It has been roughly 30 years since electric power for RC began it's popular movement. In the last 5 years (mostly due to Lithium Polymer Cells becoming available and reliable, it has become the fastest growing segment of RC. There are some great advantages to electric power, some disadvantages, and most importantly: some major changes to the way we deal with these aircraft. SOME NEW SAFETY ISSUES ARE ALSO EXTREMELY IMPORTANT.

We have finally arrived at a technical place where electrically powered RC aircraft are as powerful and light weight as more conventional power systems. Many of our RC Power Player Flyers (Big contest winners) are now using electric power. Also I notice that many of the national champion pilots are now flying almost-ready-to-fly (ARF) models. This has lead to the possibility that almost anyone with the money can fly an identical airplane to the ones that win national contests. What a development this is!

In this information paper, we will examine some of the equipment and techniques that make this power source such a popular one.

We will start out with SAFETY DISCLAIMER: The following article is going to go into considerable detail about electric power flight. This is a great way to fly. However, the technology is new and evolving. It may seem to you that it is too complex or risky to use. However, like everything else in life, you normally get out of it what you put into it. If you buy good equipment and find out how to safely use it, you have a very high probability of success. Anything less is asking for problems and or property damage, bodily injuries or worse.

SAFETY: It is difficult to think of a battery pack being as dangerous as a tank of gasoline. However, you must remember either will provide about the same amount of power that is needed to fly your model. Either power source can be used under controlled (slow energy release) conditions to fly your model. Either may be also used up quite quickly by causing an explosion and releasing all of its stored energy at one time. Somehow you must discipline yourself to look at a battery pack and a tank of fuel as being equally dangerous if not cared for properly. LiPo batteries, if defective or not properly handled and charged can easily cause a fire or even an explosion. If the leads from the LiPo are accidentally shorted, they can melt in about one second. That means the big # 12 wire gets red hot and can and will burn anything combustible that they come into contact with. I've heard of a documented case of a modelers getting battery leads shorted across a ring on their finger and turning it red hot. Think about what that would do to your finger. If you quickly pull the ring off, much of the skin comes off with it and you burn the crap out of the hand you used to pull it off. If you don't pull it off, it continues to burn thru skin till it finally cools off. It would be a long, long time before you used the finger again and you could possibly end up needing it removed. This is not meant to scare the crap out of you, but cause you to have respect for your equipment and develop safe techniques and procedures for using and storing it.

LiPo's like any other type battery cell can be defective. If they short internally while they have any power remaining in them, they can burn, explode, or just quit working properly. Also they are a higher risk while charging. If any problem is present while charging, it is possible there will be cell swelling followed closely by a fire or explosion. LiPo battery packs should never be charged while unattended - Always be in the immediate area where you could identify smoke or flames and take appropriate action. A set of protective eye wear is a good idea while working with charged cells. I keep a fire extinguisher in my garage / shop. I also bought some 4 inch ceramic tiles from Lowe's and made some totally fire proof boxes to put my LiPo's in while charging and while in storage. Never store a LiPo in the airplane. Most of the newer chargers are the BALANCING type chargers. This does not mean that they cannot malfunction while charging. I repeat NEVER LEAVE LIPO CELLS UNATTENDED WHILE CHARGING.

Batteries: The 3 phase AC Motors with modern electronic speed controllers (ESC) would not be nearly so useful to modelers without a high current power supply to power them. Since flying a model airplane with a long extension cord is not practical, we need self contained power supplies light enough to be installed in the model.

A battery is made up of cells. The first known electric cell is now called the Baghdad Battery. It was developed in ancient biblical times. We know they had it but we are still trying to figure out what it was used for. Thomas Edison didn't come along to invent the electric light for many centuries. The first popular electric power source for model aircraft was the Nickel Cadmium Battery Pack (Nicad). The Nicad battery cells had been developed for the space program in the 1950s. It was just barely capable of being a limited electric airplane power source. In the 1980s the Nicad chemistry was modified a bit and called Nickel-metal-hydride (NiMh). These improved battery cell effectively and roughly doubled the Nicad efficiency. Electric modeling became more popular. Then around 2000, Lithium Polymer (LiPo) cells became available and affordable for model airplanes. These cells more than doubled the efficiency of the NiMh cells. Suddenly the popularity of electric power model airplanes took off (pun intended).

