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Old Koreelah

Intermittent electrical power loss

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4 hours ago, Yenn said:

Before you replace the screw, just give all the wires a bit of a twist, so that the joint is disturbed, then see if you still have the problem. No problem means that there was corrosion, causing a poor connection. That cold tell you if you have solved it and you can then go about putting in a  better connection.

I'm going to do just that tomorrow, Yenn. My MGL CHT/EGT gauge makes a loud beep each time it's powered up, so it's pretty easy to find a loose earth or power wire. 

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Good luck OK... hope you solve it quickly and easily!

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On a more relevant note you find areas of high resistance when under load. ie if your starter is sluggish  feel all components after a period of use and a poor connection will be warm.. Most aircraft starters have a maximum period of continuous use, then they should be given a period to cool, before further use. Nev.

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I went flying this morning and the power only cut out for about 10 seconds- I didn't even have time to grab the camera to record the strange behaviour of the gauges as it recovers. What was different? I tightened the two screws holding the wire feeds together. 

Tomorrow morning I'll do some more testing. In this perfect weather, flying over country that's had a bit of rain, it's not much of a chore...

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1 hour ago, Old Koreelah said:

I went flying this morning and the power only cut out for about 10 seconds- I didn't even have time to grab the camera to record the strange behaviour of the gauges as it recovers. What was different? I tightened the two screws holding the wire feeds together. 

Tomorrow morning I'll do some more testing. In this perfect weather, flying over country that's had a bit of rain, it's not much of a chore...

Good news O.K.; sounds like your getting on top of the matter; like skippy said coat a thin smear of electrical approved grease between the terminals (I use a form of electrical splicing grease); recommend your clean each ring terminal both sides fully (can use an electrical contact spray for this).  I have three negative posts in my Nynjas electrical system placed at convienent places that all negatives attach to.  They are also tightened with a nylock nut and spring washer.  Always need tight security and no movement of the terminal ring ends.  Enjoy the flights. Cheers

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Posted (edited)


 
 
 
 
 
 Yesterday's test result didn't seem to very conclusive; I doubt the strange power outage is associated with poor connections, because it happens after a full-power climb and because of the way it resolves itself with wild swings of volts and amps.

This morning I repeated the test and the same sequence of power loss, wild fluctuations and recovery repeated itself.


Then, as suggested, I installed the old lead battery again and did two full-power climbs to 3,000' and cruised around for half an hour. No power loss.

I suspect Jetboy's post is close to the money: "The behaviour you are describing is typical of an overvoltage cutout system operating when it thinks the 20V or 40V spikes put out by the Jabiru dynamo (PMA ) occur , which will be most prominent after the battery has been topped off from the starting and ground idle discharge period. "

 

On the strength of this, and following advice from Flyboy, I plan to replace the regulator/rectifier. As with Methuselah, I'd like to install a Powermate, but that business hasn't replied to my email. Does anyone have a contact number for them?

 

 

Edited by Old Koreelah
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Well done - looks like you may have found your problem.

 

Electrical issues  are often solved by dogged elimination, one by one,  of potential factors. I find I have to fight the urge to go for the most obvious and often expensive/complex solution and try the mundane cheaper issues first.

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5 hours ago, facthunter said:

Go back to when it worked and determine what you changed. Nev

That usually works, Nev, but in this case I can't figure out what changed. This configuration worked well for a couple of years, then the problem arose.

Dogged experimentation by changing one thing at a time normally works, but if the problem becomes intermittent what then?

This morning I blu-tacked a multimeter to the panel, connected it directly to the LiFePO4 battery (to see if its internal circuitry was disconnecting it) and went for a fly. Nothing went wrong. 

 

All part of life's rich tapestry.

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Posted (edited)
On 7 April 2019 at 3:51 PM, FlyBoy1960 said:

I would replace the regulator/rectifier. 

 

The Jabiru ones have caused lots of problems at my airport with electrical issues when they are under heavy load and lots of demand. They overheat and when the cool down they behave again. 

This has firmed as a possible course of action, but which regulator should I replace it with? The Power Mate bloke has replied to my emails and says his unit is definitely not suited to my Lipo battery. Lots of net research later, I'm learning a bit about the charging needs of these batteries, but haven't discovered any recommendation about what regulator to fit.

 

Among the good advice found: It's not a bad idea to check the continuity / quality of the connection between the regulator and the power bus. Dodgy connections can confuse the regulator and send the voltage up. 

 

The Jab factory says to check for a bad earth on the yellow reference wire, which could cause spikes to 17v.

Is this what causes my problem? 

The Lithium shop said not; the Lipo battery's internal circuitry would not disconnect it from the system. If not, what is cutting the power?

 

Several sources claim these batteries are compatible with automotive/aviation alternator charging systems.

