Forming a recent NiMH purchase on the Hitec X4 and other computerized chargers.

Ed writes me about properly forming a recent NiMH purchase.

Hi Dave,

I recently bought one of the FDK Twicell 6.0V 5-cell 2000mah NiMH AA Flat Pack and would like to try it in one of my airplanes . I read all your comments about this battery pack and I have the HiTec Multi-Charger X-4 and not sure what is the best way to charge it. The charger is fairly new in my collection and I am still learning the best way to use it any thoughts?

Thanks,

Ed

Ed,

The best way to do it on most computerized chargers is:

General procedure,

1. Go into setup, make sure the mah limiter and time limiter are both off.

2. Put charger in PB mode, yes for Lead acid.

3. Set charge rate to 100mah, any more will ruin the battery eventually.

4. Set voltage of battery to 8V

5. Start charger.

If it refuses to start, set voltage to 6V and let it run a minute or two, the go back and restart with setting at 8V

“Generally” Eneloop’s (Twicell’s) come to you about 1/2 charged. So, the hole your filling is about 1000mah. (Hole * 1.4) / charge rate in mah = time in hours. 14 hours in this case.

What we are doing with the procedure above is tricking the charger into functioning like a dumb wall wart where it will just plod along indefinitely until we disconnect the battery.

The best practice would be to connect the cells to a dumb charger that charges at 50mah for about 30 to 40 hours and is the ONLY method for which I would ever consider warranting a pack. People try to break in new batteries in peak detection modes all the time which is the cause of my slightly “acidic” warnings against such acts on my website. One issue is there are no makers of chargers like that that I know of in the hobby world today. The last one (Sirius) seems to have become inactive. The best chargers to own for this forming purpose at this time are an ACE DDVC, ACE Digipulse or Sirius Pro-Former. Should you run across one at a swap meet or on Ebay, snap it up.

Dave

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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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Is Daily Low Self Discharge Rate and Important Factor in RC?

A customer asking about an unusual cell size of ours asks: “Are they are low self discharge?”

They are not Eneloops which would be the only NiMH I would classify as Low self discharge. This is almost a silly thing to consider because we come off the charger and go to the field in this hobby. We do not charge a battery, then start a 1 week hike at the end of which we fly the model. That specification makes sense for a flashlight or an emergency radio, not an RC aircraft. Others may have a different view. I don’t fly unless I’m coming off a fresh charge at the beginning of the day. Other systems are to the choice of the users but reckless in my view. Yet I offer the Eneloops for those seeking this value. There are no Eneloops this small. Also, I don’t like the Eneloop under fast charge “ever” conditions.

For RC, lets go over how silly this is;

Standard self discharge x 2 would be only 2% per day.

After charging, if we let a 500mah pack set for 2 days before flying, it would lose (500x.01) 10mah the first day, (490 x .01) 9.8mah the second day. Value at end of 2 days 500-10-9.8=480.2mah. 19.8ma lost over 48 hours or about .416mah per hour dissipated.

If we come off the charger and go to the field, a trip that takes 2 hours, the same rate of loss would mean our pack would be about 499mah since we loose about .416mah per hour.

So, perhaps, a low discharge pack is good for about a .2% advantage when you get to the field. And, to come up with that .2% I had to exaggerate the loss by double and suggest a very long trip to the flying field.

This is why this specification is essentially moot when it comes to normal day in and day out use of receiver packs in RC aircraft. Is it better? We’ll yes in some microscopic way, but to get it, what are you going to have to do? Accept an Eneloop you can never fast charge? Use a non-Sanyo cell? I see a lot of effort hunting something that has no real measurable benefit in our application.

It’s more arguable in a TX battery because we often use that battery over a number of weeks between charges.

Dave

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Understanding Wire Size

This page intended for reference purposes and will be updated from time to time.

