I have a 1998 Ford Ranger (http://evalbum.com/4674) that I bought as a lead-acid EV and converted it to Lithium. In the process I replaced almost everything. I bought an AutoblockAMP from RechargeCar (sadly, discontinued). It's a slick hall-effect current sensor that measures current and counts amp-hours. It outputs a pulsed signal to show amps on a tach (works great). It has another line that puts out 12v to light up a "low battery" light at some specified threshold and a third one that, I believe, uses PWM to ground to simulate a variable resister to drive the fuel gauge to show SOC.
I have the service manual for the truck and indeed it shows a single wire from the gauge to the sensor in the tank. 22ohms empty and 240ohms full (that's from memory so don't quote me). The problem is it doesn't work. Connecting that wire to ground through any resistance does nothing. The engine computer (PCM) was removed during the initial conversion. The fuel sensor wire also went to the PCM but I don't see anything in the wiring diagram that should influence the gauge. What I have discovered is that I can make the gauge work by supplying voltage rather than a connection to ground. 2volts is empty and 9volts is full. I haven't got a clue as to the piece of magic that the PCM (or some other wire) must have provided such that the gauge is now "backwards." So I've tried seeing if I can convert the AutoblockAMP signal. My first attempt was to use it as 1/2 of a voltage divider and that sort-of worked except for finding the right value to drive the gauge full scale. Plus if, while I'm adjusting the ABAMP and I get too close to one end of the scale the resister burns up. My second attempt, thinking it was a PWM signal, was to use a PNP mosfet. That looked promising but isn't driving the gauge linearly enough. It goes from full to empty in the first quarter of the SOC. So I'm looking for ideas. Any thoughts? --Rick _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
