Packs, Chargers, Power Supplies and more – Packs

So with my move to bigger E-powered aircraft I have started buying larger packs (mostly in the 6S 3000-5000 range.  These things can easily cost $100-200 and for that kind of investment I wanted to get something that would both perform well and would have a minimum cost in terms of how long the packs would continue to work.  This lead me to a lot of reading and research on internal resistance, C ratings, and care and feeding of batteries… there’s plenty to discuss about all that but for now I will just cut to my understanding.

First and foremost, C ratings on batteries are almost pure marketing.  What most people understand that number to mean… that you can safely draw this number multiplied by the pack capacity until the pack is drained without damage to the battery pack … is apparently NOT what most of the sellers understand.  To be charitable, I would assume they are expressing a number that can only be reached by testing to destruction (in some cases, a very quick and fiery destruction).  In my more pessimistic language, I would say the C ratings advertised are pure bullshit.  Not only will many of these packs not sustain that level of current draw for the amount of time it would take to discharge the pack, but some of them are so ridiculously labeled that the wires would simply melt, the connector would disintegrate and then whatever was in proximity of the pack would likely burst into flames from the heat generated in the pack if you tried.  The consensus among those who have done independent testing seems to be that no LiPo available to us should be labeled above 35-40C continuous.  70C is a cruel prank… 150C is pure snake oil.  I can and probably will write a whole other post or two on this but for now that is all I will say about the C ratings in this post.

Internal resistance (IR) is a much less understood but much more important and useful rating but it is not typically a published specification for most hobby grade batteries.  It is temperature and capacity dependent but is still a very useful tool in comparing batteries and could easily be published as a number of milli-ohms at a certain temperature.  Some folks have suggested a calculated value called FOM or figure of merit which would take into account both the IR at some standardized temperature as well as factor in the battery capacity.  It isn’t perfect, but it would be a much more useful specification than the C ratings published now.  Of course it could be “exaggerated” just like C ratings are but measuring the internal resistance of a battery can easily be done with a few available tools and the FOM can thus be calculated so it would be much easier for hobbyists to spot these exaggerations and react accordingly.  Hopefully the market could then sort it out… but I digress.  The reason IR is so much more useful is simple.  IR is directly related to the current allowed to flow from the battery pack and the amount of heat generated from the battery supplying the current.  Though IR is not the only factor that affects a batteries overall health and ability to provide power to the attached circuit (primarily your motor!) it is probably the most easily understood and has the most direct correlation with these things.  I will likely post more on this later but for now what follows are the basics.

Generally speaking, lower IR is better.  Keep in mind that if you measure IR, you must do so at a constant temperature to be useful for comparison and also keep in mind that only like capacity batteries can be compared.  The relationship between cell size and IR is not linear so no simple way to compare between two different capacity packs is available.  The total IR of a series pack is the sum of the IR of each cell.  This total number is indicative of the current that the Battery can produce overall because the battery IR will cause a voltage drop as the current flows out of the battery.  A battery with a higher overall IR will supply less voltage under load (the loss being “used” to heat the battery).  This results in less power from the battery reaching the motor, which is the real purpose of the whole exercise!  While overall pack IR is important, having each cell in a pack with a similar measurement is equally important.  Having all the cells in a pack with a similar IR indicates a pack that is well balanced and matched and will therefore likely have a longer life.  The reasoning is that every cell will heat up in direct relationship to the IR of that cell and since excessive heat is typically the cause of battery failure, the cell with the highest IR will be first in line to be damaged from the heat thus produced.  The overheating will likely cause the cell to develop an even higher IR over time which will just add to the issue until the cell IR reaches such a high value as to render the pack useless due to the large voltage drop in this weak link or the cell simply fails from the heat.  There are tools available to make this measurement both for the pack as well as each cell and published values and calculations available as a guideline to what is considered to be “good” and how much current you can really expect to draw without damaging the battery so you don’t have to totally re-invent the wheel here either.  If you want to learn more, do some web searches or check in for my further posts on the subject.  If you don’t care that much and just want to know what to buy I will give you some guidance based on my experience a bit later in this post.  If you’d like to measure IR in your packs for yourself so you can start to recognize the good from the bad and become a more informed consumer one of the best tools I have found to do so is available here:

With this device you can measure and compare the IR of each of your LiPo packs.  It will help identify which packs are best used for high current draw versus more routine use and with this an a little math determine how much current is safe to draw from this pack (there is even a webpage that you can enter the result into and get a calculated max draw).  There are several different models so make sure you pick the correct one for your needs.  There are some chargers available that can give you a similar reading but do some research to see if the charger you are considering gives a useful reading.  My research indicates this meter is better than any of the chargers but there are a few chargers that may be good enough for your purposes.