When trying to understand wire sizes, it’s important to understand the measurement system. Not all the world uses AWG (American Wire Gauge). Most wire available for our hobby today comes in metric, some sizes are close to familiar gauge sizes, some in-between. Most high quality wire today is not sold at an exact AWG size although some is. This leads to some confusion when trying for example to purchase wire that is “about 16 gauge” (or whatever your looking for). Because in America most people are looking for a certain gauge size, we try to list on RadicalRC.com with the nearest approximation of the AWG gauge size. Many vendors claim wire offered is larger than it is in order to exaggerate the perceived value.

To figure the cross sectional area of a stranded wire, measure the diameter of an individual strand. The radius is 1/2 the diameter. If the strands are 0.08mm (typical with the high end wire we offer) then the radius is .04mm. To figure the circular area, we figure that area for a single strand. In the case of the above example, the area* is .00502654832mm^2. Multiply that by the number of strands to get the total area in square mili-meters (mm^2). For example, our Silicone Sub-C wire has 399 of these strands. Multiplying the overly long number above x 399 strands = 2.0055927796 or rounded to 4 digits after the decimal point (proper procedure) we find the area of the 60 strand wire is 2.0056mm^2. When we look down the chart in the Square mm column we see most approximates 14 gauge.

Armed with information and a metric caliper, you figure out if your being “out figured” (hustled) or not.

The following chart is general in nature. I suspect the resistance is calculated based on single strand wire. This may be different for high strand count wire and not the subject of this article.

AWG Diameter(mm) Diameter(in) Square(mm^2) Resistance
(ohm/1000m)
40 0.08 . 0.0050 3420
39 0.09 . 0.0064 2700
38 0.10 0.0040 0.0078 2190
37 0.11 0.0045 0.0095 1810
36 0.13 0.005 0.013 1300
35 0.14 0.0056 0.015 1120
34 0.16 0.0063 0.020 844
33 0.18 0.0071 0.026 676
32 0.20 0.008 0.031 547
30 0.25 0.01 0.049 351
28 0.33 0.013 0.08 232.0
27 0.36 0.014 0.096 178
26 0.41 0.016 0.13 137
25 0.45 0.018 0.16 108
24 0.51 0.02 0.20 87.5
22 0.64 0.025 0.33 51.7
20 0.81 0.032 0.50 34.1
18 1.02 0.04 0.82 21.9
16 1.29 0.051 1.3 13.0
14 1.63 0.064 2.0 8.54
13 1.80 0.072 2.6 6.76
12 2.05 0.081 3.3 5.4
10 2.59 0.10 5.26 3.4
8 3.25 0.13 8.30 2.2
6 4.115 0.17 13.30 1.5
4 5.189 0.20 21.15 0.8
2 6.543 0.26 33.62 0.5
1 7.348 0.29 42.41 0.4
0 8.252 0.33 53.49 0.31
00 (2/0) 9.266 0.37 67.43 0.25
000 (3/0) 10.40 0.41 85.01 0.2
0000 (4/0) 11.684 0.46 107.22 0.16

*Area of a circle = 3.1416 X (Radius X Radius)

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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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High Cell Count Packs

Sonny P. Writes:

What is the proper way to charge a 14 cell A123 battery?

Sonny,
I take from your question that your concerned about the large cell count and not the rules of charging this particular chemistry of pack.

Since you need to balance it from time to time, it should be charged as multiple lower cell count packs from time to time. All rules must be observed regardless of cell count or type of lithium chemistry. So, were I building a 14 cell aircraft pack for myself, I’d build it probably as two 5 cell and one 4 cell packs. In this way I could hook up to my balance charger and balance it. If you have a charger capable of balancing 8 cells, you could do two sevens. I am un-aware of any chargers capable of balancing more than 8 cells even though there probably are chargers that could manage a non-balance charge of 14 cells. Even if you owned one, you’d still want to be able to break the pack down (electronically) and charge it in shorter segments from time to time to maintain balance.

In the case of two 5 cell and one 4 cell packs for example, The pack could be literally 3 packs that are put in series in the model. You might use Anderson Power poles to do this to minimize the number of connectors needed. Each pack would of course have it’s own balance harness for plugging into the node port (balance port) of you charger.

