FMA CellPro 10S Charger System

Overall photo of the new FMA Direct/Revolectrix CellPro 10S charger

Let me first provide some background information before getting into the new FMA Direct CellPro 10S charger. FMA Direct, under its founder, AMA Hall of Fame member, Fred Marks, has been involved in much of the electronic aspects of our hobby for a lot of years. They have produced RC systems, auto pilot systems, ARF and RTF aircraft, test equipment and in recent times, lithium battery chargers and battery packs. Fred’s sons, Tim and James, now run the day to day business with the technical development area being headed by FMA President, Tim Marks.

I think it safe to say that FMA was just about the first company in the USA to get into the lithium polymer (Li-Poly) battery business. That was something like five or six years ago. As we now all know, Li-Poly batteries provide about 95% of the power requirements for electric powered model aircraft. There are literally dozens of companies now involved in distributing both Li-Poly battery packs and their companion chargers.

Much has happened over these six years. For example, there was obviously a learning curve involved with the application of Li-Poly batteries. Early on, some fires were reported and the safety aspect of using these new cells initially became a big concern. (See Part Three of the Sport Aviator article “Those Things We Call Batteries” for complete Li-Poly details.)

The techniques employed for charging and discharging Nickel Cadmium (Ni-Cd) and Nickel Metal Hydride (Ni-MH) batteries had to be learned all over again when it came to the new Li-Poly batteries. But, with a few years of experience under our belts, safe Li-Poly battery operation has become once again the routine for experienced electric power flyers.

One of the first lessons we learned is that Li-Poly battery cells should not be charged over 4.20 volts and they shouldn’t be discharged below approx. 2.70 volts per cell under load (3.00 volts being better!). Going higher in charge voltage or lower in discharge voltage will ruin the battery cell quickly. Normal charge current rate is recommended at a “1C” level or 1 times the capacity of the battery; rated in amp/hours. A 2 amp/hour rated battery would be charged at 2 amps and if that battery were close to being fully depleted, it would take approx. an hour to reach full charge. Everyone learned early-on these several constraints associated with the use of Li-Poly batteries.

But the real breakthrough with Li-Poly batteries came as a result of development work done by FMA Direct. They were the first to recognize that, upon completion of charge, Li-Poly cells within a pack must all have the same voltage or close to it. When each cell is at the same voltage the pack is said to be “balanced”. Following this concept you will be able to safely charge and discharge your Li-Poly battery packs and obtain excellent service life from them.

To make this concept work, FMA Direct wired all of the battery packs they sold so that each cell was brought out separately into a multi-pin connector. This connector has now been called a “node” connector and can have any number of pins based on the total number of cells in the pack. With node wiring, each cell can be charged separately until they reach the same voltage. The concept is actually more technical than that, but I think you will get the basic idea.

Besides having this added connector you need a special charger with multiple outputs. As part of this “balanced” Li-Poly battery pack process, FMA Direct developed the necessary companion charger, the Balance Pro 6S.

The Skyvolt Charger, later known as the BalancePro 6S, which is now being phased out in favor of the new CellPro-10S Charger

When balance packs and charging was first introduced, FMA Direct introduced their SKYVOLT charger and Li-Poly battery packs. The name was changed later to BALANCE PRO 6S. It was their first time effort. The node connector was large and heavy. The battery packs were sized primarily for larger models. There was no LCD screen on the charger to tell you what was going on. To obtain any info on the charging parameters you had to connect up to a PC and use special, FMA supplied freeware. This proved a great nuisance at the flying field. But the charger did work well! I’ll have some further comments on the “6S” later on.

CellPro 4A Charger, the forerunner of the new CellPro 10S, can handle up to 4 cells and at up to 4 amps charge current

Recognizing some of the BALANCE PRO 6S shortcomings, FMA developed the now very popular CellPro 4A charger. This is a “balanced” charging device that can handle up to 4 cells in series and at up to 4 amps charge current. It also has a multi-function LCD display that tells you important parameters, such as the capacity remaining in the pack, the individual cell voltages, the charge current when charging and when charging is complete. This charger can be used with battery packs intended from micro indoor/parking lot size on up to approx. 3 pound model aircraft. You might be able to extend this limit to even larger models, but then the charging time would have to be increased.