The LiPo batteries have been improved upon a lot in the last few years and now different chemical variations of them are coming onto the scene for models. The technology is evolving rapidly and it is difficult to keep up with the modified techniques and improvements. Also charging equipment and techniques are still evolving. Unfortunately this means that all the relatively high priced batteries, chargers, and ESCs that you purchase are apt to become proverbial dinosaurs in short order. It also means that good reliable technical information is hard to keep up with. I guess it's just natural to expect to pay the piper if you want to keep current with technology which seems to be moving at a rapid pace these days.

If LiPo battery packs are accidentally dropped on a hard surface, they should be recycled/discarded. They are relatively soft, and internal damage can occur. If they are damaged there may be no way to know it happened, or they may begin heating and possibly burning immediately. DISCARDING LIPO CELLS: When the time comes to discard used LiPo cells, don't just throw them in the trash. If they short out, they can easily set the trash on fire. The only safe way to discard them is to discharge them first. This is best accomplished by hooking a resistor across the output leads till the voltage is zero. You can get a 10 watt 100 Ohm or 500 Ohm resistor at Radio Shack. Just hook it across the leads. It may get warm while it discharges the cells. it is best to leave it attached for a few days. When the cell/battery is dead (you can be sure by checking for zero volts across the leads, you should turn it in for recycle. When you disconnect the resistor you can put the cells in the trash. It is much safer and environmentally friendly to take them to the RADIO SHACK store and turn them in as a recycle item.

When LiPo cells are damaged, or charged improperly, they normally begin to swell up. If a LiPo battery pack looks swollen, immediately discharge it with a resistor and recycle or discard it. The cells are not serviceable if they are swollen.

LiPo cells are relatively expensive; however, when the initial cost is averaged over the life of the cell, they normally are a less expensive way to fly than glow fuel. If the cells get damaged or otherwise show problems, it may be mentally difficult to recycle and discard them because of the high cost. However, you should think about this as the cost of a new battery pack verses the cost of a new house or shop that gets destroyed in a fire. Also, the cost of LiPos is rapidly coming down. In the last 5 years, the price of reliable LiPo cells has been effectively cut in half. However, many "CHEAP" off-shore manufacturers have also jumped onto the LiPo band wagon and are selling batteries of questionable quality.

LIPO DESIGNATIONS: LiPo cells may be used individually, or connected in series and or parallel, to increase the voltage and or current. The designations that have become popular is to define a battery in terms of it's mili-amp/hour output current capability - a mili-amp/hour is 1,000th of an amp/hour. An amp/hour is defined as 1 amp of current flowing for one hour. So a 3 amp/hour cell is called a 3,000 cell and a 3 amp current flow is referred to as 1C. This cell may have a 10C rating, meaning it can safely deliver 30 amps of current until effectively discharged. If a cell is connected in parallel (positive to positive and negative to negative) to another cell, the current capability is doubled, but the voltage is not affected. If cells are connected in series positive of one cell connected to negative of another, the voltage is doubled and the current output is not affected. SO, a 3S-1P LiPo battery is one with 3 cells connected in series and no parallel connections. A 3S-2P battery is one with 3 pairs (2 cells connected in parallel), connected in series. If you have no idea of what I am talking about, either do not try electric flight, or stay with the ARF/RTF matched flight systems. Experimenting with electric power flight can be very dangerous if you have no idea about how electrical systems work and their limitations - remember those red hot wires I spoke of.

CHARGING LIPO CELLS AND BATTERY PACKS

LiPo cells may be charged in series or individually. However, charging LiPo's is very much different than charging Nicad or NiMh Batteries. With the Nicad/NiMh's charging was done with a more or less constant current varying voltage method. These chargers could be extremely uncomplicated and very inexpensive if you were willing to wait 16 hours for a full charge, with little or no danger of problems if you forgot them and accidentally overcharged them. However, most modelers were willing to spend considerably more money and live with the risk that they would not accidentally overcharge those type batteries in order to achieve a full charge in 30 minutes.

LiPo cells and batteries require a charger designed especially for charging them. The cost will be higher and the methods and techniques are complex enough to require a computerized charger to detect when the cells are fully charged and cut-off automatically. Although LiPo cells may be charged in series, this is not a good idea. If one cell gets full prior to the other(s), that cell will over-charge while the other(s) get full. Over-charging will almost always result in a decrease in the effective life of a LiPo Cell. The greater the over-charge, the shorter the effective life. Over charge them enough and you can destroy them on the charger with a high probability of a fire. The LiPo cells that are in use today may be charged safely in an hour. Any charge rate greater than this causes the risk of serious problems and the shortening of cell life. You can expect to see some vendors advertising a safe 30 minute LiPo charger. I am very skeptical about charging at greater than the one hour rate.

