Balancing Severely Out of Balance A123 Pack

The following is a recent exchange discussing some charging logic that is impacted often by time-out settings in chargers. Not a bad thing all in all. The same logic can be applied to Lipo packs as well.

Hi, Dave:
Here’s my situation: All of my A123 batteries came from you and I’ve got several. All of them (except 1) work perfectly and I enjoy being able to take advantage of all that A123 batteries have to offer. My one that doesn’t work properly is a 2300mah, 2S receiver battery that I can’t get to balance. I charge it on a Turnigy Accucell-6 with the cutoff voltage set at 7.2 volts. My charger timed out at 120 minutes with one cell at 3.6 volts and the other at 3.25 volts. When I first started using these batteries, I was negligent about balance charging and would as often as not, just quick charge them and go fly. So, this is not a warranty question at all, but one as much for my knowledge as anything. First of all, is this battery safe to use (as a receiver battery), and second, is there anyway to get the second cell back up to voltage? I’ve cycled and balance charged it probably 3 times trying to get it to respond, but nothing I know to do has worked. I guess I could used it on an electronic ignition where sudden failure wouldn’t likely be as catastrophic as losing receiver power. What is your recommendation?
Thanks,
Steve

When balance charging, the first cell getting up to 3.6V causes the charger to start stepping down the charge rate. Ultimately, the charger cannot go over the maximum dissipation rate of your balancer. In other words, if it can only dissipate 100 mah, then the charger will drop back to 100 mah. It’s charging the pack at 100 mah but at the same time discharging the full cell at 100 mah to keep it from going over 3.6v. If the low cell is 1000 mah behind, in the two hours of the time out, it will only be able to bring the lagging cell up about 200 mah. It will still be lagging by 800 mah and some measurable voltage difference will be the evidence. Because the charger times out and stops working, your still out of balance.

Procedure options:

A. You could just keep repeating a 100 mah charge rate and let it time out 4 or 5 times.

B. You could also go into the setup and disable the time out.

C. There are some safety concerns with both “A” and “B” above. The best and quickest method that we use at our shop is to connect the charger through the balance port to only the low cell. You can do this through the standard XH balance connector by taking a JR or Futaba RX charge cord, crack off the outer shroud exposing the two pins. These two pins will be .100″ apart, just like those in the balance harness. Plug the bullet end of the cord into a volt meter, plug the business end into the balance harness, probing the different combinations. In the case of a 2 cell RX pack, you’ll only find 2 combinations. Offset to the black wire and offset to the red wire. One of these will read about 3.6v (the full cell) the other will read 3.25v (in your example, it’s the low cell). When you find the low voltage position, carefully pull the banana plugs out of your volt meter and plug into your charger. Set the charger to charge 1 LIFE cell. Set the rate (for a 2300 A123) to something between 1 and 2 amps (we don’t want to overheat the delicate balance connector) and let it charge that individual cell through the balance harness until it’s full.

When it’s done, both cells should be at similar voltage.

If you want to get really fine, there could be a slight calibration difference between your charger charging a single and a two cell pack. To really refine it, reconnect the pack to the charger as a 2 cell pack in the conventional way. Put the charger in discharge mode set at 2 amps. Let it take our 100 mah or so out of the pack. Then, switch back to Balance Charge mode and charge at 2 amps. Now the charger will put the 100 mah or so back in and at the same time balance both cells to each other. Since the pack is almost full, it won’t actually charge at 2 amps, it will read something lower. When complete, if the cells are good and the charger is working properly both cells should be very close.

It is possible the cell is bad. If this is the case, the above procedures and logic won’t result in a balanced pack. (presuming the charger is working correctly) It’s OK to repeat the procedure if you want to try again however, it’s likely your results will be the same.

If you are able to balance it successfully, do a discharge on the pack at capacity/2 or near. This is the standard for testing lithium type cells. So, a discharge rate of about 1.1 amps would be correct. Realistically the A123 2300’s should test within 50 mah of 2200 if they are in perfect condition. If the pack tests below 80% of 2200 (below 1760 mah) it should be replaced.

As to safety, I hesitate to ever say any battery is “safe”. I would say that if I could not get the pack behaving properly, I’d replace it. The cost of any pack is always a tiny fraction of the value of a model. It never makes you feel like a winner to put one in the dirt over saving a few bucks on a simple part, especially if you were suspect of it before you flew. Get it right, get confident or replace it.

Another safety warning here is you should be extra diligent when working with any battery where it’s condition is suspect. Do it outside and/or supervise closely. Never charge unattended inside a structure or vehicle. Always use a fireproof container for charging, especially when dealing with anything suspect.

If you follow through those procedures and that logic, you should be able to rule the pack in or out and have good confidence in your decision. Hope this helps you sleuth out the pack. Dave

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Scratch Building: Transfer A Drawing To Wood

1928 Fairchild FC-2W2
1928 Fairchild FC-2W2

We’re converting a Hobby Lobby Telemaster into a 1928 Fairchild FC-2W2 for a National Parks Service program. This aircraft was the first ever owned by NASA and later the first owned by the National Parks Service. Information link at bottom.

