Electric car conversion: Project ForkenSwift

[bennelson]

Originally Posted by MetroMPG

Ben, what was the person's thinking when they said they were surprised you hadn't killed yours yet - was that because of the heat?

Yep, because of heat. My DC/DC converter on the motorcycle is about an inch and a half square - pretty compact for a 100 watt converter. It has no built-in heat sink. It's just a plain black brick from the outside.

Apparently, that style is designed to sit directly on a heat sink, similar to how a computer CPU does.

I have a match to that converter that I may install in the Electro-Metro. If I do, I will make sure to add a heat sink to it.

-Ben

[MetroMPG]

Originally Posted by bennelson

I think we could actually edit this thread, mine, and MPaul's to make a book.

"The Cheap, DIY, way to build an Electric Car: Learn from our mistakes!"

I don't think that's a bad idea. It's a question of time, of course (not enough of it, and too many projects!). But an e-book might be popular, especially when gas prices go back up again in the next couple of years or after the next natural (or human-caused) disaster.

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Battery swap complete!

I'd like to say "WOOO!" after having driven the car just now, but I'll reserve judgment for another day or 2. (But I'm pretty sure it's WOOOOooo!)

For comparison purposes, I left in the best battery from the existing pack, and put in 7 of the "new" ones. Now the problem is the batteries were likely at different states of charge (the 7 and the 1), so I can't be certain of what I was seeing.

But every one of the 7 was significantly "stiffer" than the old best battery - meaning while I watched the LED pack monitor when under significant load (100-200A), their voltage sagged much less & later than that one batt.

If that's true, it means the car has significantly better "hard" acceleration potential than it used to - an additional benefit of healthy batteries that I forgot about.

I went for a short run and they're all charging together now, so I'll get a better picture over the next day or so...

[Intrigued]

Woohoo from Missouri! Sounds like after you find your new "A" and "B" packs, you should use the "A" to take Paul (and Ben) up on their race challenge - of course after you secretly install the Zilla 1K that you are going to secretly buy "for the conversion that ISN'T on a budget."

Kidding aside, it would be good to see just how different 72 and 48 volts are. Which reminds me: I still haven't gone through Mullet's thread, because Paul made me fear... I mean, I've got to recover from the late nights staring at this stupid computer screen. Maybe we could have a 4-way race: YouTube and all!

[Intrigued]

Live and learn, I guess... I heard about Mullet's thread and assumed it was an electric. Got over fearing him today, and found out it's a 3-cyl gas!

Maybe we could have it and the Flea do some comparisons...

[MetroMPG]

Quick update: 43 km / 27 miles on one charge. Was still able to get up the last little hill in 2nd gear without torturing the batteries. Basically a 100% improvement!

Car's on the charger now - I'm curious to see if there's any noticeable change in overall efficiency with the healthier batteries.

[MetroMPG]

Whoops!

Just went to check the charger: it was still in the bulk charge stage, but in "overheat protection" mode - current output was scaled back.

And it's not even hot out - only about 12 C.

I unplugged it for a minute, and left the hatchback open so it could get some air. Seems happy now.

I guess that's one downside to a pack with more capacity: the charger has to work harder, longer, and can get hotter.

I suppose that's why I have literally burned out a component on the 24v charger twice now: Not designed to be on two parallel strings for that length of time.

[MetroMPG]

Let's call this the "A++/Hallowe'en 08" pack. (I picked the best 8 batteries from the 16 latest recruits.) The charger definitely works longer - more like 8 hours now to fully recharge the car.

Updated the car's fuel log. I've run it through four (recorded three) drive/charge cycles since putting in the A++ batteries. Averaging mid 130's MPGe / 250 Wh per mile / 150 Wh per km.

And that's with freezing weather for two of the cycles, and some uncharacteristically "hard" driving on the warm weather (probably 12C average) cycle.

Other efficiency considerations: I've been using the 100w DC-DC converter; because the car has a mugh higher range, it now goes more days between recharging so it's experiencing more self-discharge as a proportion of energy "used" than before.

But I think I'll cautiously say if you look at the previous entries in the log, these batts look like they have improved the car's overall efficiency. Which is a big "woo!".

Soon I'll be heading east for the winter so Ivan will get to babysit it for the duration. It'll be a long wait to next spring for more upgrades/refinement and curiousity about whether the best efficiency of summer 08 will be beaten!

[bennelson]

Guess I'll have to be doing all the Winter Electric Geo testing then!

Planning on building some INSULATED front battery boxes this weekend...

[trebuchet03]

Not every detail, just the milestones.

I think you should instructablize this, Darin

I am biased, however - I interned there and think the operation is awesome

[bennelson]

I have been thinking for a while about doing an Instructables for my car.

Just gotta get it a little more done first....