Worth Upgrading Alternator?

[CharlieWaffles]

I have heard that a good planning base line is that your amperage load shouldn't exceed 80% of the Alternator output. According to the Vertical Power planning tool my load is at 52.6 Amps and the stock alternator on my engine is 60A. The 80% puts the max at 48A.

However, my load includes several ACCESSORIES that will not necessarily be used regularly or for extended period of time. For instance, I have two accessory power plugs (cigarette power plugs) to be able to charge a phone, ipod, etc... I have those down for 2 Amps each. So right there I'm at 48A if they arent used. While other things are short period - landing lights, taxi lights, etc... But they are not truly intermittant (flap motor, trim servos, etc...)

So, is it worth selling the stock alternator and buying a 70A alternator to cover ALL these items and assume they are in use at all times?

[Jerry Cochran]

Originally Posted by CharlieWaffles

So, is it worth selling the stock alternator and buying a 70A alternator to cover ALL these items and assume they are in use at all times?

Mark,

Very doubtful if ever you would run out of electrons. Plus, you have a battery, right? Fly it and you will soon know. Stuff like this got me off track a lot, maybe that's why my RV build took six years.. :=)

.

[CharlieWaffles]

Thanks Jerry. The benefit of traveling for work is it makes me think ahead in my build. If I know I am going to need more amps now, I can sell the unit as new. If I wait and fly it and find I am too low, then I have to sell as used.

[Jerry Cochran]

VERY good point... I would love to have a 10... So many aircraft, so little time...

[rleffler]

With out seeing your entire list, it's hard to give a specific recommendation. I'm in a very similiar situation, as I suspect many RV-10 drivers are too. I decided to stay with the 60a for awhile.

This decision was reached by talking with other flying RV-10 builders to understand their average flying current draw as oppose to their predicted current draw per their plans. I think some of the ratings may be conservative and will yield more headroom.

[N15JB]

I don't remember what my calculated load was, but my all electric panel with most of the bells & whistles draws 28-30A with everything running, including heated pitot and tablet pc. A little higher when actuating flaps and/or landing lights.

Jim Berry
RV-10

[Strasnuts]

I thought I had a lot of amps being used and was worried about the alternator but after 200 hours I never see more than 32 amps and I have two cig. adapter chargers, heated seats, pitot, (4) HID lights, full IFR panel and so fourth. Normal cruise I see about 18, If I turn a bunch of stuff on I will see around 32. I wouldn't worry about a 60 amp like mine.

[CharlieWaffles]

Cool, I'll stick with the stock one and see what it turns out to be and upgrade if needed later.

[MCA]

"Mark"

The final test when you're doing your phase 1 flying is to turn everything on and watch the voltage. If it stays steady over time, then your alternator can provide the necessary current. If it starts to drop then it can't provide all the power and you need to upgrade (or just don't turn everything on).

Each alternator vendor rates the alternators a bit differently, and some will certainly provide the full rated power. So I agree that waiting until you're flying and testing before making a trade-out decision is the way to go.

[CharlieWaffles]

Thanks Marc, it was your presentation at OSH last year I even learned about the 80% guideline. If I have learned anything during the course of my build is if it's anything electrical, your opinion is the one I trust.