Charging LiPo's is best done with a so-called BALANCING CHARGER. This type charger will have a separate multi wire connection (one wire greater than the number of cells in the pack) to the battery pack just for charging. If the battery pack has 3 cells, the charging connector will have 4 wires, etc. Connecting these type chargers to the battery involves using a separate (multi-wire plug). Charging is not done thru the output wires. These balancing chargers effectively charge each cell individually, all at the same time. When each cell gets a full charge, that cell charging is stopped while the other cells continue charging. When the voltage finally gets to the correct value for each cell, all charging is stopped. Charging is done to a constant voltage with limited max current for the charging process. All sorts of chargers are available. Some have capabilities to charge different number of cell packs up to some maximum number. Some chargers have displays that allow you to see the voltage and current going to each cell and some have no display at all. No matter which charger and which price range you choose, you are relying on the computer circuit to monitor the charging process and protect your expensive LiPo battery packs. As with any other electronic or mechanical equipment, LiPo chargers are guaranteed to fail sooner or later. Electric equipment is so reliable these days that failures are very rare. However, I had one charger fail in the first 10 hours I used it. If the failure mode causes the charger to shut down, then more than likely no damage will be done to the battery pack, however, if the failure causes runaway charging, then a fire is probably not far away. That is why it is imperative to never charge LiPo battery packs unattended. I normally spend a little more to get chargers that have the displays so I can monitor the voltage and current during the charge.

LiPo CHARGING LIMITS: No matter what kind of charger you use, It is imperative that a LiPo pack never be charged to more than 4.2 volts per cell. Doing so will quickly destroy the cell and normally leads to swelling and fires. The computerized charger's function is to accomplish this charging process. LiPo cells are rated at 3.7 volts per cell and that can be considered NOMINAL (average) voltage. The cells will provide about 4 volts per cell under load in use when they are fully charged and about 2.8 volts per cell under load when they are effectively discharged. So, unlike glow/gas power, you are going to loose a little power as you fly.

LiPo Discharging: Discharging a LiPo cell to lower than 2.8 volts per cell will shorten the battery life. How much you shorten the life depends on how low you discharge it to. If you discharge too low, will probably find it begins to swell the next time you charge it and if you continue the charge, a fire will be in your future. So, when you are flying your airplane, you must be sure you never fly too long and discharge the LiPos too far. I have a timer on my transmitter and I set it to remind me my batteries are getting low. Of course, if you fly at high power settings, the cells will discharge more quickly than flying at low power settings. Be sure you account for these things or you will be buying lots of relatively expensive batteries. Some ESC manufacturers install a limiter in the ESC. This limiter cuts power to the motor if any cells get too low while you are flying. It is sort of like running your glow engine model out of gas. However it only works for a given number of cells and if you change cell numbers, it will no longer offer any protection. There is at least one I know of that automatically determines the number of cells in the pack and sets itself up to avoid too low of a discharge. I am quite skeptical of this thing making the correct selection. If it selects too many cells, you won't get much flying time in. Pete had that happen recently. Shortly after takeoff, the ESC determined that the battery pack had low voltage and shut the motor off. Pete's airplane was not in a good place to land and he had a hard landing.

STORING LiPo BATTERIES: When you are not using your LiPo batteries, you are effectively storing them. Long term storage (more than one month) can cause loss of efficiency for your LiPo packs. The most common recommendation from many manufacturers is that the batteries be stored at about a 50 percent charge. I know of only one charger that has a setting to charge for storage. Most chargers require that you monitor the charge and remove the cells from charging at about 3.8 volts per cell for storage. The best method for storing LiPo cells is probably the most evolving technique about using the cells. I am sure there will be more information and recommendations in the future about this topic. Right now if you store them for more than 2 years, you should probably just discard/recycle them and get new ones. They do have a limited life.

NEW IMPROVED LiPo: (LiPo A-123 series) These cells were introduced a few years ago and the stated advantage is that they are said to have no danger of catching on fire if they are abused. My own personal feelings are that they are more resistant to catching fire, but not fool proof. A sufficiently talented fool can make strange things happen. Nothing is fool proof. A disadvantage is that they cannot supply as high a current as the LiPo Polymer cells can, so they are not used much for electric power. Many modelers are now using them to power airborne receivers/servos.