One thing you can do immediately and without spending much/any money is to learn to care for you LiPo batteries correctly.  Care and feeding of LiPos is actually pretty simple.  Avoid physical abuse (punctures or compression may cause a fire).  Always balance charge your packs with a charger that is made for the task at an appropriate rate (1C when possible for longer life, even if the battery says you can go faster).  Don’t discharge them to fast or to far if you can help it (85% discharge is a nice goal).  Store your packs at a 40-50% charge level and in a cool/dry place (the fridge is almost perfect but you will need to watch out for condensation and allow them to warm before use) whenever you can.  Avoid extreme heat and extreme cold pretty much always.

Other than the physical abuse and charging rules you can violate just about any of the other rules with the understanding that you are taking a bite out of the life of your battery and sooner or later you will pay for it!

For now suffice it to say that I own a single E-Flite 6S 3200mah 30C pack that I bought with my Carbon Cub…, a G-Force 6S 3700mah 45C pack, and 4 Glacier brand 6S packs in 30C rating.  2 each of the 3300mah and 4000mah variety.  Here are my feelings on each based only on my personal experience.

The E-Flite is a mediocre pack that I believe would be destroyed if asked to deliver the 96 amps it advertises for any length of time.  It does fine in the Carbon Cub which only draws a max of 70A on occasion and for very brief intervals, but I wouldn’t try to pull more than about 60A from it for a sustained period.  (Just in case you’re wondering, that means the battery is about a 20 C pack or at bit less if you subscribe to my definition of C ratings as expressed earlier).  The cells do not seem to be exceptionally well balanced (IR varies quite a bit between cells in the same pack).  In short this pack simply doesn’t measure up.  I don’t consider it a terrible battery, just not a good value.  There are many packs out there that are as good or better for at least 30% less… I will say the folks at Horizon (who sell this pack) have great customer support so I would be confident that they would take care of me if a quick failure occurred.

The G-Force pack is somewhat similar in that it is more than adequate for the Cub but it’s ability to deliver current I would estimate to be far below (half or so?) the C rating posted on the label.  The difference is that the G-Force is significantly less expensive so it is a little easier to swallow the limitations.  It is also quite a bit better balanced from cell to cell than the E-Flite pack.  I have flown it in both the Carbon Z and my Aeroworks Extra 260 powered with an E-Flite power 60 motor and found it adequate in both.  I don’t know what kind of warranty service I would get from the manufacturer/reseller, so it is hard to give a solid final opinion.  Overall I wouldn’t rush out to buy more at this point but at least it is more reasonably priced and compared to the E-Flite is a better value.

The 4 Glaciers are my favorites so far as they are some of the cheaper packs I have purchased and yet outperform (provide all the needed current and barely get warm!) my other packs and purportedly are as good as the best out there.  They certainly test out as excellent when I use my own internal resistance meter and according to my calculations they are the only batteries I have any personal experience with that might actually be able to sustain the rate that is implied by the label.  In addition the balance (measured IR) between cells is very close.  All this and they are in the same price range if not cheaper than the G-Force packs mentioned above.

Here’s a link to the web page where you can find these packs… Buddy RC

I have also had some limited exposure to Admiral and Thunder Power Packs in this range and the Admirals seem to to be on a par with most of the other packs out there and are in that same average price range.  The Thunder Powers I have experience with have been disappointing so far.  I am withholding final judgement as I have not had a chance to test a new TP pack in this range but the used ones I have played with have not measured up.   The price on them is premium and while I have always heard good performance reviews, my measurements and experience with some slightly used 70C (hah) 4400s gives me the impression that the 30C Glaciers are just as good if not better.  I do know from second hand reports that the TP folks will take care of their customers but that excellent service comes at a very steep price.  I’d love to say it’s worth it… If I have the opportunity to test some new packs I’ll be happy to report back but right now they won’t be getting any money from me.

