs had died. The only thing that could really cause this, I reckon, is voltage spikes caused by switching. The problem was that when I removed all the DC bus capacitance (except for some small snubbers near the IGBTs) I didn't count on all the inductance I had added to the system in the form of cabling and the battery pack itself (essentially a big loop of wire). When the IGBTs try to turn off, this inductance causes the bus voltage to rise until something happens, in this case catastrophic failure of the IGBT itself. Pictures of the carnage soon!<br />Luckily, I was able to source off-the-shelf replacements, which will be arriving along with some bigger snubber caps later this week.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-53501995330830848212008-11-01T15:14:00.000-07:002008-11-01T15:29:02.212-07:00Still learningI have learned quite a bit about motors since setting out to rewind mine. First, I was wrong about my old motor being a 2 pole machine. It turns out that most 4 pole motors use something called consequent, or phantom poles, where there are 6 coil groups, 2 for each phase, so identical windings to a 2 pole motor. The difference is, the coil groups opposite each other (in the same phase) are wired to produce the same magnetic polarity, say North, in the air gap. This produces two consequent South poles at 90 degrees to the two North poles, making four total poles for each phase.<br /><br />As far as the rewinding, I have put that off. I have bought a nicer motor-- aluminum frame, inverter duty, and will probably rewind eventually. For now, though, I will convert it from star to delta topology, which is as simple as bringing the central star point out in three leads. This has the effect of converting a 208 volt motor to 120 volts, meaning I can run at 3033 rpm instead of 1750 at full (240) volts. This means I can run the motor at 10 Hp continuous instead of the 5.5 rated. Since peak torque is roughly 2.5 times rated torque for a motor of this type, I should be able to get 25 Hp peak. How long I can keep that up will depend on my cooling scheme, which I haven't really settled.Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-6571198271026982518.post-28550767595200821772008-09-22T18:50:00.001-07:002008-09-22T18:55:47.769-07:00Winding updateIt turns out that I made an error in assuming that there must be an even number of slots per pole. There is a method of winding called lap winding (as opposed to concentric winding) that allows almost any number of slots per pole by winding coils with constant pitch. I will post more as soon as I learn how to do that in this case.Unknownnoreply@blogger.com2tag:blogger.com,1999:blog-6571198271026982518.post-9840382003539745202008-09-21T22:38:00.000-07:002008-09-21T23:34:48.220-07:00Nameplate mysteryI decided to tackle removing the motor and beginning the process of rewinding by having a look at the old windings. It turned out that the nameplate was wrong--- It's not a 4-pole motor at all. It is a 2-pole motor, meaning the full-load speed was around 3500 rpm, not 1750 at the nameplate advertised. There are 36 slots in the stator, meaning that 6 slots are used for each pole, times 2 poles, times 3 phases. I would like to increase the number of poles to increase the torque. Rewinding for 4 poles is impossible, as 36 slots divided by 3 phases gives 12. 12 divided by 4 poles gives 3 slots per pole. The number of slots per pole have to be even, though. The number of poles also has to be even, and there are only two even numbers that multiply together to get 12 -- 6 and 2, so this motor has to have to have 6 poles with 2 slots per pole or 2 poles with 6 slots per pole. Two slots per pole isn't enough because it results in a poor approximation of a sinusoidally varying magnetic field around the stator, so I guess I'm stuck with 2 poles. This means that at 180 Hz, the motor is spinning about 10000 rpm, which isn't too good for the transmission, I'm sure.