Project: The Electric Booger (budget EV conversion - '92 Mazda MX-3)

[bennelson]

I actually DID think about doing a virtual EV race.
At that point, I think it would have been between Darin, MPaulHolmes, and I.

The idea is that everyone mounts a video camera on the dashboard of their car and also has somebody else film them from the side of the road. Then, everyone sends me their videos, and I edit them together as though we are all in the same place actually racing against each other, complete with music, sound effects and an announcer.

Hmm. Maybe time to revisit that idea. I think there are enough DIY electric cars on Ecomodder now for a Grand Prix!

[MetroMPG]

I'm in! But only if there's a booby prize.

[mechman600]

This is getting out of control fast.
I'm in. Let's wait till the ForkenSwift is out of storage (so at least Ben and I won't be last!) and the warmth of spring makes my batteries perform like they mean it.
Just say "go" and consider my video made.

[mechman600]

The new chargers are in!

Some testing revealed that they work exactly like I want them to. They bulk charge to 14.7-14.8V, absorption for about half an hour at this voltage, and then float at 13.6-13.7V. I measured them to be 75% efficient no matter what output current/voltage is at.

I tied pairs together as "charger stacks". One stack is behind each seat and the other stack is on my control board under the hood.


And here is a picture of something that I have yet to do with any of my chargers so far:

Float charge. Probably something that most other EV owners take for granted. I left them on float for about five hours to make sure the batteries were fully saturated and extra happy (for once).

Now it charges up in less than half the time of my Mastercraft chargers because the current does not slow down as the battery voltage and resistance rises. Finally! A charging solution that works!

[Daox]

Looks good! Any idea how much this has reduced your wh/mile from the wall?

I'd like to caution stacking your chargers though. I'm not sure how warm those things get, but at 75% efficiency I'd assume they get warm. You might want to stick something between them so they run a bit cooler.

[mechman600]

Thanks for scaring me! Just kidding.

Each charger has a cooling fan that runs constantly, so I wasn't too concerned about heat. This morning I charged for 1-1/2 hrs after my commute to work and the chargers were cool to touch.

The chargers were drawing a total of 1060W (+20W for my accessory battery charger), and amazingly (to me), all batteries were at 14.0V after an hour, which would have taken three hours with the old transformer based/regulated chargers at 800-900W. All thanks to the magic of PWM.

Like last night after my commute home, I didn't do a full top up. I cut the charge off once the power consumption dropped under 600W, which occurs just into the absorption charge when all the voltages are holding at 14.5-14.7V.

Round trip: 3.73kW/8.1mi=460wH/mi. Wow...massive improvement over the previous chargers (700wH/mi!!). It's roughly 35% better now, so I am very happy.

[Daox]

Very nice improvement.

Ah, fans, good good. I mention it because I have some 3A Soneil chargers for my lawn mower. They have no fans and actually are in a plastic case and get a bit warm in the middle of summer.

[mechman600]

Time to tally up how much this really cost me.

Original Performance Goals
Top speed: 80 km/h (50 mph)
Range: 25 km (15 mi)
Budget: $2000

Well, lets just say I blew the budget on this one. But I think I ended up with a car that is proportionally better. The main budget offender was the batteries that I ended up buying. I originally thought I could get away with using free truck battery cores, but the Electric Booger just kept murdering them.

Total Costs
Car: $448
Controller: $358
Contactor: $48
USB Serial Adapter: $6
Vacuum Pump: $70
Volt Meters: $44
Motor: $463
Adapter Plate: $100
Adapter Plate Machining: $50
TPS, Fuses, Resistors, Vacuum Switch: $160
Battery Rack Steel: $70
Extension cords, battery hold downs, zip ties: $82
Relays, Connectors, terminals, wire, loom, etc.: $116
Field Controller system: $220
Chargers: $270
Batteries: $1491

TOTAL: $3996

Actual performance
Top Speed: 90 km/h (56 mph) - this is as fast as I have been, but it will go faster.
Range: 25 km (15 mi) - just a guess, going by how it feels after 15 km (in winter with the heater running). I haven't tested this either. Do I really want to?

When spring comes and it starts warming up outside (and my batteries are more willing to comply), I will be sure to test top speed and range a little more thoroughly.

[MetroMPG]

Nice improvement with the new chargers.

And $4k for a car with new batteries & chargers and those capabilities is pretty decent, in my opinion.

EDIT:

PS - you're welcome for the penny vs. cigarette lighter diagnosis.

[mechman600]

Here's an illustration of the dramatic effect that charging efficiency has affected the Electric Booger over time:

Any modern charger will be a PWM charger, so it usually isn't an issue in a "normal" EV conversion. But when a guy like me decides he needs to cheap out and buy "hardware store type" chargers, the difference is amazing.

I finally registered at the MX-3.com forum. I introduced myself with a whole bunch of pictures of the eBooger conversion just to see what the reaction was. It was kind of funny - mostly "wows" and "that's kind of neat" type stuff. One guy said the original 1.6L is such a gas sipper that I am probably paying more for electricity now, so I attempted to teach him about EV efficiency.

Other than that, it's mostly just drive->charge->repeat these days. I am already starting to wonder what my next one will be. I really want to convert a motorcycle.....