On to some other concerns that I think are worth noting.  Firstly, you obviously want to make sure whatever you buy will physically fit and isn’t so heavy as to cause an issue.  In smaller planes, weight can be critical, so take this into account but for what I fly I haven’t seen a huge or at least unexpected difference.  Sure the Carbon Z Cub doesn’t have quite the straight up pull with a standard 4000mah pack as it does with a 3200… you do give up something for that weight.  But it’s still pretty spritely and it can fly for 15 minutes on the 4000 versus about 10 on the 3200.  One thing the C rating is good for is it seems that higher C rated cells tend to be heavier, so keep that in mind.

Second, take a good look at the gauge and type of wire being used to build these battery packs before you purchase.  I can tell you that if the balance leads are not very flexible, they are likely to break off at some point and now you have a potentially dangerous (to your personal property as well as your health) problem.  That loose wire can contact another terminal of the battery and cause a short or simply cause the charging of that cell to fail.  Next stop is a forced landing in a bad place or worse.  At a minimum you will be trying to repair that connection very soon and that means some fairly demanding dis-assembly and re-assembly of the pack.  It is not a task I would recommend to anyone who isn’t both knowledgeable of pack construction and fairly experienced with a soldering iron.  The main leads need to be both flexible and heavy enough to handle the current load as well.  The gauge of the wire is usually adequate in my experience but I have run across some that were made from very stiff wire which makes them difficult to connect and position properly in the aircraft.

Lastly, pay attention to the balance and load connectors on any pack you consider purchasing.  Of course it has to work with your charger and speed controller or you will need to adapt it to fit.  I don’t like using adapters on the load connector (in flight) as they just add another voltage drop and possible failure point so can affect both longevity of the model and performance.  I eventually will swap out whatever comes on the battery for whatever I deem appropriate for my use.  I am currently using some JST 2 pin (red) connectors on my smallest aircraft, Deans ultras on my mid size birds and EC-3s almost exclusively on my larger aircraft.

Great-Planes-MM3107-Female-2-Pin-Bec-Connector-22 Pin Red JSTs

Deans Ultra

Image result for ec3 connector

EC-3

The EC-3s are reasonably easy to assemble, make a good secure connection and are rated at 60 amps of continuous current flow.  So far I have only seen 70-75A for very short periods on my larger craft so these seem to be quite adequate.  Many folks favor the Deans, but they are only rated at 40A continuous and I find they become difficult to get soldered to 10 gauge wire without melting the housing and just about impossible on anything larger.  They work well for 12 gauge and smaller wire and I use them almost exclusively on my 3S powered craft where smaller wire and ~30A draws are more the rule.

On the balance connector pretty much everything I own uses the XH style connector.  It’s not my favorite in the world but it is almost universal these days which is a nice change.  I think Thunder Power is one of the few holdouts on this which I really don’t understand.  At this point they need to just concede the point and move to the XH with everyone else.

Big Electrics need big power… Packs, Chargers, Power Supplies and more

Recently, I’ve been spending more quality time with my electrics… especially my newer/larger electrics like the Carbon Z Cub and the AW Extra 260.  Both of these planes are a blast to fly and the AW is, if anything, even better since its conversion to electric.  I’ve almost gotten to my goal of only flying either electric power or gas (no glow fuel for me).  I recommend the AW Extra for a nice mid-size electric acrobat and the Carbon Z has a wide flight envelope combined with the ability to fly off floats, tow gliders and fly anywhere from wild to mild.  Both are great.

The only drawback to this whole scenario is that these bigger electrics need bigger batteries.  Bigger batteries need a bigger charger to charge them up and bigger chargers have bigger power needs…  In short a whole new series of challenges arise when you get into large electrics.  I’m working my way through all of them and have done a bunch of research and some experimentation of my own that I’d like to share.

First, let’s try to put some parameters around the size of the issue…  In my case, I started out in what I would call “large” electrics with the Carbon Z Cub.  This airplane uses 6S LiPo power with a recommended capacity of 3200mah.  Many folks fly larger capacity batteries in the cub to get some longer flight times with sizes up to 5000mah being common.  Two other conversions currently underway will use similar size power systems.  To charge a single 6S pack at a 1C rate takes a considerable amount of power.  For instance a 5000mah 6S pack means charging at 5A and ~25V.  Since power (expressed in watts) is equal to current in amps times volts that means about 125 Watts of power are required to charge just one of these batteries at a standard 1C rate which takes about an hour.  You can charge slower or faster of course.  If you don’t mind a 2 hour charge you only need 62.5 Watts… if you want a 30 minute charge than you need 250 Watts of charging power.

