Parts Placement · 23 May 06

Excuse the somewhat lame attempt at a 3D rendering using a 2D photo editing program. Let’s call it an artist’s rendition. ‘:^)

What I am working on here is a possible approach in laying out the main electronics for Eve. Last week James recommended covering all of the firewall holes with metal plugs and, just like an echo down an empty tunnel, it bounced around my mind for the rest of the evening.

Why not cover all of the firewall?

But first a quick update on batteries. Last week I emailed a bunch of folks on the EVAlbum who listed their battery type as a Deka Gel cell. The Deka’s were next on the list of battery candidates and on paper it looked pretty good.

Sure enough everyone who wrote back agreed that it was a good battery…for their purpose. The thing I had missed with each of the entries is that they were running Solectria AC drives. Jeff was good enough to explain that the Gels don’t like to put out heavy current loads (i.e. greater than 250 amps). This isn’t as big of a deal for AC drives, I guess, although I’m not completely sure why. Jeff says the controllers have more control over the max current (the Curtis has a few pots, I need to read up on what they do).

On to Plan C. Jeff said Deka AGMs are good batteries and generally cheaper than Optimas. David mentioned on the EVList that he was going to buy Powersonic PS-121000 AGMs (PDF). Again, they look pretty good on paper and Mouser has them at a quantity discount of $143 each.

Here’s something I ran across on the EVList:

A comparison:

12v Hawker Genesis AGM 70ah batteries cost over $220
12v Powersonic 100ah gel cells cost around $110
6v T-105s at 225ah run about $75 these days (at best)

Under 50amp load:

Hawker and the Powersonic AGM have about 50ah capacity
T-105 probably about 170ah

So:

12v Hawker Genesis 70ah at 50amps: 36.7cents/wh
12v Powersonic gel 100ah at 50amps: 18.3c/wh
6v Flooded T-105 225ah at 50amps: 7.4c/wh

Or, as Willie would say:

Mama don’t let your babies grow up to be converters
Don’t let ‘em pick batteries and convert them old cars
Make ‘em be doctors and lawyers and such

Mama don’t let your babies grow up to be converters
They’ll never stop tweaking and they’re always alone
Even with someone they love

Converters ain’t easy to love and they’re harder to hold
And they’d rather give you a NEV then diamonds or gold
Battery specs and old faded data sheets each night begins a new day
And if you don’t understand him and he don’t die young
He’ll just silently drive away

In the middle of all of this my wife was making calls for me based on some half remembered names that a friend of a friend’s friend got from a conversation last year regarding batteries and hospitals.

Still with me?

Way back in August Hans left a comment on Eve’s second post and suggested we check with local hospitals to see if they have recycled UPS batteries available, free or at a great discount. Since the UPS machines are used for life and death situations they tend to not wait for the batteries to die before replacing them. So, we contacted a guy who’s going to contact another guy and maybe our battery problem will go away?

In the meantime I’ve been putting the wiring back together and starting to think about doing the high voltage wiring.

Which brings us full circle back to the 3D/2D rendering at the top of the page (click to see the full sized view).

Here’s a few of the items that need to be mounted (follow along using the schematic if you like):

• Controller (20lbs?)
• Two Contactors
• Current Shunt
• A few small, 12vdc relays
• DC-DC converter
• Potbox
• Low voltage fuses and interconnects
• High voltage fuse and interconnects

On the Mazda electric car I used a hunk of MDO board (plywood with a nice, paintable surface) mounted on top of the motor and batteries. It was a horizontal mount, which meant the first time I drove uphill in a torrential downpour the electric car came to a stop.

Oh, right…

Raising the terminal blocks off the surface fixed that problem (the long term problem, the short term stall-out was fixed with a quick toweling). Still, the board took up a lot of prime real estate and made it difficult to show off the DC motor to folks.

The great thing about using MDO board? It’s wood!

My mom lives in a log cabin and whenever she wants to hang one of her paintings, put up a thermometer/spice rack/knickknack she gets out the hammer and a nail and has at it. No searching for a stud or messing with dryrock anchors, nail wherever you want.

Same goes with an MDO board for components. Non-conductive and with a nice coat of paint it can even look purty, if you are into that kind of thing.

A few of the parts to go on the board: two contactors, the shunt, and the heater relay. Another appealing aspect of the vertical mounting approach is that the wires coming from the driver’s compartment don’t have to be strung across the engine compartment and can run right to where they need to go.

That’s the plan so far.

Oh, and I have another time-lapse video coming soon.