# Curtis Makes A Sluggish Conversion



## Nathan219 (May 18, 2010)

What is the volrage dropping to when 400 amps is requested from batteries? Sometimes controllers are set with too high of a low voltage and this causes the controller to limit power when the low voltage is reached. See if you can lower to low voltage set point and see what happens. 400amps at 120volts is 48kw or 64hp


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## piotrsko (Dec 9, 2007)

He is probably getting 50 hP useable, about the same as the 4 banger. Not stellar performance. I wasn't happy at 120 v, I'm at 100 / 150 hp now, and the li-on pack cut out 400 lbs, so I'm back to stock 2.9 performance. 196 v @ 250-500 amps.

Any way to measure motor current when running?


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## Ziggythewiz (May 16, 2010)

What's the truck weigh? When my bug had 600 lbs of lead it was quite zippy, but when I upped it to 1000 lbs it turned sluggy.


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## evmetro (Apr 9, 2012)

Inframan said:


> I bought this electric truck already converted and the I figured I would use the curtis controller because it was already all set up for it I took it for the first few drives today and it has no get up. It is the 120 volt 400 amp model and it was put in a 1989 ford ranger with an advanced dc 9 inch motor. The acceleration does not feel like 400 amps more like 200. Is this normal for a 400 amp curtis? Is there some sort of adjustment for the ramp function?


I would verify how many amps with a meter to determine if you are having technical problems or if that controller is just too small to do what you want it to do. I believe that they also offer a 500 amp 144 volt unit that may have been more appropriate for your needs.


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## onegreenev (May 18, 2012)

Is the controller connected to a proper heat sink? Also 400 amps is just not enough for a large vehicle and low voltage. 120 volts is not much and you will sag below 100 with no problem. You need a minimum of 550 amps. That extra 150 amps is going to make a huge difference but you still won't have stellar performance. You need 144 or more volts and upwards to 800 amps to get that truck to move with some gusto. New batteries? Lead? Lithium? Your motor should be OK.


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## major (Apr 4, 2008)

Inframan said:


> Is there some sort of adjustment for the ramp function?


http://www.google.com/url?sa=t&rct=...8s7XXHqW3zme87g&bvm=bv.70138588,d.b2U&cad=rja 

That is the Curtis manual. See page 25 for the ramp adjustment.


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## piotrsko (Dec 9, 2007)

Ziggythewiz said:


> What's the truck weigh?


Something like 3700 to 4400 in stock XL trim with 2.9 6 banger. Motor swap was about equal, maybe a hundred # less in fuel system stuff. Maybe has 3:07 rear end. 4X4 s had either 3:73 or (rare) 4:10. A4ld slush trannies suck because they shift early for economy.


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## Inframan (Jan 30, 2011)

Well 58lb per battery the 6 volt energizer 215 amp hour sam's club brand. There's twenty, so 1160 lbs worth. The truck weighed 2800 lbs before the conversion I would say sans motor etc probably weighed 2500 lbs, so 3660 plus 100 lbs of solar panels plus the 100 lb motor with controller and two chargers etc probably about 4000 lbs. 

Yes the controller is connect to a large heatsink below it with a fan blowing up on it and another sucking air off it toward the back of the truck.

I just took it for a ride today and the voltage sags to about 110 volts or maybe a little below and the motor amperage that is measured by an analog meter goes to a little below 400 amps maybe 350 to 375. 

And another thing that may or may not be the whole problem but as I pulled it back into the shop I look underneath and there was rear end grease splashed all over the rear left (driver's side) tire so I think the seal needs to be replaced on that side. Would this affect performance? There may also be a bearing out.


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## onegreenev (May 18, 2012)

Bad bearing could be an issue. Thats a heavy vehicle for less than 400 amps. That alone will give pretty poor performance. You need a controller that can deliver much more or get the lead out. That was an issue with my VW Ghia when I did my first conversion. 1020 lbs of lead in a little Ghia. I was running originally 72 volts but at 550 amps. It was OK. I then changed the controller to a synkromotive and bumped the voltage to 96 and it was night and day as I had my amperage current set to 800 amps. I actually got that little sucker to go 85 mph. Performance was on par with a good stock VW 1500 engine. Too much weight. Felt dangerous. Hugged the road well. 