While making a complex former, I felt the method was simple, interesting and important to share. Having arrived at the shape, I used the following method to copy it onto the material I wished to cut it from. The simple technique could help you build any aircraft from your own or purchased drawings.

Drawing of Fairchild FC - 2W2 Former
Drawing of Fairchild Former

1. First we need a drawing. If your making “one off” parts as I am in this example, simply draw the part on standard 20 lb copier paper using pencil. I make lots of changes and mistakes as I go, so it’s important to have an eraser equipped pencil.

Headless Telemaster/Fairchild

1B. Here is the front of the modified fuse where our soon to be made former will be installed.

Fairchild Imagination
Fairchild Imagination

1C. Holding up our drawing to imagine what it’s going to look like. Does it look correct?
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.” Albert Einstein

Former Drawing and Copy
Former Drawing and Copy

2. If your using an obtained drawing or you wish to preserve your drawing, use a copier or all in one printer to make a copy of the area containing the part you want to make. In this case, I made a copy of my pencil drawing just in case I discovered and error and wanted to alter the drawing before I finished.

Fairchild Former Heavy Pencil
Fairchild Former Heavy Pencil

3. Heavily pencil over the lines we wish to transfer to the wood. I used a standard #2 pencil.

Fairchild Formula 560
Fairchild Formula 560

3B. There are multiple uses for Formula 560.

Fairchild Former Drawing Face Down
Fairchild Former Drawing Face Down

4. Place the drawing, heavy pencil down against your material. You will notice the grain is running the wrong way in this former. However, it’s just a jig for building the nose, it’s not intended to provide any structure. The nose of this model has many facets of 1/4″ thick balsa. Although I’ll leave the former in the model, it could be removed if I wanted too. As this model has a short nose needing weight up front, I’ll be leaving it in.

Fairchild Plan Pin Down
Fairchild Plan Pin Down

5. Place two pins through the paper into the wood to prevent the drawing from moving. I choose top and bottom locations. Notice you can see the drawing through the paper. Makes me feel like Superman, you?

Fairchild Nickle Rub Down
Fairchild Nickle Rub Down

6. Find something curved and smooth like a coin, I choose a nickle to rub the pencil into the wood.

Fairchild Lift & Inspect
Fairchild Lift & Inspect

7. Because we created a way to register the drawing to the wood, we can lift the paper up and look at our results as we progress. No danger of losing our alignment.

Fairchild Former Transfer Finished
Fairchild Former Transfer Finished

8. Ahhh, thats what I’m talking about! The drawing has new been transferred to our material. It will be easy to cut it out now.

Fairchild Former On The Bandsaw
Fairchild Former On The Bandsaw

9. Doing what the band saw does best.

Fairchild Drill Hole
Fairchild Drill Hole

10. Drilling for the Scroll Saw

Fairchild Former Installing on Scroll Saw
Fairchild Former Installing on Scroll Saw

11. Installing on the Scroll Saw

Fairchild Scrolling Along
Fairchild Scrolling Along

12. Doing the inside, what the scroll saw does best.

Fairchild Former Against Print
Fairchild Former Against Print

13. How does it look against the print?

Fairchild Former Goes About Here
Fairchild Former Goes About Here

14. The former goes in about this position.

Fairchild Former Positioned
Fairchild Former Positioned

15. Former positioned and ready for addition of next nose sheeting segments. Since we are working with a model that is already built, we elected to jig the next two formers to the front of the fuse. when the 1/4″ thick balsa segments are added from the front of the fuse to this former, many facets will be formed representing the nose of this model. Using this method, we only need to make the 3 sides of each sheet accurate, they can be allowed to extend past the former. We can cut them off and sand them down against the former as we go. After all plates in position, we’ll snap out all the scrap sticks used to hold the former in place. The sanding bars are banded tightly to the fuse sides so I could measure and put the former in the center. They make a great straight edge.

I thought solving the problems of making and installing this former would be interesting to readers and hope you made it this far into a very long post.

Story of the National Parks Service first aircraft in the National Parks Traveler

Stars And Strips, a Fairchild FC 2W2 at the target=”_blank”>The Virginia Aviation Museum.

Byrd's Fairchild
Byrd’s Fairchild

Admiral Byrd used the Fairchild FC 2W2 as a Aerial Photography Platform including in the South Pole.

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Crash Investigation, Why did it crash?

Just as in full scale aviation, crashes are often because of a sequence of things going wrong. I received a letter recently asking my opinion on a set of circumstances. At the time of this writing there is no 100% sure answer, not enough info is provided, however there is enough info to draw boil it down to a few likely reasons. It’s easier to take a cucumber cool Sherlock Holmes look at the facts when it’s not your own model. However, you should always investigate crashes and failures with cool logic looking for every possibility, particularly the human element. Read through John’s letter and see what idea’s you have based on the info provided

Hi Dave:

I have an Orbit Charger–up graded by you to accept A123 cells.–Number: 0650-05601OK

Until recently it has worked flawlessly–but that came to a “Crashing” end several weeks ago when I took of and immediately ran out of power, airspeed and ideas, all about the same time.

