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Discussion Starter · #1 ·
I had an S-10 with a Curtis 500 amp. Did 77MPH. I sold it,:(, and bought a better S-10 and have installed a Kelly 650 AMP controller. Problem is, I'm only getting 45mph. Dont have amp meter yet, so I'm not sure what its putting out, but with the old truck, I had a Kelly 500 AMP and it only reached a maximum of 300 amps initially and quickly went down to a maximum of 170 amps after warmed up. It only did 40 MPH and creeps up hills.

Why do I get better acceleration/top speed with a Curtis 500 than with a Kelly 650?
 

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Why do I get better acceleration/top speed with a Curtis 500 than with a Kelly 650?:confused:
It sounds like they don't rate their controllers the way the rest of the controllers do. Amp ratings are based on a Temperature rating on the FET's inside, as well as a duration. Sounds like they're running hot, and not for very long... which limits their output current. I haven't heard one person say they actually live up to those current ratings. A couple of EV parts distributors say they're more like 1/2-1/3 the rating, and they they've NEVER reached their max.

Measured is one thing, but going off the FET datasheet for max amps unrealistic. I seriously doubt they've actually measured their absolute max current output.

Are you sure your batteries are not sagging? That can limit current too.
 

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I had an S-10 with a Curtis 500 amp. Did 77MPH. I sold it,:(, and bought a better S-10 and have installed a Kelly 650 AMP controller. Problem is, I'm only getting 45mph. Dont have amp meter yet, so I'm not sure what its putting out, but with the old truck, I had a Kelly 500 AMP and it only reached a maximum of 300 amps initially and quickly went down to a maximum of 170 amps after warmed up. It only did 40 MPH and creeps up hills.

Why do I get better acceleration/top speed with a Curtis 500 than with a Kelly 650?
I hate to be the bearer of bad news, but I'm sorry to say you are not the first one to see a drop in performance after switching from a curtis to a to a kelly controller that was supposed to have more power. You could try and contact kelly and see if they can help you because there are some on the forum here that are satisfied with their kelly controllers.
 

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Which amps?

The controller rating is typically the output rating, i.e. motor amps, not pack amps. If your ammeter was on the pack side of things, 300A is probably about right, as it can pull less amps at higher volts on the input to make higher amps lower volts on the output.
 

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Which amps?

The controller rating is typically the output rating, i.e. motor amps, not pack amps. If your ammeter was on the pack side of things, 300A is probably about right, as it can pull less amps at higher volts on the input to make higher amps lower volts on the output.
Ahh, another very good point from TX_Dj!!!

you won't ever see 650A on the battery side, and I honestly don't think they could supply it without sagging/crackling/popping...etc.
 

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What kind of heatsink are you using for the Kelly?

I too have a Kelly, but I have not measured the AMPS coming out. However, I did notice my Kelly getting pretty hot doing short runs and I had heatsink (3/4" aluminum plate) with thermal grease. I then wiped off the thermal grease and used a high AMP thermal pad, and now my controller is pretty much stone cold after a high power run. I am actually worried about frying my motor with the 400 AMP Kelly since my motor gets a lot hotter than anything else.
 

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Discussion Starter · #8 ·
What kind of heatsink are you using for the Kelly?

I too have a Kelly, but I have not measured the AMPS coming out. However, I did notice my Kelly getting pretty hot doing short runs and I had heatsink (3/4" aluminum plate) with thermal grease. I then wiped off the thermal grease and used a high AMP thermal pad, and now my controller is pretty much stone cold after a high power run. I am actually worried about frying my motor with the 400 AMP Kelly since my motor gets a lot hotter than anything else.
I have a heat sink I pulled and cut from an industrial drive. Mated it to the Kelly with thermal grease. In the old truck, I had fans blowing through the sink, but with this one, its so cold now, I figure I didn't need a fan.

Doesn't matter, I just got a call my Curtis 1231C is in the mail, and it runs better than a Kelly 650 any day.
 

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I have a heat sink I pulled and cut from an industrial drive. Mated it to the Kelly with thermal grease. In the old truck, I had fans blowing through the sink, but with this one, its so cold now, I figure I didn't need a fan.

Doesn't matter, I just got a call my Curtis 1231C is in the mail, and it runs better than a Kelly 650 any day.
I still think that throttle setup is holding you back with the Kelly. On Wednesday I am putting my EV back together and I am going to find my top speed and I am going to try the different controller settings.
 

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I'm not driving my truck around lately, its been snowing, so I guess I'll try the other throttle variations and see what happens. My last truck was wired with one of those variations, and it didn't work at all. The diagram, at the time, showed a block with three wires going into it, and my throttle was a two wire. So I had to e-mail Steven at Kelly to get a good version to wire it up, and he gave me the current version I'm using in this truck. My Curtis will be in by this weekend, so if I can't get anything more out of the Kelly, its gone! Will make a great paperweight, or toy car controller.
 

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I'm not driving my truck around lately, its been snowing, so I guess I'll try the other throttle variations and see what happens. My last truck was wired with one of those variations, and it didn't work at all. The diagram, at the time, showed a block with three wires going into it, and my throttle was a two wire. So I had to e-mail Steven at Kelly to get a good version to wire it up, and he gave me the current version I'm using in this truck. My Curtis will be in by this weekend, so if I can't get anything more out of the Kelly, its gone! Will make a great paperweight, or toy car controller.
I just wired up the three wires and took an ohm meter to figure out where which connections to hook up. Most of the equipment/devices I use are prototypes and usually don't have manuals or in depth wiring diagrams so I work my way through it. However, with the Kelly and the three wires, the Curtis has three connections on the POT- one of the outside connections is GND and the other outside is +5 and the center is the Throttle. Now if you hooked it up this way and it didn't work, its because you have the +5 and GND connections reversed and the Kelly will see "high pedal" and not function.
 
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