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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Swap And Fly August 11, 2012 – Wingmaster Field

Wingmaster Field
Wingmaster Field
Every year in August the Dayton Wingmasters host a Swap and Fly. This year is the 4th annual Swap and Fly, it’s scheduled for Saturday August 11th. Last year we had a full house with a lot of merchandise being bought and sold. Every year it seems to grow and grow. This is an outdoor tailgate swap, bring your own tent/tables if you wish, give a good deal and get one. In addition we welcome you to fly with us at one of the area’s nicest fields. Cost to enter is free. $10 for selling space, first come, first serve. Food is available on site. We hope to see you there!

Swap And Fly
Swap And Fly

Gate Opens At 8:30 For Sellers / Set-Up Swap Meet Starts At 10:00 – Flying Starts At 12:00 – Flyer Below

2012 Wingmasters Swap And Fly Flyer

Wingmasters info and maps on Radical RC Workbench Blog

Wingmasters Club Website

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Remember Back In The Day & Fructose

Pepsi Deposit Bottles
(Warning, the following post weirdly isn’t sure if it’s about green politics, recycling or man made sugars.)

Back in the day, before the anti-capitolists hijacked the movement (they call it green now), we actually did recycling. Almost everybody participated. Do you remember? One of my first jobs (1978?) was sorting a nearly continuious flow of bottles at the Little Farm Market in West Carrolton Ohio.

Photo’s of historic Woodies Market and Little Farm Market:
Rusty Cans Feb 2011
UrbanOhio.com

I remember, you could recycle metal, newspapers, oil, about anything. We paid our dues to the local boyscout club by collecting paper for recycling. Maybe it was 200lbs every 3 months or something similar. Been going on a long time hasn’t it?

1978 was before HFCS (High Fructose Corn Syrup). That product started to be pumped into america’s diet in the middle 80’s. According to Wiki’s High Fructose Corn Syrup page “Soft drink makers such as Coca-cola and Pepsi use sugar in other nations, but switched to HFCS in the U.S. and Canada in 1984.” I don’t remember so many people having diabetes back in the day before High Fructose Corn Syrup.

According to many, including DiabetesHealth.com – “However, fructose does not stimulate insulin secretion or require insulin to be transported into cells, as do other carbohydrates.”

According to the Wiki page, Type II Diabetes “is a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency.”

I try to keep beverages and other products that use HFCS out of my diet. There are many claims that Diabetes has risen in lock step with the increased use and consumption of High Fructose Corn Syrup. I like being able to enjoy real sweets and real sugars too much to risk becoming a diabetic over soda pop. I’ll have water please.

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1905 Wright Flyer Kit Wins Award

Flightline Photo borrowed from Ampeer Newsletter
Thanks to Ken Meyers and Keith Shaw (now both AMA Hall of Fame members) for all the work and effort continuing the country’s oldest ongoing electric fly in. The Mid-America Electric Flies. This years event was held July 7 & 8 2012 and is usually scheduled the weekend after July 4th holiday. This event is a gathering of friends and is attended by many builders. The group is full of electric flyers that were working hard at making electric work since long before it was cool or easy. It’s always a great time.

Sunday included an award for the Radical RC 1905 Wright Flyer kit “1st Place CD’s Choice” award. All of us at Radical RC appreciate the award and recognition. It’s such a fun airplane to fly. Several people at the event flew the model including Keith Shaw who is now the proud owner of a kit. He reports to me this is only the 8th kit he’s purchased in his lifetime. Keith normally makes his own plans or occasionally builds from plans scratch building nearly all of his models. We consider it a high compliment that our 1905 Wright Flyer kit will cross the same workbench as a lifetime of award winning and hobby expanding projects Keith Shaw has completed.

The EFO group’s newsleter, the longest running journal for electrick flight. In this issue, coverage of the 28th edition of the Mid-America Electric Flies event. The Ampeer August 2012

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Spam Email Turns Out True

I get so many “forward this to everybody” emails. When you investigate the outragous claims, almost without exception they are false. A great site for this is Snopes.com. I’m reprinting this here, I enjoyed the follow on history lesson and there are some good links on investigating internt rumors that I use and you may enjoy.