I was hoping to be able to charge 2-4 such batteries at once which means drawing as much as 500 Watts from my charger and power supply system for a 1 hour charge and up to 1000 if you want to get it done in 30 minutes!  Keep those numbers in mind.

My mainstay charger to this point was the Hitec X4.  This charger has 4 separate channels (independent charging outputs) which can each charge at a 50W rate.  For my previous usage where I would sometimes charge as many as 4 of the 3S 2200mah packs, this was not a problem.  At around 12V, the 2.2 A charge rate only required ~27 Watts….  No problem.  Four batteries charged in an hour with only a little over 100W of input power was easy to take care of.  Even pushing all four to double the charge rate (or nearly so) was within reach at the max 200W combined output of this charger.  A small 12V supply capable of 20amps or so was more than enough to supply the needed power and the 200W load was easily supported by my existing 900W cheap-o generator.  Unfortunately this is clearly inadequate for these 6S packs.  At the maximum output of a single channel of the Hitec, the maximum charge rate into the 6S pack is about 2A.  A 5000mah pack is going to take 2.5 hours to charge.  That’s a long way from the performance I’m looking for.  For smaller jobs, the Hitec is still a great charger that I expect to continue to use and highly recommend.  If 3 or 4 cell 3000mah or smaller packs is all you need… it is a fine choice.  The one I have linked to here is a slightly newer and higher power version of what I have and would work reasonably well for up to 4 cell 5000mah packs or even 6 cell 3000mah packs at 1C charge rates.

Since I already know I want to run 6S 5000mah (max for now) batteries and I want to charge 2-4 packs in 30 minutes, I can start shopping for a charger, power supply and generator (if needed) and of course a few extra flight packs!  I’ll try to do a few posts in the near future outlining the buying decisions I made in each case and how they affected each other.  Let the fun begin.

 

Taft Hobby DO-27… Last Flight!

Unfortunately, Steve’s DO-27 didn’t make very many flights between it’s first and last flight.  Steve was never thrilled with the flight characteristics, though it seemed to be quite capable.  I think he was expecting it to fly a bit slower/lighter and it required just a bit of speed to maintain control authority.  In addition the wing mounting method seemed to always need at least 3 hands to accomplish and the servo wire connection into each wing was painful to accomplish.  If you get one of these, you should plan on modifying those servo wires to move those connections to a more easily accessed area.  I also wonder how long the plastic/spring wing connecting clips would last?  I’m not a big fan of those either.  Bolts have always worked well so not sure why they decided to use something different here.

Having said all that, the DO-27 is an oddly attractive aircraft and did seem to be fairly capable of some nice rolls and similar basic aerobatic maneuvers.  Unfortunately we never got a chance to fully explore its capabilities.  On the first flight of our most recent day at the field the plane suddenly lost all power and dove into the ground nose first… rolling slowly while gathering more speed as it fell.

Here is what the crash scene looked like….

2015-05-04 17.20.20 2015-05-04 17.20.26

Ugly, I know.  The impressive thing is that the wing not only didn’t break in half on impact but wouldn’t even break over Steve’s knee when he tried to do so in order to shove it in the trash bag!!  When I picked through the wreckage and sorted out the good stuff, I did a little exploratory surgery and found there were a pair of CF square tubes embedded in each wing half.  No wonder this thing is tough!

It also took no time to find the cause of the crash and it was NOT (unusually in my experience) pilot error.  Or at least not a case of dumb thumbs.  The apparent cause of the crash was a poor solder joint on the positive lead of the battery load wire which had broken off in mid flight!  So Steve’s mistake was trusting his mechanic/electrician (that would be me) to make this solder connection.  I hate that this happened… sorry Steve… but it does make the case that maybe a separate battery to run the receiver and servos would be a good option… especially for the larger/more expensive electrics.  Will have to look into that soon for my 90 size Extra and maybe for the Carbon Cub.