Typical Li-Poly battery packs at the top of this photo, with an A123 Li-Ion battery at the bottom – The CellPro 4A and 10S can charge both types of batteries

With the success of this CellPro 4A, FMA added a feature that allows for charging the A123 Lithium Ion (Li-Ion) batteries from this same unit. It also has a “STORE” mode for Li-Poly battery packs that charges the pack only to half capacity, which provides the most optimum storage life. Best part of the CellPro 4A is that presently (April 2008) it sells for only $74.95.

Li-Poly balanced battery charging is now employed almost exclusively throughout our hobby. It is safe to say that except for the smallest of packs, all new Li-Poly batteries now have individual cell wiring to permit balance charging (charging each cell in a pack to the same voltage level). To allow you to select and purchase a Li-Poly balanced battery pack of your choice, FMA is offering an extensive array of adapter cables that will allow almost any node connector on the market to plug into their CellPro chargers.

New CellPro 10S Charger on the left and the CellPro 4A on the right. The CellPro 4A Charger will continue to be offered to modelers who are only interested in charging up to 4 cells with a 4 amp maximum current

The new FMA CellPro 10S charger does every thing that the CellPro 4A charger does and much more. If you don’t own any balanced Li-Poly charger at this time, you would want to consider stepping right up to the “10S”. If you were going to concentrate on parking lot size models, as well as moderate size models up to approximately 3 pounds total weight, the CellPro 4A might fill your needs and it costs less than half of the CellPro 10S.

But if you contemplate much larger electric powered aircraft ,upwards of 10 to 15 pounds, or you need to charge two packs simultaneously (such as the Hobbico NexSTAR EP or the Hobbico ElectriStar trainers), then you will definitely want to consider the “10S”.

The CellPro-10S is charging two separate Li-poly battery packs simultaneously

There is also another important consideration. With FMA balanced charging technology, you can now safely charge at current rates higher than “1C”. You can, in fact, go as high as 3C, which will provide full charging in 20 minutes or less depending on the state of charge in the pack.

If you own the CellPro 4A the maximum current is 4 amps. That means that the highest capacity pack that you can charge at the 3C rate is going to be around 1300 mAh (3 x 1300 = 3900 mA or 3.9 amps!). When you move up to the CellPro 10S, you can charge packs at the 3C current rate with up to approx. 3300 mAh (3 x 3300 = 9900 or 9.9 amps.). The higher output current allows for faster charging times in larger capacity packs.

Of course, the 10S can also charge at a slightly lower rate of 2C, which provides a full charge in 30 minutes. It can do that with packs rated up to 5000 mAh. So, the higher current output of the 10S can charge at higher rates and in faster times.

Another nice feature of the CellPro 10S is that two Li-Poly packs can be simultaneously charged. Think of two packs being charged at the field, while you are flying with a third pack. Let’s just summarize the CellPro 10S capabilities at this point:

It can charge Li-Poly, Li-Ion and A123 battery packs up to a total of 10 cells and at a total maximum current of 10 amps.

Backlit LCD screen showing individual cell voltages in a three cell li=”Poly” battery pack

The new backlit LCD screen on the 10S works much the same as on the CellPro 4A. It tells you the capacity remaining in the battery pack, the voltage of each cell in the pack, the charge current and when charging is completed. A new feature is a reading of the IR (internal resistance) of each cell in the pack measured in milli-ohms. Once we get used to reading and recording this parameter, we will be able to determine the quality of the cells in the pack and will be able to note early on when cells are beginning to lose capacity and drop off line. Much will be said about this feature in the future.

This screen display shows the percentage charge presently in the battery pack. In this case it is almost fully charged.

The CellPro 4A allows you to connect to a PC to record and store (file) battery pack data and plot graphs using an FMA freeware called “Viewer Software”. The new 10S goes much further, utilizing new 2-way interface between the PC and charger, the “Charge Control Software” or CCS allows you to establish, and download to the charger, up to six pre-set charging routines for your favorite battery packs.