...automatic over-voltage circuit protection is recommended for your charging system. This is an important backup safety feature to protect the aircraft electrical system from high voltage events (typically > 16V

 

What I need:

My battery has 16 cells in groups of four and charging should be limited to 14.5v max. 

So this is my problem: can anyone recommend a unit can that will do this?

 

 

Edited by Old Koreelah

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Posted (edited)

Old K - Li-Po batteries have a greed for charging input like no other battery. They will gobble up 100 amps or more of charging input with pleasure, and be looking for more.

For this reason, nearly all the bigger Li-Po batteries today come with inbuilt charge controllers, to limit the charging input to avoid damage to alternators and regulators.

 

If you have fitted a Li-Po that doesn't have a charge controller inbuilt into the battery, that could account for a lot of your problem.

If a Li-Po is sucking a huge amount of amperage from your charging system, it will be reducing the charging voltage, thus possibly creating problems.

 

You need the correct charging algorithm and a charger specifically set up for Li-Po batteries. Li-Po's must never be overcharged and charge input must be stopped completely when the Li-Po is fully charged.

In fact, Li-Po's perform better, if not fully charged. They will cycle more efficiently and for longer, if their SoC is kept between about 20% SoC and 90% SoC.

The Li-Po charge and drawdown parameters are vastly different to Lead Acid batteries, because their chemistry is vastly different.

Battery University is a good site to study up on battery technology. The bloke who runs it is a former battery engineer, and he knows all the various battery technologies inside-out.

 

https://batteryuniversity.com/

 

http://www.enerdrive.com.au/can-charge-lithium-battery-lead-acid-charger/

Edited by onetrack
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I'll be checking that site too, as I would prefers a light-weight battery to a very heavy lump.

spacesailor

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Spacey, the general rule is, if you want a much lighter battery, be prepared to have your wallet lightened considerably.

Lead-Acid is cheap power, with a weight penalty, Li-Po and Li-FePo4 is lightweight power with a major cost penalty.

You can be looking at several hundred dollars for a Lithium battery, as compared to maybe $130-150 for a simple old Lead-Acid battery of comparable power output.

 

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YES

But I,ve been offered lead acid batteries at half the retail rate.

So why the Big markup on the "mobility scooter" batteries, ?.

$ 185 the cheapest mobility battery, compered to your $145 for a golf-buggy battery, the same size AND Brand.

spacesailor

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Retailers price their product according to what the competition is, and the demand. High demand means the product flies off the shelves faster than they can order it in, so the retailer ramps up the price.

That's the beauty of the internet and search engines today, I can go looking for a product, and usually find a 30% to 50% reduction in pricing from the initial price quoted, within a few minutes.

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Am I the only one that would ask why you would be flying at all - if the problem happened after the 2nd time?  Or is that just me? LOL!

 

Glad you have it sorted though!

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1 hour ago, onetrack said:

Spacey, the general rule is, if you want a much lighter battery, be prepared to have your wallet lightened considerably.

Lead-Acid is cheap power, with a weight penalty, Li-Po and Li-FePo4 is lightweight power with a major cost penalty.

You can be looking at several hundred dollars for a Lithium battery, as compared to maybe $130-150 for a simple old Lead-Acid battery of comparable power output.

 

 

 

Over the last 10 years or so there have been great improvements  in the good old lead acid battery - weight is way down and  amp hours way up.  Get the right one for the job & it can almost be installed at any angle - still work and not spill a drop. So I am happy with my lead acid.

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2 hours ago, onetrack said:

Old K - Li-Po batteries have a greed for charging input like no other battery. They will gobble up 100 amps or more of charging input with pleasure, and be looking for more...

Thanks for the info, 1T. That adds to my store of knowledge, but doesn't help me find a suitable regulator.

My battery supplier claims it has all necessary charging management built in, being a "drop-in replacement" for normal lead batteries. Trouble is, he's not going to divulge any details of how it works.

 

It appears I need a regulator that will guarantee the charge voltage won't exceed 14.5v- and/or a spike arrester.

 

Any advice welcome.

 

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46 minutes ago, BirdDog said:

Am I the only one that would ask why you would be flying at all - if the problem happened after the 2nd time?  Or is that just me? LOL!

 

Glad you have it sorted though!

Don't worry, BD. A temporary loss of electrical power doesn't threaten the safety of the aircraft. The engine keeps going and the main flight instruments are unaffected. You can fly quite safely without all the engine gauges. 

Some of the auxiliary gear has its own power supply, such as the radio, iPad running OzRunways, CO monitor, weather station and flight cameras. Like plenty of other little planes, this one flew for years with no electrical system at all.

 

My main concern is that the battery or another component may be damaged if I don't find the problem and fix it. Each time I go up has been a test flight to eliminate one possibility or another.

