A few years back, Oval racing made a decision to go to 4 cells rather than 6 in an effort to slow the cars down, especially in Open Modified. Speeds were getting to a point that some racers were getting out of control and Open Modified was only raced by the exceptional racers. There were good points to the change; fewer cells meant less expensive batteries. And for the price of what we were use to paying for two 6 cell packs, we could get three 4 cell packs. Speeds slowed down and made it easier for the average person to compete. But did it turn out to be a good move in the long run?

It certainly didn’t keep people in the hobby any longer as it was intended to and in fact, it may have caused a few that raced different forms of RC to move away from Oval because of it’s now specialized batteries. They could no longer have a few packs of good 6 cells and use them in all venues of racing. They needed 6 cell packs for Off Road, Dirt Oval or TC plus they needed additional 4 cell packs strictly for Oval. Looking back on it, this could have caused a major loss in Oval racers. But, at the time Oval was beginning to dwindle and something had to be tried to keep it alive.

There has been another eroding situation that has been around for as long as I have been in the hobby and there is nothing that can be done about it. That would be the continued increase in battery performance. Products progress with technology, there’s nothing that can or should stop that. However, the byproduct of this development in relation to our hobby has caused a constant need for the racer to change batteries because of their ever increasing run time and voltage. There is no “clamp” or “moratorium” that we can place on these changes because those that are developing new battery technology for electric automobiles and power tools care very little about how often we have to buy new batteries. And for as long as we race battery powered cars (especially with the demand on the battery industry to create a better product) we will just have to suck it up and deal with it. When they stop making the “old issue” we have to buy the new one.

In the years that I have been involved in racing, I have seen the battery change to higher values at least seven times starting with the yellow 1200’s and this is not counting the times when there were better “date codes” or an “unadvertised” increase in voltage in the same series of cells or new battery companies coming and going.

Could LiPo’s stop this?

All this excitement about the new LiPo technology will not change that. Battery research and development will continue. In fact in my research of this article I read that one battery company has received a 102 million dollar investment to go towards the study, research and development of the practical use of battery driven automobiles. In time these studies and advancements will trickle down to power tools and remote control use and eventually will cause another revolutionary new batter.

Maybe one day the Vulcan’s will share their technology with us and we will put one of their Dielidium power crystals in our cars that will last a life time. (Mr. Spock, where are you when we need you!) But until then, we are stuck with our meager earthly developments and will simply have to deal with it as it changes.

What the Industry is working on …

In February 2005, Altair NanoTechnology,^[16] a small firm based in Reno, Nevada, announced a nano-sized titanate electrode material for lithium-ion batteries. Its prototype battery has three times the power of existing batteries and can be fully charged in six minutes. The company also says the battery can handle approximately 20,000 recharging cycles, so durability and battery life are much longer, estimated to be around 20 years or four times longer than regular lithium-ion batteries. The batteries can operate from -50ºC to over 75ºC and will not explode or result in thermal runaway even under severe conditions because they do not contain graphite-coated-metal anode electrode material.^[17] The batteries are currently being tested in a new production car made by Phoenix Motorcars which was on display at the 2006 SEMA motor show.

In March of 2005, Toshiba announced another fast charging lithium-ion battery, based on new nano-material technology, that provides even faster charge times, greater capacity, and a longer life cycle. The battery may be used in commercial products in 2006 or early 2007, primarily in the industrial and automotive sectors.^[18]

In November 2005, A123Systems announced^[19] a new higher power, faster recharging Li-Ion battery system^[20][21] based on research licensed from MIT. Their first cell is in production (1Q/2006)^[22] and being used in DeWalt power tools and Hybrids Plus Prius PHEV conversions (although the conversion costs more than the original price of the car, mostly due to the price of the batteries).

All these formulations involve new electrodes. By increasing the effective electrode area — thus decreasing the internal resistance of the battery — the current can be increased during both use and charging. This is similar to developments in ultracapacitors. Therefore, the battery is capable of delivering more power (watts); however, the battery's capacity (ampere-hours) is increased only slightly.

In April 2006, a group of scientists at MIT announced that they had figured out a way to use viruses to form nano-sized wires that can be used to build ultrathin lithium-ion batteries with three times the normal energy density. ^[23]

As of June 2006, researchers in France have created nanostructured battery electrodes with several times the energy capacity, by weight and volume, of conventional electrodes.^[24]

Today, the latest and greatest development in our hobby is the Lithium Ion Polymer batteries, or more commonly called lithium polymer, Li-Poly or LiPo. This is the technology that has developed from Lithium Ion.