The problem was a combination of several things.  One, the battery has 10 gauge stranded wire which is a bit unusual for a battery this small (4c, 3700mah).  Second, the supplied speed controller connectors were some smallish bullets which is a bit unusual in my experience and we had nothing to match them and even if we had it would have been tough to get these big wires into the matching bullet connectors.  Third, we decided to swap these for Deans Ultra connectors.  While I love the Deans for current carrying capability and the snug connection that results, this is another case of having problems connecting the wires to these blades.  Easy to do for 14 gauge and smaller but for these 10 gauge I was having a lot of trouble getting things attached without melting the housing.  I thought I had pulled it off but in the case of the positive lead the wire had pushed away a bit and the gap between the back of the blade and wire was filled only with solder.  Unfortunately solder bends easily but also quickly fractures under a repeated bending as will often occur when installing batteries in our airplanes.  Mind, I am not making excuses… I should have done a better job on this solder joint.  I just want to point out that getting this right would have been a lot easier if we had picked a more appropriately sized connector considering the wire size involved.  I must be slipping.

RIP DO-27…  it appears all the electronics, including the servos, receiver, speed controller and motor have survived.  What can we do with all of this?

 

 

Conversion of the Aeroworks Extra 260 to Electric Power – P4

Took the Extra to the field last night and ran a couple of batteries through it.  I had fear that it would become much heavier and not fly as well but that is definitely not the case.  The weight is virtually unchanged… added a few ounces at most… and the plane flies very well.  Power from the E-Flite Power 60 with a 16×8 Xoar E prop is unlimited vertical even when the battery falls to 15% of capacity!  I have several batteries but one I highly recommend the current crop of 30C 3300-4000mah Glacier 6S batteries for this setup.  Mounting the battery with the tail end butted right up against the wing tube seems to put the balance point right on or maybe just a smidge toward nose heavy.  The motor, battery and Castle Talon 90 never even get more than warm after a nice 8 minute or so flight.

The best part is that I had to do virtually no trimming as this was based on an existing radio setup.  I think I added (or took out) 1 click of elevator.  If you have this or a similar size bird you want to electrify I highly reccomend this setup.  Here are links to the speed controller, motor and prop I used…

The Glaciers seem to outperform many brands that are 2-3 times as expensive and testing on my bench definitely bears that out so far.  I have borrowed a couple of the higher price packs from a friend (6S 4400s) and will try those as well very soon.

I am amazed how well the plane flies.  For reasons I can’t put my finger on, I think the plane flies better with this configuration than it did with the DLE-20 gas engine.  Maybe it’s the smooth application of power (the DLE has to have a crazy throttle curve to even come close to smooth throttle application) or the lack of noise and vibration.  The other thing I can’t put my finger on is any gas or oil residue on the plane!  Clean up is solely for the purpose of removing bugs and grass from the air frame!

Aside from the cost of batteries and an appropriate charger (but to be fair I will use both to provide power to 2 other airplanes) the conversion to electric I consider to be a huge success and actually less expensive than I expected.

Perhaps the only thing left to address is the need to remove the canopy to connect and disconnect the battery.  With screws holding it on it’s likely going to get a bit tedious.  I am thinking of adapting it to magnets or perhaps some sort of slide latch system.  For now I’ll probably just try to get in a few more flights, get a battery voltage monitor hooked up so I can watch my battery voltage using the on board telemetry and experiment with some different props.  Perhaps a current probe for the telemetry will be added as well to help choose that perfect prop.  There’s always more to learn and experimenting while flying the “E” Aeroworks Extra 260 is going to be a lot of fun.

Taft Hobby DO-27… First Flight!

If you read the first look post on this plane you will recall that we ran into problems trying to install the first wing set due to (apparently) a misaligned tube in one wing.  Once again the folks at Falcon took good care of their customer and shipped out a new wing set and tubes.  The new set slid right into place but at this point we noted another issue.

2015-04-28 18.13.27

 

As you can see one of the servo leads in the wing is so short that it is very difficult to plug in at all when you are assembling the aircraft.  You don’t have a lot of wire coming out of the wing root either, though it is adequate.  The problem is you can’t hold onto this servo lead and apply any pressure to assemble it…  Forceps are NOT optional!  This is an annoyance, but not a showstopper.

Finally, the last complaint I have about the Taft DO-27 is the hinging of the control surfaces.  The folks at Taft obviously know these things are a bit fragile as they include a bag of hinge points to install in case the molded in hinging fails.  We added some wound tape in the aileron hinge line on Steve’s plane and we will see how it goes but both the returned wing set and the new set are already showing signs of hinge failure so I think I would consider adding tape to all hinge lines or cutting them loose and installing the hinge pins from day 1 if it were my airplane.

