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Update 11-07-2010

The gauges were a lot of work but worth it! My original idea was just to mount the amp meter, voltmeter, ect on top of the dashboard. But at the behest of a friend I DID take the dashboard apart to get at the instrument cluster, it wasn’t as bad as imagined it, after multiple configurations ( 4), I ended up with a very attractable presentation on the instrument cluster. My first Instrument Idea involved the adaptation of a digital volt meter as the pack voltmeter. I got a $3 dollar DVM from Harbor freight cut down the box, wired in a 9 volt dc to dc adapter to the 9 volt input, made a hole in the face plate of the instrument panel that corresponded to the display size of the DVM and mounted this on the panel. This looked very nice from the front of the unit and fit nicely in the cluster. As I tested the unit before instillation, the display started showing a wild variety of numbers and than went blank……. Kaput! Oh well. I bought another unit installed it and had the same result…… dang! At this point I gave up on adapting a DVM for that purpose and switched to a plain old analog voltmeter. According to my “Meter Manual” one just needs to measure the resistance of an analog meter and divide that by the voltage to determine the resistance per volt. Therefore my meter was 518 ohms/12 volts = 43.16 ohms/volt, and my pack is 120 volts ( or an even easier way to figure out the required resistance, I bought a 12 volt gauge and I wanted it to read 120 volts so I needed X10 more resistance!!)…. So I needed a total R of 5.18Kohms for the proper meter reading of X10. Fortunately the multipack of resistors that I got from radio shack had a 4.7K( this + the integral resistance of the meter = 5.2K!) resistor in the pack, this suited my needs surreptitiously well indeed. Next, I mounted the voltmeter and ampmeter on the same side or the cluster, wired in the lighting to the existing lighting structure, to make a very presentable presentation in the dash! All of this went back together very nicely and concluded phase 3 of the project ( choose, purchase and install the electronics of the EV conversion) .
At this point I still hadn’t tested the Unit. So I scavenged all of the batteries that I own and came up with a 72v pack and the accessory battery. These I carefully wired together hopped in the rig, took a deep breath, and turned on the ignition. With the tranny in neutral I gently taped the gas peddle and noticed the ampmeter deflecting backwards! Glitch #1, I disconnected the hot lead and reversed the ampmeter leads. After reconnecting the leads, I turned on the ignition, now the voltmeter read just under 8 ( X 10 my outside reading of the pack said 77 volts YES!), and a gentle tap on the gas peddle popped 100 amps on the meter…….. so I put it in reverse and pulled out of the garage! Next I drove down the driveway (about 400ft) shifting from 1st to 2nd pulling 200-300 amps, reversed, and drove back to the garage! Success!!!! I now have enough confidence in the controller ( curtis 1321c), motor ( AMD FB 4001c), switches ( Albright sw200’s), relays, gauges, and wiring, to progress to phase 4 ( the selection, purchase and installation of the batteries)……Its Alivvvvve!


 

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Nice work, Lou-ace. A couple things occurred to me.

Try one of your digital meters with its own battery. If that works, the problem is that your DC/DC is bad or is not isolated.

If your analog meter measures 518 ohms, it draws I = 12v/518ohms = 23ma at full scale. That's a lot! It will run your pack dead if left on a long time. And, your 4.7k series resistor will be dissipating (120v-12v)^2/4700ohms = 2.5 watts! The Radio Shack resistor is probably 1/4w or 1/2w and won't last long.

Analog meters that draw less than 1ma full scale are pretty common. That would solve these problems.

Another thing: Cheap meters aren't very accurate. Battery voltage doesn't change much between full and dead (like 12v=dead, 13v=full). So, what you want is an expanded scale meter, where the bottom end is around 100v and the high end 150v (for a 120v lead-acid pack). To do this, pick your resistor so the meter reads 0-50v, and then put a 100v zener diode (or string of zeners that add up to 100v) in series.
 
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