Voltage Regulator Failure

HI all

Good discussion.  The root cause, I assume you are looking for that, is the heat cycle.  All circuit boards that use solder (not all solder has lead anymore) has temperature changes.  Normally it is not the solder component itself that fails as a few people have seen.  The solder releases primarily from a mechanical bond failure (cracks) and the part is then failed.  Rotax puts a limit on this part, like all the electrical ones they have, at a limit of 80C (175F) and even calls out an OEM to verify that the parts within their design do not exceed this.  

The different potting compounds I dont think are the issue but they do show the changes from the older production to the newer versions.  The heat at 80C is not enough to fail the solder itself, it is the heat cycle that fails the mechanical bond.  Relatively speaking this is a rather inexpensive regulator.  The major failures generally are from poor grounding of the body of the regulator and a solid path back to the engine.  In homebuilts I always recommend a ground wire from the attachment of the regulator directly to the engine and not rely on the airframe and all issues that can cause.  

There are some good papers on this phenomenon online if you take some time to look.  Reduce the heat of the regulator body as it needs to be a nice stable temperature to avoid deep heat cycles. 

I can post some picture of the inside of a regulator (old version) if you like.  As noted by some others it is a simple device and normally effective.  As Roger noted test the heat with a temp strip to verify you are in the ballpark for max temperature.

Cheers 

Like RW I appreciate a good debate/discussion & this is one.

I am currently tossing up between three aftermarket VR replacements;

B&C AVC1 -  a drop in replacement, which comes across to me, as a more robust, sophisticated version of the Rotax/Ducati. ie similar technology https://bandc.com/product/avc1-advanced-voltage-controller-14v-homebuilt/

Schicke GR6b-OVP - likly MOSFET https://www.aeroakku.com/REGULATORS/Schicke-Regulator-GR6b-OVP-12V::1901.html?language=en

CARMO CARR5115 MOSFET  https://www.vectriqparts.com.au/product/rotax-voltage-regulator-carr5115/

Your thoughts on the above will be much appreciated😈

Sean 

I checked some of the links, here is the English translation of one...note the advanced temperature controls, it actually switches off to protect itself if you exceed 85C...nice feature. 

Thanks RW.

I agree the SILENT-HEKTIK F4112se specifications are top notch AND it has a solid reputation.

Unfortunatly the S-H  is not available for delivery outside Europe. Some devious (in a good way) US owners have arranged for Euro based friends to purchase & deliver on their behalf.

I could probably make similar arrangements to acquire, however such an arrangement would likly take several weeks - a month. My aircraft is currently grounded and my flying itch gowns exponentially each day, so that brings me back to the above list.

I can get a CARMO CARR5115 MOSFET today. The other VR's - B&C from USA and Schicke from EU will take at least two weeks (or more).

I would wait for what is perceived to be a superior product - hence my request for recommendations on the above VR's however the itch grows stronger aaaaah!

😈

RW

This conversion is relative to actual failed regulators, not the wider range charging systems not working. The root cause of the regulators with internal failures is “Design Deficiency.” More specifically the mechanical design and thermal management. 

Your statement “Normally it is not the solder component itself that fails as a few people have seen.” Isn’t true. Solder is the medium that connects the component lead to the PCB and this is the failure point in a Rotax regulator. If the statement was intended to be literal, than the reason it’s only been seen by a “few people” is because only a “few people” have opened it up to look. The statement simply doesn’t hold up relative to the failure rate and failure mode we’ve seen. 

There are no issues with electronic circuit design or in the ratings of the electronic components used. The regular failures are with the mechanical attachment of components. Yes, heat is a contributing factor, so let’s talk about heat. This regulator by design, will generate heat, particularly at higher currents. Since Rotax chose this design it’s their responsibility to deal with heat generated from that choice. If Rotax is claiming thermal cycles as the cause of the lead stresses and the associated lead failures, that’s is an admission of a design defect. Rotax’s derating the regulator temperature limits is self serving, it doesn’t resolve the design flaws and only delays the failure so it happens outside of warranty. 

You made a reference to solder and lead, I’m not sure why? My use of the word lead references the wire connection to an electronic component, not lead, the heavy gray metal.