The good news is, once we got the plane assembled and at the field… It looks good and flies really well.  The scale details really add to the look and the lights are a nice touch as well.  Taxiing on our grass field was easy and with almost no wind and a short takeoff run the DO-27 picked itself up and climbed quickly.  Steve shortly had it doing loops, rolls, snaps and more.  Power was good and flight times look to be 8-10 minutes of general sport flying… maybe longer with some throttle management.

I’d like to rant about how nice the plane is and in the air it really is.  Flying characteristics (based on the two flights so far) seem to be excellent.  Plenty of wing, good roll rates, just a generally good flying airplane.  Looks too are a plus with nice lights and a distinctive shape and color scheme with a few details thrown in makes for a nice combination.  Assuming the wing tube problem is unique, you have to deal with a few issues… First rearrange things to get the tail linkage setup correct.  Second, you should probably get some short extensions to permanently attach to the 2 shorter servo wires and make them easier to connect and disconnect.  Third, get out your hinge tape or go ahead and install the hinge points day 1.  With those 3 things out of the way, the airplane should be a winner.  Time will tell for sure.

Conversion of the Aeroworks Extra 260 to Electric Power – P3

Well the glue dried and I got the motor mounted using 1″ spacers, 2.5″ bolts with fender washers in front and behind the firewall and nylon insert nuts on the back of the firewall.  These nuts are so much better than any combination of loctite, lock washers etc…  They will not vibrate loose even in big single cylinder gas applications (only heat can effect them and that takes quite a bit).

2015-04-21 21.58.44

Also mounted the speed control on the bottom of the motor box where there is a natural air flow and (by adding a hole in the bottom of the motor box) kept it close enough so the motor wires can plug right in and the battery wires can reach without any extensions.  Only the throttle wire may need an extension.

2015-04-21 21.58.25

Added the side air scoops as you can see above with Gorilla brand expanding glue.  It’s great for many things… seems to have great adhesion to so many surfaces and materials… just have to keep an eye on it to prevent problems due to expansion of the glue.  Here’s a link to the stuff I used.


Also opened up the bottom of the airplane for exhaust as directed in the instructions.

Need to close off the old switch opening, decide how or if to address the fuel dot, work on the battery hold down and do some general clean up of the internal wiring and it will be time to do some measurements and a bit of radio adjustment.  The last critical bit will be insuring the balance is on and it will be time to fly.

Taft Hobby DO-27… First look

During his recent trip to the Weak Signals show in Toledo, my flying buddy Steve made an “impulse buy” from the good folks at Falcon Hobby Supply and came home with the Taft Hobby DO-27 in Red and White.

THLTP-03C-2

The purchase started out with a bit of  misstep when the folks working the booth there assured Steve that the plane would accept the 6S LiPos that he had on hand.  This is not the case!  The DO-27 is setup for 4S use and I very much doubt the speed controller or motor would last long if a 6S was installed!  With no 4S batteries in his inventory, Steve was considering returning the aircraft but the folks at Falcon stepped up and offered to send a free battery at no charge.  Shortly thereafter Steve has a 45C Pulse Ultra battery in hand and is looking forward to flying his new airplane.

Today, Steve brought the DO-27 over and we started unpacking and assembling.  Visually the airplane is striking with a nice paint scheme, quite a bit of scale detail and a very distinctive look.  Packaging seemed to be excellent with no damage noted and everything held tightly in place.  The model is also very complete with everything needed including a nice wood prop, spinner, nice looking wheels, etc…  Assembly is very simple with only a few steps to complete but during the process we did note a couple of issues.  Two were especially troublesome.

First, the front wing tube in the port side was impossible to install.  It went in an inch or so and then became very stubborn.  After forcing it a bit further it just continued to get more difficult to slide in.  Visual inspection seemed to indicate the tube was misaligned with the plastic wing root as a lip can be seen on one side.  With no way to move the tube (it seems to be quite securely installed) we tried using a drill bit to open up the entry to the tube and eventually managed to get the tube in place but it is very difficult to install and I think another call to Falcon is imminent!

Secondly, when Steve attempted to connect the linkage to the tail surfaces we quickly realized one was far to short and the other far to long!  It was quickly decided that the linkages were simply swapped at the factory so we traded them out and things looked a bit more promising until we realized that both were now to long…  a bit more head scratching and we realized that if we physically reversed the servos, essentially moving the output shaft forward a bit, we might have something that would work.  With that done, we got to a workable linkage layout and all seems well.