I would never consider any thing less than 550 amps for a street driven vehicle. The larger the more the need for more voltage and amperage. 

It will work but it won't be very peppy. 

So check the bearings and check the oil seal and oil and fill your tires up as much as you can without blowing them out. 40psi maybe. It can help. 

How new are the batteries? What charger are you using to charge them and how far have you been able to go? Don't take your car down to where it is just crawling. It is hard on the Lead Acid batteries. You have about 50% capacity you can safely use. Trust that. 

Performance drops as you drain your pack. At 50% charge the performance is pretty lousy. If you need like only 10 miles or so then the lead should do you just fine. Keep a good eye on your cells and keep them filled with water and keep check on the Specific Gravity of each cell. A monthly routine should do just fine.


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## gunnarhs (Apr 24, 2012)

Inframan said:


> I bought this electric truck already converted and the I figured I would use the curtis controller because it was already all set up for it I took it for the first few drives today and it has no get up. It is the 120 volt 400 amp model and it was put in a 1989 ford ranger with an advanced dc 9 inch motor. The acceleration does not feel like 400 amps more like 200. Is this normal for a 400 amp curtis? Is there some sort of adjustment for the ramp function?


 Hi, look at the points posted above from the community very valid points here I just want to add about my experience.
We have used this kind of DC-controller for a small car (up to 1200 kg).
This controller (as most of the DC ones I have tested) does not provide 400A continuous but only for short time and usually at lower revs/voltages.
In most manuals they give you the continuous rating which for a 400A controller is about 200A. This is the amperage you can rely that is provided for the whole voltage range and for longer than a few minutes.
The more advanced controller manufacturers (most AC and Soliton for DC) give you the Power rating (continuous and max), which is the product of voltage and current and gives a better comparision to the previous installed ICE. The maximum power should be the same as the spec of the ICE if you want to get similar performance at higher speeds. Because you have more torque at lower speed with the e-motor you can use a lower power setup than ICE but when you need accelearation at higher speeds, the max power is the limit. 
So for this kind of vehicle you have I would recommend a more powerful controller like the other guys here have done. I would say at least 140V / 800A, you should be able to keep the same motor with that.


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## EVfun (Mar 14, 2010)

Major pointed out a link to the Curtis manual. The ramp rate and max amps should be adjusted to their maximum values. After verifying that it is still going to be a slug.

You are trying to move a 4000 lb. vehicle with less than 50 horsepower! With golf cart batteries you may have 110 volts at your peak current of 400 amps. That is 44 kW of power input and at 100% efficiency 746 watts equals 1 horsepower. So you are putting 59 horsepower into the motor at perhaps 80% efficiency at full power. That will give you about 47 shaft horsepower for a 4000 lb. vehicle. You have to push about 85 lb. with each horse! Your power to weight ratio is about the same as an old l36 HP VW Bug with 4 adult men crammed inside.


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## Ziggythewiz (May 16, 2010)

^^^ yup. This curtis is great for a 2000 lbs vehicle, and okay for 3000 lbs. Much above that you're asking the little girl with the barbie bike to burn you off the light.


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## Inframan (Jan 30, 2011)

OK ok. I'm going to adjust ramp and amperage if that doesn't work I WILL put in the Netgain I have and possibly buy a few more batteries for more voltage.


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## major (Apr 4, 2008)

Inframan said:


> OK ok. I'm going to adjust ramp and amperage if that doesn't work I WILL put in the Netgain I have and possibly buy a few more batteries for more voltage.


So what happened? Any adjustment to be had? It help?


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## Inframan (Jan 30, 2011)

It helped a little bit but with this controller I would really say its purely a city car I'd say 0 to 60 is over 20 seconds I have to use 1st gear its not even an option and forget taking off on a hill. I'm going to have to take the time sometime next month to put that controller in. Good news is the batteries kick ass I went 25 miles today and didn't even get down past the third bar on the SOC meter but that might be totally to just the wimpy controller.


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