How to determine when a LiPo Battery is DEAD

It’s known that like most things in life, LiPo batteries do not last forever. Eventually, LiPo batteries degrade to a point which makes them become unusable for your application.  The real question is, how do you know when an RC LiPo Battery is DEAD? Did you know that using a dead battery can actually be dangerous and could lead to catastrophic failure of the battery pack? A dead battery pack can also place extra strain on your ESC due to higher ripple voltages. If you are looking for more information on LiPo batteries it is recommended to check our LiPo batteries page.

Visual Inspection – When a LiPo Battery is DEAD

The most obvious way to determine if a LiPo battery is dead is to visually inspect it. What you are looking for when you are inspecting your LiPo battery pack is any sort of ballooning of the pack itself. A ballooning pack is caused when gases are released inside of the LiPo battery. Gases being released from a cell in a LiPo battery can happen for a number of reasons.

Generally, excessive heat is a contributor to packs that enlarge or balloon. If this happens to you during charging you must dispose of the pack immediately. You should dispose of the pack if this does happen at any time during use or no use. Ballooned LiPo battery packs can be very dangerous. 

Performance Test – When a LiPo Battery is DEAD

One of the easiest ways to determine if a LiPo battery pack is dead, is to review it’s performance characteristics.  This can be done by  placing the LiPo battery in the application that you intent to run the battery pack in. There are a few things to watch out for that would suggest your battery is around or past is expiry date. Let’s take a look.

Aggressive Run – Dead LiPo Test

The performance test  is quite simple and does not require much preparation other than a fully charged battery pack. What you will want to do is fully charge the battery and then place this in to your most power hungry vehicle that would of course use that battery pack.  You must be experienced running this vehicle to ensure that there are no power system concerns and everything has ran well before.

Run the battery pack more aggressively than you typically would. If your flying an airplane or driving a boat, maintain a higher average throttle setting than you typically would. If you are running an RC car accelerate more aggressively and frequently than you typically would. Keep in mind that if you are basing your run off a timer and you are driving more aggressively, you will burn more power. Don’t forget to consider this when setting your run time “timer.”

Only discharge the pack down to a maximum of 20%. Do not over discharge the pack as this won’t help or make your test any more conservative.

Once you have run your RC vehicle, these three items is what you should look for.

  1. Are you getting the expected performance out of your battery for the entire duration of your run?
  2. During the duration of the run, were there no low voltage cutoffs during the run?
  3. Is your battery operating at less than 60 degrees celcius or 140 degrees farenheit? (Dangerous if not)

If you have answered yes to these questions above, your pack is in fair condition. If you have answered no to any of the above questions, this could be a sign that your battery pack is in poor condition.

Looking at the Numbers – When a LiPo Battery is DEAD

If you have a more advanced charger, you may be able to use the information it offers to help you out. Take a look at your LiPo charger and see if it is possible for it to measure internal resistance often abbreviated IR. The unit of measurement is commonly in milli-ohms. (m Ω)

To use the resistance value determined by our charger, we first need to start with a discharged battery and use the charge function. Or you may start with a fully charged battery and use the discharge function. Discharging a pack to get a resistance reading is only recommended if your charger can discharge a significant amount of power.

It’s highly recommended to use the resistance determined by the charger during a charge cycle as you will be charging the battery regularly presumably. It’s also best to know the internal resistance of your packs cells when you purchased them new.  Determine the internal resistance  by charging your LiPo batteries and recording the internal resistance computed by your charger.

Once you have charged your pack and record the internal resistance you can determine the health of the cells in your LiPo battery pack. Generally speaking, if the resistance goes up by 2-3 times the original amount, your LiPo cells are suffering in performance. Depending on the application these packs are used in, 2-3 times the internal resistance may make them completely useless.

If you don’t know the internal resistance per cell of your LiPo pack when purchased new, here is a quick reference chart. Keep in mind these values are general values.

 

C Rating Capacity (mAh) IR per Cell (m Ω)
30 850 0.02
30 5000 0.0029
45 2200 0.0065
45 2200 0.0026
65 1200 0.0092
65 5000 0.0019

Conclusion – When a LiPo Battery is DEAD

The method I typically use is actually a combination of the above.  If I’m happy using a half dead LiPo in an application that allows it, even with the weaker performance / capacity, then so be it.  As long as the LiPo is not in a dangerous state.When I can no longer use the LiPo battery pack, it is disposed of accordingly and a replacement is purchased.

 

Brushless Inrunner vs Outrunner motor?

