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skippydiesel

SSB Lithium Iron batteries

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16 minutes ago, Markdun said:

I assume you have installed a sliding track from a front car seat for your wing attachment so you can easily adjust your CoG. I wish I thought of that when i installed a lighter Jab engine to replace a VW, requiring moving the engine forward 50mm, new engine cowls, and then 1kg of lead in the tail because 50mm forward was too much!

Why not go the whole hog and be a weight-shifter!

 

Moving my wing involved a lot of weighing, measuring and rebuilding. No matter the fuel or luggage load, or where it's packed, I can't get CoG anywhere near the limits. Test flying successful, but I do worry about my flywheel bolts. The first start, as you describe, is a slow wind up, but when the engine is warm, the Li battery cranks over the Jab with violence.

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The big difference I've found in use is that on a cold morning when you press the 'start' button the starter rotates the engine to the first compression and really struggles to move it through TDC, this occurs on the second compression too, but then the battery seems to finally wake up and gets the message that it is required to deliver lots of Amperes and voila, the engine spins like crazy & starts. And it does deliver lots of Amps....I had to increase my battery fuse from 100A to 125A.

Markdun - I'm in complete agreement with Skippydiesel here. Lithium batteries don't need to "wake up". I'd suggest you have an electrical or wiring problem, which is presenting when dead cold and initial high amperage draw is present.

I'd be looking for a dirty or loose connection in the starter circuit, which is creating resistance and preventing the starter from getting full voltage. 

Or, the alternative is an internal starter fault which is producing similar symptoms.

"Poling out" is a fault which occurs when the starter armature bushes get worn and the armature drops too close to the field windings, creating a short-circuit condition, and slow starter rotation speed.

A high resistance problem can sometimes be found simply, by placing your bare hand (carefully) on connections, or on the starter, and finding an area which is producing heat, right after the initial starting attempt.

Edited by onetrack
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2 hours ago, Bruce Tuncks said:

My system is to suit a cheapskate. A $100 Hobbyking 8.4 A-h LiFe battery with a $10 digital voltmeter on the panel. The engine is started and as soon as the voltage reaches 14.2, the master is switched off so no overcharging can take place. ( capacitors act as the "battery " for the radio etc )

I don't really recommend this setup for others. If you forget to turn off the master you can overcharge the battery, and some people get alarmed at the non-standard idea.

But it has gone well for years now, and the old Odyssey ( $260) battery is going fine in the farm buggy.

 

 

I wonder if a system is possible where a small lead acid/agm is used and this charges the lithium? 

The lithium can discharge on start up but when running, the lead acid is the "duty" battery.

 

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Not sure what type of battery this is but very scary.

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Bruce, be careful with the human voltage regulator.  My comment about a destroyed Jab stator comes from experience on a delivery where the Jab/Kubota regulator failed and the voltage started to creep up towards 17V (this is with a lead acid battery on my side of the firewall just near my toes). The aircraft had a nifty switch in the cockpit (Alt) that open circuited the charging wire from the regulator. So I did what you do; as soon as the voltage reached 14, I switched it off. But I also switched it back on when the voltage dropped to 12.5V (it had a big panel with old instruments)...big mistake. ...blue smoke etc at 7500' and drops of molten copper dripping on the carb (we discovered that on the ground).

 

Skippy, the slow start is only from an early black Jabiru starter motor which is a bit underpowered.  I think its just that the lithium battery doesn't deliver the current until it warms up a bit...the same as a lead acid battery...but to warm those batteries up I understand you roast them in a camp fire for 15 minutes -- well that's what I saw on the TV series Bush Mechanics.  The other thing is that lithium batteries' voltage doesn't drop away as you extract energy like a lead acid battery.  I'm not that fussed about it as starters are pretty robust. ..i once drove about 250m in 3rd gear in a Mazda on the starter motor across a floodway on the Nullabor when the distributor got wet. And I've seen a few times people endlessly cranking a Jabiru refusing to start (because the rpm was enough for the ignition system to fire)...This would be far tougher on the starter motor compared to the few seconds it takes to get my motor going. 

