Paul & Sabrina's cheap DIY 144v motor controller

[GrahamMc]

Roger/Lectruck - Thanks for the heads-up. Right now I think I want to focus on the controller, and build this car backwards. I will get the glider/donor car last. In the meantime I think I would use my wife's treadmill to test a controller, and build it as a learning experience/hobby/practical start to my electric car. But I am in no great hurry as we recently bought an investment property and that is about all the projects I can handle right now since it was foreclosed and neglected. I would, however, love the Warp 9 motor, if I lived in Atlanta I would have a hard time resisting.

Paul - I went to the ZEVA page you linked in an earlier post and read through the story of that controller, and have also been poking around Futurelec. Still trying to wrap my head around the wiring, but I am getting closer. I am excited to assist the open-source speed controller effort in any way I can. Any luck with the schematic and parts list, or are the ones from page 3 or so still pretty much the current revision? Best Wishes and happy motoring.

Oh yeah, I also came across Firefly Batteries while poking around. They are actually located here in Peoria, IL. They will hit the market soon, but are essentially deep cycle lead-acid batteries with half the lead so therefore twice the energy density. They have prototypes in trucks and buses here now, so I am watching them with interest as the solution promises almost Lithium-Ion performance for almost Lead-Acid cost. (also a company called Axiom doing something similar but is further behind in getting to market).

Oasis Battery - fireflyenergy.com

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[MPaulHolmes]

Schematic is attached. It had to be shrunk down quite a bit, so I hope it's still readable. It's almost identical to the working controller's schematic. Just a few improvements suggested by some of the motor controller experts out there.

[GrahamMc]

Paul -

Thanks so much! I sent a note to Futurelec asking them to verify the information from this thread is accurate and quote some pricing for a board. I was not able to find many of the components by searching Futurelec, is there another site that you use to order components? (I bet it is somewhere in these 76 pages). Also, I thought I read you wanted to use an ATMega16 controller, but I don't remember why? Just wondering if that upgrade is difficult or advantageous. I am a bit skeptical that Futurelec will just design and make a board for as little as was stated, but I am hoping that proves incorrect! Thanks again for your help, you are the man.

[MPaulHolmes]

I don't think they will design the board for that price. The example that was quoted was for a 2 sided 3"x4" PCB, when you supply the design layout. I'm scared to ask about them designing the layout! Our PCB might have to be more like 4x6 or so, but single sided. I got all the parts from digikey.com and mouser.com.

I was changing to an ATMega16, because it has more analog to digital converters, so that we can also monitor and control things like RPM, Pack voltage, etc...

In the schematic there also needs to be a ferrite bead between where the digital and analog grounds meet. I forgot that.

I've been working on a cleaner, stronger way to connect the controller together. No tapping needed, and no bolts bolting down the M- bus bar. Much better heat transfer to the heat sink from the heat spreader. All at once!

I just need to find three 1/4" diameter (grade 8??) bolts that are 3" long.

It will be nice to have the controller's heat sink in the up position, so fans could easily be attached to blow down on the fins if heating is an issue.

[Blue Bomber Man]

Paul, I can't remember if you said if this works only with a standard DC motor or if it will work with a Brushless motor.

I've been studying up on motor designs and different types of motors, and recently learned that a brushless DC motor is very similar to an AC motor. I also remember you previously that an AC controller was not happening anytime soon.

[MPaulHolmes]

Ya, it only works on brushed DC motors. Dang it! Oh well. hehe.

[Roger Heuckeroth]

DC Series would motors are cheap, available and have plenty of torque. That is why they are favored in EV conversion projects. AC motors and controllers are better for EV applications many ways, but they are currently not cheap or available. It is doubtful that you could ever get and AC controller that can put out 144X500=72 kW of power for under $300. They uses matched sets of high power IGBT for each phase. Six IGBT/freewheel diode pairs. For 72 kW of power your looking at about $800 for the IGBTs alone. So, if you want cheap AC is not in your conversion plans.

I have heard of some people using industrial AC motors and VFDs off of Ebay to make a cheap AC driveline, but performance is kind of lacking verses DC and you need high voltage (>300V) battery packs to run them. So, although AC is the technology of choice for Tesla and all the other serious EV guys, its not cheap.

[lectruck]

QUOTE=GrahamMc

Oh yeah, I also came across Firefly Batteries while poking around. They are actually located here in Peoria, IL. They will hit the market soon, but are essentially deep cycle lead-acid batteries with half the lead so therefore twice the energy density. They have prototypes in trucks and buses here now, so I am watching them with interest as the solution promises almost Lithium-Ion performance for almost Lead-Acid cost. (also a company called Axiom doing something similar but is further behind in getting to market).

Oasis Battery - fireflyenergy.com



Wow, I check out the entire web site, these batteries look a good at Nimh and lithium. Their next generation batteries will be smaller and stronger yet.

[Roger Heuckeroth]

Firefly Batteries:

I hate to sound negative, but I have been hearing about these batteries for years. They were supposed to be available for over a year ago, but they still are not available. Also, someone on the EVDL called them and they said they were not planning on selling to the EV conversion market. I also heard they will be selling in the $400-500/ battery range.

Their spec sheet says they have an energy density of 39 Wh/Kg. Compared to Lithium that is pretty low. The LiFePO 100 Ah cells I'm using on my conversion are 97 Wh/Kg. If the $400 + price range is correct they are also not a big bargin over Lithium. Its anout half the price of a lithium pack with BMS, but they are only rated at 600 cycles at 80% DOD. Lithium can do 2000+ at 80% DOD. So they lifecycle cost of lithium is more favorable.

The biggest problem with lithium is the up front cost. Imagine if you went to the car dealer and bought a new ICE car for $20,000, however, at the time you bought it you had to pay for half the gas you would use over the next 150,000 miles. The deal would be if you prepay this gas, the actual gas you would buy at the pump would be 10% of retail price. Sounds good, but now you have to buy that $20,000 car for $30,000. This is a good deal for those that can afford it, but puts the car out of the price range of many other buyers.

When I first was looking into Lithium it was available for about $1.60/Ah. Its now down to $1.1 Ah. That's for the cells alone, not including BMS. I'm paying about $1.60/Ah for the whole pack with a really high tech BMS and charger delivered cost.

I've tested a 100 Ah cell and it can put out up to 300 Amps continuously, and can do short intervals of over 500 amps. If I stepped up to a 200 Ah cell it could do 600 amps continuous and up to 1000 amp short intervals. That's some serious power, and your not decreasing the cycle life that much by pulling that amount of current. Do that to a golf cart battery and you'll be lucky to get 200 cycles out of it.

Personally, there are only two types of batteries I would consider. Golf cart batteries, or Lithium. AGMs cost at least twice what golf cart batteries cost and don't last half as long in the typical EV application. If I was converting a small pick up truck I would go with golf cart batteries. The truck can take the wieght. For a car I would go with Lithium. Even a small lithium pack would be better than a comparable AGM pack.

Anyway, this is only my opinion based on lots of research I have done over the last two years. I'm not passing judgement on anyone who has gone down another path.

[GrahamMc]

Roger-
I will always appreciate the thoughtful input of the well-informed. Thanks for the insights.