It also allows you to adjust the contrast of the LCD screen, set LCD scrolling options and adjust the speaker volume. There is also a special check box for setting charge optimization to choose between faster charging and accurate balancing. But perhaps the most exciting new capability provided by the new software is the ability to automatically receive the latest software and firmware updates for your charger via the Internet.

It works much the same, and is based on, the basic “engine” used by Microsoft ™ Corporation for Windows Updates and has been adopted by many other industries. This substantial innovation to the industry is something that will be incorporated into many other FMA Direct products and stands to bring the R/C industry into the “modern age”.

Never return a charger to the factory again for firmware updates. Keep up with the latest updates at the click of a mouse button. It’s easy and it keeps your charger tuned up and equipped with all the latest features “for free”.

A special 2-way USB PC interface cable is available as optional equipment, or can be purchased as part of a combo deal. FMA provides the proprietary “Charge Control Software” as a free download and promises to continually update this software as experience is gained with the 10S in the future.

The two cables that make up the FU1M2 cable assembly are used to connect the CellPro 10S to your PC allowingyou to download software revisions or to record and plot charging data

This is how the FU1M2 interface cable attaches between the CellPro 10S and a USB port on your PC

PHYSICAL CHARACTERISTICS

Considering all that is does, the CellPro 10S charger measures only 7 inches long by 3 3/4 inches wide by 1 3/4 inches thick. It has a main power cable exit from the case that is 34 inches in length. That cable terminates in two large alligators clips to enable connection to an automobile battery. These alligator clips can be easily removed, exposing a pair of banana plugs, which might be easier to use with AC operated power supplies.

Alligator clips on the input cables can be removed exposing banana type plugs for alternate connection to a 12-volt power source

FMA also sells the perfect plug and play companion power supply which is perfectly matched to the charger (FMA PN: PS13.8V28A-BP). This power supply is also available in combo deals.

FMA Direct/Revolectrix 350 watt AC operated power supply that provides a nominal 13.8 volts DC at up to 28 amps current

An auto type mini-fuse protects the input circuit and is accessible from the outside of the case. Two sets of node connector jacks located on the right side of the case will accept one or two separate battery packs for charging purposes. Also on this side of the case are the START/STOP button and the MODE button.

The right side of the CellPro 10S charger showing the two 6 pin node connectorports as well as the START/STOP and MODE push button switches

These are basically the only two controls you have to be concerned with. Along the lower right front of the case are two sets of banana plugs, which are also a part of the charging process and will be explained in a moment. On the left side of the case is the jack that accepts the computer (PC) the optional PC interface cable (catalog # FUIM2). Two node connector adapters and a special shorting plug (they call a “Plug Blocker”) are provided with the 10S charger.

This is the provided “PLUG BLOCKER”

The large backlit 2-line 16-character LCD screen measures 1.54 inches by 0.64 inch.

Typical backlit LCD screen image. In this case it is indicating that a pack attached to output-1 (Ch1) is DONE or completed

This is really the heart of the charger/user interface and will continually let you know what is going on at any time during the charging process or even after charging is complete. The 10S charger also has an internal cooling fan, which is controlled by the microprocessor to turn on when needed for additional cooling.

POWER REQUIREMENTS

The CellPro 10S charger can be powered from a 12 volt DC automobile battery. With the average size battery you should be able to obtain the full 10 amp charge current output. You can also use an AC operated power supply that delivers a 10-16 volt DC output. FMA offers a 13.8-volt, at up to 28 amp, switching power supply (Catalog No. PS13.8V28A-BP). This is a very efficient unit. This supply is a little “pricey” at $129.95, but it is capable of operating as the perfect plug and play companion to the CellPro 10S charger.

The power supply will outperform and outlast a car battery. This will enable you to do your charging indoors in your shop. With the high capacity of these Li-Poly batteries many of us now find that we charge more at home than at the flying field. It is sometimes possible to obtain 3 or 4 flights on a single charge!

DETAILED CELL PRO 10S OPERATION

The instruction manual that comes with the CellPro 10S charger is typical of all FMA Direct manuals and is excellent in every respect. If you are a prospective purchaser, this manual is available to you right now as a .pdf file at this exact website link:

http://www.fmadirect.com/support_docs/item_1258.pdf.