If you will bear with me I will run through the sequence of events:

*Prior to going to the Field I threw my Plane on Charge (6 x A123)–The Charger quickly indicated “Full and I assumed I had charged before leaving the field the previous day.

* Commenced T.O. and promptly BECed at about 15 ft–gliding smoothly into a vertical Metal Post just off the side of our runway—cleverly ripping the wing in two and tearing it off the Fuse.

*Checking the battery back at the Pits, with my Buddy’s similar Orbit Charger–the pack indicated full and would not accept any charge.

OK, that is what happened–here is the rest of the story:

On arrival at home–(I did not take my charger to the field as we have similar chargers and packs and intended to use my buddy’s) I put my Pack on MY charger–and was horrified to see, when it was turned on–“LiPo 4.2” instead of the usual 3.6!

So all was clear–somehow my Charger reverted to Lipo 4.2V/Cell, overcharged (very quickly I might add) and ruined my 6 cell pack. This without any abnormal heat or any indication (other than the initial charge settings–which I have never paid as much attention to, as obviously I should have– as it’s been “Bullet Proof” for years).

Battery Pack ruined–Airplane wing history, ego damaged–etc!

But what I would like to know–is WHY???–did my charger revert to 4.2V/Cell as I have never used Lipo Batteries with this charger since you upgraded it– and I must say it has preformed flawlessly–until now!!

I hope this ramble was understandable to you,

Regards
John, Canada

John, Sorry to hear of losing a favorite model. You say it ruined your pack, however, you don’t provide any cycle data or voltages to back that up. So, I’m going to make a guess or two to follow that presumes your pack is not ruined from over voltage charging.

You may not know, but when A123 first came out there were no chargers really. We all charged them with Lipo mode chargers. As long as they are perfectly in balance this can be done. The high voltage fuse does not open up and fail the cell until just a little bit over 4.2. So, if a fuse opened up (your pack would be reading zero) it would have to be out of balance to begin with. You don’t say your pack is reading zero, just throwing out there some information you may not be aware of. Obviously it is less risky to the HV fusing if charged to 3.6 per cell and as chargers (Orbit was one of the first) became available to do it correctly we started only charging them in A123 modes.

There is no capacity (or not much) above 3.6v so there is no advantage to charging them higher than 3.6v, just risk. They are not lipo which will puff or risk of fire if you charge them even a tiny bit above their max voltage of 4.2. A123 is a little more forgiving of it’s 3.6v cap. Not suggesting you take up this practice, just history to chew on which bears on your question.

No idea why it may have reverted. Have you run a test to satisfy yourself it is true? If it is, you could tell it that it was charging a Lipo pack of 1 cell less and it would stop at 4.2v x cell count. In this case, set to 5 cells it would stop at 21v on your 6S A123. This would prove for certain your correct.

Also, bear in mind you had some period of time of testing it and it worked perfectly. It’s possible something happened here that you may have not expected yet was exactly what was supposed to happen given the circumstances. Bear with me while I roll through the some possibilities. Anything is possible some some things are more likely than others.

Also, havn’t used one lately in A123 mode but I am wondering if the screen reads differently? It’s late or I would check it, time to go home.

****For the benefit of readers, the Orbit charger starts the charge procedure as soon as you plug in the pack. Plugging in the pack is like hitting the “start” button on many chargers. It looks at the pack for a few seconds then displays on the screen the number of cells it “thinks” it’s connected to. The user then adjusts by hitting the up or down arrow and once you hit “start” and approve it, it starts applying current and charges the battery.****

Scenario’s I’d put forth:

1) If it were in fact in Lipo Mode, an A123 Discharged to 2.7v per cell would be only only be 16.2V, the charger would have guess it was only 4 cells and charged it to 16.8v. You’d be not fully charged and your flight would end very early. Your charger would “peak” out quickly. It would be very reasonable for you to fly the pack down to that level, so this scenario could hold some water. If your BEC voltage is hard set to something reasonable like 2.3v per cell or so, you can see how quickly putting a load on the partially charged pack would cause you to hit BEC cut out.

2) If it were a tad higher than 2.7v, lets say 2.9v, it might still only guess 4 cells. Same scenario as above, you’d be not fully charged and your flight would end very early. Your charger would “peak” out quickly.

3) If you had a short flight and the cells were at 3v+ then the total would have been 18+v. The Orbit tends to guess a tad low (to be fire/damage safer on your packs) at higher cell counts, so I’d expect it to count 5 cells in Lipo mode at 18v and only charge your pack to 21v. A full A123 would be 21.6v, it would have flown fine and you’d not have detected the slight short charge.

4) The charger could have been in A123 mode, the pack could have been discharged lower than normal. Did the last flight on the prior day end in a BEC cut out? Was it a great day, perfect conditions, where you reallying enjoying yourself extra well? Maybe you put a couple more minutes on it. Maybe it was discharged a little further than normal habits and counted 5 cells. Out of habit you approved it without looking and you had a short charge at 18v to start the flight.

