Reviving Dead Gauges - Fuel Economy, Hypermiling, EcoModding News and Forum

TomEV · 12-08-2012, 10:24 AM

When I got my newest EV, it only had one operational gauge in the instrument panel - the speedometer. The other gauges - tachometer, fuel gauge, and temperature gauge - just sat there, pegged to the lowest reading. I suppose they don't really need to work, as the Electricar had been driven over 25,000 miles without them. However, I find that driving around with dead instruments is somewhat annoying.

I found a group in Australia that makes a small device which turns the fuel gauge into a state-of-charge (SoC) gauge, and the tachometer into an ammeter. It also incorporates a system to light up a LED when the pack reaches a certain low level, mimicking the low fuel light in many vehicles. The adapter is called a ZEVA Fuel Gauge Driver Plus.

Here's a picture of all the gauges working - even the temp gauge. I bought a temperature sender for the original ICE engine - about $10 - and attached it to the motor case. The temp gauge is working, but the motor just isn't hot enough after 13 miles to make the needle move much - probably about 80f in the picture below. I drove for 30 miles on the freeway the other day, and the needle moved towards the higher end of the 'normal' range. Actual temp of the case was about 140f at that point.

The fuel gauge is fairly rudimentary, but is much easier to figure than a 'wagging finger' volt meter, and doesn't need another instrument box attached cattywompus to the dashboard.

I have the tach/ammeter set for 8-cylinder mode. 2,000 RPM = 100 amps.

Ryland · 12-08-2012, 02:03 PM

So it can run the tac based off of the amp meter style pickup that goes around one of the motor cables??? I know that motors draw current in pulses but never thought that you could get an inductive pickup that was sensitive enough.

For your temp gauge it seems like a resister in parallel should allow you to fine tune it.
I also suspect that other thermoresister temperature pickups should work, say from a remote thermometer, so you might be able to find a smaller pickup that you could get deeper in to the motor.
On my C-Car I'm planing to mount a 1/16" thermal couple drilled and epoxied in to one of the brushes seeing as how they are one of the most sensitive parts to getting hot and heat up fastest.

gone-ot · 12-08-2012, 02:26 PM

...instead of "reviving" I'd recommend using the word "repurposing"

TomEV · 12-08-2012, 02:44 PM

I suppose re-purposing might apply to the tach, but the 'fuel' and temp gauges are pretty analogous to their original purpose .

The ZEVA driver converts the amount or power moving through the HV cable to a set of pulses the tachometer can understand. It also 'counts' the amount of total power used, and adds a bit of resistance to the fuel gauge, making it move down. When charging, it subtracts the resistance, making the fuel gauge go up. If you only give it a partial charge, (like at a public station) it only goes up the amount of charge it receives. Pretty clever, and it seems to me to be relatively accurate - I haven't had to reset it since I calibrated it a while back.