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

[allen_dodge]

Well I agree, free always wins in my book. Plus, as long as you're just commuting, range doesn't really sound like an issue.

Just for argument's sake though, did you figure 10kw with the current weight of the car, or without the batteries? Because if you size it to run the car indefinitely, then you wouldn't need hundreds of pounds of batteries, and without that extra weight it seems like you could get away with something smaller. Even a generator that replaced only half of the energy lost would pretty much double your range? Or am I missing something... Just wondering for my own curiosity.

[mechman600]

10KW is just a guess.

I have 800 lbs worth of [poor] batteries. Reducing this weight by half or even a third will not make much of a noticeable difference in energy required to move me along. Remember that energy required to move a car is mostly altered by rolling resistance and aerodynamics changes and less so by weight (if driven properly). And going with a controller that can do regen braking would make weight saving even less beneficial.

[MetroMPG]

How the heck did I miss this thread until today??

3 Thumbs Up for another successful low-budget EV conversion build!

Originally Posted by mechman600

It's just that, well, my pack was free and continues to be free as batteries die and I replace them with more free ones.

That's a pack selection approach I understand 100%.

Today I installed my poor man's BMS - a remote set of six volt meters that I can plug into the car to monitor each 12V pair while I drive. On my commute home I quickly found out that I had a dud pair.

Woohoo!

As I was reading this, I was going to chime in and chide you about not having an "active" battery monitoring approach. Glad you've put something together. The LED battery pack gauge in the ForkenSwift is the key instrument in the car. Critical for preventing battricide of old, weak floodies.

I'm curious to know if the dud you discovered had been otherwise "hiding" behind an acceptable looking resting voltage.

[MetroMPG]

PS: I'm going to be in Vancouver over Dec/Jan this winter. I'd love to get a chance to see your car while I'm there.

[mechman600]

Originally Posted by MetroMPG

I'm curious to know if the dud you discovered had been otherwise "hiding" behind an acceptable looking resting voltage.

All of these particular batteries rest at 12.77-12.83V fully charged. This one was exactly the same. It even passed my 1/2CCA (350 amp) 15 second load test, ending at 9.7V (minimum is 9.6V). When I used our little handheld battery tester at work it showed "Good Battery", not that I put any faith in that thing. I think it just measures battery impedance or something.

I ended up replacing it with a "fresh" one today and the results were nice climbing the hill on the way home. This is my strongest battery pair now, aside from the two AGMs. This hill has me at FULL throttle in second gear at 55-56 km/h for about 1-1/2 minutes (I haven't actually timed it ever - maybe it just seems like that long as I anticipate my tiny motor going up in smoke!). The Alltrax controller delivers full current all the way up (until I run out of volts, of course) - pretty impressive, I'll say.

Originally Posted by MetroMPG

PS: I'm going to be in Vancouver over Dec/Jan this winter. I'd love to get a chance to see your car while I'm there.

Definitely. PM sent.

On another note, I have ordered all my bits to build my PWM field current controller addition:
-24-72V 100A Kelly Controller
-Hall effect amp transducer with 0-5V output
-Various resistors, capacitors and potentiometers to fine tune things.

Simply put, the amp transducer will measure armature current and signal the PWM controller accordingly to a max of 50 amps at full armature current. I will also employ a simple circuit to ensure a minimum field current of 10A any time the throttle is depressed (activated by the idle microswitch) to avoid brush arcing. (I have experienced audible brush arching with only 12V at 72V and full current and it makes your stomach turn).

It really sucks that I have to do all this since I bought what I thought was a used series wound motor but was sent a sepex instead. I should have sent it back in the first place, but I'm into now. At least I'm learning!

[mechman600]

Here is my "BMS" hard at work:

Crude but awesome.

Here is my latest schematic for controlling my field controller with an amp transducer:

The bit with the microswitch simply raises the signal voltage slightly when the throttle is depressed to a minimum field amperage, adjustable with "Min Current Trim". Not sure if the transducer will like that very much, but I didn't want to install a diode on the output of the transducer that will eat 0.4V off the bottom of its 2.5-5.0V output range.

I hope it works!

[wsc01q]

Am enjoying your post. Here's my project so far, an Urba. 48 volt, 400 amp, D&M sepex direct drive motor & Curtis 1244 controller. I get around 40 MPH on level ground drawing 100 amps with a range of 60-70 miles. Weight is about 1500 lbs with 8 Interstate 6 volt golf cart batteries and one 12 volt deep cycle accessory battery. I would like to add 2 more cells for 60 volts and a 500 amp controller.

[tiderfish]

Great work on this! You made this happen in a very short amount of time! KUDOS to you!

Have you determined how much this is costing you to run per month VS. gas cost in the same car?

[mechman600]

Originally Posted by tiderfish

Have you determined how much this is costing you to run per month VS. gas cost in the same car?

Not per month.

Right now with my unbelievably inefficient battery chargers, I am getting the equivalent of 55 mpg (US) at an equivalent price of $3.70/L. One third of that energy is free when I plug in at work.

I do have a Kelly 72V 96% efficient charger on order and I estimate my MPGe to increase by 75%.

[ctgottapee]

I have seen that people who do PS deletes T that line and put some sort of breather on it. That way you don't have to steer against the pressure of the looped hose, but still can keep some fluid in there

Originally Posted by mechman600

Yesterday I took care of my power steering issue. I have converted it to armstrong steering. As in...my strong arms will do all the work. Sorry, bad joke.
The hose is joining the input and return of the steering rack, basically just to keep crap out.