Photo and statement follow:

Theodore Roosevelt 1907 Speech
Theodore Roosevelt 1907 Speech

‘In the first place, we should insist that if the immigrant who comes here in good faith becomes an American and assimilates himself to us, he shall be treated on an exact equality with everyone else, for it is an outrage to discriminate against any such man because of creed, or birthplace, or origin. But this is predicated upon the person’s becoming in every facet an American, and nothing but an American…There can be no divided

allegiance here. Any man who says he is an American, but something else also, isn’t an American at all. We have room for but one flag, the American flag… We have room for but one language here, and that is the English language.. And we have room for but one sole loyalty and that is a loyalty to the American people.’
Theodore Roosevelt 1907

When I Google’d “Snopes 1907 Roosevelt Photo”, the link came up snopes.com: Theodore Roosevelt on Immigration.

There you will find a nice little history lesson on Theodore Roosevelt and his views on Immagration. Many speech’s he made talking about these important issues. I thought the debate on immigration, hyphenated Americans and what language we speak was only something that has happened during my lifetime. Turns out forces have been pushing these issues for at least the last 100 years.

A couple of other sites that deal with email claims of this nature also attribute the words to Teddy actually came from a 1919 letter yet agree the email is true. Even thought the originator may attribute this to the wrong date, it seems clear these views were emblimatic of Theodore Roosevelt during his time in and after the Whitehouse. Snoopes site above is the best read on the subject.

Other useful sites for investigating internet rumors (Roosevelt links within the sites)
TruthOrFiction.com
UrbanLegends.com

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Chance To Fly At Huffman Prairie Aero Carnival


Please Tweet, Post or do whatever you can to help me the the news out to pilots that might want to fly their early aviation models at the Wright Aero Carnival at Huffman Prarie.

I am working with the National Parks to bring demonstration flying of early aircraft to the Wright Aero Carnival at Huffman Prairie. The Carnival is a celabration of the Wright Brothers and early aviation. Models may be brought for demonstration flying of any aircraft through 1916. All models are welcome, not only Wright machines. You may bring any aircraft, Curtiss, Langley, Bleriot, many WWI aircraft qualify, even controversal or failed aircraft are welcome. Essentially anything the Wrights might have read news accounts of, hear rumors of, anything that might have been part of the what was going on in the development of flight up to 1916. All of these aircraft help to tell the story of early aviation and that is the point of participating in the event. Flying will be from 10am to Noon and 1pm to 3pm on Saturday August 18, 2012. The public will be in attendance. It’s is a very special and rare opportunity to get a photo of you and your aircraft flying at the worlds first airport, Huffman Prairie.

Aero Carnival Flyer 2012
Aero Carnival Flyer 2012

Aircraft need not be museum scale. Stand off scale, is welcome also. Models of any size are welcome. We will be flying over the same grass as the Wrights flew over. A paved road ajoining the field is available for a runway. I plan to be there with my 1905 kit which is stand off scale. Won’t you bring your model an help fill in the story of early flight?

Flying is not allowed at Huffman Prairie at any other time.

Please contact me if you can come. davthacker77@aol.com (remove the 77, it’s there to foil spam email spiders) There is a limit of 10 pilot slots for this event.

This rare opportunity to fly at Huffman Prairie is also a great way to set a positive example for modeling with the US Airforce and the National Parks Service. Decision makers within the National Parks Service across the country will be reading accounts of this event. What you do here in Dayton on August 18 could have a big impact on modelers elsewhere in the country.


View Larger MapMap showing overall area including I-75, I-70 & I-675 highways.


View Larger Map
On the day of the event, you’ll enter at the Golf Course and follow the signs in. (zoom the map 1 level + to see the road names) On the map above, the west end of Pylon Road will be closed. You’ll drive around the field by following Hebble Creek to right on Marl to right on Symmes to right on Pylon. Our pit area will be between the replica launch derrick and Pylon road at the turn circle.

1905 Wright Shed & Derrick Photo
1905 Wright Shed & Derrick Photo

The view from the flying area of our pit area.

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Wire Caculator AWG to Curcular Mils

A calculator published by the Mogami company. It is helpful to understand wire size a little better. For example, a solid core 22 gauge wire has a different overall diameter if it’s 16 strand or 32 strand or 198 strand. Don’t get fooled into thinking AWG is the diameter of your wire regardless of strand count. Actually as the strand count of multi strand wire gets higher and higher, the overall diameter of the cable gets smaller. Think of it this way, the smaller the wire, the smaller the air pockets or gaps in the bundles of copper become. In other words the wire bundle becomes more and more dense. I run into people from time to time that think it’s as simple as measuring OD of the bundle, some get quite insistent defending their theory. We’ll perhaps they are just wishful souls dreaming about how great the world would be if it was as simple as they wish it was? Below is a handy site to help you figure out what size your wire (or any wire we sell) really is. It’s not super simple but you can work it out and learn something.

Wire Gauge Calculations

If you run across any interesting calculators please forward them to me.

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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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