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1 hour ago, Markdun said:

 

Skippy, the slow start is only from an early black Jabiru starter motor which is a bit underpowered.  I think its just that the lithium battery doesn't deliver the current until it warms up a bit...the same as a lead acid battery...but to warm those batteries up I understand you roast them in a camp fire for 15 minutes -- well that's what I saw on the TV series Bush Mechanics.  The other thing is that lithium batteries' voltage doesn't drop away as you extract energy like a lead acid battery.  I'm not that fussed about it as starters are pretty robust. ..i once drove about 250m in 3rd gear in a Mazda on the starter motor across a floodway on the Nullabor when the distributor got wet. And I've seen a few times people endlessly cranking a Jabiru refusing to start (because the rpm was enough for the ignition system to fire)...This would be far tougher on the starter motor compared to the few seconds it takes to get my motor going. 

Sorry Markdun - I still think there is a problem.

Just may be if the system cranked slowly at all times & I had  had a few beers, I might be persuaded that it was "normal" (withe one eye closed)

BUT

To crank at different speeds, man even totally blotto, I doubt that I can be persuaded that all is okay.

Hay! but if you are happy that's all that counts.

 

Just so you get my comments in perspective - I am the anally retentive person who goes out and purchases a new battery, as soon as I notice even the slightest drop of in performance (usually in winter). This all started after experiencing a few Canadian winters and their impact on the good old lead acid automotive battery.

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4 hours ago, skippydiesel said:

...This all started after experiencing a few Canadian winters and their impact on the good old lead acid automotive battery.

I bet there are a few good stories there, Skippy. I just spent a month on Yukon-BC but didn't get around to asking about batteries. I believe Lithiums batteries are much more cold tolerant.

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Lithium batteries are well known for requiring a warm up before they crank at full capacity. The recommendation in vehicles is to run the headlights for a few minutes.

 

MARKDUN, do you have any more details regarding the blue smoke and molten copper, particularly what overheated and what melted.

 

Mike

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Good point about the human voltage regulator . I will be in line to buy a better regulator if Kyle coms mate gets one for sale. The other thing would be to install a warning  buzzer which would sound off if the battery got over 14.2 volts, but a better regulator would make my plane more standard.

Only yesterday, doing a local flight, I forgot to turn off the switch for about 15 mins and the battery was up to 14.5 volts before I remembered. This is not good for the battery.

On starting, I have the old starter motor and have never noticed anything funny about starting in cold weather.  When the LiFe battery was first installed, I put 2 in parallel because I thought one would not be enough. Well the motor belted over so hard that I got a fright, thinking about burning out the starter motor. 

 

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1 hour ago, Bruce Tuncks said:

....................................................... I put 2 in parallel because I thought one would not be enough. Well the motor belted over so hard that I got a fright, thinking about burning out the starter motor. 

 

Hi Bruce,

I am sure the smart people on Forum will explain this better than I do:

 

A starter motor &  associated circuitry will only draw what it needs from a battery supply that is equal too or better than demand. So in practice if you get a fast cranking response (usually judged as speed) that just great, good nothing to be concerned about. In fact it is the opposite  (low cranking speed from a weak or too small a battery) which is most likely to cause  damage to the system, overheating and a fire.

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Mike,  the stator windings melted. We removed the stator completely before another flight because we couldn't exclude a short circuit developing in the melted stator windings which could lead to more smoke & hot stuff dripping on the carbie.  At 2900rpm the alternator can obviously deliver a current that exceeds the capacity of the stator windings.

The starting of our diesel firefighting pump with a very tiny lipo battery also starts off slowly and as Old Koreelah said,  then it cranks it with some violence.

No landing lights on my planes,  and my LED strobes are hardly likely to warm up the battery.

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1 hour ago, Markdun said:

..........................................................The starting of our diesel firefighting pump with a very tiny lipo battery also starts off slowly and as Old Koreelah said,  then it cranks it with some violence.

No landing lights on my planes,  and my LED strobes are hardly likely to warm up the battery.

I hear you  - the way I see it is - for those few seconds (or less) that the circuitry is cranking slowly it will be overheating. Unless it is designed for this sort of "staged" current delivery it will shorten the life of the stating system (particularly a Rotax sprag clutch). 

