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Lost electric over mountains at night

Mine is a Lamar unit and it was pulled and bench tested (after a 'jump start' followed by losing electrical in flight). The alternator passed but as I said the 40amp breaker got fried so I could not reset the Alt bus after total electrical failure.
Mark

Is it a 40 amp alternator? 42 Amp? What is the breaker protecting? If the battery was dead and the alternator was going full tilt to charge it, plus the electrical loads, it is possible it was putting out greater than 40 amps. If the breaker is upstream of the battery, the breaker may have been right on the edge of tripping for a while and melted instead of opening. Take a hard look at the alternator/battery circuit design as well as the alternator sizing.
 
Mark,

Some clarification please. By the ALT breaker being totally fried do you mean that it was permanently open?

I suspect that breaker is inline the alternator output. You should probably try to confirm that my ohming it out if you don't know.

If it was open and it is inline with the alternator then yes you were running just on whatever capacity you had in the battery.
 
Mark, so glad you made it safely.
Aviators, when you are doing your flight plans it is wise to always consider this type of failure and try to mitigate the risk!
Mountains at night= two engines, two electrical sources

While I would never fly at night over mountains, I’ll take liberty with Jim’s post to again tilt at the windmill. Two engines, two alternators (or six if you want) is not two electrical sources. Read the NTSB reports on twin engine aircraft loosing all electrical power even with both engines running and both alternators working. The root cause being a, by design, single point failure that took out the battery and both alternators from the main buss.

My point - dual alternators mitigates only the risk of loosing the primary alternator. The loss of the alternator (single alternator plane) is the most likely failure we will have, but the impact is minor if you have a healthy battery.

All you guys adding a backup alternator as the magic to keep the panel going when something bad happens should take a close look at what else can happen, how you ensure you have a healthy battery, how you design around single points of failures, etc.

Simple examples for IFR panels:
- Do both your EFIS displays or both comm radios get power from the same place (or via a common switch)?
- Are your backup battery(s) big enough and healthy enough to support full IFR flight for at least an hour or so?

These design issues are an order of magnitude more important for electrically dependent engines.

Stepping off my soap box....
Carl
 
agreed

...
My point - dual alternators mitigates only the risk of loosing the primary alternator. The loss of the alternator (single alternator plane) is the most likely failure we will have, but the impact is minor if you have a healthy battery.

... take a close look at what else can happen, how you ensure you have a healthy battery, how you design around single points of failures, etc.

Simple examples for IFR panels:
- Do both your EFIS displays or both comm radios get power from the same place (or via a common switch)?
- Are your backup battery(s) big enough and healthy enough to support full IFR flight for at least an hour or so?

These design issues are an order of magnitude more important for electrically dependent engines.
I could not agree more. This is the kind of thinking that Bob Nuckolls promotes with his book, and I think it's very valuable.
 
Fully agree with everyone about knowing your electrical system intimately and having the redundancy if flying IFR. However, your aircraft seemed to be designed with redundancy to handle your situation. As sucky as it may have seemed, your steam gauges got you home and dry.

Also...highly recommend a battery maintainer specific to the battery type you have, and loan to the shop working on your airplane. This is what I have and it has a 12V supply setting when running the panel for maintenance...

https://www.amazon.com/gp/product/B07W3QT226/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
 
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Here is a real, regulated power supply to hangar fly your panel while keeping the battery topped off: https://www.dxengineering.com/searc...+brand:mfj&sortby=Default&sortorder=Ascending

Some thoughts on “battery maintainers”:
- Most modern batteries retain most of their charge after sitting for months.
- Many chargers have very dirty output (as in hash). Be careful running expensive electronics with them.
- Many people have killed their battery by leaving it endless on a trickle/tender/maintainer charger. As there is no need to do this why risk it?

Carl
 
Mark,

Some clarification please. By the ALT breaker being totally fried do you mean that it was permanently open?

I suspect that breaker is inline the alternator output. You should probably try to confirm that my ohming it out if you don't know.

If it was open and it is inline with the alternator then yes you were running just on whatever capacity you had in the battery.

The 'Alt Bus' breaker cannot be reset based on ohming across the contacts. If you wiggle it and press real hard you can transiently get it to close the circuit but only briefly. The Alternator is 40 amp unit.
 
Here is a real, regulated power supply to hangar fly your panel while keeping the battery topped off: https://www.dxengineering.com/searc...+brand:mfj&sortby=Default&sortorder=Ascending

Some thoughts on “battery maintainers”:
- Most modern batteries retain most of their charge after sitting for months.
- Many chargers have very dirty output (as in hash). Be careful running expensive electronics with them.
- Many people have killed their battery by leaving it endless on a trickle/tender/maintainer charger. As there is no need to do this why risk it?