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-74345201439738223272008-09-19T20:14:00.000-07:002008-09-19T20:44:19.710-07:00Heat deathSince the last post, I drove the car back and forth to work (2.5 mi each way) a few times, and enjoyed getting the control settings to be a little more driveable. The car accelerates well, but has only a 35mph top speed. The problem seems to be that the torque falls off fairly rapidly as the motor is driven above 60Hz because of field weakening. The way induction motors work, they need a voltage proportional to the frequency to maintain constant torque. As my drive system peaks out at 240 volts or so, the torque falls off, because I am not able to force enough current though the windings. The solution to this is to rewind the motor to run at a lower voltage, say 80 volts. Then, we don't run out of voltage in a 240 volt drive system until we hit 180 Hz. The result is that the motor will have usable torque over a much wider speed range.<br /><br />Luckily, I was able to speed up the process of rewinding the motor by overheating it to the point the windings shorted. I thought it would be a good idea to drive down to Stanford and back (10 miles) on a hot day, and as I was about to pull into my place, the inverter shut down because it had detected a fault. I knew perfectly well what had happened. I had been meaning to install some sort of temperature instrumentation, as well as a blower for cooling air, but had been putting it off. I figured I would test my luck with my $150 ebay motor...<br /><br />I've never rewound a motor before, so I am practicing with a smaller motor from my blower, which I also got on ebay, and which I will be installing in the car when I have the motor off. I bought the blower with a 575 volt motor, which I will rewind as a 220 volt motor and run off a smaller inverter. Here's the stator of the small motor:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9-W5CAlSUr-yB6m5X7p6-BoW7RA4ZAvcuWhu3ECdYgiem8ay7Ai2wTbJqB0gohTnTwQY6tqin2r_mf7-nuHKRL-JA7xNxijugfLi9Y1qQ1WHX_g6vlR93oyMLhWq7AEZz-yj6q2uzPABf/s1600-h/DSC_1959.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9-W5CAlSUr-yB6m5X7p6-BoW7RA4ZAvcuWhu3ECdYgiem8ay7Ai2wTbJqB0gohTnTwQY6tqin2r_mf7-nuHKRL-JA7xNxijugfLi9Y1qQ1WHX_g6vlR93oyMLhWq7AEZz-yj6q2uzPABf/s400/DSC_1959.jpg" alt="" id="BLOGGER_PHOTO_ID_5247942442892888002" border="0" /></a><br />It's a 2-pole, 1/2 hp motor, with 4 slots per pole, star wound. The windings are 25 AWG, which I am replacing with 20 AWG to do the voltage conversion. There's about 2.5 lbs of copper in this, which works out to about 1000 feet of 20 gauge.<br /><br />Here's the rotor, along with the end bells and the impeller from the blower. Such elegant machinery.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBBK1Hilio9_mQiJHFwuvvcfs1kDeJ5vQ-RRgK9UXlwXLsKRyLRxnpDZb8Hg7VGH2k1V60ldBHhZ_PhKmeX4_66LJXTeGu2TEOstD0_MApAY54sfTXbAvyHfJ_2v7EO5Hqy8kQfads_ug-/s1600-h/DSC_1960.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBBK1Hilio9_mQiJHFwuvvcfs1kDeJ5vQ-RRgK9UXlwXLsKRyLRxnpDZb8Hg7VGH2k1V60ldBHhZ_PhKmeX4_66LJXTeGu2TEOstD0_MApAY54sfTXbAvyHfJ_2v7EO5Hqy8kQfads_ug-/s400/DSC_1960.jpg" alt="" id="BLOGGER_PHOTO_ID_5247942449407054818" border="0" /></a>Unknownnoreply@blogger.com6tag:blogger.com,1999:blog-6571198271026982518.post-12587524192010357712008-08-18T23:40:00.000-07:002008-08-18T23:53:16.024-07:00Kermit comes homeKermit left his home of the past 15 months at TechShop, and made the 10 mile trip back to my house in Mountain View this evening. It was a little bit nervewracking setting out on the open road for the first time, but we made it without assistance from AAA. I set the maximum current to the motor at 30 amps, and limited the maximum RPM to about 3600, so I definitely didn't set any speed records. It was a trick accelerating from a stop through certain traffic lights before they turned yellow again, and I'm sure I irritated more than one other driver. Accelerating from 0-5 mph was very difficult, with torque not picking up until the car got going a bit. Once rolling, though, it felt peppy, at least compared with the stodgy original acceleration.