My guess without having anything here to measure or double check is that scenario 4 happened It is even possible you could have had the pack so low (depending on BEC settings and nature of model) that the orbit only counted 4 cells and only charged to 14.4v. This kind of oversight when your distracted or in a hurry is very easy to make. And with a floaty model with very low cruise power requirements, it’s even easier to fly a pack very deep by mistake.

I would wager (unless there is mechanical damage) that your pack is just fine, just undercharged due to approving the charge at the wrong cell count and not hitting the up arrow to correct it.

If in fact it really and truly is in Lipo mode, I have no idea how that could have happened and it’s likely that scenario 1 describes the chain of events.

Some positive action to take:

When anything happens that is unexpected, it’s worth a closer look. You had the little red flag early on that the pack filled quicker than usual.

Really looking at that screen before you approve the charge is the first step in not having a problem. The second is looking at the finish voltage when you take the pack off. Your packs should be reading close to 3.6×6 or 21.6v. Seeing this end voltage is your second charging check and really your first step in pre-flight inspection of the model. The third check is listening to the ESC and make sure it’s counting 6 beeps. If it only beeped 4x or 5x when you plugged it up, it’s a big red flag something is amiss. If you pay careful attention to all three of these steps, it would be very difficult for something like this to slip by you again.

(You might actually be listening for 5 beeps as most ESC’s presume they are counting LIPO’s to set BEC Cut Off voltage. Being aware of the regular beep count that represents a full pack is the point, not the precise number in this case since your flying A123 cells and I dont’ know which ESC your using or it’s settings. So, correct could be 5 beeps, wrong could be 4.)

Hope those ideas will let you craw back through memory and your equipment and find a satisfactory explanation. Obviously, anything that goes unexplained can easily happen again so you want to figure out as much about it as you can. This should allow you to be alerted before flight if ever there should be a next time that circumstances stack up in a similar way.

If you did mechanically damage the battery, we can usually repair them. We keep cells on hand here.

Dave

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Iowa City AeroHawks Nice Remarks

Good Morning Dave: Attached please find a flyer advertising our 10th annual swap meet scheduled for January 20th 2013. You participated in one of our first swap meets several years ago and gave us some very valuable suggestions which we took to heart. We have grown our event each year and last year moved to a new venue to accommodate the need for additional parking. We have grown this event to be the largest in the state with people in attendance from 7 states last year. We had 694 paid general admissions plus 125 tables rented and already have people reserving tables at a record rate for 2013. Over the last 3-4 years we have also seen a strong increase in the interest of electrics and the demand for these types of products at our meet. We are trying to scratch where it itches so we are trying to have more of these types of new products offered. We would love to have Radical RC be part of our event if at all possible. Please see the attached and let me know if you would like to attend. I think it would very much be worth the trip. Regards, Rich VeDepo Iowa City Aerohawks Event Coordinator

Iowa City Aerohawks

Iowa City Aerohawks 10th Annual Swap Meet & Auction

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Lipo Battery Disposal

Lipo Discharging
Warren Behymer asks and interesting question:

I need to know how to dispose of LiPo battery that has swollen due to an overcurrent.

There are two issues.

1. We want to discharge the battery in such a way as there is minimal risk of fire during the discharge and later when the battery is in the recycle or trash bin.

2. We want to dispose of the depleted pack in a recycling container.

The first thing to do is remove all potential from the battery. We do this with an 1157 light bulb (Brake/Marker type bulb). It’s handy to use because it gives an indication of ongoing discharge by emmitting light and doesn’t tie up one of my ever working chargers. We have our bulb wired with alligator clips and a switch to choose between one or both filaments. I don’t remember what the draw is per filament, but we considered that a small cell would be more safely discharged at a lower rate than a larger cell. When discharging a large cell, we set the switch so both filaments burn. We use an ammo box as an oxygen poor fire safe to do this, since we are indoors and we’re working with a suspect pack in the first place.

Lipo Discharged

This is allowed to burn until the bulb is out, then allowed to set connected to the bulb until the following day. This way we are 100% certain the pack is completely exhausted.

Lipo Leads Soldered Together

Next we solder together the leads on the pack. Just in case any recovery or bounce back of capacity in the pack were possible, it is constantly discharged through the short. There should now be no chance of any kind of arc or spark starting a fire in the recycling container. Being that the pack is completely empty, there should not be any energy present of any kind.

Battery Recycling Box
It’s now okay to discard /recycle the pack properly. We won’t have to worry about the pack accidentally being shorted and causing a fire in any container. It’s electronically inert.

Federal law (49 CFR 173.185) states lithium type batteries must be individually packaged in non-conductive material and transported to a “permitted” recycler. In our shop, we use Call2Recycle (also known as RBRC 1-877-723-1297). They provide free recycling materials and processing. A bag is provided for each pack, we wrap the back in the pack, seal it, drop it in the box. When the box is full, we contact UPS for a free pickup and delivery to the recycling station. Any local battery seller should have this capability on site. We accept lipos for recycling at Radical RC.