Carl

Agreed, I wouldn't use the NOCO to "maintain" the battery as there's no need for a healthy one. I recommended this model specifically because it has regulated DC power supply setting which outputs constant 13.6V rather than the variable voltage in its charging mode.

You're right about normal battery charger though...I had an old one I was using and noticed it was outputting more than 16V at one point because it tripped my OVM.
 
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While I would never fly at night over mountains, I’ll take liberty with Jim’s post to again tilt at the windmill. Two engines, two alternators (or six if you want) is not two electrical sources. Read the NTSB reports on twin engine aircraft loosing all electrical power even with both engines running and both alternators working. The root cause being a, by design, single point failure that took out the battery and both alternators from the main buss.

My point - dual alternators mitigates only the risk of loosing the primary alternator. The loss of the alternator (single alternator plane) is the most likely failure we will have, but the impact is minor if you have a healthy battery.

All you guys adding a backup alternator as the magic to keep the panel going when something bad happens should take a close look at what else can happen, how you ensure you have a healthy battery, how you design around single points of failures, etc.

Simple examples for IFR panels:
- Do both your EFIS displays or both comm radios get power from the same place (or via a common switch)?
- Are your backup battery(s) big enough and healthy enough to support full IFR flight for at least an hour or so?

These design issues are an order of magnitude more important for electrically dependent engines.

Stepping off my soap box....
Carl

I know of an event in a piston twin where the first alternator belt broke. Then the other alternator tried to take on the load, but the extra load snapped the other alternator belt too. It was at night in icing conditions, so the battery lasted about 10 minutes trying to carry the load of all the electrical ice protection equipment. Fortunately, the 10 minutes happened shortly after touchdown during the taxi to the ramp.

And to your point, you can have 6 alternators feeding an electrical system, however if the bus shorts to ground, the whole system is done. A smart avionics master system design I saw was where it is a normally closed solenoid. Turning the switch "on" actually removed power to the master solenoid and it closed to turn on the avionics. The procedure in the event of a switch failure is to pull the CB to remove power from the solenoid, and it fails closed to deliver power.
 
Problem found problem solved

Just to complete this thread: I finally got a new 40amp breaker from AC Spruce and replaced the faulty breaker. Fully charged the battery with trickle charger and after pre-heat (here in CO its been below zero F in the early morning! Ouch...time to go south for a few months), she fired right up and showed 14+ volts on the EFIS.

I think the problem was an accidental arc across the bus which fried the breaker and I could not re-set the Alternator Bus inflight. Avionics shop has 'owned up' but they say the arc was a '5amp spark' not a 40amp spark. Another possibility of course is 'jump starting' the dead battery/engine with a power-pack, something I will never ever do again!

The shop owner, who has many years in the avionics business is a fine fellow and I do actually trust his judgement. But mistakes happen, even in the best professional shops, and I was on the receiving end of this one! As noted, my lapse in judgement and 'get-there-itis' doubled down on the problem leading to my blood pressure spiking higher than my pre-selected altitude to clear the pass.

Hopefully, we can all learn something here. Someone (King's?) said 'a good pilot is always learning'. As a recovering academic, I strongly endorse this idea.
 
But did your electronics die? :)

I often read that using a generic battery charger to keep your battery level up during an extended ground avionics run puts your sensitive electronics at risk. But, I have never heard of a report of such an outcome.

Has anyone had this happen? And, if so, was your battery in the circuit during the charger operation or was the charger the sole source of power? I have the impression that having the battery in the ground power loop (meaning a charger to the battery while the battery is in the normal circuitry and the avionics master on) buffers even the ragged-est of battery charger output and protects electronics.
 
I often read that using a generic battery charger to keep your battery level up during an extended ground avionics run puts your sensitive electronics at risk. But, I have never heard of a report of such an outcome.

Has anyone had this happen? And, if so, was your battery in the circuit during the charger operation or was the charger the sole source of power? I have the impression that having the battery in the ground power loop (meaning a charger to the battery while the battery is in the normal circuitry and the avionics master on) buffers even the ragged-est of battery charger output and protects electronics.

Having a battery in parallel with a noisy charger will only mitigate DC voltage fluctuations (if not too severe). It will do little to filter out the AC hash and various harmonics that will be floating on top of the DC voltage. Read you manuals, some have specific cautions about running with a battery charger connected.

Sure - some chargers are better than others but why flight it? For about the same price (or cheaper) a $99 30 amp regulated DC power supply will run the panel forever and keep your battery(s) topped off, just like when you are running the engine with the alternator on line. Get a power supply with adjustable output voltage so your can match to whatever battery you have.

Note, no matter how you put juice back in your battery(s) I strongly recommend never leaving any charger or power supply connected unattended, and never for days/weeks/months on end.
Carl
 
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