It would also be possible to build the pack as one 14 cell block with one set of output wires for the ESC. However, you could put tap wires in that are heavy enough for charging at the union between the 5th/6th cells and 10th/11th cells. You would build in balance harness respecting this same cell spacing. So that “electronically” (if not physically) you have 3 battery packs, two 5’s and one 4. NOTE! This type of pack bould, the central tap wires would be positive or negative depending on which segment you were charging.

With a 14 cell charger you might be charging through the main output leads while your at the flying field. Yet, when your prepping the model for a trip to the field, you would be able to charge the pack in 3 steps (one step for each pack division 5 cell, 5 cell, 4 cell) with balance harnesses connected to your charger. In this way you’d be getting regular balance charges to keep all cells equalized.

Happy Flying!
Dave

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Ryno Motors

At first I thought this was a fake viral video, however, it’s all true. Imagine a device that can go anywhere you walk, on the sidewalk, on the street, in an elevator or to the mall. Yet on only one wheel. It’s the on set of accelerometers and similar devices that are used in toy’s, phones and yes, in our hobby with FPV autopilots, multi rotor stabilizer boards and the like that make these kinds of device dreams a possibility. Could you build and program a project like this? You may not think you can, however, the stuff of this dream is all out there, all parts of the RC hobby you already are exposed to.

Explained in a diagram but not in words or text, if your quick, you see he’s telling you when it senses it’s leaning backward, it apply’s the brake or in the case of it standing still it reverses the motors. When it senses your leaning forward too much, it adds forward power to the motors to bring the wheel back under you. This is essentially how a Segway works. The mono-wheel seems so much more courageous however.

Visit Ryno Motors homepage.

Other attempts at the Monowheel:

And another take on this old problem:

History Channel Monowheel episode:

A Monowheel man powered cycle that really seems to work:

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Tin Whiskers

I’m not a big fan of the gradual banning of lead. Sure, I love kids and all that. However, the enviromentalists take everything too far with what they clothe in “for the greater good” arguments. It’s really an anti-capitalist movement. And, I’ve been trying for a long time to figure out what is pro-job about being anti-capitalist.

I can understand how lead in paint which breaks down slowly over time, becomes chips which get smaller and eventually turn into dust. It makes sense not to put lead in paint because we’ll eventually breathe it. However, no matter how hard I try to kick the dirt around on the floor, electronic circuits soldered with leaded solder or lead free solder don’t jump into my mouth. Maybe the difference is hard for some to see? What is it like to wield the power to ban an element on the perodic table?

So, on to tin whiskers…..

RoHS is an EU (European Union) directive that has become enforced law. RoHS means “Restriction of Hazardous Substances”. The problem is little consideration given to what is a Hazardous use of a substance and what is not. I don’t hear reports of children eating circuit boards or solder joints in wires for example. Is it about health and public safety, or about creating a portal by which government and regulatory bodies can exert command and control over huge industries and the influx of goods into a country?

Since the EU has issued RoHS directives, lead has been removed from most solders and from the tinning on electronic leads. Pure tin is now used for almost all electronic component lead tinning. Over time it forms whiskers of tin which are thinner than a human hair. They are only one crystal in thickness and they reach out and touch leads of other components. It’s often the reason why today’s TV’s and other electronics (including our RC gear) doesn’t last as long as yesterday’s. Failure of expensive satellites have been attributed to lead-free tinning of leads causing tin whiskers. It’s our punishment for letting the “zero tolerance crowd get traction and get this nonsense pushed into law all over the world. When you get a chance, in any way possible, do your part, do something about it.

Here are some great links, good reading and photos of our gift from the enviromentalists, “tin whiskers”.

I’m still looking for examples of children that were poisoned from eating circuit boards and wires.

Find lots of tech article links at: NASA Tin Whisker Homepage

An excellent blog post by Steve Smith: Tin Whiskers

1.4 Million Results on Google

As long as possible, you’ll always be able to get “real” solder from Radical RC: Solder Pastes & Supplies

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