ELECTRIC MOTORS: When electric powered flight became popular, the motors that were available were the conventional DC electric motors that used copper wire windings on the rotor with heavy current brushes to do the power transfer and internal switching which made the rotor turn. Normally permanent magnets were attached inside the outer case. The disadvantages to these motors were several. They were relatively heavy and produced relatively lower power when compared to glow type engines. The brushes were relatively short lived because of the heavy current they carried and switched. Most of them had bronze/oil-lite bearings that wore fairly quickly. If the rotor shaft with the coil windings were rotated too fast, the windings could be slung off the rotor and be destroyed when they touched the outer case. However, because battery packs and current controllers were relatively low powered (when compared to modern components), they were all that was practical to use. When the state of the art began improving, motors, electronic speed controllers (ESCs) and battery packs all began to improve together.

Over 80 years ago, the advantages of 3 phase alternating current (AC) brushless motors were readily recognized. However there was no way to convert high direct current (DC) from batteries to AC, so these motors were not practical for portable use such as in RC Models. When such equipment became available, modelers quickly turned to 3 phase AC motors for power. The model AC motors have an unusual construction. The copper wire coil windings are mounted to one end of the outer case which is mounted to the firewall and does not rotate, so high current brushes are eliminated. The other end of the outer case has the permanent magnets installed; it is not attached to the non rotating part on the firewall. It rotates and is attached to the shaft for support. These motors weigh about half what the previous motors weighed. With the copper wire windings not rotating, the RPM could be extremely high, up to 50,000 RPM

One problem with this arrangement is that he torque developed by the motor was not too high due to the short moment arm of the permanent magnets from the center or rotation. Someone finally figured out how to solve this problem. The fix involved increasing the diameter of the motor so the torque produced would be higher due to an increased moment arm of the permanent magnets and the RPM lower to aid propeller efficiency.

Whoever discovered this fix is, in my opinion, a genius. Seldom do relatively simple changes solve many problems without introducing new problems, come along like this and at the same time lower the production cost. This new motor design needed a new label. OUTRUNNER was the name someone coined and it quickly became a new term used by modelers. Modern outrunner motors have only 3 moving parts: the rotating part of the outer case turns on 2 ball bearings. The rotor is effectively half the outer case. The shaft is fixed to the model and the propeller is attached to the end of the outer case which is rotating, or the non rotating half of the case is fixed to the model and the propeller is attached to the shaft . (OMG, we have reinvented the 100 year old rotary engine in an electric format.) This means that the motors will have a really long life limited only by the bearing life. When the bearings finally do wear out, they may easily and relatively inexpensively be replaced. With bearing changes, the electric motor life is almost indefinite, and this reduces motor cost. Currently high quality electric motors and high quality gas/glow prices are fairly comparable. Without taking any crash damage into account, the electric motors can easily outlive 2 or 3 comparable power gas/glow engines.

With these improvements, the modern 3 phase AC model motors are lighter and produce as much or more power than comparable glow engines at roughly the same price. And, the life expectancy of the electric motor is many times longer than the glow engines. The electric motor does not produce vibrations that cannot be eliminated from piston engines. Because of no piston torque pulses, the propellers can be lighter and more efficient.

A really big advantage to the 3 phase AC electric motor is how easily it can be made to run in either direction. There are 3 wires running from the ESC to the motor. Disconnect any two of them and reverse them and your motor will reverse directions. It sounds too easy to be true, but it really is that easy.

Since I have been buying and using electric power motors, I have noticed that some brands run much hotter than others. Any electrical power which produces heat is not being used to produce flying power. There are many motor and ESC manufacturers out there wanting your business. I had no idea which to go with when I started. Many years ago I went with Astro Flight and they are a very reputable company and in the USA. However they were slow to go to the AC Motors. So, I moved to AXI motors and JETI ESCs. The reason I went with this brand is that HOBBY LOBBY sold them. Hobby Lobby got seriously into electric power many years ago and are one of the most successful and reputable dealers. I figured they would only handle first class equipment. I believe I was right and have stayed with them. In the cases where I have purchased packaged planes with different motors/ESCs I have had many more problems and I also found that some motors run very warm. Kinda like ole Billy Pearce used to say, "you make your choice, you pay your money, and you take your chances."