The picture to the right is of NASA Lithium Ion batteries.

Getting even more technical for a minute; the lithium salt electrolyte is not held in an organic solvent like in the lithium ion design but it’s in a solid “polymer” composite called polyacrylonitrile. The advantage of using a polymer is that unlike the organic solvent, the polymer is not as flammable.  But this does not mean they will not burn or explode if abused. I don’t want to under emphasis the fire and explosion dangers with this new battery, it is present and very real and as was stated in one of the references that I read, if you are not willing to take a few more precautions in charging and storage of these batteries, it is best that you don’t even try to mess with them.

In my case, this means reading and following the instructions and not trying to see how much “more” I can get out of them! Something I am not use to doing but in this case I think I will try to restrain myself.

On the other hand, if they are used and charged correctly, they are very safe to use. Charging and re charging over and over in one day is quite expectable because there is no memory in the LiPo cells. This makes a “one pack” race day looking very possible. Racers that are already using these new batteries say that they come off the track and put the pack right back on the charger and the pack will actually cool down while being charged.

Just in case you have a doubt about over charging…..

Cells “vent”, even with the NiMH batteries and accidents have occurred. Granted, all that I have read about were due to user abuse but never-the-less they have happened. It will be the same with these new LiPo’s; used properly, they will probably do all that we expect them to do but if abused, they will cause problems, except this time they will simply not “vent” they will get your attention with real fires and real explosions. Take a good look at what can happen. Just bear in mind that what you’re about to see was done intentionally for a test. http://video.google.com/videoplay?docid=3690260570423705609  but it’s still an eye opener.

Putting this a little more into prospective; we also race cars that use 20% Nitro! So, as with all things, a little common since and maybe a little more concern with safety should be emphasized.

Another real advantage to the polymer design is that they no longer need a metal case to enclose the cell. This new “soft cell”, as it’s called, has brought on the possibilities of “shaping” the cells to specific needs i.e. the thin line battery in the Razor phone and the ability to make lap tops and other electrical products a lot smaller and thinner. But, this too is some what of a draw back to using them in a racing environment. “Stuff” happens, crashes occur, batteries are dropped, and many other things that can happen that will affect the shape and performance of the new soft cell. When these soft cells are “dented” or their shape some how deformed, they are usually not safe or will lose performance. This safety factor alone is why it will be so important for our hobby to use LiPo’s that are enclosed in a hard case such as the Orion 3200 Carbon. It is also real important to inspect your pack more often to be sure they are not distorted especially after a crash.

A different way of looking at things

Run time ratings will be assessed differently as will. It is excepted that because of the LiPo’s very low IR’s that a 3200 mAh pack will provide about the same run time as a 4200 NiMH will. If this proves “not” to be the case in Oval racing, then another pack with more MAh’s will have to be selected to ensure that the pack will not go into a deep discharge. As you will see further down in the graph, the discharge line is pretty flat, so more run time will not necessarily mean you will go faster at the end of the race, the line is already flat, it’s just important to keep the pack from going below 6 volts. (More on that later.)

Understanding LiPo ratings and terms

Charging and discharging is also critical and the “C” factor will be talked about a lot. This is the maximum average recommended discharge current for the cell. Now don’t get excited, it’s easy to understand.

For example: the Thunder Power 1900mAh packs have a 6C rating. To determine the maximum recommended discharge rate; multiply the capacity times the C rating. 1900mAh x 6C = 11,400. So the maximum recommended discharge rate would be 11,400mA or 11.4 amps. Also remember that LiPo cells can be wired in parallel, and with 2 cells in parallel each cell sees half the total current. With 3 cells in parallel, each cell “sees” one third the current.

The Orion 3200 Carbon back is rated at 20C so 3200 x 20 = 64,000 or 64,000 mA or 64 amps. And this is rated as continuous by Orion.

Another rating you will see is 1S or 2S or 3S2P for example. This refers to how the cells are put together; Series or Parallel. A pack like the Orion 3200 Carbon is a 2S1P meaning it has two cells in series and one in parallel (Series raises the voltage and Parallel, raises the capacity) So two 3.7 volt cells in series makes a 7.4 volt pack, adding one more cell in parallel will not change the voltage but will increase the capacity.