There are many options that we have for RC brushless motors regardless of the application. Motor come in many sizes to fit certain power ranges. One of the biggest factors that could effect your brushless motor purchase, is a brushless inrunner option or a brushless outrunner. Which motor option would you choose, inrunner or outrunner?

Key Differences – Brushless Inrunner vs Outrunner Motor

Take a look at the image below. You can see that the brushless outrunner motor has the output shaft, connected to a propeller in this case attached to the case of the motor. This would suggest that the motor shaft when spun would also spin the outer motor case.   This is exactly what happens. The permanent magnets on the outrunner are placed on the rotor and the rotor spins on the outside case. On the inside of the motor are the stator windings which do not rotate, they are fixed in position.

Brushless Outrunner Motor vs Inrunner Motor

Brushless Outrunner Motor vs Inrunner Motor. Outrunner on right side

On the inrunner motor, you essentially have the complete opposite true for how it is built. On the outer side of the motor is the case. The case in this situation does not rotate and is fixed. The stator windings are placed on the inside face of the case. When you spin the motor shaft of an inrunner, you are spinning the rotor which also contains the permanent magnets much like the outrunner. The difference of course being that they are now at the center of the motor.  For most, this would be the more conventional type of electric motor, especially if you are familiar with large AC motors or even old brushed DC motors.

Performance Differences – Brushless Inrunner vs Outrunner Motor

This can be easily debated as to which motor has the best performance when you dive deep in to the specifics. For simplicity let’s loosely consider motors of equal size and weight in order to compare the possible performance differences.

Physical Size differences

Generally speaking brushless outrunner motors will have a larger diameter and a smaller length vs a comparable inrunner motor of similar weights.  Conversely, Inrunners are smaller in diameter and typically larger in length.   Physical size is one area that your application may be limited in, however there are other trade offs that would have to be considered as we will get in to below.

RPM / Volt (Kv)

When you consider the RPM per volt of a brushless motor, (rotation speed per one volt applied) this is one of the biggest factors in choosing the correct motor for your application. Often times when one does not correctly select the appropriate Kv motor, risk of burning a power system component out is greatly increased. An inrunner motor of equal size to a brushless outrunner motor will have higher Kv. Although different motor wind selections (same size motor with Kv options) provides a decent range, outrunner motors will typically have a lower Kv value. This is key in your selection of a brushless motor to directly fit your application.

How does an outrunner produce lower Kv? Well, we already did speak about physical size difference. Physical size does represent a primary factor that effects kv. The larger can diameter of the outrunner allows a higher quantity of magnets to be used in the outer case. More magnets alternating magnetic poles forces the ESC to switch more rapidly slowing down the overall speed as there is more work to be done by the ESC. You could also more simply look at it as the larger diameter creates a larger circumference for the motor to travel in one rotation. The larger can diameter also represents a larger moment arm for an outrunner that is a good segue in to the next topic.

 

Torque Comparison of a Brushless Outrunner vs Inrunner motor

The larger moment arm that we have spoken about above converts directly in to more torque being created. Therefore the brushless motor will generate more torque as a general comparison against an inrunner motor. The relationship ties in with the fact that outrunners do have a lower RPM per volt. The relationship with Kv and torque are inversely proportional. As RPM per volt (Kv) increases, torque of the motor decreases.

Efficiency the same between inrunners and outrunners?

This can be a tough question to answer actually as the true answer has many dependencies. These dependencies can be anything from the effective size comparison to quality of the motor, manufacturer of the motor, power output of the motor and several more. In general for most applications in RC, a brushless inrunner motor has the potential to be more efficient than a brushless outrunner motor.

Waste Heat of Inrunner vs Outrunners

Let’s consider waste heat that a motor outputs. If we look at the brushless outrunner motor, heat must be dissipated through the center of the motor. The source of heat generation is of course the stator windings of the motor. The stator windings of the outrunner is located at the core of the motor. heat must transfer from the windings to the center of the motor being the motor shaft. Heat is then conducted outward through the motor shaft. An outrunners solution to heat is to  have large accessible cooling vents in the case to allow air to flow over the windings directly.

Brushless Outrunner Motor Windings

Brushless Outrunner Motor with large vents to the stator windings

An inrunner motor on the other hand has the stator windings directly on the inner face of the outer can. This direct point of contact provides an excellent surface with a very large area for heat to transfer. Air is a very poor conductor of heat. Increasing the amount of surface area for heat to gather in order to dissipate in to the air is how an inrunner can get rid of excess heat energy.

