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onetrack last won the day on February 7

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About onetrack

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  1. Old K - I'm not sure where to start - but I'll start on the Jab alternator. 1. Every engine-driven alternator produces an AC current, which is rectified into DC by about half a dozen diodes, and the charging current is then controlled by a voltage regulator. Every automotive/aviation alternator ever made has a VR - it is sometimes mounted on the outside of the rear of the alternator, other times it is mounted internally. Current-design alternators often have the brushes and VR combined into one unit. You remove the VR and the brush assembly comes out with it. 2. The Jab alternator does use permanent magnets, so it does not need the exciter wire from the battery for electromagnets, which is the normal design for nearly all other automotive alternators. 3. You must never totally disconnect an alternator whilst the engine is running. To do so will create a massive voltage spike which will fry the alternator, and possibly, many other electrical components in the system. The Jab community website discussion (below) gives some information on the Jab alternator setup. Their alternator regulating and controlling system is different to the standard automotive arrangements. The use of a crowbar module (usually a box of combined electrical trickery) is not common, but I can see what they're trying to achieve. The Wiki mob describe crowbar circuitry devices quite well. https://jabiru.net.au/community/engines/voltage-regulator-functionality-and-connections/ https://en.wikipedia.org/wiki/Crowbar_(circuit) Onto the LiFePo4 battery. 1. It's a lie that all LiFePo4 batteries can be a total drop-in replacement for L-A batteries. This has caused a lot of grief to a lot of people, particularly because of the highly specific charging requirements of LiFePo4 batteries. 2. A standard automotive/aviation alternator and regulator arrangement is inadequate for charging LiFePo4 batteries. 3. A 12V L-A battery has 6 cells at approximately 2V per cell. In practice, the L-A cells run around 2.1 to 2.2V. They need a fast initial charge, then a float charge - and they can cope with being overcharged fairly constantly. At the worst, an L-A battery receiving a constant overcharge will boil the acid solution in the cells. At the very worst, the cells will boil dry, and you will end up with a buggered L-A battery. It takes a lot to do that, they're a pretty durable and forgiving device. L-A batteries like being charged at around 13.8 to 14.2V. Alternators usually max out at around 14.5V. You can charge at a higher voltage, but anything over about 14.7V creates gassing and heat in an L-A battery. Alternator regulators are set up to charge L-A batteries - to provide an initial fast charge, then reduce the charging rate to a float charge. The L-A battery provides the "cushion" in an electrical system - taking current from the alternator, even when charged, to ensure the alternator doesn't blow, with a complete current draw shutoff, and a severe voltage spike. 4. A 12V LiFePo4 battery has 4 cells at 3.2V each. It needs a charging rate of around 14V to 16V, and it is more tolerant of higher charging voltage than an L-A battery. 5. An LiFePo4 cell will be damaged if the voltage over the cell falls to less than 2.5V, and damaged if the voltage over the cell exceeds 4.2V. Here's the important bit - 6. The cells of an LiFePo4 battery do not auto-balance at the end of the charge cycle. The cells in an LiFePo4 battery are not 100% identical. Therefore, when cycled, some cells will be fully charged or discharged earlier than others. The differences in charge between cells will increase if the cells are not balanced or equalized from time to time. In an L-A battery a small current will continue to flow even after one or more cells are fully charged (the main effect of this overcharging current is decomposition of water into hydrogen and oxygen). This current helps to fully charge other cells that are lagging behind, thus equalizing the charge state of all L-A cells. The current which flows through a fully-charged LiFePo4 cell however, is virtually zero, and lagging cells will therefore not be fully charged. Over time, the differences between cells may become so extreme that, even though the overall battery voltage is within limits, some cells will be destroyed due to over-voltage, or under-voltage. An LiFePo4 battery therefore must be protected by a BMS that actively balances the individual cells and prevents under-voltage and over-voltage. The type of BMS fitted to LiFePo4 batteries can vary widely, according to manufacturer and according to how the manufacturer thinks the battery will be used. The BMS of these batteries can also vary widely, according to how cheap the manufacturer is. Most of these BMS use dual MOSFET's to switch the charging current according to the cell demand/requirements. The MOSFET's are coupled with an Integrated Chip with additional electronic control devices built into the chip to prevent voltage spikes, indulge in cell balancing, and control other electrical parameters. We're getting into high-end electronics here. Suffice to say that the simple basic engine alternator and regulator is not up to the job of charging LiFePo4 batteries - a dedicated LiFePo4 charger really is required to match the electronics and requirements of the LiFePo4 battery. As regards your intermittent and transient power loss - I'm struggling to envisage exactly what is causing it, but I suspect it's related to the peculiar Jab alternator charging arrangement, and the crowbar module - and the LiFePo4 battery possibly causing a sudden and major drop in amperage draw, as it rapidly reaches full charge - thus causing a voltage spike, and activating the crowbar module, and making it shut off the electrical power. I'm not sure if the Jab crowbar module stays shut off, or reconnects the power once the voltage spike ceases. One would imagine the Jab electrical designers provided the security of the latter. Without an inspection of the aircrafts complete wiring and charging circuitry devices, and what they comprise exactly, and how they operate - by someone highly skilled in electronics, I think you will be shooting in the dark.