<br /><br />I need to fiddle with the voltage, current and frequency parameters a bit until I get acceptable performance. Mostly, I wanted to be assured of getting home without overheating my motor, which was no problem. I could hold my hand on the motor once I got home.<br /><br />It feels really good to have come this far. Even though the car is by no means done, it is a usable means of transport at this point, and I will be driving it to work and dragging groceries home.<br /><br />I'll keep updating this space with further news as Kermit rolls on.Unknownnoreply@blogger.com3tag:blogger.com,1999:blog-6571198271026982518.post-70519910968784375712008-08-18T00:11:00.000-07:002008-08-18T00:25:18.639-07:00We don't need no stinkin' capacitorsOne solution for the inrush shenanigans described in the last post is to construct an inrush limiting circuit with a large resistor and a contactor- the capacitor is charged through the resistor until the operating voltage is reached, when the contactor is closed, bypassing the resistor. The other way is to yank out the capacitor. The purpose of the capacitor is to filter the rectified AC mains supply so that it is a smooth DC source for the inverter. A battery is already a nice smooth DC source, so the capacitor isn't really needed. I already ditched the 20-plus pound inductor that was the other part of the line filter, so I had no qualms about getting rid of the capacitor. Luckily, the capacitor was its own easily removable module:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkgqwgeyo0LWZh9ectAfvDUPRp5Qo6NtO8eFE5FOUntkm5MPSTCcWUcMH-NPHTGOAB8qe_vd-hcRbzz6WK4tfQ0QMoDNjZd0sWM7BaPFu7Hev9LRHI0mPyFP5z-eUJKah5L-bZvBz9zWyF/s1600-h/DSC_1938.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkgqwgeyo0LWZh9ectAfvDUPRp5Qo6NtO8eFE5FOUntkm5MPSTCcWUcMH-NPHTGOAB8qe_vd-hcRbzz6WK4tfQ0QMoDNjZd0sWM7BaPFu7Hev9LRHI0mPyFP5z-eUJKah5L-bZvBz9zWyF/s400/DSC_1938.JPG" alt="" id="BLOGGER_PHOTO_ID_5235753240575699698" border="0" /></a>The other plus is now the inverter can be put in a much smaller box, and will have considerably less need for interior ventilation, making weather sealing a possibility.<br /><br />Of course I tested the capacitorless inverter/motor setup the way my pappy taught me -- by revvin' er up real good a few times.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-11124729725036310422008-08-17T23:45:00.000-07:002008-08-18T00:06:05.893-07:00Kermit on a rollWell, the big day finally arrived. Kermit moved under his own power for the first time! It was very exciting doing a few laps around TechShop's parking lot. Matt Heck took some video, which I'll post here soon.<br /><br />There are a few issues before I can drive it home, however. The first is that when I connected the pack to the inverter for the first time, the inrush current to charge the capacitors caused a spark that was, well, cinematic. Of course I had all my safety gear on (gloves, face shield, etc.) and I was expecting a spark, so no injuries or soiled britches, but jeez... the blinding flash and deafening KAPOW were pretty exciting. Obviously, we can't have that kind of drama each time we fire up Kermit to go get some milk.<br /><br />The second issue is that the 12V system isn't working yet, both because the DC-DC converter isn't converting, and because interfacing with the MGB wiring is a real head scratcher.<br /><br />The third thing is related to the control issues mentioned in the last post. As I was driving around the parking lot, it was very difficult to accelerate and decelerate smoothly. The good news is, there's plenty of torque.