I have added three new instruments to the dash board. The left one is the ammeter hooked up to show battery current. The voltmeter shows the voltage of the entire battery pack (144V). And the rightmost instrument is the auxillary voltmeter telling what voltage there is on the cars 12 volt system. The aux. voltmeter is only connected when the EV has it's "ignition switch" on.
The wires to the ammeter and the voltmeter are inside small size
plastic hoses in order to double insulate it from the EV's body.
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The ammeter is used to optimize range. I probably look at the ammeter ten times more often than the other instruments. When flooring the pedal it goes all the way to 400 A and beyond. By adjusting the foot on the accelerator pedal, I try to use 100 A or less when ever possible. Using 150 A in stead of 100 A may increase speed only slightly, then I'll just stik to 100 A. This all depends on traffic, of cource. When entering the highway I usually see 300 A for 10-15 seconds and then decreasing to 100-150 A when approaching cruising speed. When ever possible I just coars using zero amps. It is incredible how many "free rides" you can get when you get used to let go of the accelerator pedal so early that breaking becomes a rather rare activity.
The voltmeter is my fuel gage. The batteries voltage measured under load gives a good idea about how much further I can go. I have gotten used to look at the voltmeter when ever I happen to use a steady 100 A. Above 145-150 volts is "No problem". At 140 volts I am getting nervous and would like to be very close to my destination. At 130-140 volts the EV is loosing power when accelarating, and it is like my body can feel the pain I am putting my Optimas through. At this point I can go slowly for maybe 5 km before the voltage just drops like a rock to 70-80 volts under load. Time to stop, wait five minutes to "grow" some amps, then go 2 km more. (I have only done this once). When plugged in and charging the voltage increases to almost 180 volt. My voltmeter only goes to 160 volts. One that goes to 180 volts would have been more appropreate...
The auxillary voltmeter tells me if the 12 volt battery is getting charged or not. I am using a 13.3 A 14.5 volt DC/DC converter that takes from the 144 volt traction batteries to charge the good old 12 volt battery. 13.3 A will do fine if driving in a country where you do not use to drive with the lights always on. For my EV it is just barely enough since the low beam lights are always on. When ever using the fan, high beam or other extras the 12 volt battery gets drained, and every other week I need to connect a garage charger. I am planning to add a small 2-4 A automatic charger that will charge the 12 volt battery when ever the EV is plugged in for a charge. Anyway, looking at the auxillary voltmeter, anything above 13 volts tell me that the battery is not getting drained and that my Vicor DC/DC converter i functinal. When it goes to 12 volt, or slightly lower, it is time to turn off the lights to check that the Vicor is still working ( voltage increases slowly to almost 14 volt) and to add charge with my garage charger.
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