134: Monday 29th March 2010

I found out that using the cutback inputs on the motor controller does limit the speed of the motor, but does not make it any more efficient. For this a reduction in current is needed. I also found out that if the brake and throttle inputs are activated at the same time then the current is reduced to 500A maximum. So I got to rewiring the relays. In sport mode when the throttle is pressed you get the full 800A available and it accelerates really well. I have used the relay to provide 120v to the brake input (switches it off), so just the normal disc brakes, and when the throttle is release then this activates cutback 3 that is set to maximum speed limit and reduces the release regen to the minimum level and is cutback. When the throttle is pressed again the cutback is disabled so full beans again. For the economy mode, pressing the throttle activates the throttle and brake inputs together giving reduced current and the speed limit set by cutback 2. releasing the throttle removes the brake input and provides the release regen braking. pressing the brake pedal on its own provides extra brake regen charging. As the motor speed is limited then there is no arcing. There is no arcing in sport mode as there is only a tiny amount of regen. So then the motor can go full speed. During the week I am getting a comfortable 25 miles on a charge in economy mode and 17 miles in sport mode if I take it easy.

That was all done during the week, but the weekend just gone I was finding out some of the characteristics of the gauges. I want to use the old fuel gauge for state of charge and the tacho as the ammeter (x100). The fuel gauge shows exactly at the bottom of the scale (empty) with 2.7 volts on the input and full when the voltage is zero. Now I need to make 114v = 2.7v and 134v = 0v. I have a plan and it will be isolated between the batteries and the gauge itself using an opto isolator. The tacho did not respond to voltage at all. I suspected it would only work from a pulse train, but I tried it all the same just to be sure. Using a simple voltage controlled oscillator a hall effect current sensor and a transistor I can drive the tacho. This will also take some working out, but I will get it working soon enough. Then I will have instantaneous current and state of charge. The state of charge will only be measured when the throttle is released so it is off load.

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