Being able to get rid of waste heat allows the inrunner motor to run cool being more efficient for similar power outputs on a motor of equal size/weight.

Common Brushless Outrunner vs Inrunner motor Applications

Motors that can be fit as direct drive offer simplicity which increases reliability, reduces weight that a transmission would add, and reduces amount of component wear items. The amount of load or torque required also plays in to the overall equations of an inrunner vs outrunner choice. Lastly required RPM is considered.

Here’s a chart to outline the most common approach for motor selection. Note that not in all cases this chart is followed. Deviating from it is entirely possible and really depends on other factors that we didn’t speak about. These can be availability, cost and other similar factors.

In general when I am selecting a motor, I am looking for simplicity and reliability. My first pick would be an inrunner motor and if this does not fit, then I select an outrunner.

Application Motor Choice
3D Airplane Outrunner
Trainer Airplane Outrunner
Pylon Racer Airplane Inrunner
Electric Ducted Fan Jet Inrunner
RC Car, Stadium Truck, Monster Truck Inrunner
RC Fast Electric Boat Inrunner
RC Scale Electric Boat Outrunner
Drone or Quadcopters, Hexacopters, Octacopters Outrunner
RC Helicopter Outrunner

Summary of Differences – Brushless Inrunner vs Outrunner Motor

Parameter for comparison Inrunner Outrunner
Can Diameter Smaller Larger
Can Length Larger Smaller
RPM per Volt Higher Lower
Torque Lower Torque Higher Torque
Efficiency Best
Heat Dissipation Best

How to measure gear pitch on an RC Car

You could have just bought that used RC Car right off of some website selling used RC’s. Or maybe you can’t find an instruction manual for your 5 year old RC car. Now you want to upgrade your gearing, however you are unsure of the gear pitch you need to buy.

Well in my case, I wanted to change up the gearing on a 1/8 buggy that I purchased. So what I did was look at the manual to try and find the correct gear pitch. To my surprise there was no such luck when reviewing the manual. However on the website (tower) where I purchased the buggy there were gear specs listed. I used them and made a gear purchase at the same time I bought the buggy. Upon receiving the new pinions for the buggy and recieving the buggy as well, I ended up throwing a new pinion gear on. To my surprise yet again, the gears were not properly meshing, I definitely had the wrong pitch. The spec listed on the site was not correct.

Did you know it’s entirely possible to measure gear pitch on an RC car? Now that we are passed the long winded introduction, let’s take a look at how we can measure gear pitch on an RC car. It’s quite easy actually.

What you will need to measure gear pitch

  1.    RC gear with an unknown pitch – Can be a pinion or spur gear
  2.    Vernier Calipers (if you don’t have this a ruler can be made to work)
  3.    An internet connection to access this website

That’s it!

How to measure gear pitch

 

Step 1.

The first step to measure gear pitch is to count the number of teeth that are on the gear that you are measuring.

Step 2.

Next, measure the outer most diameter of the gear. It’s important that you are measuring right to the outside of the gear including the teeth.

Step 3.

Lastly, record the number of teeth that you have either counted or found in a manual as well as the outer diameter that you had measured. Place these values in to the calculator on the gear calculator page.

It’s that easy. The number that the calculator spits out can be used to find a gear that meshes perfectly with the gear you have in your hand. No more guessing pitch values.

 

 

Torque vs Horsepower

In this article we are going to look at Torque vs Horsepower and settle that debate once and for all. We will be focusing in on how these terms work for us in the RC hobby.

Many questions that you may see pop up or often question yourself in the world of RC are the following:

What is Power?
What is Torque?
Does Torque or Horsepower win RC races?
Does Horsepower sell engines?
Do Electric Motors produce more power or torque vs gas or nitro engines?

We will be answering these questions throughout.

What is Power? – Torque vs Horsepower

Power is simply defined as the amount of work that can be performed at a specific rate. This just means that if you have power, you can perform work that accomplishes tasks. Generally we are talking about mechanical power when looking at torque vs horsepower. The important factor to remember in the definition of Power is that mechanical power is the product of Torque and RPM, where RPM is revolutions per minute.When we talk about mechanical power we are considering torque already but at a certain RPM. The unit of power is horsepower, watts, kilowatts. etc. Nitro or Gas engines use horsepower where Electric motors use watts or kilowatts. 746 watts is equivalent to 1 horsepower. Before we look at what torque is I will leave you with the formula to calculate Horsepower. P = T ω. Now we will define and better understand what torque is.