The manual is 20 pages long and covers everything from a “Quick Start Guide” to downloading procedures for the free ware.

I’m not going to repeat word for word what is in the manual, but I do want to highlight some of the important points associated with this new 10S charger. If you own a CellPro 4A already, you will be able to easily jump right into the “10S”. If you are a first time CellPro user I will give you enough of an overview and then the manual can fill in the rest.

The CellPro 4A charger employs a 5 pin node connector jack that allows you to connect up to 4 cell packs. The new CellPro 10S employs two 6 pin node connectors. A 5S pack can plug directly into each of the 10S node connector jacks. Packs with 6 to 10 cells (when we get that high) will have a 5-pin node connector as well as a second, 6-pin node connector and cable. They will be referred to as the lower number nodes and the higher numbered nodes respectively. Recognizing that many pilots will have packs with the 5-pin node connector, FMA decided to supply two adapter cables that allow a 5-pin connector to plug into the 10S.

The two-supplied 6 pin to 5 pin adapter cables, one for each output

If you are using FMA packs, these connectors and adapters work directly (plug and play). If you are using another brand battery pack and you already own existing CellPro 4A adapters, you will need to go from the 6 pin node to the 5 pin node and then through another adapter that mates with your particular brand battery pack. By the time of publication, FMA estimates it will have a new series of adapters ready to support the 10S directly. FMA lists all of the currently available adapters at the following web link: http://www.fmadirect.com/cellpro_adapters.html.

Extension cables can be purchased which allow the battery to be located further away from the charger. They also offer node connectors and cables along with instructions on how to add these to your existing packs that have no balance node connectors. You might say that FMA has “all the bases covered”.

When dealing with the CellPro 4A charger, the maximum charge current is only 4 amps. As such, the lighter gauge node connector pins and wiring are adequate for charging purposes. But when you move up to charge currents of 5 to 10 amps, as is the case with the CellPro 10S charger, a new charging technique will now be necessary.

THIS IS MOST IMPORTANT! With the 10S, if you want to go above 4 amps charge current, you must charge through both the node connector/cable AND the discharge cable.

This is actually a “faked photo”. If this were a high capacity pack that required more than 4 amps charge current, you would need to connect both to the node connector and the discharge cable to be able to obtain to 10 amps charge current)

The discharge cable is the heavier gauge pair of wires that goes from the battery to the Electronic Speed Controller (ESC). In this regard, the battery gets charged two ways. The current going through the node connector does the actual individual cell balancing. The discharge cable allows for higher charge current to go into the battery pack at the same time.

More than likely, when you try to charge at the 3C rate you will need to use both cables (node and discharge). As already pointed out, there are two sets of node connector jacks and two more sets of banana jacks to accept the discharge cables. Whenever you charge with only the node connector, a shorting plug (plug blocker) must be placed across the two outermost banana jacks. If you don’t remember to do this a warning (reminder) will appear on the LCD screen. Obviously the circuit technique that allows this form of “dual balanced charging” is proprietary to FMA Direct.

The way the CellPro 10S is programmed, you could actually connect a Li-Poly battery pack with a capacity of up to 4000 mAh, press the start button and the charging would begin. The factory default setting for one Li-Poly pack is the 1C rate. If the pack were rated at 1000 mAh (1 amp/hour) the charge current would be adjusted to 1C (1 times the capacity) or 1 amp. A 2000 mAh pack would be charged at 2 amps and a 4000-mAh pack would be charged at 4 amps. Up to this level the charging can be done strictly through the node connector/cable.

What I just told you is essentially an automatic setting, nothing to really think about. You can, at your option, change the factory default setting by pressing the MODE button. You will learn to press this button, briefly, rapidly a single time or multiple times depending on what you are after.

Keep in mind that the only button that lets you do everything is that MODE button along with the LCD screen display. You can alter the default (1C rate) to 2C or even 3C. The higher the charge current, the faster the battery will be charged. The charger can detect whether the discharge wires are connected or not. If they are not, the charger will automatically limit the charge current to 4 amps to protect the small node wires.