Another minor issue was clearance between the landing gear blocks and the foam hatch that screws on over it.  Once the straps were added to hold the landing gear in place, the belly hatch was held slightly away from the body of the plane.  Some simple trimming in the area took care of the problem.

We still have high hopes that solutions to all the issues will be found and Steve will get to actually fly the bird soon.  With any luck it will fly as good as it looks and we can leave the issues behind.  More to come….

Lots of LiPos… maybe parallel charging is one answer?

I recently picked up a higher power charger… In my case, I chose the Revolectric FMA PL-6.  This is a very highly regarded charger and I did not pick it for just the power but that was a basic requirement in the decision making process.  So far, I am enjoying it and I will have another post up shortly with more info on that product.  The important plot point for now is that this is a single output charger that can crank over 400W of charge power at 12V and over 800W at 24V.  Compared to my previous chargers that have always (at most) been limited to 50W per output this thing is a real power house… but I was thinking I had to trade off quite a bit to get the big power.  For instance…

The first big trade off when looking at these higher wattage chargers is that they typically have fewer outputs.  On my old trustworthy Hitec X4 I have 4 outputs, each capable of 50W of charging power.  When you start looking at chargers with 400W or so you usually get 1 output or occasionally 2 outputs with 200W of power each.  By the time you get to 600W or higher you are typically going to get one output.

This was an acceptable trade off for me because my main goal in purchasing this charger was to allow me to charge my 6S 3300-4000mah LiPos in a reasonable time.  A 4A charge (one hour recharge for the 4000s) at 25V (approx.) requires a 100W charger.  With my 50W, charge times were in the range of 1.5-2 hours.  With my new charger I can charge at 2C (8A) which at 25V is 200W and charge in 30 minutes or less.  Not bad!  In a pinch I can even charge faster as the batteries are rated for 5C (20A) max charge rate which would bring me to a 12 minute charge provided I have at least a 24V supply!  I don’t like to push the batteries that hard normally but it’s nice to have that ability.

The problem, it would seem is that I now can only charge one battery at a time so if I charge at 2C or so I could charge another battery every 30 minutes.  That’s great but it sure would be nice to be able to charge multiples… Oh well, I guess I have to give up something for progress… or do I!  As it turns out there is a way to get there, and it really isn’t that difficult.  Enter the parallel charging board…

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With this nifty little board plugged into the 6S balance port on the included balance board as well as the main charge ports of the PL6, I can now connect up to 6 similar batteries at a time and using the high power charging capabilities of this charger I can charge all 6 at once!!    There are many versions of this board with various types of charge plugs, so be sure to get the version that is right for your batteries.  It’s really fairly simple to use and quite effective.  Basically as long as the batteries are all similar cell counts and are starting the charge cycle at fairly similar states of charge, you can simply plug all of them into the board (main charge lead first, then the balance plug from each battery) and you’re ready to charge.

As an example, let’s say I’ve flown 6 flights on my T28 using 3S 2200 mah LiPo batteries.  Assuming I’ve run them all down near exhaustion I simply plug in the main leads and then the balance plugs to the balance board, set the charger for 2200mah charge rate as normal but specifying that I am charging 6 parallel batteries.  The charger will then multiply the charge rate and start charging at 13.2A.  In an hour or so, all 6 will be charged.  If all the batteries can handle a 2C charge rate of 4.4A then we could charge them all in about 30 minutes as the charger would be pumping out 26.4A.  26.4A at 12V (all approximations) would require a bit over 300W which is easily attainable with even a fairly modest 12V power supply or battery.

There are a couple things to keep track of when parallel charging.  You should take it seriously when I say that the batteries need to start the process at near similar charge levels.  Any difference in voltage between the packs will equalize by current rushing from one pack to the other through whatever connections are available (thus the advice to connect the main load connectors first since they can handle more current).  This rush of current if pretty much unrestricted and could overheat another battery or smoke the balance board if the difference is to great.  Also, note that all the packs need to be of equal cell count so no mixing 3S and 6S etc…

When this really gets to be impressive is when you look at what happens if I want to charge up all six of my 6S batteries.  I have 2 4000mah, 3 3300mah and 1 3700mah 6S packs for use in several of my planes.  Using my old 50Wx4 charger getting all 6 packs back to charged state after a full day of flying would take at least one full charge cycle of 1.5 hours (at least) for the first four and an additional 1.5 (or more) hours for the second batch of 2.  This is 3-4 hours of charging.  Now, I can hook up all 6 packs in parallel and even if I pick a modest 3.3A charge rate the charger will then do the match and start charging at about 20A (assuming adequate DC power).  The charge cycle will likely take only a bit over an hour and all 6 packs will be race ready again!

