rotax 912 battery charging troubles (CH 701)

[karlhaagsma]

Hi there. New to this site. Please help if possible.

 

Currently trying to get through last 10% of build process. Zenith CH 701 with rotax 912 uls and Dynon Flightdek 180. Having problems which transpired at last runup. Electricals seem to be running well static. On battery with master on have incremental amps draw on dynon as well as what I think may be good voltage indication (on fully charged battery). Engine starts and runs fine. However, with engine running there is no appreciable amp draw (indicated) from accessories, unless I turn everything on, which in theory should draw about 12 amps, but maybe only indicates 3 amps tops, and then it is quite variable (mostly 0 amps). Also, it appears that there is no battery charging going on, as while engine is running with no accesories the voltage seems quite stable at about 13.9, but with accesories on it drops significantly to approx 12.1, and when back in static mode the voltage has dropped to same. Anyone have any ideas? May this be a voltage regulator problem? Please help. I have spent 6 years building this machine and now I am stymied in the final furlong. Best Regards, Karl Haagsma.

 

 

[rick morawski]

Hi Karl

 

When you say "transpired at last runup" do you mean that the amps readings changed from a previously normal run?

 

If so you you may want to borrow a reg from somebody with a 912 and see if normality returns.

 

If it has always had slightly erroneous amps readings you may have the shunt or sensor in the wrong line or reversed. If you have a hall effect sensor it has to be zeroed. also you could check the actual reading with an ammeter. I have no experience with the dynon but have put in a couple MGL efis's and I had to try the sensor on a couple wires and reversed it before I was happy with the info it was giving me. Also have you installed a 22000uF capacitor across the output of the reg as per the rotax install manual?

 

You'll get there Karl, don't worry.

 

Cheers

 

Rick

 

 

[Downunder]

When at idle my 912uls struggles to charge the battery and run the lights and accessories. Barely 12v

 

But with accessories off manages to maintain a charge.

 

In flight it all comes good at 13.7v with all on.

 

The generator just doesn't put out the power at idle it seems.

 

This maybe some help, http://pointsforpilots.blogspot.com.au/2012/12/testing-rotax-912914-generator-and.html

 

 

[karlhaagsma]

Thanks Rick and Downunder! Truth be told, I never previously looked at amp guage when I was doing previous engine tests. I was much more inclined to watch the tach and the oil pressure and the oil temp. I was disconcerted to see no acessory power draw on amp meter during engine run, but perhaps as suggested maybe there really is not power generated by the engine at low RPM's. I never got about 1500 rpm. Will check out your advice and see if different outcome. Thank you for your encouraging words. I need to fly this beasty.... Karl