What is Torque? – Torque vs Horsepower

Torque production - Torque vs Horsepower

Torque production – Torque vs Horsepower

Torque is best defined or explained by looking at static torque. When we take a Torque Wrench and apply an appropriate amount of force on the handle of the wrench we create a torque at the socket. The force applied at a distance produces a torque that can be used to tighten bolts such as lug nuts found on your car. This torque is static meaning you can not perform any work when peak torque is reached as nothing will move.

Now if we consider dynamic torque, the exact same action is happening except the torque is being applied constantly as a shaft rotates continuously.

In conclusion, torque creates a twisting or turning force to a shaft or flywheel. Torque can be measure in inch-ounces, pound-feet, or Newton-meters.

Torque and Power of Gas/Nitro Engine vs Electric Motor – Torque vs Horsepower

Torque vs Horsepower Curve - Nitro-Gas Engine vs ELectric Motor

Torque vs Horsepower Curve – Nitro-Gas Engine vs Electric Motor

If we consider the torque vs horsepower characteristics of  an electric motor verse a nitro or gas engine, they are fairly different. The power/torque curve of an internal combustion engine such as the nitro or gas engine is quite linear, where power builds as RPM increases and torque increases as RPM increases. Eventually torque levels off and begins to decline.

Now when we consider the electric motor, the characteristics are quite different. Torque is exceptionally strong in the lower RPM ranges and then tapers off at the higher RPM range. Horsepower build strongly at the lower RPM range as the amount of torque available is significant. Using the graph to the side, you can visually see the difference between the two power sources mainly in the torque curves.

The nitro and gas engines tend to perform very well at the higher RPM range and the electric motor tends to perform very well at the lower RPM range. The most important characteristic to take from this is the torque curve and how it forms for each power source. Although these characteristics are very evident in general terms, it is important to remember that these curves can vary dependent on specific motor or engine characteristics.

Does Horsepower sell engines? – Torque vs Horsepower

The real answer to this question is not necessarily as technical as much as it is a marketing explanation. When you are looking at power values of combustion engines specifically, you must take this information with a grain of salt. It is easy to publish values in order to make a product appear more superior against the competition.

Now if we change the question so that it reads Does true Horsepower values sell engines? If we can be assured that the horsepower value of a specific engine is accurate, the answer to the question should be – it should definitely help. We will investigate the answer a little further in the next question below.

Does Torque or Horsepower win RC races? – Torque vs Horsepower

This question is rather interesting and often pops up in many forums around the internet, focusing in on which characteristic provides the solution to racing.

Now if you already have read up to this point in the article, you have 85 percent of the answer to this question. This is why:

If we look at the definition of torque, torque is its own entity. When looking at horsepower, power in itself is not its own entity. The interesting part of horsepower is that the equation for it includes torque, where Power equals torque multiplied by RPM! This is very relevant as when we are talking about power, we are really just talking about torque but at a specific RPM.

Consider this question: A car outputs 1 horsepower and 1 pound feet of torque somewhere in its power band at the engine. If we assume no power train losses and look at a transmission with a ratio of 1:1, what is the torque and power after the transmission.

Well this question may appear easy, the correct answer would be, after the transmission we would see 1 horsepower and 1 foot pounds of torque.

Let’s add a twist to the question. What if we use the exact same scenario but with a transmission that has a 1:2 ratio? That is where the output shaft turns once and the engine turns two revolutions.

The correct answer is that the horsepower remains at 1 and the torque at the output shaft from the transmission doubles to 2 pound feet .

We actually gain torque by sacrificing RPM. Remember Horsepower is derived from torque and RPM. Why would we want to purchase an engine based on torque values vs horsepower values when we can manipulate the torque values ourselves and we can NOT change the horsepower values.

What would you Choose? – Torque vs Horsepower

Would you choose Engine One or Engine Two?

Engine One has 0.5 horsepower and 1 pound feet  of torque

Engine Two has 1 horsepower and 0.5 pound feet  of torque.

If it was up to me and I wanted to win races, I would most definitely select the engine that has the higher horsepower. I know that if I require more torque at a certain speed I can just manipulate the gear ratio in my transmission to provide me with a better torque value. However if I selected the engine with a lower horsepower, I can not alter the horsepower value to improve it. Regardless of what transmission is used, the power output never changes.

Therefore engine Two has the most potential to win races.

Conclusion – Torque vs Horsepower

Horsepower wins races, torque just confuses people with what is actually occurring. Horsepower is derived from torque and RPM, when you are talking about horsepower you are talking about torque at a specific RPM. Horsepower accomplishes work, the more of it you have, the more you can do. That is purely by definition.