Help finding a Call2Recycle RBRC Recycling Location near you.

There may be other safe and accepted ways of doing this, the above is how we handle it at Radical RC.

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Converting A Model From Lipo to A123 (LIFE) Cells

Chris from Michigan Asks;

Hello Dave,
I would like to power my Ryan with A123 cells. I have been using a 9s 4p 6000mah Lipo pack to power a Hacker C50 motor.
If I understand things correctly, I believe that I need 4packs 6s 2300mah to equal the same watts and flight duration as the Thunder Power packs that I have been running.
Because of the cost of these A123’s, I want to be sure that what I am ordering is correct!

Chris,

To match duration of a 6000mah Lipo, you’ll need at least 6000mah in A123 which will be 3P. You’ll actually be a little over as the 2300mah A123 cells actually test most of the time around 2200, at 3P you’ll have 6600mah which should result in slightly more flying time.

I assume your 6000mah lipo is made up of 1500mah Parallel packs. So, 4 1500’s in parallel = 6000mah.

If what you really meant was your running 6000mah cells, 4 in parallel, then your pack size is 24000mah which would be about 11P or 11 A123 in parallel. I am not thinking you meant you had a 24000mah pack.

If your running 6000mah total in the airplane, and are thinking of running A123 in 2P for about 4400mah real world, this may be just fine. I generally only use the top 60% of a Lipo (70% max) on a routine basis. 60% of 6000 3600mah, 70% is 4200mah. I’m more comfortable running A123 cells a little deeper than Lipo’s as the risk of hitting BEC cut off cause me less worry. (Hitting BEC cut off is hard on Lipo’s) So, running a 4400 A123 down 80% is 3200mah. So, a 2P A123 should get close to the Lipo in actual use. However, your not running as much cushion between a solid end of flight habit and the bottom of the battery.

For matching running voltage, you’ll need 10 to 11S A123. I’d probably go to 11. At 12S, you’ll definitely have 3-4 more running volts. It will be like 9.8 Lipo or something like that.

To do conversion at nominal voltage, (# Lipos * 3.7) / 3.3 nominal of A123 = cell count.
To do conversion at full voltage: (# Lipos * 4.2) / 3.6 full voltage of A123 = cell count.

Nominal conversion is: 9 Lipo = 10.09 A123 cells

Full voltage Conversion is: 9 Lipo = 10.5 A123 cells.

Since you do most of your flying between full and nominal voltage I lean towards the full number for this estimation. 11 is the best choice. 10 you might notice a slight decrease in performance by your motors KV * volt reduction of the 10S pack. Right in the front of the pack, the 9S Lipo is 37.8v. Right in the front of a 10S A123 your full voltage will be 36v. So, KV X 1.8 = drop in top rpm. If your running a 500kv motor, that’s 900 rpm.

If you go with 11 cells, you’ll be starting out at 40.4v meaning your over the Lipo voltage by about 2.6v. So, you pick up (with 500kv motor) 1300 prop rpm.

Either choice means to get back to exact performance you had on Lipo you may need to alter the prop slightly, maybe an inch more pitch for the 10S A123 and an Inch less pitch for the 11S A123 or something similar to re balance things back out.

So, on balance, not knowing everything about the model and power system, I’d lean towards 11S. If you go 12S as your proposing, you’ll likely end up way over on RPM and Watts from where you were with the 9S Lipo pack. Important considerations here are if you mind a little more or a little less power (if the ESC minds more amps/voltage) and if you would need to change props, is there a convenient prop up or down that would suit the model and flying preferences. For example, if your running right at the edge of the ESC at this time and didn’t want to upgrade it, a slight decrease in power is acceptable, 10S becomes the obvious choice.

Another consideration not taken into account above is there can be a wide variation in quality of Lipo’s people are using out there. (not picking on Thunder Power, remarks for general readers of this post) Your current pack which may be performing just fine for the application may be worn and not really up to snuff compared to the original new condition. Thus if the current lipo has more voltage depression than it should, an A123 10S pack depressing less by some significant amount, could end up taching and watt metering out higher than the battery you are now using.

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Holding A Swap Meet: Date Planning

The following advice is written with RC hobby swap meets in mind. However, the same logic and solid advice apply’s to any club event you are contemplating.

Why:
The largest reason for an event failing to take root and grow strong is often poor date planning.

Context:
Generally swaps are held during the winter months. In the Ohio and probably most northern states the season runs from October thru March. It might be different in your neck of the woods.

Here is how to do it:
Print out calenders for all the months you will be considering. Collect together the AMA magazine “Model Aviation” for the past year or two. Go through the non-flying events advertisement in the back. Write down every swap meet within 2-300 miles on the date it occurred. Look in the Flying Events section for things like indoor fly ins and other large open public events. Don’t worry specialized contests and such things that probably have 20 or fewer people attending. It’s not a bad idea to do this for a period reaching back 2 years. This will give you very good idea what what the flow of events looks like. Usually event planners will tend to repeat the same dates like the 1st Saturday of November or whatever. Why consider events so many miles away? You’ll find the closest event (within 150 miles) have the biggest impact and the furthest ones the least. However, if a major event like PERRY (worlds largest swap) is going on, you won’t get any professional or armature vendors and perhaps only a few swappers, they will all be at Perry or Toledo or Joe Nal, whatever the major is. Same advice goes for certain flying events. Don’t schedule over a major indoor flying event like the JR Indoor Fest or the Hobbico E-Fest.