Charging

Charging LiPo batteries requires a very different charge method than other types of cells. It's imperative to use a charger designed specifically for LiPo batteries, and with most LiPo-specific chargers it's necessary to correctly select the cell count (1, 2 or 3 cells) manually. Fortunately, several good chargers are available. These chargers give a constant current charge rate at 75% the cell capacity until the pack voltage reaches 3.6 volts per cell. This charges the pack to about 80% of total capacity. At this point the charger switches to a constant voltage charge rate of 3.6 volts per cell to top off the battery.

With NiCad or NiMH cells, if we were pressed for time, you could push the charge amps up from 6 to maybe 7 or 8 without any fear of harm. Not so with the LiPo’s. If you have a time problem with these, it’s best to miss the heat and wait for the next one. (Remember the video.) The up side is, they do charge faster and can be recharged right after a run.

Another concern is; you should not “walk away” from the pack as it is being charged. Some of the less expensive chargers may “miss-read” the number of cells and begin to charge them too hard, so a closer monitoring of your charge progress is in order. That is also another reason to select a charger with a manual cell setting.

I am not preaching doom and gloom for these new batteries; in fact, I fully believe that they are our future. But at the same time it would be remiss of me not to present you with the good and the bad sides.

Today, with the development of LiPo batteries, the past decision to change to 4 cells may be coming back to haunt us even more because if they do become a viable alternative to what we use now, we will have to revert back to the higher voltages. But keep an open mind for a little while longer and let’s look at something.

Since the beginning of organized racing, classes have been formed and racers chose what type of class they wanted to run depending on their ability and sometime their budget. The control of individual speeds in those classes (other than Open Mod) has always been done mainly with the battery as the controlling factor. For example: the Spec class uses Spec Batteries, Stock and Mod was getting too fast so we went to 4 cells etc. The problem with that concept is that the batteries are constantly improving and increasing in voltage. What use to be a fast 6 cell stock speed is attainable now with today’s 4 cell batteries. This has put “the cart before the horse” in the way classes should be arranged. A more efficient way to do things is to control the class speeds by the motor not the battery such as they do in Open Modified.

This concept has a better chance of working with Brushless motors and LiPo batteries because each class of motor is very close to being the same and, from everything I have read, the LiPo batteries are also very consistent. With those two factors being equal, the projected speeds are much easier to calculate and will remain reasonably the same. This will present a lot more stability in growth because someone who chooses to race in Stock can pretty much be assured of how fast he will be going and will not be too concerned with the speeds getting faster than he is able to handle (or afford). Nor will he have to be very concerned that his racing buddy has a faster motor or better batteries then he does.

Being able to afford the hobby you love is important and as of recently, our hobby has in some ways gotten way out of control. We need several battery packs to practice and race with and, as stated above, they are constantly changing. We not only need several motors but also the peripherals to maintain them like com truers, zappers, brushes, springs, alignment tools etc.  All of which can be left at home with the brushless motor.

LiPo batteries are unique in many ways as well; they are considerably lighter for one thing, with a 7.4 volt pack weighing in at around 10 ozs. That is about the same weight as a 4 cell NiMH pack. They are charged differently and because of that, they require a special charger. Do NOT use your standard NiCAD or NiMH charger to charge LiPo batteries. I can’t over emphasize that enough THEY WILL NOT WORK. Use one of the many chargers that are specifically designed for LiPo’s!

Their discharge curve is also different and it appears to be quite a bit for the better. As you can see from the accompanying graph, it is essentially flat and in fact on the 40A (red) line it actually seems to get better before it dumps. That is something we are definitely not use to!

BUT, since I mentioned “dumping”; DO NOT let the battery (speaking of a 7.4 volt packs) go below 6 volts and DEFINITELY do not deep discharge them. Damage WILL occur and in most cases it will be irrevocable. This is why it will be important to choose a battery that will have plenty of excess run time. Not for performance but to prevent a “dumping” condition while racing. In most cases if they are left on a load and are allowed to deep discharge, such as leaving them plugged into the car overnight with the speed control still on, they are toast. And remember they are about 90 bucks a shot! These are truly a race, re charge and race again battery. After the race you want to put at least 40% charge back in them.

But, as stated, the biggest difference we will have to deal with is their individual cell voltage. A “regular” NiCad or NiMH cell has a voltage of 1.2 volts. This is what the industry has dealt with from the beginning and what all of our electronics are geared to. LiPo’s have a cell voltage of 3.7 volts and it makes it impossible to get the 4 cell voltage (4.8 volts) that we are use to running today. However, they, like the new brushless motors, seem to be the way the future of our hobby is headed and I feel that this is the direction Oval racing should be thinking about in order to get it back into the main stream of RC racing. As it stands right now, we are a small portion of the hobby that most RC’ers can’t really afford or are not willing to invest that much into. Brushless and LiPo’s should help in that department.