SAFETY ISSUE: Any time an electric motor is connected to an electronic speed controller (ESC) which is connected to a battery, it may start itself at full power. If your body parts are in the path of the prop blades, you can be seriously injured. Most of us are very casual around engines with propellers attached because we instinctively know that the engine must be started for it to run. Not so for electric motors which are self starting. Also….If you are running a glow/gas engine and your hand gets into the prop arc, it will slow the engine down and if your hand stays in the prop arc it will eventually stop. If you get your hand into the prop arch of an electric motor, it will slow down and then increase its power trying to catch back up to full RPM. It will not slow down and stop. Effectively you have a tiger by the tail and you can't let go. With the power now available from high-power electric motors, this can get very ugly very quickly. Electric Modelers BEWARE.

SIZE MATTERS: We have yet to come up with a good way to label our electric motors as to how much power they produce and how it may effectively be used. Some manufacturers just tell you how many WATTS (DC Volts times Amps) the motor can effectively use over a period of several minutes without overheating to destruction. WATTS is a scientific way to define power; however, it is far from an effective description of how large a model you want to install it on or what propeller size to use. Astro Flight tried to compare their motors to a "more or less" average 2 stroke glow engine, i.e. 60 size. Some manufacturers use the terms 400, 500, or 600 type designations. Perhaps someone will one day come up with a good way to designate electric motor capabilities, but I am not holding my breath. Most of the better manufacturers have done some testing and offer charts that show different power outputs under varying current flows with several propellers. They may tell you at a given volt / amp input, what the output will be with given propellers. Some tell you how many unloaded RPM you can expect per volt input. Some offer advice on the weight of a model to install it on and what propeller to use. Again, Electric Modelers BEWARE: don't buy it if you don't have a good idea how to effectively use it. Or, you can stick with the matched (airplane, motor, ESC) set of equipment.

SELF DESTRUCTION: If you install too large a propeller on a glow engine, the engine RPM will sag and the engine will overheat effectively letting you know you have over-propped the engine. If you install too large a propeller (within reason) on an electric motor, it may turn it up just fine. However, what you don't know is that the current being drawn from the battery pack is way too high. You can easily destroy a battery pack, an electric motor, and or the ESC just by installing too large a prop. And, you most likely never know what caused it to burn out. If you are going to be buying and matching equipment yourself, a high quality amp meter is a must. Only with this device, can you tell what size propeller to use. It must be a high quality amp meter which does not rob much of the voltage and dissipate it as heat. Ordinary multi meters with amp scales won't work well for this application.

Many manufacturers are now selling ready-to-fly (RTF) or almost ready to fly (ARF) models that have matched motor, battery pack, ESCs, propellers, and probably chargers. This keeps the modeler from needing to find a way to match these key items. Buying models this way is an easy and relatively low cost way to get into electric power. However, if you stay in electric power, you will eventually want to swap some of this equipment around or replace some of it trying to change the performance of the model. Experimenting without knowing what is happening electrically will cause many modelers to want to proverbially beat their head against a wall because of destroyed equipment that seems unexplainable.

ELECTRONIC SPEED CONTROLLERS -- ESCs: The 3 phase AC electric motors would be useless without a means of converting DC current to AC current with an economical, light weight current controller. Thanks to new solid state electronic devices that were being introduced for industrial use, this equipment quickly trickled down to modelers. Industrial users demands were so high that costs quickly fell and this also trickled down to the modelers. I am not going into any lengthy explanation about how DC battery power is converted into 3 phase AC power, however, it is important for the electric power modeler to know there are limitations on all ESCs. Again you must have an accurate way to measure the amps that flow thru these devices or you can easily smoke them (destroy them.) The old electric joke is that these high-tech devices work because we trap smoke inside them. If the smoke ever escapes from them so we can see it, they are history.

WIRES AND CONNECTORS: Early-on in the movement to electric power, most modelers used the battery packs, wires, and connectors that were supplied with the popular electric model cars. However, as electric power flying got more popular, many modelers with electrical experience knew that larger wire and high current connectors would be needed. Gradually these modelers found the # 12 wire made up of over a hundred strands of tiny wires that was extremely flexible and would carry 40 amps in the relatively short lengths needed for airplane installations. What is needed for RC wiring and connectors is a heavy wire and connectors that will easily pass high current without causing voltage drops. If you are flying the low power "PARK FLIERS", you can get away with small wire and small connectors. If you are flying between 10 and 20 amps, then you need # 16 or better # 14 wire, between 20 and 40 amps, then # 12 wire should be used, above 40 amps, you need # 10 wire. If the wire is very flexible, so much the better for easy installation.

