Battery Voltage Oscillations

tfriest · Post by **tfriest** » Wed May 17, 2017 4:38 pm

The battery voltage data from my RCPmk2 looks a little odd.

I have a coil-x hooked up for RPMs, a GM style temp sensor (with pullup resistor) and a air/fuel mixture sensor (that has a 5v feed off the gauge).

The battery voltage oscillates a half volt (or more) and the RPM readings seem to oscillate a lot more than they should also.
However, the water temp readings are nice and steady, as is the GPS speed...

Is that somewhat normal, or an indication I have a wiring/ground problem?

Post by **brentp** » Fri Jul 07, 2017 8:12 pm

Hi,

Sorry nobody replied to this.

Are you still seeing the fluctuations?

RPM fluctuations might be due to a noisy RPM signal; how do you have it connected? How much does it vary?

Battery voltage as well, depending on the load on the car's electrical system. 1/2 volt is not uncommon.

tfriest · Post by **tfriest** » Tue Jul 11, 2017 2:14 pm

I was at high plains in CO July 1-2...
Attached is a screen shot from podium of several laps (zoomed onto the straight)...

I have a 2-cycle (Rotax 593) engine and RPMs are critical. The Coil-X has been modified with a bigger resistor and attached to the wire that goes from the engine stator/magneto to the MPEM (computer controller).

I was not able to get the coil-x to work attaching wires to the coil input and it burned out the standard resistor on the coil-x.

Post by **brentp** » Fri Jul 14, 2017 12:28 am

Hi,

Those are large RPM fluctuations!

What type of ignition system is on the motor - is it a capacitive discharge system, or more like a conventional coil?