EV progress
Well, I identified a few items that didn’t make it to the list..
I’ve ordered a replacement for the 12V system battery, because it’s been sitting dead for over a year and is unlikely to take a charge.
I’m thinking more and more about the mk3 inverter interface. So far, here’s what I’ve come up with:
Using one of the mk3 boards with mostly the standard mk3 codebase, wire up inputs to the inverter’s three system failure outputs (via 1k resistor), and wire up outputs to three reed relays – one of which will then drive a pair of paralleled ATO relays to bypass the accessory switch and turn power on to the car’s main 12V bus, and one of which will activate the start switch, and one of which will ground the brown input wire. (I could probably just use a opto for everything but the bypass relay, but the nice thing about relays is that they’re pretty much trouble free). Note to self: do not forget bypass diodes or relays will set fire to microcontroller.
I think that this board will probably get installed before the rest of the BMS – possibly before I take the car to the DMV. Properly programmed, it will remove the requirement for any complicated instructions prior to having someone new drive the car.. and, as another neat trick, it can also close the main contacter on the inverter to let it charge up the 12v battery whenever it gets low.
Mental note to self: probably it would be a good thing if it was not *possible* for the drive enable relay to close while the car is on bypass power. This shouldn’t be that hard to finangle.. if the reed relays are SPDT, I could just have the ground for the enable be provided via the NC contacts on the bypass relay. Maybe I’m overly paranoid here, but I really don’t think I want the car to be able to engage it’s own drive without a key inserted. Kit is cute and all, but…
I also think the inverter interface board will be a good programming exercise to get me back into the mk3 project – probably at first it won’t include a bootloader and won’t actually be able to measure voltages or be network addressable or anything.. then as I get the bugs out of the mk3 codebase, I can make it a proper mk3 node.
I really could kick myself for letting this project drag on so long. I’m a little apprehensive of the paperwork that’s going to be required to get the car street legal again – but once I get the drive to spin up, I will call Geico and put the car on my insurance, then try driving it around the neighborhood to make sure everything’s intact (and hopefully the inverter won’t blow up again)
I’ve decided to leave the pack positive point under the car, although I’m upgrading it to a plastic junction box *with a cover* and a real binding post to connect everything to. I’m also tempted to go ahead and wire back in Bruce’s nifty watthour-meter-widget while I’ve got the whole front of the car taken apart. If anyone wants pictures, let me know 😉
I’ve also been trying to decide what to do about the climate control. My last attempt at peltier devices was kind of dissapointing, but the complexity of a freon system disturbs me. If I were a better hardware hacker, I would just build myself a inverter / motor control and get all the guts out of a commercial heat pump. However, I think I may take another stab at the peltier thing instead because at least there’s no high pressure hosery needed. I’m thinking maybe I will get another motorcycle radiator and install it in the space where the rack for the peltier devices was, then build a cold-plate sandwitch of two peices of aluminum with holes drilled in them, then run two seperate liquid loops. Anyone know where I can get small, quiet, low-flow 12V pumps? Ideally for a very low price? 😉
Obviously climate control is not a very high priority.. but recently I’ve been reminded that even in SoCal, cars need heat.
I seem to be returning to my 2002 obsessing on this. I don’t know what that means, but it’s better than some of the other things I’ve obsessed about since then.
February 15th, 2008 at 11:01 am
Yeah. So much to do. It’s actually incredible how it seems so much more managable when it’s all broken down.
I honestly can’t understand why but; the cooling/heating issue is for one reason or another more or less something that I ponder at great length, frequently. But unfortunately with a lack of funds I haven’t been able to get a big pile of them to break and experiment on. Especially since my big issue is really just how to most efficiently get the desired temp into the air.
Why that’s my big issue and the thoughts I have on it, I could probably ramble aimlessly about for pages so I’ll conserve bandwidth a little and cram a bastard in it.
Nice to see another burst of motivation and inspiration to get back on the ball with this one. I’m mostly useless and transportationally challenged (and mentally challenged)… (and physically challenged)… (ok I’m just challenged all around)… but be happy to help out & hang out one of these days if you get a hankerin.
BTW- have you ever seen http://www.emachineshop.com/ ? Dude. I wish I could do 3d design. I’d make all kinds of cool stuff out of all kinds of cool materials.
February 16th, 2008 at 9:06 pm
I can’t answer for Sheer, but personally, I’d love it if you’d hang out. There were, I’m thinking, all kinds of restaurants that you were going to suggest for the three of us to hit, so we could actually GO to one and then we could come out here and you could help Sheer with his car — actually, I’m hoping I could help, too. Anyway, neither of us has friends over very often, and I’d like to encourage that to change. We did have a beautiful golden retriever over last week, and that was nice. We need to encourage her and her human to come back sometime soon, too.