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-22321966888025571362008-08-10T20:27:00.000-07:002008-08-10T20:37:12.160-07:00Control issuesThe way the motor controller is currently hooked up, I have the throttle position sensor supplying a voltage to the speed control input of the inverter. The problem with this is that in all other cars, pressing on the accelerator gives more torque, not more speed. Some inverters will allow a torque input, but with my motor/inverter combination, that isn't possible. What my inverter does have, however, is an analog output that represents the current being given to the motor at any instant. If I connect an opamp with the positive input to the throttle position sensor and the negative input to the current output from the inverter, and feed the output of the opamp in to the speed control input, the throttle position sensor should control the current supplied to the motor. Current is related to torque, so this hack should make the car a lot more drivable.<br /><br />I'll wait until it gets around the block under its own power to try this, though.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-50039760143394388022008-08-10T20:17:00.000-07:002008-08-10T20:26:44.444-07:00Kermit gets some batteriesI took a couple of days off of work to make a final push on getting the car rolling, and it paid off. I finished all the sheet metal work around the battery box, and gave it a shot of primer gray. I also finished up all the wiring. I used 3/4" flexible waterproof conduit run in the tunnel above the driveshaft and transmission from the battery box to the front of the car where the inverter lives. I got 70 cells (the remaining 28 are still being conditioned) and installed them:<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4-xqfSo1XxnmuKUzjdeAR5t9qMRjD9Rm3TcHrfReOd6eRY0p5aVNFz7sySKYjXDY5SxDVwj91jpQ0oq2hkM-O947_-WTf9yRrYq0xhCEh68WzGqrog_XLfRoDAMp9lHy0Q1smikRui7E8/s1600-h/DSC_1936.JPG"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4-xqfSo1XxnmuKUzjdeAR5t9qMRjD9Rm3TcHrfReOd6eRY0p5aVNFz7sySKYjXDY5SxDVwj91jpQ0oq2hkM-O947_-WTf9yRrYq0xhCEh68WzGqrog_XLfRoDAMp9lHy0Q1smikRui7E8/s400/DSC_1936.JPG" alt="" id="BLOGGER_PHOTO_ID_5233094604374753986" border="0" /></a>I was hoping to take it for a little spin with this partial pack, but 244 volts from these 70 cells was not enough to start up the DC-DC converters for the 12 volt system, and without 12 volts, the main contactor would not close, so no joyriding yet. I should get the remaining cells put in sometime this week.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-73434015311338211092008-07-07T23:29:00.001-07:002008-07-07T23:32:13.723-07:00Contact!I bought what will (hopefully) be one of the last components for the car:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuDM3FLdmNlglUbh3fig_yS50lm9z2MVAvjo5GOASIumXetkdavIctFTDKzvZhy9-n_hsw-BZ782fMlW6FLjgeoUrJmrKtrDvamoYrrUkwMOvb__9D_nKD0Rr2HOdtEQ69ftB9uarvtNJC/s1600-h/DSC_1843.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuDM3FLdmNlglUbh3fig_yS50lm9z2MVAvjo5GOASIumXetkdavIctFTDKzvZhy9-n_hsw-BZ782fMlW6FLjgeoUrJmrKtrDvamoYrrUkwMOvb__9D_nKD0Rr2HOdtEQ69ftB9uarvtNJC/s400/DSC_1843.jpg" alt="" id="BLOGGER_PHOTO_ID_5220526812963053682" border="0" /></a><br />This is a sealed contactor, which will connect the battery pack to the motor controller when I turn the key.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-45823819319276890222008-07-07T23:18:00.001-07:002008-07-07T23:27:28.990-07:00Apologies to PininfarinaI have finished the battery box and tacked it in its proper location in the car. Unfortunately, to avoid striking the rear differential, the box had to be moved back to the point where the corners protrude from the rear skirt of the car. <br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg99s0Ue_i09AlunS1REcrIb3xNuObMhUFvpwoSUtuGZv4Gv9an9xfy_A3e-Jes5B4Ma2f-OJZflmioH8uRHE85vcP0umpa-bh_M42UK8ABnhGJ_xQ1L4xl_0oVDMMrwUgS8K66QdvosYRw/s1600-h/DSC_1841.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg99s0Ue_i09AlunS1REcrIb3xNuObMhUFvpwoSUtuGZv4Gv9an9xfy_A3e-Jes5B4Ma2f-OJZflmioH8uRHE85vcP0umpa-bh_M42UK8ABnhGJ_xQ1L4xl_0oVDMMrwUgS8K66QdvosYRw/s400/DSC_1841.jpg" alt="" id="BLOGGER_PHOTO_ID_5220524255353261554" border="0" /></a><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0Z8bTY5ZBZek_2L9ws_WqIlot1if3TyUu8QlXwbMLXtApJE7Ii_7XUVLtqugr-SFz0JGd4I5r-x4D91vzfETX_fbNxJscqmFNRjImd08OtXVouh_iaw9qVbn-KKXro01KMv8tuPSK1gXz/s1600-h/DSC_1840.