Be realistic:
If you put yours on the same day as the regular ABC Dog Fighters meet 100 miles away, your likely to get exactly what you deserve for this sillyness, NO VENDORS AT ALL. And, 20% of the locals will be going to the ABC Meet. Additionally, all the people 1/2 way between you and there are going to choose the sure thing, not the new event. I’ve run into many event CD’s stuck in a prototype thinking mode. It goes something like this: “I’d never go 100 miles for a swap meet, how can that event possibly effect us?” Here is the fallacy of that kind of thinking, not everybody is like “you”, and in fact, who cares about “you”, your going to your own clubs event no mater what. Where the profit from these events comes is getting “others” to come. So, forget about “you” and think more openly about “others”. Additionally, leave all ego’s aside. You don’t have to beat the competition, you can simply put your event on a different date and be the only game around. It’s a simple formula.

Question: A club in the next town holds and event in January, when would be a good time for us?
I’ve found two clubs in the same region, county or town can have great results but one thing is important. Think of the new year as a dividing line. If one club holds an event on the last weekend in January and it’s close by, you don’t’ want to have yours in February. They’ve already consumed the bulk of the enthusiasm and energy for a swap meet. It takes time for that to build up again. Consider running your event on the opposite side of the calendar. Why not choose November or December? I’ve found two clubs can have meets even in the same town and they both work well as long as they are on opposite sides of the calendar. Putting your event a week or month in front of another one without the calendar year division is a somewhat unfriendly thing to do. There is room for everyone. Think cooperatively. Your members are going to the other event, you want them feeling good about showing up at yours.

The Sister Event or Opposite Day Strategy.
One really effective way to build a big meet fast is find another meet and sister with it. Lets say there is a decent event 150 miles away usually held on the 3rd Saturday of February. The following Sunday is open and would be a great day to host your event. Your far enough away that your not sharing “most” of the shoppers and those in between your events may just attend them both. Also, the regular swap vendors will see your event on the AMA schedule and even though it’s new, they are already packed up, they will come to yours also. Packing the goodies up and getting two shows in one road trip is an irresistible temptation. Snagging some good vendors really helps build credibility for your event. And, don’t think we’re just talking commercial venders. There are plenty of hobby swappers who just love trading and swapping that attend many events each year, you’ll snag some of these guys from the other event also. This strategy works well and really ends up helping lift up both events. Some new vendors might attend that never attended either event because travel and fuel costs of going to a single event was never worth it to them but as a pair of events it is a more cost effective trip. If your going to do this, be sure you verify the scheduled other event date with the CD. It’s also a great idea if you can catch somebody attending the other event to put a stack of fliers at the entrance of the Saturday event. Likewise, if there is a large Sunday some similar distance away, you can always stick yours on Saturday. Be sure to to contact the other club and do things out in the open. It benefits everyone. It’s always a nice gesture to stick the other clubs swap flier into your own club newsletter. Most newsletters are online today, it won’t cost you anything to be friendly. What goes around comes around.

Q: Saturday or Sunday, which is better? Most events are held on Saturday. Since few are in church that day, you have the largest pool of volunteers on Saturday. However, I’ve found over the years, there really is no difference in the size of an event on Saturday vs Sunday. You might get a few grumbles for planning on Sunday, just remind them they haven’t been to Sunday evening service in a long time. 😉

Q: We’ve been having a swap for years, but this year we have to pick a new date for reasons beyond our control. We are afraid nobody will come.
Let me put you at ease right now. Modelers are not lemmings. Nearly every event CD over estimates how “conditioned” the attending public is. Let me be clear, probably few if anybody remembers exactly what your regular date is. They are all going to look up the date every year to be “sure”. We’ve had to shift our event a weekend this way or that a couple times and our numbers at the gate were just fine. Don’t get stuck in a rut thinking you can never change your date. Do what you need to do for the health of the event.

Q: But we’ve always held it on X day?
Your still asking? I’m sorry, you just may be too hard headed to help.

Q: Ok, we’ve picked a date, now what?
Refer back to your calendar, call those event CD’s on and around your date. Double check they are actually planning to repeat on the dates you are expecting. Be as certain as possible before obligating the club treasury. There is almost nothing more important than a clear date.

OK, but there is a huge fun-fly a few hundered miles away. Is this really going to have an impact?
YES, pick another date! Even an event 300 miles distant will impact you. Where do the RC’rs in between go? If you miss 15 people at $5 a head and 5 tables at $12 each, your mistake cost you almost $130 and it means fewer people are there to spend money, fewer people will be there to offer items for sale. The impression you leave is less successful. Don’t be hard on yourself, pick another date. We are at this time considering moving our well established event for this very reason.