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Posted (edited)

Hmm.. Ok... But what if on a flight, the power does not return - maybe there is no power being generated.  Once the battery goes completely dead, so will the engine!  That was all I was thinking.  If you are close enough to the strip, might not be too much of a concern I guess.

 

Edited by BirdDog

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51 minutes ago, BirdDog said:

Hmm.. Ok... But what if on a flight, the power does not return - maybe there is no power being generated.  Once the battery goes completely dead, so will the engine!  That was all I was thinking.  If you are close enough to the strip, might not be too much of a concern I guess.

 

Once the engine is started, its continued operation is not dependant on the battery...... Bob  

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My battery supplier claims it has all necessary charging management built in, being a "drop-in replacement" for normal lead batteries. Trouble is, he's not going to divulge any details of how it works.

 

It appears I need a regulator that will guarantee the charge voltage won't exceed 14.5v- and/or a spike arrester.

 

Old K - The basic problem you have, is a LiFePo4 battery has a need for its charging system to shut off, period, when the battery is fully charged. Essentially, a disconnect of the charging system.

You can't do that with an alternator, its internal voltage will soar and it will fry itself. So, you need a dedicated onboard LiFePo4 charger to handle the charging current supplied by the alternator.

Redarc make such a unit - but it's not cheap. It's aimed at the RV, 4WD and boating market, where solar panels are often used in conjunction with an engine alternator, to provide dual supply paths for the battery charging.

I'm not sure that this charger is the exact answer to what you're looking for, for your aircraft - but it does possess the correct charging algorithms, the correct charging voltage, and the correct charging method (including a total shutoff) for the LiFePo4 batteries.

The problem is that all other chargers and regulators work on supplying a "float" charge to enable the alternator to keep functioning properly and to enable batteries to receive their system of final charge.

But the LiFePo4 has no requirement for a float charge, and a float charge is actually detrimental to an LiFePo4 battery.

So a way must be found to set up a separate charging system for the LiFePo4 battery, whilst ensuring that current being produced by the alternator is not shut off completely, and that there's some way to utilise the charging current produced by the alternator, even if it's only a trickle of power useage.

 

It's annoying that the battery supplier will provide no information on what the inbuilt BMS is on their battery, or how it even operates.

But the system they provide is bound to only be a current-limiting arrangement, and not have any extensive ability to produce charging algorithms, or control the system of charging.

 

https://www.redarc.com.au/dual-input-25a-in-vehicle-dc-battery-charger

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6 hours ago, BirdDog said:

Hmm.. Ok... But what if on a flight, the power does not return - maybe there is no power being generated.  Once the battery goes completely dead, so will the engine!  That was all I was thinking.  If you are close enough to the strip, might not be too much of a concern I guess.

 

As Biggles says, the engine produces its own spark, and doesn't need electrical power.

 

But wait, BD. What you say was actually true of this plane's first engine. It had a total-loss ignition system drawing power from a small, pre-charged battery. This was topped up by a tiny solar panel mounted on the turtle deck. A previous owner said that during the ferry trip from Leeton to Wedderburn, every time he passed under a cloud the voltmeter dropped dangerously close to ignition-failure territory!

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16 minutes ago, onetrack said:

... you need a dedicated onboard LiFePo4 charger to handle the charging current supplied by the alternator.

Redarc make such a unit - but it's not cheap...

Thanks for that info, 1T. I had a good look at the Redarc unit and it seems to be quite large and intended for auxiliary battery situations.

Quote

...The problem is that all other chargers and regulators work on supplying a "float" charge to enable the alternator to keep functioning properly and to enable batteries to receive their system of final charge....

My understand of electrics is limited, but isn't the Jab "alternator" actually an AC generator?

If it has permanent magnets, does this mean it doesn't need a battery to create a field?

Quote

But the system they provide is bound to only be a current-limiting arrangement, and not have any extensive ability to produce stem of charging.

If that is the case, I guess all those rally cars and everyone else who has fitted one of these is the same boat as me.

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OK,

Your jab alternator is indeed an AC device. However I point out that the Jab regulator is not what one would call "automotive' type. Maybe motorcycle type. It has no form of current regulation, and due to the lithium battery having a amazingly low internal resistance, it is quite possible that the Jab alternator/regulator combination is overloaded during climb out. After all, the battery has just discharged significantly during cranking, the motor is running at high rpm, so the alternator is putting out max power,and the regulator won't be cutting out until battery voltage reaches its fully charged voltage. Until then, the battery will be fully loading (maybe overloading) the charging system.

In the absence of a ammeter, you can't prove or disprove my theory.

 

This is the 'problem' when using  a lithium battery in a system that was designed for a different kind of battery.

 

It needs a regulator that limits the voltage and the current. I am not aware of any. BTW, this applies equally to Rotax, as they have a crude Ducati system similar to Jab.

 

Edited by nomadpete
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