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0Z8bTY5ZBZek_2L9ws_WqIlot1if3TyUu8QlXwbMLXtApJE7Ii_7XUVLtqugr-SFz0JGd4I5r-x4D91vzfETX_fbNxJscqmFNRjImd08OtXVouh_iaw9qVbn-KKXro01KMv8tuPSK1gXz/s400/DSC_1840.jpg" alt="" id="BLOGGER_PHOTO_ID_5220524088411288226" border="0" /></a><br />This spoils the lines of the car somewhat, but the protrutions will at least be hidden behind the bumper. I don't feel too bad about cutting up the car anymore, though. I wirebrushed off some paint to do the welds, and discovered quite a bit of bondo, so apparently Kermit has had more than one surgery.Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-6571198271026982518.post-73643375584629945092008-06-14T23:14:00.001-07:002008-06-14T23:18:14.166-07:00Throttle testI did the first test of the throttle control of the motor and drive. Everything went well; the drive was flexible enough to account for the idiosyncracies of the ebay special throttle position sensor I am using. More good news, the motor drive will fit in the engine compartment, freeing up more space in the back, and simplifying the wiring. I am running off mains power here, but it was a good feeling sitting in my car and revving the electric motor.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdZmk6VVtW8Bt_bOjm6QFPu7lmUMgBvjNPSFCEdIiR0Di7m1SwFr-8_56fYmyloyFnvZk05c5FfznYI9VV0vs2ydsHIqpBvADA4xlMo-Gcq4pt42QigBlBCrfe4kKyy4tgfnoLGeoNQeAJ/s1600-h/DSC_1828.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdZmk6VVtW8Bt_bOjm6QFPu7lmUMgBvjNPSFCEdIiR0Di7m1SwFr-8_56fYmyloyFnvZk05c5FfznYI9VV0vs2ydsHIqpBvADA4xlMo-Gcq4pt42QigBlBCrfe4kKyy4tgfnoLGeoNQeAJ/s400/DSC_1828.jpg" alt="" id="BLOGGER_PHOTO_ID_5211987831487683474" border="0" /></a>Unknownnoreply@blogger.com2tag:blogger.com,1999:blog-6571198271026982518.post-18246966871486856772008-06-14T22:56:00.000-07:002008-06-14T23:14:03.422-07:00Battery boxI have started a sheet metal box to hold the battery. This will be welded in place of the spare tire and gas tank. I need 100 cells, give or take, and the squarest pack I could make with about that number turned out to be 7 cells wide and 14 cells long, giving 98 cells. I started with a pristine sheet of 16 gauge steel:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyjFFnrL48jz7uRyko1zEz0An0oZq75tpvruiFNO-FT71Yjfft5UvYZ7u24aLDmo-vKu-Ko1pqWPP6la4TWPzUDKbnpLY9qlOwi4TBCiLHxZLZ5l4PPzErhPVNJNZ7k0zvnT753-B1Imsf/s1600-h/DSC_1676.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyjFFnrL48jz7uRyko1zEz0An0oZq75tpvruiFNO-FT71Yjfft5UvYZ7u24aLDmo-vKu-Ko1pqWPP6la4TWPzUDKbnpLY9qlOwi4TBCiLHxZLZ5l4PPzErhPVNJNZ7k0zvnT753-B1Imsf/s400/DSC_1676.jpg" alt="" id="BLOGGER_PHOTO_ID_5211984608127853634" border="0" /></a>Which got a little less pristine as I taught myself sheet metal fabrication:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMtnHjOudNN1zj0e_l88-vTTeUUxdVHlKTY2tiCmYDjMr-1FH2Tr7okTALlHwZXFUrYF0q8zRpIoL2pEZwlfhr9i3wImmUZbaeh56oQpjYFk4vFcsnATWSa_F_ym90N1MOvJL1UvE6g6Ei/s1600-h/DSC_1677.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMtnHjOudNN1zj0e_l88-vTTeUUxdVHlKTY2tiCmYDjMr-1FH2Tr7okTALlHwZXFUrYF0q8zRpIoL2pEZwlfhr9i3wImmUZbaeh56oQpjYFk4vFcsnATWSa_F_ym90N1MOvJL1UvE6g6Ei/s400/DSC_1677.jpg" alt="" id="BLOGGER_PHOTO_ID_5211985322289030098" border="0" /></a><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15B7Gto-dFPotOMzKk2N-ttsLWPr0dZnR-DDjGUSiMzQPZOlJdumcecO_rNTQNAikDGzfl1NmvYDiDl0Jis01xjLex6a5H0-9tu7UYIvcHuJv2SZrZuf4y3gxIvkuRMLb89mFBIlvesLe/s1600-h/DSC_1678.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg15B7Gto-dFPotOMzKk2N-ttsLWPr0dZnR-DDjGUSiMzQPZOlJdumcecO_rNTQNAikDGzfl1NmvYDiDl0Jis01xjLex6a5H0-9tu7UYIvcHuJv2SZrZuf4y3gxIvkuRMLb89mFBIlvesLe/s400/DSC_1678.jpg" alt="" id="BLOGGER_PHOTO_ID_5211985328857219426" border="0" /></a>The finger brake at TechShop wasn't big enough to bend all four sides of the box, so I had to do some old fashioned whacking it with a hammer and a dolly to get a nice fold on the last two sides. I won't show any closeups of the hammer marks.