EnviroKarma.org - Electric Vehicle (EV) Conversion '...it's (NOT) hard to be Green' - what Kermit should have said


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Instruments for the Suzuki Swift (Geo Metro/Pontiac Firefly)...

    My goal was just minimal useful instrumentation... and hoping not to mess around under the dash too much. I decided to try a 3-gauge pillar mount; knowing I wanted at least a state of charge 'fuel gauge', and an ammeter, but not sure whether a voltmeter or temperature would be more useful in the third spot. A voltmeter would show me instantaneous voltage that the 'fuel gauge' does not. This is really only useful to prevent leaning on the motor too hard too long and operating with voltage 'sag'. The temperature of controller and or motor is perhaps more likely to be a problem and deserve closer monitoring, but my standard kit from KTA included a voltmeter, but no temp gauge. My understanding is that both the controller and dc-dc convertor have built in capacity to handle a significant amount of 'sag', so I am not sure how important it is to monitor the instantaneous pack voltage.

    The 'missing' tachometer...

    Since I don't have a tach, and its probably not worth buying one... I found a nice formula for figuring mph from rpm if you know the gear ratios. Gears can sometimes be found in user manuals, or online in some spec sheets for used cars or repair sites. :

      mph = (RPM * Rtire)/(G1 *Gf *168) where G1 is gear selected, and Gf is final ratio in my case with: RPM = 5000 Rtire (radius rim+tire) = 11 Gf = 3.79 gives: 86.38/G1 = mph so I set my 'redlines': 1st: G1= 3.58 -> mph= 24 2nd: G1 = 1.89 -> MPH = 46 3rd: G1 = 1.28 -> mph = 67 .... enough! I slapped stickers right on the speedo...

The installation went well... I found easy access to illumination power by tapping into the illumination dimmer switch wires , and my gauge wire bundle fed thru the firewall nicely right along with the old ICE harness. I had minimal time under the dash and it came out looking pretty spiffy.

'modifying' universal ABS pillar mount: 1.75 hr
install and pre-wire gauges : 2.75 hr
install, find illum wires, etc : 2.5 hr
total : 7 hrs


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