What Does all that Battery Talk Really Mean?

Voltage, mAh, C ratings, S ratings, capacity what does all this mean? I do agree these terms are some of the most confusing in the RC world.

The capacity of a battery pack is expressed in “mAh” or milliamp hours. You can easily remember this as the gas tank size. The larger the gas tank the longer the run time you get. You can also find small changes in the amount of acceleration you get. But I am going to avoid this for confusion ( or lack of) sake. This means that a 5000 mAh battery will run longer than an 1800 mAh battery.

The voltage of a battery can be thought of as the speed the battery can push your car. Voltage is not to different from the octane level of your gasoline in your real car. This is one area that you do have to be careful. If you attempt to run a battery that has to high of voltage you can do permanent damage to your
ESC and or your motor.

RC Flat battery pack

Here are two terms that are hard to get straight: Series and parallel.

Series wiring increases voltage but not the amp/hour capacity mAh. Here is the way to remember this… 3 – 2 volt/200 mAh cells wired in series, = 6 voltz/200 mAh.

Parallel wiring increases capacity not voltage. Here is the way to remember this one.. 3 – 2 volt/200 mAh cells wired in parallel = 2 volts/600 mAh.

For those of you that do use Lipo batteries there are two more terms that really get mis-understood. These two terms are the S-rating and C-rating. The “S” rating means the number of cells that are wires in series. 2S means 2 cells in series, 3S is 3 cells in series and so on. Packs that are wired in series have their voltage higher which means higher top speeds.

C ratings show the level of current a pack can output. Now I have lost you right? It just means it will spit out the juice faster, so you get more acceleration.

OK you were right ! Sometimes there is a “P” rating. And yes, it means the cells are wired in parallel. This will increase the packs capacity as you would expect. These are not common. It is far easier and more reliable just to increase the size of the pack. Cells that are wired in parallel have a lot of solder joints, this can cause the packs to become out of balance. We can discuss this in a later blog.

Now that I have cleared all this up, I am going to mention that you can get battery packs that have their cells wired in both series and parallel….So why did I have to say that

The Truth About Balancing LiPo’s

What does balancing really mean? Balancing means equalizing the voltages between the cells of a LiPo pack.   You can balance before, during or after charging the pack.

So why would you balance a LiPo pack? Balancing a LiPo pack improves performance.  It will also improve the life of the pack and increase the safety.  This happens because balancing prevents one of the cells from going below the safe range, while one or more of the others is fine.  Most Lipos have a safe range somewhere between 3 to 3.25 volts.  RC cars that are equiped to handle Lipos have a low voltage cutoff programmed into their ESC’s.  This feature makes the car or truck LiPo safe.  But if the packs cells are out of balance the ESC is going see a voltage of 6 volts and continue to draw power.  The low cell could be damaged during this time because it is lower than the 3 volt safety range creating a safety concern.

So, when do I balance? This definitely depends on how often the pack is used.  I race or practice almost every weekend, so I balance mine after charging at least once a month.  There are manufacturers that claim that their packs do not need balancing, but I really do not feel this is true, so for safety reasons I would balance them anyway.  New packs should be balanced on first use because they may have been sitting on the shelf for a long period of time and could be out of balance.

Is there any special equipment needed? For the most part all LiPo packs have a balancing plug installed.  Most of the good quality peak detecting chargers have a balancing cycle, or will balance during charging.  You can also purchase stand alone balancers that the plug will plug into.  There are a few different styles of balancing plugs so make sure the one that you purchase is compatible with your packs.

A good quality charger that has a built in balancer is the best way to go.  These chargers will use different methods of balancing.  Most will use the balance plug which is preferred. There are some that just use the balance plug to check voltages, but this method is not nearly so effective. On these types of chargers; when they detect an over voltage situation they will stop charging.  You are now aware of the situation, but the pack is still out of balance.  The better chargers will detect which cell is over and it will slow down the charge rate.  The charge rate will remain the same on the other cells allowing them to “catch up”.

If you do want to use a stand alone balancer; these devices work by using the balance plug to slowly discharge the high cells to match the lower ones.

So what does all this mean?  Balancing will not hurt you packs in any way.  It will increase the life of your investment.  I recommend purchasing a charger that has a built in balancer.  Use it every time you charge.  I run a separate balance cycle about once a month just as an additional measure. This will allow you to maintain a safely balanced pack that will perform just as you expect it to.

The 2.4 GHz Radio Revealed

Over the last several years there has been more and more talk about the new radio technology.  This technology is the 2.4 GHz Spread Spectrum System.  So why is this technology better than conventional AM or FM frequencies.  I am going to visit some of the most common advantages and let you determine if this is the new direction or just hipe.

1. The 2.4 GHz radios use a range of frequencies tht are much cleaner.  They have very little interference and therefore much less chance of glitches.
2. The antenna is rarely over 4 inches in length and is flexable.  This greatly reduces the chance of bending or breaking the antenna.
3. The 2.4 GHz system uses over 4 billion signals.  This means that you will never have to wait for your channel to clear.
4. The transmitter and receiver do not use crystals. They automaticaly search for an open signal when switched on.  Just think how nice it is to not have to scramble around swapping out crystals before that big race.
5. The nature of the the technology allows for additional information about you RC car to be transmitted to a display on the readio.  Speed, RPM, running temperatures are examples of information that can be brought directly from your car to your display.
6. The antennae on your car is also shorter.  This means there is a smaller chance of damage.  It also means your car will look more scale.  It definitely is more realistic without the antennae hanging out.
7. The radio itself is more lightweight.  Most of these radios will use only 4 “AA” alkalines rather than the bulky 8 we are so used to.
8. Less trouble with receivers.  It is the crystals that usually go bad over time.  For those of use that love off road cars are used to the fact that all that vibrating will eventually cause the crystals to fail.
9. Faster response.  Because the transmitter sends data to the receiver more often than AM or FM transmitters.  This means you get a much faster response time.

So in an nutshell it looks like 2.4 GHz spread spectrum technology gives a definite increase in the safety of the RC hobby by reducing the chances of runaways and glitches.  It also increase the performance of your radio signal.  This gives you a much better experience whether you are a basher or a racer.