<br /><br />Next, remove the gas tank. I'm going to try to find a new home for this, as it is in good shape. <br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmGIAJEbyhKdyxbNmEjQD2GfkiMwGObX3fcMo4LDLrqAP3-54jGOdzwrYBdSJI5bzrmp7qeYqa_EgXvz6iLVi1fBsQp3AxHbQjfitLt2oXMaIQfJBRzP9OjX-ngNNHaKTgYZP-5HQnpAhq/s1600-h/DSC_1825.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmGIAJEbyhKdyxbNmEjQD2GfkiMwGObX3fcMo4LDLrqAP3-54jGOdzwrYBdSJI5bzrmp7qeYqa_EgXvz6iLVi1fBsQp3AxHbQjfitLt2oXMaIQfJBRzP9OjX-ngNNHaKTgYZP-5HQnpAhq/s400/DSC_1825.jpg" alt="" id="BLOGGER_PHOTO_ID_5211985331789353602" border="0" /></a><br /><br />Next, I had to grit my teeth and cut a bloody great hole in the bottom of my car. Not an easy thing to do with a classic car with decent sheet metal.<br /><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhphcIafUhpzX9eM6srVE-0cyzcWjvT9Uy4oyulWEX4jisVaN4SZLYHxHq2a4FZ_gG3HQ1ZZqJKZQhOjjY6D5N5xNzYaHbZvLRc-_Exc2tu4eN0H-NOqKDikIG19D96e84qXx-u5-RB2YvE/s1600-h/DSC_1826.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhphcIafUhpzX9eM6srVE-0cyzcWjvT9Uy4oyulWEX4jisVaN4SZLYHxHq2a4FZ_gG3HQ1ZZqJKZQhOjjY6D5N5xNzYaHbZvLRc-_Exc2tu4eN0H-NOqKDikIG19D96e84qXx-u5-RB2YvE/s400/DSC_1826.jpg" alt="" id="BLOGGER_PHOTO_ID_5211985334729614802" border="0" /></a><br />The hole will be bigger in the end, but I don't want to get too excited about cutting and end up getting rid of some metal that would help hold the box in later.<br /><br />Test fit!<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlPUMf6hpSrT859xNZKE9urkjTqwF7yEcgE9PMaZVSdwaOV5MVY9Vpmn1nUUipBtJzm8kKfw0KU8NbLFBJX1bLlE8ucJ_Va22oppKCqVTJ8m2E6nV1tds2WNAVOwwzOt1sPFdQHpNtxoH3/s1600-h/DSC_1827.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlPUMf6hpSrT859xNZKE9urkjTqwF7yEcgE9PMaZVSdwaOV5MVY9Vpmn1nUUipBtJzm8kKfw0KU8NbLFBJX1bLlE8ucJ_Va22oppKCqVTJ8m2E6nV1tds2WNAVOwwzOt1sPFdQHpNtxoH3/s400/DSC_1827.jpg" alt="" id="BLOGGER_PHOTO_ID_5211985341740050626" border="0" /></a><br />Astute readers will notice the complete lack of welds. Unfortunately, Saturday is welding class day at TechShop. so I wasn't able to get a welder all day. I need to weld some separators between the rows of cells as well.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-18677460674089220062008-04-11T23:01:00.000-07:002008-04-11T23:09:28.534-07:00Mmmm, toast!I needed a way to discharge the battery pack during my BMS tests, so I headed down to my local K-mapart to pick up a space heater. It's spring here in Califoria, though so there weren't any. I figured a nice Toast-R-Oven uses lots of electricity too, and I can make toast with it later. It's pretty funny to go to the store to find something that uses the most electricity.<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjzhYn3WRy5mNJLVaWA1VY7achJhPPeeanBmM5PvVEfXTXFqav29h79wxFVSVhpQX5fZv5paZmZn095SnfcjSFC4vC2C8gRZjCx8g5uTHviisqVZqR69rUp6vf8VLxMovfOBcSkeb8CHUjL/s1600-h/DSC_1599.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjzhYn3WRy5mNJLVaWA1VY7achJhPPeeanBmM5PvVEfXTXFqav29h79wxFVSVhpQX5fZv5paZmZn095SnfcjSFC4vC2C8gRZjCx8g5uTHviisqVZqR69rUp6vf8VLxMovfOBcSkeb8CHUjL/s400/DSC_1599.jpg" alt="" id="BLOGGER_PHOTO_ID_5188236373915923346" border="0" /></a>Unknownnoreply@blogger.com3tag:blogger.com,1999:blog-6571198271026982518.post-25402586003450971762008-04-11T18:10:00.000-07:002008-04-11T18:22:38.788-07:00One Logger per ChildI got one of the xo laptops from the <a href="http://laptop.org/">One Laptop per Child</a> project while they were having their give one get one promotion. It's really a neat device, but I haven't had much time to play with it. It really makes a good datalogger, though. I can hook it up to the battery pack and collect data on charge/discharge cycles while using my grownup laptop for grownup things.<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg663wCM8-ctSdsxsbmazcYnHYwmK8tpCLP5tBaDnPhyphenhyphenPOWqqz1XOMhVI5qscLoh2k7YbWI6B2p5HmiUkdPQjQhxILsnVOzyJR4MDM3OwlBbsk_xIbca69LeVq0Y_6Ehm-mtK-hwEMLEuBO/s1600-h/DSC_1596.