Closing Concepts:
The most important thing in your planning is how to maximize the event for your club and also for all those that attend. Think beyond the direct benefits your group is getting. What your doing is actually a benefit to many inside and outside your region. I always try to take a non-partisan, non-selfish approach to every decision. It’s not about any one thing other than the best possible health of “the event” and the greatest benefit to your modeling region. Taking actions with this attitude in mind will result in the greatest success over the long haul. Encourage whoever is heading up your event to think in this way.

Dave Thacker
CD Midwest Model RAMA

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Checking A123 RX Packs For Recharge Point

Radical RC A123 2300 2S RX Pack Example
Radical RC A123 2300 2S RX Pack Example

A123 RX Packs can be tricky to deturming how much is left in the pack by checking voltage alone. Variations in connectors and length of wire can have a big impact on actual volt readings when loaded. Using an RRC1000 digital voltmeter with load capability of 0.0A, .5A, 1A and 1.5A we get the following results measuring a 2300 2S RX pack with 6″ 20 g silicone JR pigtail and the included 22 guage battery checker pigail with the meter. Note: the meter (which ever you are using) is reading the voltage on it’s board, not at the pack. The voltage at the pack will actually be higher by the voltage drop across your checkers connector, pigtail, checker/pack connector and the pigtail on the pack. Here are the results we measured at varous loads. Room temperature was 74 degrees F, each load held aproximately 5 seconds before reading taken.

RRC1001 Voltmeter Image
RRC1001 Voltmeter Image
State Of Charge No Load Resting Voltage .5 Amp Load 1.0 Amp Load 1.5 Amp Load
40% 6.58v 6.37v 6.18v 6.09v
30% 6.52v 6.38v 6.17v 6.06v
20% 6.45v 6.32v 6.19v 6.08v
10% 6.38v 6.25v 6.14v 6.04v
0% 5.43v 5.19v 5.08v 4.98v

As can be seen from the data above, at some loads, the pack actually increased slightly in voltage as we went down even though the overall trend was lower in voltage. Note this test was not over a multitude of packs which would be more accurate and likely nuetralize the unexpected results mentioned.

Notice how little the pack is falling off in voltage and that the biggest consistant drop is in the resting voltage column, not a result I expected.

Notice the results at 0% capacity remaining as measured by my charger/discharger. As it is important to understand the context of the data and how I was checking the voltages, it is also important to understand the context of the data and how I was discharging the pack in 10% steps until empty (more explanined below) All discharges to make this chart after the initial 60% discharge were at 1.1A and in 230mah steps. The discharge harness was made from 22guage wire, 24″ long and plugged only into the JR output lead on the pack. Even though after 5 seconds of holding the load, I got the voltages above on the 0% line, putting the pack back on the discharger and trying to discahrge it some more resulted in the pack falling off to the 4V cut off (the empty point) in only about 10 to 15 seconds. Yet, I was still able to measure almost 1.5 higher than that when the pack had come off the first discharge to empty and been allowed to set for only 10 minutes before I measured anything. We can see that a wide range of voltages over 5 to 15 seconds with differing loads were all the same thing – EMPTY! Pay attention to the context of everything or you’ll get fooled! Because the context of how you are checking the voltage has such an impact on the reading, you should check your packs the same way every time with religious zeal.

A123 Systems cells ability to hold a strong voltage under load all the way until they are empty is one of the primary reasons they are so popular as RX packs, yet it is the very reason they are somewhat more challenging to voltmeter check from flight to flight.

To devise your own chart, cycle the pack to deturmine it’s actual value (ours was 2250), recharge, then set your chargers limiter to 60% of the actual value (ours was set to 1350) and discharge at capacity/2 (we used 1.1amp for our pack). After you’ve discharged it to this point, take the reading with the equipment and through the switches or whatever you have installed in your ship. Now you will know the readings at the 60% discharged (40% remaining) point. This is where you should be recharging any mission critical pack such as a TX or RX pack. To arrive at another row of data aproximately 10% further down in the pack, we simply set the limiter to 230mah and repeated the discharge. Repeat for each line of data you’d like to collect. You could start from full and discharge in 230mah steps generating data for 100%,90%,80% & etc….. Science, don’t you love it!

It would be my advice to think about making your own chart so you can learn something and become firmiliar with the voltage drop across all the gear in your model. You’ll be measuring the pack across a switch harness in most cases which will give you lower voltage readings than these.

General practice should be to taxi the model back to the pits, and before you’ve turned it off, plug your loaded volt meter in, turn off the model and take your reading immeadiately. Note your own chart for the correct cut off voltage and always recharge at the 40% remaining point. Flying below 40% is dipping into your reserves and should be avoided for any mission critical pack.

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Being a Good Test Pilot: Part 4, Trim Pre Flight – Flight Plan

Our series about becoming a solid test pilot continues…..

Make sure every surface is perfectly nuetral. No slight rudder, or aileron inputs. Check the elevator for “slight up”. I would define this as the elevator being set dead nuetral then putting in about 1/32″ up or about 3 clicks of up trim. It’s always easier to control a model that is climbing too much than to fight on that is diving for the earth.

