Sometimes you have those days when it takes you forever to accomplish something so uninteresting that you have a hard time explaining where all the time went. Yesterday would be one of those days. Though I always end up getting less done than I plan for, yesterday was actually a really productive day. It’s just that the result isn’t much to write about.

But, you know, read on anyway. (Updated, 01/17)

We started off with my harebrained plan to wire up some UPS batteries I have lying around for 348V so I could test using the heater elements in various configurations to figure out how best to wire them up, how many to use, etc (parallel units of 3 in series? Or two?) I wanted to test using the actual vehicle system voltage, not trusting that I’d get it right going with lower voltage and extrapolating from there.

As we were gathering the batteries together though, I realized that I wasn’t really prepared to do it safely. The thought of 348V sitting in an open stack in the middle of my garage was not appealing, nor the thought of fatally brushing up against it. Once you have 40-50 volts, it’s enough to get through your skin. And once it does that, it only takes milliamps to kill you. So you could accidentally touch almost any two places in the stack, and the chances are high that there’d be more than enough voltage differential between the two points to at least give you a strong zap, if you’re lucky and it’s not a lethal one. What I needed was a sturdy enclosure, and fortunately, I decided to be lazy and scrap the whole battery idea.

It was fortunate because a while later clearer minds (obviously not mine) prevailed when Mark Farver suggested that I not worry about how I’m going to wire the new heater core until the whole thing is constructed and installed. I just bring out all the wires between each junction making no attempt to connect them, and I figure out the best way to arrange the current flow later in a separate wiring box when the core is in place with the blower running. As a final detail, I added that because the voltage of the system is so high, this also means a very high voltage swing between fully charged and empty — anywhere between 310V and 380V or so. It will actually approach 400V with the battery charger on, in the event that I want to run the heater with the truck plugged in on a cold morning. This wide swing implies an active control system for effective heating, so I’ll probably attach some thermistors (resistive thermal sensors) to the assembly and bring wires out for them as well.

So ok, a bit of time spent, and nothing to show for it. So what did we actually *do* yesterday? Well, it ended up being something that was needed but produces no visible progress for the truck. I have this idea for a clever hack for the motor (I’ll post about it once I know whether it works or not) which I think would be pretty easy to implement if only I had better access to the brush wires. I imagine it’s possible to get at them entirely through the vents, but I’d rather have full access by removing the commutator-end plate. There’s no way I’m going to do that horizontally, fighting the massive weight of the armature, so I have to stand the motor up vertically. And to do that, I have to have somewhere for the 5-inch shaft to go. So I spent the rest of the afternoon building a stand, and spent a chunk of the evening putting the motor on it. (It’s ok, I’m not impressed either). Additional benefits are that the motor takes up less space in my garage, and I since I attached casters I can move it around unassisted — that last point is a really big deal. So I’m unhappy that I blew a whole day on it, but I’m glad it’s done.

Some pics of all this are in a sub-album with the motor pictures. (It’s polite to cover your mouth when you yawn.) Helping for the day were Vivek Gani and Erik Bigelow.

UPDATE: Well, although the stand may be a good idea for storing, moving and working on the motor, it’s apparently bad for one important thing — testing it. I’d feared that the bearings wouldn’t appreciate running with a thrust load (due to the armature’s enormous weight, which is now entirely supported by the bearings) and it turns out this seems to be the case. Hooking up the battery, the motor draws a hefty spark, which means it’s pulling quite a bit more current than before. It also runs more slowly. Looks like I’ll have to create some method or apparatus to more easily transfer the motor between vertical and horizontal, so that I can do it without help. To say this is an unusual challenge is an understatement — even a 9″ Warp or ADC motor can be moved around by one person. A 10.7″ Kostov can be uprighted or laid down by one person. This motor is just heavy.