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg663wCM8-ctSdsxsbmazcYnHYwmK8tpCLP5tBaDnPhyphenhyphenPOWqqz1XOMhVI5qscLoh2k7YbWI6B2p5HmiUkdPQjQhxILsnVOzyJR4MDM3OwlBbsk_xIbca69LeVq0Y_6Ehm-mtK-hwEMLEuBO/s400/DSC_1596.jpg" alt="" id="BLOGGER_PHOTO_ID_5188161358017131394" border="0" /></a><br /><br /><a href="http://laptop.org/"></a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-61190375065844239642008-03-27T22:21:00.001-07:002008-04-13T22:08:33.236-07:00The BMS finally works<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUU4N5MfSCF3ncxp0HOBeFR7OPT8VoXY_JExGr4z-RPpPYpKa67C1EGI2ZCRacRABlbpcYoEssCkBhd6NwNHAHMCWu3vOdx5AZBJyDApqOiGdO4HfZ3eq7pKNH9HGFelLgmu4-q6E6m9u0/s1600-h/DSC_1407.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUU4N5MfSCF3ncxp0HOBeFR7OPT8VoXY_JExGr4z-RPpPYpKa67C1EGI2ZCRacRABlbpcYoEssCkBhd6NwNHAHMCWu3vOdx5AZBJyDApqOiGdO4HfZ3eq7pKNH9HGFelLgmu4-q6E6m9u0/s400/DSC_1407.jpg" alt="" id="BLOGGER_PHOTO_ID_5182658539111563330" border="0" /></a>It's been three months, but I finally have a working battery management system. Here I'm testing it with 24 cells in series and the Manzanita charger. I deliberately discharged one of the cells, and the system is bringing it back in balance as it charges the whole pack. It's been a lot of work, but this system should give the best life possible to my pack.<br /><br />I'm sure there will be some fiddling with the control algorithms, but at least the hardware is done.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-87935120557228635182008-02-19T21:38:00.001-08:002008-02-19T21:44:02.033-08:00What a thousand boards looks like<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEis4CNb7TxoKZL_wCqJQkdl4NZ6rDuUeZRMnK8aIKUPtC-qjTmd808G6_FNdxYpW7ReLO9lnfmZO-s56i6OslutpEtHUzuIhJaHBeHIXlgC-4lS5q1HGDKgk5-Uwx1birhXh80t2jZQraQ4/s1600-h/DSC_1373.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEis4CNb7TxoKZL_wCqJQkdl4NZ6rDuUeZRMnK8aIKUPtC-qjTmd808G6_FNdxYpW7ReLO9lnfmZO-s56i6OslutpEtHUzuIhJaHBeHIXlgC-4lS5q1HGDKgk5-Uwx1birhXh80t2jZQraQ4/s400/DSC_1373.jpg" alt="" id="BLOGGER_PHOTO_ID_5168932814465044178" border="0" /></a>The production run of BMS boards arrived today. Richard Hatfield of <a href="http://www.treehugger.com/files/2007/06/lightning_lithi.php">Lightning Motors</a> went in with me on an order of 1000 to bring costs down.Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-6571198271026982518.post-12178720748797180092008-01-31T23:01:00.001-08:002008-01-31T23:04:40.536-08:00Beginnings of a battery packI've finally entered the home stretch with the BMS system, and have 3 final prototypes installed on cells for testing. Cat for scale.<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKU-qgjlkzGjKpdjj4vLfKxwKLYgH1bF5zIXmM4npdJGSqWafNPCRtszmchFekbwBVITK5stm7jdNQ4TLurvii5ih19Wm4QTk0aN60a4HD4IHK5rIklBEvFwaWif1u_xDJtSWPmLDNFPS-/s1600-h/DSC_1342.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKU-qgjlkzGjKpdjj4vLfKxwKLYgH1bF5zIXmM4npdJGSqWafNPCRtszmchFekbwBVITK5stm7jdNQ4TLurvii5ih19Wm4QTk0aN60a4HD4IHK5rIklBEvFwaWif1u_xDJtSWPmLDNFPS-/s400/DSC_1342.jpg" alt="" id="BLOGGER_PHOTO_ID_5161903514146979874" border="0" /></a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-90841930466064664992007-12-26T16:25:00.000-08:002007-12-26T16:34:50.502-08:00Stickers!I am spending Christmas in Wyoming with family, so no work on the car lately. I have been debugging the BMS code, and designing a sticker for the car:<br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsss6bi1ld0zotyepxuSOYL7FDwjx3zMHuxDuEPHwTMC9RBWLDtD6Xb31jkNj2G5FaMAb80T7qNXQwNjwpr4w85mqgANXbdbOgvA-qdQhzUmnsM36964mtP9CdQlR5YhHqB_lhprCgWPTy/s1600-h/sticker.jpeg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsss6bi1ld0zotyepxuSOYL7FDwjx3zMHuxDuEPHwTMC9RBWLDtD6Xb31jkNj2G5FaMAb80T7qNXQwNjwpr4w85mqgANXbdbOgvA-qdQhzUmnsM36964mtP9CdQlR5YhHqB_lhprCgWPTy/s400/sticker.jpeg" alt="" id="BLOGGER_PHOTO_ID_5148442855393473522" border="0" /></a>The equation is the differential form of <a href="http://en.wikipedia.org/wiki/Electromagnetic_induction">Faraday's law</a>, which is one of <a href="http://en.wikipedia.org/wiki/Maxwell%27s_equations">Maxwell's equations</a>, which describes induction. If this seems like something that belongs on your electric car, I can send the full size image.