Need advice on alternator.

[6adan]

I am building a 6A with a Dynon SkyView. I was told a 35a would be enough and I got one but now am not sure that I got the right one. This one will be turning backwards. Will it work this way? It also dose not have the built in regulator which I wish I had got. I need to know if this one will be ok or should I get something else.

Thanks Dannie

[vlittle]

Originally Posted by 6adan

I am building a 6A with a Dynon SkyView. I was told a 35a would be enough and I got one but now am not sure that I got the right one. This one will be turning backwards. Will it work this way? It also dose not have the built in regulator which I wish I had got. I need to know if this one will be ok or should I get something else.

Thanks Dannie

Depends on your mission. 35a is fine for day VFR, including strobes and position lights. For night ops, it may be not enough depending on the landing lights you use and other loads. Even then, these are intermittant loads that can be powered from the battery.

Make sure you feed the alternator diodes some blast air.

Externally regulated alternators are in some ways superior to internally regulated ones, so that should not be an issue if wired properly and an OVP is used.

Finally, if the alternator ever fails, you can usually get one locally as opposed to the fancy 'aviation quality' ones.

I have had both types fail. In th 35a case, I melted the diodes. In the 'aviation quality' case it was a bad OVP-regulator module. The 35a one was replaced by a local alternator shop, the other one I had to wait for an international shipment of a replacement part.

[WingsOnWheels]

Dont forget about some sort of overvoltage protection system. Having an external regulator makes this a lot easier. Just put in a crowbar ov module so it will trip the field breaker in an ov condition. B&C has them and they come with install documentation.

[BillL]

Originally Posted by 6adan

I am building a 6A with a Dynon SkyView. I was told a 35a would be enough and I got one but now am not sure that I got the right one. This one will be turning backwards. Will it work this way? It also dose not have the built in regulator which I wish I had got. I need to know if this one will be ok or should I get something else.

Thanks Dannie

You should look at all the loads and satisfy yourself that 35a will work. You can get a range of answers based on assumptions of what your equipment list is. Are landing lights incandescent or LED. How about strobes, xenon or LED. The amperage needs vary of the types of equipment you have and the quantity.

One suggestion, if you get the B&C regulator with built in crowbar (voltage limiting) circuit, you would have an improved system. Nothing fundamentally wrong with a separate regulator, and many advantages.

Haha - Colin beat me to the B&C recommendation!

[SteinAir]

You've received some excellent advice so far. I'll just mimic that most of your answer coms down to lighting (and IFR ot VFR). A full up panel in general draws about 9-12 amps all on...when you add the radio and flaps you get a bit more, and then lights are the big unknown (so are things like a heated pitot, heated seats, fuel i jection electric pump, etc..).

As others have said, make a list, add it up and you'll have a resonably good idea. That said, there are things which are run simultaneously (like a radio and transponder), but others that typically don't (like pitch and roll trim)...then there are momentary loads like flaps, radio transmit, etc...

Just my 2 cents as usual.

Cheers,
Stein

[Walt]

It still never ceases to amaze me that folks are happy to spend mega $$ on the new glass panel, but then choose to power it with the cheapest autozone alternator they can find.

My 2c, buy a high quality B&C unit (I prefer external regulator) and be done with it, or carry a spare.

PS: you should derate your alternator capacity to 80% or less for continuous loads.

[RVDan]

+1 on Walt's comment. It is interesting to note that automotive alternators, which includes many FAA certified derivitives, have ratings established per an old SAE method that test the alternator at room temperature for 30 sec or less. Alternators become output limited as temperature rises and the resistance of the windings goes up. The SAE rating ignores the effects of elevated engine compt temperatures and self heating, which commonly reduce the effective output of the alternator to 40 to 50% of the nameplate rating.

I will mention that I know Plane power uses an elevated temp continuous rating procedure that is more realistic. Not sure about B&C, they may well do the same.

[ColoRv]

I have a buddy whose internally regulated auto alternator overvoltaged and fried thousands in avionics. I learned a lesson from his bad luck, this is not a place for saving dollars. B&C for me, external reg and VPX keeping my panel investment alive.

As for amps, in cruise I can get into the 30's with seat heaters (wonderful) and pitot heat going...that's without transponder or radio transmitting. All of my lights are LED, the HID's (before I trashed them) were higher draw. Recharge after startup is obviously higher as well. I don't regret my 60amp availability and can't imagine going with less.

[6adan]

I am learning a lot, please keep it coming.

[RV10inOz]

I can hit over 60 amps with a battery sucking 20 amps and the system 40+.

Walt hit the nail on the head. Too many folk try to compete for the cheapest RV. Bad, or should I say dumb idea. Don't get into this game is my advice.