I’m not sure I’d want to do this with packs that were hugely different in capacity… have to think about what will happen and whether this might cause issues but I’m not concerned with this particular scenario.  Of course parallel charging is possible with other chargers… this is not something only this charger can do… but to be useful the charger needs power to spare.  Your average 50W charger need not apply…  Here are links to both the charger and the  balance board in case you are interested in purchasing one or both for yourself.


 

 

Conversion of the Aeroworks Extra 260 to Electric Power – P2

Some small progress has been made.  I stripped all the gas related equipment out the other day.  This includes the fuel tank, fuel dot and associated plumbing, gas motor (DLE-20) with ignition, both throttle and choke servos, power switches (2) and the main battery (2300 LIFE that feeds both ignition and flight gear).  Near as I can figure, I am taking out 2lbs 14oz of “stuff”.  So far adding somewhere around 2lbs 10oz inlcuding the motor, speed controller 6S 4000mah battery and a few other odds and ends.  Even allowing for another 4oz in battery tie downs etc… would make the change in weight zero!  I expect the new motor to produce nearly the same thrust and I could easily afford (at a guess) to give up 20% without losing unlimited vertical.  Things are looking good so far!

As I sized up mounting the Power 60 electric motor I realized I needed to strip off the firewall doubler that had been added when the DLE was mounted and close up the hole that had been cut to accommodate that setup.  With a bit of judicious application of a wood chisel I am down to the original motor box and I have overlaid the front of the box with a new piece of 1/4″ plywood to provide a nice solid platform to mount the new motor to.  With the added 1/4″ of the plywood and the addition of some 1″ spacers I picked up at the Toledo show, I should have the correct spacing to get the back plate of the prop adapter outside the cowl with 1/8-1/4″ to spare.  I even remembered to extend the center lines that were on the front of the motor box around to the sides so I’ll have reference marks to extend them back to the front when the epoxy dries and insure the new install is also centered!  Yeah me! 🙂

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Waiting patiently for the epoxy to dry now…  <sigh>

 

Conversion of the Aeroworks Extra 260 to Electric Power – P1

Whilst still in the midst of converting the Telemaster to electric power… a project that is awaiting a covering job which in turn has gotten in line behind a covering job for a friends airplane… I picked up an extra speed controller and a similar but slightly more powerful electric motor for the AW 260.  Contemplating this new project, it suddenly hit me that the conversion of the AW 260 is going to be quite a bit simpler than the Telemaster.  This is mostly due to the fact that the 260 is in “like new” condition and was designed by Aeroworks with the option for electric power from the beginning.  Here’s a stock photo from the AW website:

.60 - .90 Extra 260 ARF QB

I still have the original pieces needed to do the small amount of conversion needed (some air guides/scoops… etc…) but need a motor mount so I’ve ordered the original conversion box from AW.  The ordering process was great… free shipping… nice.  Then I got to the part where they charge $6 for handling… Of course I went ahead and ordered and just added an “explanatory note” to explain what I thought of advertising free shipping and then charging handling instead.  I still wanted the thing and the price even with handling is not ridiculous, I could just wish for a bit more honesty in advertising… probably an oxymoron but I refuse to lose ALL hope!

Update!!!  The worst part, now a couple weeks later, is it turned out that the conversion box from AW was to long to accommodate the motor (EFlight Power 60) anyway so it is pretty much useless to me… Live and learn.

In any case, I have already stripped the motor, tank, throttle servo, etc… and am just awaiting the motor box to arrive before I dig in to what I hope will be a fairly quick and simple conversion.  One of my final bits of homework is to try to determine what size battery will be needed to keep this bird airborne for a reasonable (8 minutes or more I hope) period of time.  I’m hoping I can use one of the pack sizes I’ve already acquired for use in the Telemaster or Carbon Z Cub.  If not, I’ll be in Toledo for the big Weak Signals 2015 where I plan on picking up a new charger and a few more 6S LiPos, including some for this project.  I’ll update with weight comparisons and details of the project as it progresses and hope to be able to post flight test details soon!