If we’ve done our job correctly, the model should fly well without any big surprises. We need a flight plan. First, how do we deal with an out of trim condition? If the model is badly out of trim, the two most important things to you are altitude and hang time to make the adjustments. You gain altitude by powering up to 100 feet at a minimum before you start trimming. I like to deal with the elevator first, then the ailerons. I am thinking of giving myself the best possible time to deal with the model. If it’s trying to pitch into the earth, constantly, you want to deal with this first. Be ready for it to climb too much as we started the flight out of trim to the upside on purpose. If it’s only a few clicks off, put the clicks in. If it’s a bunch more than that, slow down a bit, this will give you more time to input the elevator trim. Likewise, if the model is rolling to the right or left, start clicking in trim until it’s neutral. If by chance it’s rolling aggressively, to one side and you fell under pressure to get the adjustment in quickly before the model rolls over on you, try slowing down a bit, putting the model in a slight climb and rolling to about 45 degrees opposite the direction it’s out of trim. By doing so, you give your self a little hang time to get the adjustment in. I’ve seen models crashed because the pilot was a bit over his head with the model badly out of adjustment and they just kept fighting it without ever thinking to slow the model down.

Once we get the model in trim, the first act of business is to climb higher, perhaps to 200 or 300 feet. Do a couple of transitions into a stall, in effect a simulated landing 2 or 3 mistakes high. We want to get a fell for what speed the model is going to stall at and if it has any nasty snap tendency to one side or the other. Do this high just in case. Once you feel comfortable you can land it, fly a few figure 8’s to get a feel for control balance and rates.

By now we should be at around the 2 minute point in the flight. Land it and inspect for excessive motor/esc/battery heat, fuel leaks, jittering servos, loose control horns and the works. A general inspection is in order prior to flying again. If all is well go for it again.

Special notes for electric models: I like to spend 3 to 5 flights working my way up to a full power full aggression full length flight. If something is going to overheat and be damaged. Slowly working up my flight duration and aggressiveness gives me a chance to pinpoint any heat problems in the power system before damaging a major component. Maybe something needs more airflow or perhaps a propeller adjustment is in order.

Pay attention to how many mah your charger is putting back in the pack after each flight. This way you can get a good idea of your maximum safe flight time without ever hitting BEC cut off.

Take a minute to explain any improvements or adjustments you think the model needs. Perhaps if you have too much aileron trim in, you can look at taking a warp out of the wing if it exists or put in some sub trim so you can neutralize your radio trims.

It’s always a good idea if the owner makes these changes to put it up and reset it to good trims for them.

For my own models, I don’t really consider them ready to sport fly until I’ve put on a number of flights and gotten the throws just right. It’s always a good idea to look at any model as a work in progress for a while. Any model can be made to fly and handle better. Your worth the effort.

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Being A Good Test Pilot: Part 3, On the Wheels

A continuing series on how to be a solid test flight, we continue……

Check the RX pack, that it’s state of charge is high. For an electric model. Verify with the owner that the pack is full. When was it last charged? Did you do any setup on the bench after the last charge? If everything is not fresh, freshen it up now.

Ok, we’ve been a second set of eyes and looked over the model, both mechanics and setup (throws etc..). Now it’s time to run the engine or the motor if it’s electric. For fuel engines, we are looking for a good transition from idle to wide open throttle. Also, a good prolonged idle with instant acceleration to wide open throttle is a sign of a well tuned engine. For an electric model, we are looking for the ESC to properly arm and for the motor to reliably start. Take the motor from off to full throttle several times with different rates of increase on the stick. Make sure it’s not going to have a timing issue and fail to increase from some point of the throttle.

It’s never a bad idea to hold a model and feel the wide open throttle power for just a few seconds. This can be a heads up if a model is under powered and will take a longer take-off distance and shallower climb angle or perhaps so overpowered that it wouldn’t be advisable to take off at full throttle. I have encountered many models at both ends of the spectrum.

Standing behind the model, ALWAYS one stick at a time, move the controls and make sure everything is moving in the right direction. Check it twice.

Do a taxi test to make sure the model tracks well with neutral rudder trim. If it needs more than a little adjustment, fix it before you fly. Avoid taxing so fast that you accidentally end up in the air. This test can be as simple as driving in a figure of 8 and a couple of straight lines to see if it rolls straight. When doing your figure 8’s, are you getting adequate right and left turns? How tight are they? My clubs paved strip is about 40′ wide. A good amount of steering for a tricycle gear ship on the ground will allow me to do a figure 8 just barely in the width of the runway (turns around a 10′ radius). If it’s much tighter than that, it’s going to become very sensitive as the ground speed increases. If it’s a tail dragger, it can as tight as 1.5 to 2 figure 8’s in a 40′ long area (turns around 5-7.5′ radius). Tail draggers usually lift the tail and the wheel becomes non-effectual around 10 or 15mph, so there is no wheel on the ground at higher speeds to be a problem.

Before we fly……………To be continued…

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