# back emf



## TX_Dj (Jul 25, 2008)

I don't know for certain...

But 4700 RPM may be the max RPM for the motor at that voltage...

What happens when you go to 3rd?


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## dray (Aug 1, 2008)

hi
the current goes up but mph does not seem to increase.

dray


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## TheSGC (Nov 15, 2007)

Did you program the controller? It sounds like the controller has a programmed limit and you have reached it.


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## dray (Aug 1, 2008)

hi thesgc
well i would believe that except the current drops down and i have 120v at the motor terminals. i don't have the software yet to program the controller. but i willl have soon. the controller mfg. told me this controller is current limited at 160A, since the current drops below 100A i believe the back emf is stopping higher rpm. rpm at 40mph is close to 5000 in 2nd gear.


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## dimitri (May 16, 2008)

if controller is limited at 160 your acceleration must be really crappy, how long does it take to get from 0 to 40 mph?


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## dray (Aug 1, 2008)

it takes about 1/8 mile. not too fast. but my controller just let the smoke out so i have returned it for an upgrade to one that has a lot more current output. the one i'm getting is the kelly kdh12800b. if i ever do another conversion i will not use a kit again. i think it wound up costing me a lot more than if i had purchased seperate components.

dray


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## dimitri (May 16, 2008)

Hmm, Kelly controller and smoke, sounds familiar, there is a thread by fugdabug having similar experience with Kelly 

I am so glad I didn't go for Kelly product...


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## TheSGC (Nov 15, 2007)

dimitri said:


> Hmm, Kelly controller and smoke, sounds familiar, there is a thread by fugdabug having similar experience with Kelly
> 
> I am so glad I didn't go for Kelly product...


And the controllers are the same model too...


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## dray (Aug 1, 2008)

well i have my new kdh12800b from kelly and what difference. runs 45 in 2nd at about 100a. go in 3rd and can get up to 50mph without much effort. current at 50mph is about 150 to 175 amps. i still do not know how to judge dod of the batteries. what do other ev drivers do? would appreciate any advise.

dray


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## TheSGC (Nov 15, 2007)

dray said:


> well i have my new kdh12800b from kelly and what difference. runs 45 in 2nd at about 100a. go in 3rd and can get up to 50mph without much effort. current at 50mph is about 150 to 175 amps. i still do not know how to judge dod of the batteries. what do other ev drivers do? would appreciate any advise.
> 
> dray


That's good that you got it working. Do you have any pictures of the controller setup or maybe youtube some videos of the EV in action?


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## dray (Aug 1, 2008)

i will try to put it in the garage in a day or so. seems to run quite well but not sure of range and how far i am discharging the batteries.

dray


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## dimitri (May 16, 2008)

Dray,

those are much better numbers, so I guess Kelly was the culprit of your troubles.

As for SOC, I marked my Voltmeter with 100% DoD, 80% DoD, and full charge, you can see a picture in my garage page. Unfortunately its not a linear function, i.e. it stays around the middle longest before dropping down. You just have to keep driving it further away from home and measure round trip miles, you should expect between 30 and 40 miles range I guess.

As I drive I watch the voltmeter without load ( gas pedal released ) and make sure it stays over 80% mark. Also, under load, especially during acceleration, I try not to let it sag too much, not below 100% DoD mark.

As I return from work which is my longest EV drive of 32 miles on single charge, my voltmeter is between 100 DoD and 80 DoD mark under normal load, sags to 100 DoD during acceleration, but returns to 80 DoD when pedal is released. Once in the garage for 5 minutes, it climbs couple volts over 80 DoD.

I know this is not very scientific, but that is what I experience on a daily basis, hope it helps.


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## TX_Dj (Jul 25, 2008)

Alternatively, if you have the benjamins... the Link-10/Emeter is a great device for automatically computing these things... assuming you can get it programmed correctly.


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