  2. 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
  3. 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.
  4. 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.
  5. 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/
  6. Once again, the Brazilians have spent a heap of time, money and effort producing something that provides no real engine benefits, no technological advances, no weight reduction, and no fuel economy gains. I really do wonder what the aims of these engine development programmes are, and if anyone actually wrote down attainable and important targets for their redesign. At $12K for a MotorAV engine, you might as well go and buy a Revmaster 2300 for under $9K and have a VW engine that was designed and refined over 40 years or so, by a bloke who is an engine design expert. The bragging rights about snaring Bill Brodgen from Continental Motors doesn't hold any water for me, Continental were still manufacturing 4 and 6 cyl side valve industrial engines with abysmal power output in the mid-1970's. These engines designs dated from the early 1930's. I'd like to think that engine technology has advanced at a pretty exciting rate over the last 40 years, at least - but companies like Continental are classic industrial dianosaurs - "We've always done it this way! - it works, why do you need to change anything?" If the Japs were into aircraft engines like they're into automotive engines - by today, we'd have a Japanese IC aircraft engine available, that weighed 50 kgs, produced 200 reliable HP, ran as smooth as silk, and had a 3000 hr TBO. Honda are producing their new i-DTEC 1.6L diesel with aluminium heads and block, high-swirl combustion chambers, chrome-moly steel pistons, a variable geometry ECU-controlled turbocharger with intercooling - and it produces 118HP at 4000RPM and weighs 47kgs less than their previous 2.2L diesel engine. This new engine features weight-saving in every single engine component, high plateau bore honing to reduce friction, plus a special synthetic oil designed specifically for the engine. All this translates into 3.7L per 100kms on the highway in a Honda Civic. If Continental had advanced with their technology and design like the Japs have done, they just might be producing hundreds of thousands of lightweight aircraft engines today, instead of being an industrial and technological laggard.
  7. The 737 MAX is a classic example of a company trying to squeeze too much out of an existing designs limitations. If Boeing had bitten the bullet and started with a clean sheet new aircraft design, to match the new bigger engines, rather than trying to shoehorn the new engines into an airframe that was designed in the early 1960's, the total cost would have been much less.
  8. Most of the Zeppelin hangars were pretty impressive, size-wise - particularly when you consider they were all built in the 1920's. This one in Rio de Janeiro is still in good shape. When you can make a P-3 Orion look like a Cessna inside your hangar, you've got hangar with bragging rights. https://www.theguardian.com/world/2016/nov/27/brazil-zeppelin-hangar-nazis#img-3
  9. Thanks for the correction, men. My apologies, Yenn. I didn't know about the Cross-Channel hovercraft, I only knew about the ones across the Solent. You learn something new every day.
  10. Not quite right. They were (and still are) used to cross the Solent between Portsmouth and the Isle of Wight. They've been in operation since 1965. These hovercraft are 78 seaters. https://www.hovertravel.co.uk/about-hovertravel.php
  11. Spacey, you forgot to mention the Hirth is little-admired, because it mostly converts gobs of fuel into lots of noise.
  12. I'd rate it as a hovercraft, because it appears to run on a cushion of air - but I wouldn't rate it a "ground-effect craft", which to me, is a craft that actually leaves the ground and flies - even though it's only using ground effect for lift, not aeronautical lift. EDIT - Hang on, I'm confused now - I just watched the video above, and that rig he's got in the video, is a ground-effect craft. But - I watched some of his earlier videos, and he had a completely different rig, a hovercraft, in them? https://www.hovercrafter.com/index.php/topendhover/1456-the-first-test-run
  13. His rig raises more questions than it answers. What happens when it breaks down on a huge tidal mudflat, inhabited by 4M crocs? What's to stop a 4M croc climbing aboard, when he's broken down? (they snatch people out of tinnies on the water). How does he get rescued? The only safe way is a chopper. But does Darwin have any dedicated chopper rescue service? Careflight, maybe? A breakdown could turn into a pretty expensive outing. I'm surprised the NT has no recreational boating registration - nor it appears, any form of licensing for watercraft use. Talk about a casual approach. Looks like a good place to become Crime Central, for knocking off boats. I can recall, many years ago (must have been about '92 or '93, I had reason to get a Kenworth fibreglass truck bonnet repaired. I went to a local (Cannington, W.A.) boatbuilder, who specialised in fibreglass repairs as well as boat building. He was a good operator, and when in his office, I noticed a huge pile of boat photos on his office wall. I said, "I guess these are all your repair or construction jobs, are they?". He replied, "No, they're all photos of stolen boats that the Police send me, to keep an eye open for!". All these boats were registered, too. Most were stolen from the East Coast, and quite a few were finally found in W.A. Some of them were big boats, too.
  14. Spacey, I don't think too many RA-Aus aircraft owners are into launching their aircraft skywards on takeoff, like an F-18 on full afterburners.
  15. The rescue chopper has been grounded and unable to access the site further, due to meteorological conditions. Read, intermittent rain and low cloud. Also, quite treacherous terrain, as with most aircraft crashes in hilly, heavily wooded regions. https://www.northqueenslandregister.com.au/story/6010350/pilot-dies-in-plane-crash/