Storing

It is significantly beneficial to avoid storing a lithium-ion battery at full charge. A Li-ion battery stored at 40% charge will last many times longer than one stored at 100% charge, particularly at higher temperatures.^[5]

If a Li-ion battery is stored with too low a charge, there is a risk of allowing the charge to drop below the battery's low-voltage threshold, resulting in an unrecoverable dead battery. Once the charge has dropped to this level, recharging it can be dangerous. An internal safety circuit will therefore open to prevent charging, and the battery will be for all practical purposes dead.

In all other forms of our racing hobby where 6 cell packs are used, they are already taking advantages of “one pack” racing and maintenance free motors. Off Road, TC’s and Dirt Oval racing never made the move to 4 cells so their change simple required a new charger and a battery pack. We in Oval 4 cell will have a harder time of it. Your speed control will have to be able to handle 6 cell voltages (most do), your chassis will have to be one that a 6 cell size pack will fit into plus we will also need the new chargers. None of these are “serious” expenses compared to the gain.

The new racer will have it much easier to get started because of the equipment he will “not” have to buy, even soldering irons in some cases will be obsolete. One battery pack can really run the average racer all day and with one motor left in the car for weeks on end without the need to clean or “freshen up”, this will surely attract more new people into the hobby because of the lack of expense and in some cases the “dedication” needed in what he considers a hobby.

Hobby shop owners will not have to talk in four figures for a person to get started.  It’s much easier to sell a new racer ONE motor, ONE battery, ONE charger and a good chassis and electronics and “truthfully” tell him that he can go racing than it is to tell him what he “really” needs to buy to enable him to do the same thing with brushed motors and standard batteries.

But is it too late?

But have we gone too far to turn back? All of this change will not happen over night but as it does, there will be those (just like it was when we went to 4 cells) that will not accept it and we will lose racers. Most people, including myself hate change and some would rather quit than to try and deal with it. The only saving grace will be that there will not be many of them and that there will be a greater number that will come back to Oval and a better chance for Oval to attract new racers.

Brushless motors are already here to stay. I see no turning back in this area. It simply makes no since to buy a ton of motors when one will do the same job and last for a much longer period of time and probably perform better. If you look at that and add just a little common since, it is plain to see that the batteries will be soon to follow. Good or bad, it’s going to happen. In fact it is already happening in the other forms of racing, it’s just a matter of time before it affects Oval. But before it does we are going to have to realize that we will have to go back to the voltage of a 6 cell pack. There is just no way around that.

In the “old days” a new person had to start out with 6 cells and a stock motor but back then the batteries were no where near what the Lipos present and the motors we ran then are sub standard to the Brushless. “Stock” as we know it now, will be a pretty fast class, probably equal to what 19 turn is today. The 18.5 “crawler” motor could be an alternative in an effort to hold Stock speeds down.

All of this is going to happen; the question is how we deal with it while keeping our racer loss to a minimum. The best part is that the change will not take place over night. You will not walk into your race track next week and not be able to race what you have right now; this will be a while coming. But it is something that all of us need to start planning for and thinking about. The ones that jump on brushless and LiPo’s at first will be the ones that seriously race and are constantly looking for the best and fastest. Classes will evolve for them just as they do for anything else that’s new.

ARCOR is already considering and researching a Brushless/LiPo class with a “projected” date of October 2007 to officially recognize it. ROAR, stating safety reasons, did not legalize LiPo’s for 2007 and it will be 2008 before they are considered again by them. At this time, I do not know what the BRL is planning for next season concerning LiPo’s.

Spec racers will not feel this change at all because there is nothing available as far as brushless and LiPo’s go that even come close to the speeds that they are use to. In fact they will probably come out the best as far as the “old timers” go because they will be able to pick up some pretty good used equipment from the ones that are making the change. The only way I can see Spec staying a good class for people just starting out or running on a budget is keep the LiPo’s out. An 18.5 brushless motor “maybe” but they will have to keep the 4 cell Spec batteries to keep that class the way it should be. But that’s just my opinion and things could change with real “on track” testing.

In the months to come, I plan on doing testing on my own with this new technology and future articles will be written on my progress and findings. My thoughts right now are; it’s coming. I don’t think we can really stop it for very long. We are in the very early stages of this and while Brushless is fast growing, Lipo’s may be a little longer getting started but when they do…….they will take over.