RV-12 charging system

Need advice re my 12 with Dynon 180 & 100. When cruising, the digital voltage reads 13.5, and the vertical bar shows voltage at low end of green.
At low power (taxi) the digital voltage reads 11.5, and the vertical bar indicator shows at bottom of scale--red zone???
Does digital reading reflect battery voltage, and vertical bar reflect generator output, or ?? I don't know if regulator-rectifier is working or not??

Jimmy, my D180 shows about 13.5 V at low power, but my ammeter is essentially a float even at high RPM.
Is this something that just developed now? Have you checked your regulator connections? You could also use a multimeter on the 12V accessory outlet to confirm the D180 reading.

Rich

This is a question for Joe

Jimmy, contact Master Thinker Joe Gores regarding this. Joe is our electrical Guru and can trouble shoot this and educate the rest of us in a flash.

13.5 volts seems about right for cruise for the Rotax. Most other aircraft charging systems put out around 14 to 14.2 volts. For some reason Rotax thinks that 13.6 to 13.8 is high enough, maybe because the Rotax starts so quickly that the battery is not discharged very much.
11.5 volts seems too low. I would expect more like 12.5 volts while taxiing with a good battery unless there is a heavy load with everything electrical turned on.
So the charging system is working during cruise but not during taxi.
The D-180 digital reading and bar graph both indicate system voltage.
I suggest that before you go flying next time and before turning anything on, check the voltage right at the battery with an accurate meter. The fully charged battery voltage should be about 12.8 - 13.1 volts. If it is less than 12.5 volts, then I think that the regulator-rectifier is not doing its job. Some people have replaced the Rotax regulator with a John Deere part number AM101406, but beware of cheap foreign knockoffs. The wires must be switched around on the AM101406 and the mounting holes might not line up.
Heat is the enemy of electronics. The regulator cooling kit should be installed whether the lighting kit is installed or not.
Joe Gores

Thanks Joe

I had been wondering about my system too even though it seems to be working well except during taxi after a flight. My numbers are right in line with the ones mentioned, 13.5 to 13.8 in flight, and 12.8 or so during taxi. When I slow it down sometimes the amps go negative but with a little power things move back into charge and 12.8 volts.

I had read another post in the past where it was mentioned RPM's are needed to produce effective charging. The battery is charge up to 12.5 and the back-up stays charged at 11.6v

The ROTAX uses a permanent magnet generator as opposed to a field coil exciter so it makes sense that low RPM results in low voltage.

The voltage sounds a little low, but the Rotax alternator doesn't have much power output at low voltage. So if you have much power draw, the battery will drain at idle.

Example: CTs used to come with a 100W landing light. Turn that on at idle and after a few minutes, the voltage will start dropping.

TODR