# What controller should I try to get?



## RKM (Jun 9, 2008)

I'll be converting a Miata. I haven't finalized components yet, but had been leaning toward a Warp 9 motor and Zilla 1K LV (for 144 V) controller. Unfortunately, Otmar is suspending production of the Zilla. I'm not sure that the 1K LV can still be ordered. The site lists only HV units.

Can the 1K LV still be ordered (thought I could get a quicker answer here than from Cafe Electric)?

An option is the Curtis 1231C controller. It can handle half the power of the Zilla. Will this be adequate for factory like acceleration? I'm doubting it will be. Is the Zilla worth the extra dollars for the features, power and durability it offers?

Thanks for your opinions. 

Rob


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## chamilun (Jun 17, 2008)

a 144V Miata? acceleration should be no problem. i doubt the 500amp limit of the Curtis will be a problem

check out kiwi (gavs) video that shows him trying to calculate zero to 60


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## RKM (Jun 9, 2008)

Chamilun,

A 500 amp controller at 144 v should be good for about 96 hp (72 kw) theoretically. This is about 75% of the 1.8 l ICE engine. Will the torque curve of a Warp 9 make up for the lesser hp? Also, how much peak hp will a Warp 9 make? Maybe a 500 amp controller isn't the limiting factor. A 1K LV Zilla might only provide a performace advantage coupled to a motor that can use that power (an 11" maybe). I haven't looked at this closely enough.

It seems that many of the EVs I've looked at state accleration in the 20+ second range. That is not too inspiring.

Thanks for your input.

Rob


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## dimitri (May 16, 2008)

The only time my Miata takes more than 400 Amps at the motor is from dead stop, and only for couple seconds. The torque is impressive, I actually try to be very gentle on the pedal because I am afraid that it will strip splines or bust something in the tranny 

Having said that, I wouldn't want my controller to provide more than 500 Amp, especially if I want decent range out of my battery.

Obviously, if your goal is to race and range is not important, then 500 Amp may not cut it for you.

I have Curtis 1231C and quite happy with it, but please don't take just my word for it, I have no experience with any other controller.


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## RKM (Jun 9, 2008)

Dimitri,

I was hoping I'd hear from you on this. 400 amps is enough to cause worry about tranny damage? Bottom end acceleration must be pretty sharp then. In the garage you indicate "normal" acceleration. Are you suggesting similar to acceleration with your factory ICE? If so, this would be more than adequate. I don't want to race, but I don't want a slug either. I feel much better about the Curtis option now. Nothing like a reputible testimonial (brief though you experience may be)!

I would like to have a minimum range of 50 miles at 55 mph. You indicate 35 mile range at this speed. What is the KWH of your pack and what DOD gives you that range? I guess I'm asking for your efficiency (wh/mile). I'm afraid this range goal leaves me in the unknown land of LiFEPO4. I'd be prepared to spend the extra money if I were confident that they would perform as advertised (cycles and calendar life). That's the unknown and the risk.  What are your thoughts? 

I really appeciate the wisdom of those who have gone before!

Rob


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## e_canuck (May 8, 2008)

Hello Dimitri.

Have you tried "ramping" your controller?









DP


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## Twilly (Jan 22, 2008)

My car weights a bit more than yours and I am very happy with the accelleration. I have a 400 amp fuse protecting the Curtis and have never blown it...


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## frodus (Apr 12, 2008)

you'll almost NEVER draw 400 battery amps though..... the 500A on the curtis would be on the motor side. There's caps inside that help push more current at lower PWM duty cycle.


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## dimitri (May 16, 2008)

Rob,

I'm not going to lie to you, EV Miata is not as zippy as ICE Miata, but its not the controller issue, its a 1000 Lb of lead sitting in it, plus the motor is a little less powerful as you noted.

Ask 4 fat guys to sit on your Miata ( if you can manage it), see how zippy it gets, even with ICE 

However, it keeps up with traffic just fine and accelerates pretty normal, although a little sluggish, but coasting is much better now due to increased inertia, so there is an upside 

Frankly, my driving habits have changed since conversion, I coast more, use right lane more, get tailgated more , but so what? I enjoy driving EV and I catch up to those "lead foot" soccer moms on the next red light anyway. One day I will put in Lithium batts and it should improve acceleration and range, meanwhile I am happy with what I got.

My pack is 22.3 KWH ( 155 Ah x 144 V ) , 35 miles range gets me to 70% DoD. My average cruising current is about 150-200 Amps at the motor. 

DP, thanks for "ramping" info, but I don't feel any need to adjust it, I am quite used to my pedal now


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## dimitri (May 16, 2008)

Rob,

today with fully charged batteries I timed my acceleration. From dead stop in 2nd gear I floored the pedal, it took 10 seconds to get to 45 mph, then it takes me 3 seconds to shift to 3rd gear, then another 7 seconds to get from 45 to 55. All this with floored pedal and no regards to current, which was 350-400 Amps during entire acceleration. Since I was testing the limits I decided not to stop here, so I went to 4th gear which I almost never do, this got me to 70 mph, then 5th gear, first time since conversion and probably last  , this got me to 85 mph. I probably could get to 90 mph, but the road I was on wasn't long enough for the test 

Obviously I would not be driving like this on regular basis unless I want to be shopping for batteries every month, but it just shows you what drivetrain is capable of, if battery would keep up with it.

When I drive to work I need max range , so I keep my current under 250 and coast as much as possible, but when I do short trips around town, I can even have some fun sometimes 

Hope this gives you an idea of what to expect out of Miata with Lead Acid and Curtis controller.


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## chamilun (Jun 17, 2008)

dimitri,
nice conversion. I love how you did your battery supports. I think I will copy


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## RKM (Jun 9, 2008)

Dimitri,

I appreciate your post of quantified acceleration numbers. When people describe their acceleration with words like "good, quick, normal..." it doesn't mean much. What is "good"?

I just hope no damage was done to the pack, car or driver in the effort. The amperage draw of 350-400 amps isn't too severe. It's good to know what to expect.

I'm still making the EV adjust to disregard hp figures. I remember reading a comment made by some automotive journalist, "People buy hp but they drive torque.". This is so true in my opinion. That's why VW TDI diesels _feel_ quicker than they are.

Ultimately, I want a pack/controller/motor combination that will give me a comfortable 50 mile range if I drive for maximization of efficiency but will also make the car get up and go with some enthusiasm when I am able to sacrifice efficiency (short tripping). Like you say... Have fun sometimes.

The 144 V Curtis and Warp 9 should do for their part. The battery decision remains. My timing stinks, in 2-3 years the pack I want will likely cost half as much (maybe...). Better battery technology always seems to be 2-3 years away. It always comes back to whether or not LiFePO4 cells can be trusted to deliver as promised. If they will, they are no more expensive than lead per mile. Group purchase anybody?

In and effort to make a long post even longer (and off thread topic)... What do you think of an eventual two lithium pack system? Suppose I started with a 15 KWH pack, then added a second 15 KWH pack in a few years when cost drops. Treat the two as two separate fuel tanks, A and B. I know it means two chargers and BMS. Thoughts?

Again, thanks to everyone for input on this thread.

Rob


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