Here is what happens: As current goes up, any wires/connectors not able to handle it cause some electrical resistance. When high current is passed thru inadequate wiring/connectors a voltage develops across the wiring system and this voltage is used up heating the wires and not powering your motor. The idea is to use wiring/connectors heavy enough to cause very low resistance (you cannot eliminate all resistance).

Someone soon discovered ANDERSON POWER POLE connectors. These connectors were a type where each part of the connector was identical (there were no proverbial male/female parts.) The connectors were very versatile and positive and negative connectors could be connected so that they were effectively polarized and could not be connected in reverse. These connectors could be soldered or crimped. Here was a potential problem. Soldering any connector to heavy # 12 wire is not easily accomplished. Heat travels down heavy copper wire almost as well as electric current does. It is very difficult to get the wire hot enough on the end to where solder will flow easily. If the wire had plastic insulation, you often melted the insulation for a couple of inched away from the solder joint. If you use the more expensive silicon coated wire, the insulation does not melt. If solder connections are not hot enough, you end up with what is called a COLD solder joint and it will not conduct high current very well at all. POWER POLE connectors may also be crimped with a crimping tool that originally cost about a hundred bucks, but now is available for about 50 bucks. If you decide to solder, you will need a hefty solder iron or solder gun (200 watts or higher and it will still be difficult.

The ends of POWER POLE connectors are plated with heavy silver plating. Silver is an extremely good conductor of high currents and is internationally used as a standard to which all other conductors are compared for a measuring system. One problem with silver is that it very easily oxidizes (you know this as tarnish). However, the black colored silver tarnish carries current as well as silver, so this is not a big problem. Copper is probably the next best current conductor and is almost as good as silver. Copper also has an oxidizing problem and turns green with exposure to humidity and air. (The STATUE OF LIBERTY is covered with copper and looks very green.) The copper tarnish does not carry current and must be avoided with proper care and storage of the wiring.

A man named SERMOS somehow decided that the POWER POLE connectors were going to become very popular, he contacted the manufacturer and managed to get the entire USA as his business territory. Power Pole connectors soon became known as SERMOS connectors, because Sermos was the only person who could supply them. He did business personally and thru a large network of dealers. But, a few years later, China soon had counterfeit connectors available that cost about half as much as Power Pole. They looked exactly like and would mate with SERMOS, but they did not have nearly the heavy amount of silver that SERMOS had and did not conduct high current quite as well.

When electric power began getting more popular, ASTRO FLIGHT saw the opportunity to sell connectors that they thought were better and easier to use than SERMOS. Soon the Astro Flight ZERO LOSS CONNECTORS were introduced with a hefty selling price. Astro Flight connectors were plated with gold which is almost as good as copper for carrying high current and has the advantage of not tarnishing/oxidizing. However Astro Flight Connectors must be soldered. They have male/female parts and are installed in a plastic connector package that is polarized to prevent reverse connections.

Another few years went by and the manufacturer of the DEANS small connectors decided to jump into the high current connector market and began marketing the DEANS connectors. These also had gold plating and also required soldering and also come in a male/female arrangement in a plastic polarized connector to prevent reverse connections. When the off-shore manufacturers began making most of our electric motors and ESCs, they liked BULLET CONNECTORS. Bullet connectors got their name because the male part looks round on the front like a bullet. The male part mates with a female part. Most of these are gold plated and must also be soldered. They can easily be connected incorrectly, but that simply means that the motor will run in reverse if you make this mistake between the ESC and Motor. If they are used on the DC side of the system, a reversed connection can cause those red-hot wires in one second.

Hazarding a guess, I suspect bullet connectors and Deans connectors are the most popular these days. Bullet connectors are very popular for connecting ESCs to motors because a 3 wire connection is needed and reverse polarity connections on the AC side of the system is not dangerous. Power Pole connectors can easily be used as a 3 wire connection device, but Deans and Astro Flight cannot. However the others are still popular so what is the battery supplier to do. Some supply cells with bullet connectors, some use Deans. The only company supplying Zero Loss Connectors that I know of is Astro Flight. Power Pole connectors are still in use and the ones I use because I began using them when they were the only game in town for high current. Also with the soldering problems using the large wiring, I purchased one of those crimping tools and really love not having the soldering problems.

Remember ole Billy Pearce's words -- you make your choice, you pay your money, and you take your chances.

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