Nitro and Gas engines have great power curves but the torque curve of an electric motor provides it a large advantage. A stronger torque curve means an electric motor has a lot of horsepower available at low RPM’s. Having a lot of horsepower at low RPM’s is a great way to get a heavy RC vehicle off the starting line.

RC Tools – The must have Tools

This is one topic that often goes unspoken about. Today we will look at the common tools to keep in your tool box. Last minute tuning or adjusting of your RC vehicle is very common just before you are about to fly your plane or drive you Car or Boat. The RC tools that you will need are very important in order to make the necessary adjustments. We will look at the most common RC tools available and which RC tools I prefer to keep in my Tool Box.

C Tool Box and Radar Gun

When will you need to use RC tools?

There are many cases where you will need to use a different assortment of tools. This mainly depends on which RC vehicle you are using at the time and what kind of power source your RC vehicle uses. By nature of the nitro engine, this is where you will most definitely want to have some RC tools available at all times. As you already probably know, the nitro engine requires a different tune nearly every day.Socket Wrench

Common General RC tools

The most common types of RC tools that you will be using include precision screw drivers which is just a fancy way of describing small screw drivers such as the ones in the photo. The second most common tool that I prefer in my tool box is wrenches and or a socket set, Precision screw drivers are excellent for making any tune changes to a Precision Screw Driversnitro engine or just ensuring that all the screws are in fact tight before you go to run that 120km/h on road car. These RC tools are very common in almost any tool box but are especially important for RC as they become used nearly every run. Or at least you should be checking for loose screws etc. A flat head precision screw driver is perfect for preforming that tune on a nitro engines Low Speed Needle and High Speed needle. Most needle valves use a flat head screwdriver to make the necessary tuning adjustments.

 

The Most Common RC tools – Allen Keys

The mosRC tools - Allen Keyst important tool in my tool box for RC is most definitely Allen Keys. Allen Key screw heads exist a lot of the time in RC land vehicles as well as many RC Airplanes. Come to think about it, they are also all over the place in my RC boat. Allen Keys make excellent RC tools due to there extreme high use. Now one of the biggest reasons of there high use is due to the performance of the screw head. On small screws it is difficult to get a good bit grip when tightening up the screw. Using Allen head screws maximize the grip and reduce the chances for stripping to occur. Make certain you include Allen Keys in your tool box.

 

RC tools for RepairCA Glue

There are a couple items that I like to keep in my tool box just for those days where there is damage done or I just can’t keep a screw in it’s place well enough. What I like to use is CA glue. I tend to use CA glue a lot as it offers a very quick solution to some minor problems that you may encounter while running your RC. Without CA glue, it’s difficult to re-stick that tire on its rim or that control surface hinge.

The other item I like to keep in my tool box is Loc-tite which is a thread locker. I use the red permanent Loc-Tite for pesky screws that vibrate loose over time. Now just because it says permanent doesn’t mean it actually is permanent. The one easy way to break a screw loose that has fastened using Loc-Tite is to apply heat. There are a couple different ways you may apply heat, my preference is with a soldering iron directly on the head of the screw. This is usually enough heat to crack the screw loose with a bit of force.

Temperature Gun – RC tools

Temperature Meter

This is probably one of my most used and favourite of all the RC tools in my tool box. No matter which RC vehicle I am using on any particular day this tools gets used. After a run of the electric RC’s, I like to get an idea of how hot the batteries, ESC, and motor are getting. This is great for dialing in that gearing on an RC car or for dialing in that prop on a boat or airplane. For nitro or gas vehicles this RC tool becomes an excellent confirmation for tuning. When you feel the RC is running too lean, the Temp gun may be able to confirm this. It’s not always easy finding the perfect tune for a nitro vehicle.

 

 

 

Radar Gun – RC tools

Bushnell Radar Gun

Bushnell Radar Gun

By far my most favourite tool is the Bushnell Radar Gun. I can use it to dial in a nitro powered boat or car for absolute maximum performance. You can really see the difference in how a slight mixture change can gain so much potential speed from a nitro powered RC vehicle. You can also see the difference gearing makes with an electric powered vehicle and combining the two tools makes for a very powerful tuning session. Not only can it be used for dialing in a tune but it can also be used to determine the overall performance of your RC vehicle. This RC tool is great for finally getting to know just how fast that boat or car is traveling. And then you can either impress your friends with the real world results or challenge them by seeing if they can beat the speed you achieved.