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Thanks Skippy, well I'm not smart BUT power=volts times amps so if you have more volts then you need less amps for the same power.

BUT amps = volts divided by resistance...  gosh this is getting too hard for me.

Nowadays I reckon I should have been more worried about the flywheel bolts and less worried about the starter motor.

Anyway, they all survived but it would be good to know what the danger really was.

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Mentioned before however the breakage of Jabiru flywheel bolts was maybe linked to larger starter. Methods to overcome cold start problems could exacerbate the issue

LiFe batteries likely have the ability to spin things faster  - a good thing - however it can increase loads on flywheel attachment

CAE for this reason changed the attachment design to overcome this. 

Its maybe why Jabiru and others wont back the use of these batteries...…...until they rebadge one for sale, then they will be OK

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I reckon you are right jetjr. I also  liked Nev's idea years ago that the flywheel mating face is where the super-strong loctite should be used and not the mounting bolts themselves.

I also like the idea of a "soft start " where some electrical method is used to reduce the starter power for the first second or so. I wonder if anybody knows how to do this.

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Bruce - It's possible to add an electrical "soft start" to DC motors, but it needs electronics added, and therefore adds more complexity to the starting system.

Leece-Neville Prestolite manufacture a new range of heavy-duty diesel starter motors ("Titan") that are in-line, reduction-drive starters.

They have a "soft start" built into the design mechanically, the pinion is engaged early, and the reduction gears ensure a gradual take-up of starter motor power.

This design could possibly be introduced into the smaller starter range, if the demand was seen to be there. A mechanical soft start mechanism is the better (simpler) design.

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Thanks onetrack, I am surprised that mechanical is simpler. I wondered about a capacitor system right at the motor  where the first bit of current charged up the capacitor and so was not available for the motor windings.  Not so easy I guess..

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There's probably one main reason why Jabiru are reluctant to endorse Lithium batteries - even LiFePo4 batteries.

And that reason is - despite LiFePo4 batteries being advertised and regarded as "benign" and "completely safe", they will still go into thermal runaway at temperatures around 270°C.

They do have a lower heat release signature during thermal runaway, than the other lithium batteries. 

However - this simple fact means that if you install a LiFePo4 battery and are unfortunate enough to crash, and have a fire start in the wreckage, then the LiFePo4 will actively feed that fire, once the battery reaches the above temperature.

One could say, "Well, if you're on fire after a crash, you or your aircraft are finished anyway".

However, there are many survivors of aircraft crashes which ended in a post-crash fire, and if one can reduce the on-board items which will feed that fire, then that must improve the chances for the survivor/s of the initial crash impact.

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Yesterday I crashed my Radian XL here at the farm. It was in a thermal about 600 ft and I went into the shed to get a seat, taking my eyes off it for about 10 sec. 

When I got back, there was no glider in the sky! I headed off in the direction it was last seen, and then a fire started in a nearby paddock.

Yep, after the crash, the LiPO's  ( 14.8V) ignited and caused the rest of the model to burn.

My wife says I am as silly as that woman who put her Winnebago on cruise control on the freeway and then left the drivers seat to make a cup of tea. ( is that story even true?)

There was no risk of a bushfire as it was a calm day and not much to burn in that paddock,  but now I know that LiPO's can do this.

But I still think that LiFe's must make a safer plane because I reckon the weight savings extra safety must outweigh the negative safety of that extra bit of flammability if you are already on fire. Note that if I had only had LiFe's in that Radian, it would not have burned to start with.

Why is lighter=safer? Lower stall speed, lower inertia, less power needed to maintain height and better climb rate. 

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..th

at woman who put her Winnebago on cruise control on the freeway and then left the drivers seat to make a cup of tea. ( is that story even true?)

Bruce - Despite the story being repeated, and referred to, continually - it's not true. Definitely an urban legend of the 1st order. In the same league as the Choking Doberman.

 

Snopes - Cruise control crash urban legend

 

The stories of RC aircraft powered by LiPo's, regularly crashing and burning, are, unfortunately, true. They are the real, "bomb waiting to go off", in the Lithium battery stable.

