# What next?



## grose (Apr 30, 2008)

Sorry to be so long-winded but...

It has been a few weeks since the purchase of my EV. Many people on this forum state that their EV is "never really done" and now I think that is so true. I'm already looking at ways to improve my car.

I'm looking to improve both range and acceleration. Currently I'm running 96V through a 9" forklift motor. (8, 110AH batts in series) The car will go just over 20 miles at 30-35 mph speeds. Highways speeds apparently kill it quick. My wife ran out of juice after driving just 8 miles highway.

Right now I'm looking into two different options (maybe three)

Option #1: Add one or two more batteries in series and bump up the voltage to 108 or 120V. Obviously making sure that the motor can withstand it. I already ran a thread discussing this. Another thread on "overclocking" was helpful too.

Option #2: The car currently is using an old EV1 forklift controller. When the bypass contact kicks in I get full pack voltage and I think this is bringing down the batteries quicker too. I'm thinking about swapping out the controller in favor of a new Curtis. I am a little apprehensive because I don't know the reliability of a Curtis controller. The EV1 controller is at least 25 years old, so it is obviously very reliable. 

Option #3: I've read a bit about "field weakening." I don't know much about this, but I've read that it increases range and top speed. Is this something that can easily be done?

I'm new to EV's but so far I'm finding this to be a fascinating new hobby. Your response as to which option I should take first is appreciated.

Thanks


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## TheSGC (Nov 15, 2007)

I'd say go for a new controller. The EV-1 is a very inefficient controller, and its probably sucking a lot of unneeded power. A Curtis or Kelly Controller wiould be much more efficient and limit current and should increase range. 
Going to full pack voltage kills batteries extremely fast, and since the bypass kicks in there is nothing to limit the current.

What model batteries are you using and is your area hilly?


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## Fatboy (Oct 30, 2007)

Use 16 6v batteries and upgrade the controller.

Fatboy


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## ww321q (Mar 28, 2008)

I think Fatboy's got the answer 16x6volt or another 8x12volts > I have been thinking about your controller . If I can find some relays for a good price I might build something similar . ..............J.W.


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## grose (Apr 30, 2008)

ww321q said:


> I think Fatboy's got the answer 16x6volt or another 8x12volts > I have been thinking about your controller . If I can find some relays for a good price I might build something similar . ..............J.W.


If you want to build something similar, this is the inexpensive way to go. You can find these controllers easy and cheap. Probably a quarter the cost of a new controller or even less.


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## ww321q (Mar 28, 2008)

You know on the old relay type controllers you would use relays to rearrange the battery pack to get different voltages . I'm thinking of doing 2-60 volt packs. I think I can get a used 48 to 72 volt controller for a good price . Run it at 60 volts and use the relay or relays to connect the 2 battery packs parallel . When you hit top speed you would switch to series on the battery packs and go to 120volt . That would disconnect the controller and just run on a on/off switch contactor . What made me think of it was driving on a flat road at 60mph .I could see the light ahead was red so I kicked it in neutral . I coasted quite a ways before having to slow with the brakes . Anyway you would hit the throttle a few seconds then let off and coast . I don't think it would be that hard to do because I do it already in traffic that isn't going as fast as I want . J.W.


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## major (Apr 4, 2008)

grose said:


> Sorry to be so long-winded but...
> 
> Option #3: I've read a bit about "field weakening." I don't know much about this, but I've read that it increases range and top speed. Is this something that can easily be done?
> 
> Thanks


Hi grose,

Likely you have a series wound motor. To field weaken a series motor you need to shunt (or divert) some of the current around the field. This is done with a contactor and a low Ohm resistor connected in parallel with the series field.

When you field weaken the series motor you reduce the flux for a given armature current. This will increase RPM for a given current or torque. It also decreases torque for a given armature current. No free lunch. The amount of increase in RPM is load dependent, more at light loads. Typically one can count on maybe 10 to 15 percent RPM increase at running loads, with a similar increase in current. Meaning about the same efficiency. So one could expect an increase in vehicle speed, but not in range.

Field weakening of series motors was done frequently on forklifts. You need to control when it is employed. You need to be out of current limit with the controller full on. When you shunt the series field you mess up the motor inductance and the controller isn't going to like that. Then, when lift the throttle, you need to drop out the diverter resistor right away. So, unless your controller is set up for field weakening, you need to add some logic.

Hope that explains it.

major


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