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-61702549261568962882007-12-17T22:46:00.000-08:002007-12-17T23:44:33.328-08:00Battery charger and other stuffIt has been over a month since I last posted to this journal. I have been very busy at work, where we just launched our first product- <a href="http://inxitu.com/html/product_services.htm">a miniature XRD/XRF instrument</a> for identifying minerals in the field. Even so, I have made some progress on the car, mostly buying parts and working on the next version of the BMS. I am now the proud owner of a PFC-20 battery charger from Manzanita Micro. This charger is nice because it can output the 408 volts that my pack will require. One drawback is that it is not isolated, which means that the negative side of the battery pack is connected to one leg of the mains. This should not be a safety issue, as all the other equipment I am using is fully isolated.<br /><br />Oh yeah, I said next version of the BMS. Although I'm sure the voltage regulator style BMS that I already developed would perform just fine, I have gone ahead with the <span style="font-style: italic;">Eierlegende Wollmilchsau</span> (literally, an egg-laying woolly milk pig-- a German expression that can better be translated as "Swiss army knife") version. This version has a small microcontroller (an Atmel ATtiny25) on each cell that monitors the cell voltage and communicates with a <a href="http://gumstix.com/">tiny linux computer</a> over an optoisolated i2c bus. Each microcontroller can bypass current, either on its own or on command from the computer.<br /><br />The advantage of this system is that it gives individual information on the state of each cell. Also, if a cell controller fails, the computer would immediately notice, and alert the driver that the pack needs service.<br /><br />The other positive aspect is that each cell controller will cost less. Microcontrollers are truly amazing. For under a dollar, you can get a chip that is much more powerful than, say, the Tandy Color Computer 2 that was my first computer.Unknownnoreply@blogger.com2tag:blogger.com,1999:blog-6571198271026982518.post-60046702704970238472007-11-09T23:53:00.001-08:002007-11-10T00:04:53.686-08:00Mr FusionI've started buying the safety equipment needed to deal with a 300 Volt battery pack with something like 15 kilowatthours of energy (roughly enough to run our house for three days.) In addition to some fancy insulated screw drivers to keep from shorting things out while I'm working, I bought this monster fuse. It will go between the battery pack and everything else. Lens cap for scale. <a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2FW1p5fIbLKQ3Y_0GIMgN873fPdAp3Pj0PtvPTPIKNfactt69UuAJYJXwJ8NWBuWxHJZl2-NgsPZcEHcV9U3Mmrn_4-pHQJHgGgocmMtzHmUoRt8bmQs88hHkCpOgccwYEJZZzWovnTLS/s1600-h/DSC_1183.jpg"><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer;" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2FW1p5fIbLKQ3Y_0GIMgN873fPdAp3Pj0PtvPTPIKNfactt69UuAJYJXwJ8NWBuWxHJZl2-NgsPZcEHcV9U3Mmrn_4-pHQJHgGgocmMtzHmUoRt8bmQs88hHkCpOgccwYEJZZzWovnTLS/s400/DSC_1183.jpg" alt="" id="BLOGGER_PHOTO_ID_5131116799642930562" border="0" /></a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-6571198271026982518.post-64631818426098367222007-11-09T21:23:00.000-08:002007-11-09T21:27:10.709-08:00British racing greenWell, I've finally fallen into the biggest trap for people who have electric car websites-- I've been working on my website instead of my car. At least reading my journal (I'm allergic to the word "blog") won't make your eyes hurt so much anymore. Plus, it's now authentic British racing green.Unknownnoreply@blogger.com0