You can get LiPo-Guard protective safety bags, that are designed to prevent your house from burning down, if they catch fire when charging - which they are known to do.

Edited by onetrack
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Yep we are. Remember that in 1900 there was great worry about carrying petrol in cars.

Like anything, you need some smarts about the details.

Here's a bet.. If you buy a new lead-acid now, it will be the last one you buy. Already some expensive cars are coming out with LiFe starting batteries, and the electric cars ( and planes ) have heaps of them.

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How many of us have lost rc gliders?   Like Bruce I lost one, but about 20 years ago.  Hooked it up to the bungee, let it go. ...ooops, forgot to turn the power on in the glider. ..not to worry it will just come off and land nearby.....wrong!  It came off the bungee in a nice right turn straight into a thermal.  I lost sight of it as it disappeared into the base of cumulus about 2500' above.  No lithium batteries though,  just nicads.

 

For those wanting a 'soft start', how about a mechanical decompression lever....works ok on hand start diesels?  Or compressed air,  shotgun cartridge...that would be cool.

 

I'm now getting worried about fire from my lithium batteries; i think I'll mount them in a stainless insulated box with a quick release pin attached to a servo & temp sensor so if the tempersture exceeds, say 120C, it automatically drops out of the aircraft. And if it looks like a difficult outlanding,  I could manually pull the pin to jettison the battery before 'landing'.

 

Thinking of avoiding battery started fires on crashing, how many people have a battery fuse mounted on the battery box or positive battery terminal as motor vehicles do?

 

I also wonder how many lead acid batteries explode from the explosive mix of H2 and O2 generated when they are charging?  Or structural and corrossion damage aircraft caused by the weight and acid electrolyte? I've see at least one 24 xxxx registered aircraft with cracking on the firewall from the lead acid battery mount....it was quite difficult to rectify.

 

 

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Markdun, you're right. All technology has its drawbacks, I've had L-A batteries explode on me, and seen some spectacular hydrogen explosions from batteries gassing without adequate ventilation.

The big weight factor of L-A batteries causing cracking is a good point, one I had not considered. Acid corrosion is not the problem is used to be with better L-A battery design and better sealing.

The simple fact is, you need to familiarise yourself with every downside of the technology of the product you're using, imagine every possible scenario where that downside could rear its ugly head, and plan and design accordingly.

The figures to date show that the LiFePo4 battery has provided low enough numbers of "mishaps" in ground-based equipment, to the extent that those numbers are quite acceptable, as regards the risk profile.

However, I have not seen any "mishap" figures related to aviation use of LiFePo4 yet, perhaps the numbers in aviation use are too low yet, to start providing quality stats.

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Bruce, for aviation use, the lithium batteries do provide an enormous advantage with regard to weight.

However, I wouldn't write L-A batteries off just yet, the L-A manufacturers are fighting back with a consortium dedicated to making serious improvements in L-A design and output, to try and counter the lithium attack. 

 

Gridtential gets $6M from Battery Strategics to advance Lead Acid batteries

 

The global manufacturing level of L-A batteries is still 10 times that of Lithium manufacturers. Even Tesla's gigantic lithium battery manufacturing factory is not going to make a major dent in L-A production, globally.

However, I believe L-A will continually lose ground to those applications where the weight penalty is a significant factor in the sale.

 

Supercapacitors and ultracapacitors designed into electrical systems, along with batteries, hold great potential for vastly improved performance, particularly where there are demand spikes in power requirements.

The latest ultracapacitor developments are quite exciting, and could alter the electrical landscape substantially, with particular regards to energy storage and useage smoothing.

Very recent research developments are tantalisingly close to the possibility of making ultracapacitors replace batteries completely - even Lithium batteries.

 

Alternative to traditional batteries closer to reality

 

There are batteries available now, such as the Ecoult Ultrabattery, which uses the CSIRO-developed, combination supercapacitor and L-A battery, to produce vastly improved battery performance, faster recharging, and quick response to power demands.

In particular, the Ultrabattery performs exceptionally well when operated at PSoC, which normally kills L-A batteries rapidly. The Ultrabattery promises a 10 yr life from their L-A technology.

 

Ultrabattery technology

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