You can also alter the default pre-set to enable charging of Li-Ion and A123 batteries. There is even a “store mode” that will only charge Li-Poly batteries up to 50% of capacity which is considered optimum for long term storage.

While the charging is taking place, you can scroll through various screen displays that tell you such information as: the capacity of the battery pack expressed as a percentage of full, the total voltage in the pack during charging, the amount of capacity (expressed in mAh) put into the pack as it charges, the individual cell voltages (remember a balanced pack will have close to equal voltages), the internal resistance of each cell (to determine battery cell quality) and the charge current in amps. Also available on the display screen is the input supply voltage and current draw and a newly added timer feature.

At the completion of charging, a message will say, “DONE” and an alarm will beep for approx. 30 seconds to alert you. Keep in mind that all that was just said can also be applied to two packs being charged at the same time. In that case the display readings will say “CH-1” (pack one) and “CH-2” (pack two). To leave the charging mode at any time just press the “START/STOP” button.

There are alternate charging routines also programmed into the CellPro 10S. Based on what the charger determines about the battery condition the charger might enter what is called the “Low Voltage Restore Mode”. In this mode the charge will attempt to repair overcharged packs or packs that were discharged way below the recommended 2.7 volts per cell minimum (Ed Note: WOW!).

A “Safety Charging Mode” detects that one cell in a pack is seriously out of balance and automatically reduces the charge current to 0.5 amps in an attempt to correct the problem. A “Cold Weather Balancing Mode” automatically stops charging at 4.10 volts per cell when the temperature falls below 55 degrees F. When any of these alternate modes are enabled, you will be alerted on the LCD screen. (Ed Note: DOUBLE WOW!)

CHARGE CONTROL SOFTWARE

Now we have discussed the factory default pre-sets that allow for essentially automatic charging along with the ability to adjust certain parameters for what one might call “manual charging”. This may prove to be the most popular way to use the CellPro 10S charger. But keep in mind that through the use of the Charger Control Software, you can establish up to six pre-set charging routines. You might want to consider these pre-sets for charging certain packs at the higher 3C rate.

To use the pre-set feature, you must first download the free software made available from FMA Direct. The exact downloading process is described on page 13 of the manual. Be advised that this program is intended for PC users and is not at this time compatible with MAC systems.

Once the program is downloaded, you may connect the optional cable (Catalog No. FUIM2) between your PC USB jack and the three pin connector at the left side of the charger. Once connected, just launch the software program. The software will allow you to monitor all charging operations and to view print and file graphs of various parameters.

It will let you define a pre-set of your choice by name, battery chemistry (Li-Poly, Li-Ion or A123) and select the charging current. You can also select certain charger options like: the LCD screen contrast, Auto Scroll Cells ON (which directs the charger to scroll through various screens during charging) and adjust the speaker volume.

Each time the software is launched, and if there is a working Internet connection, the CCS will check for available new software revisions. You will be prompted to update the software. New software revisions may also include new charger firmware updates. Often the two go hand in hand. If so, you will also be prompted to update your charger’s firmware to the latest version.

Another feature of the CCS is the ability to set the charger’s input current limit. This means that if you do not have a power supply capable of running the charger full bore, you can tell the charger to cut back in order to protect the power supply you do have. Power supply selection is in your hands. No need to spend more than you have to. But remember, if you select a lower input current limit, it will take longer to charge your batteries. Additionally, if you have a low current supply that you use at home, but you still want to take advantage of the full power at the field, it is easy to over-ride the input current limit you set using the CCS. It’s a matter of holding down the MODE button while you turn the power on. This procedure is spelled out in the manual and it must be completed each time power is cycled on the charger or until the input current limit is revised back to full power in the CCS.

DISCHARGE PROTECTION MODULE

Several years back and just before cell balancing became the accepted method of charging, FMA developed a Discharge Protection module (DPM).

This is typically what the Skyvolt/BalancePro discharge module looked like. It was large and heavy add-on device that stayed inside your aircraft

This device went inside your model and monitored the individual cells in a pack, using the pack’s node connector. The theory here was that if one cell exhibited lower capacity than the other cells in the pack, the DPM would sense that and cut back on the throttle as a warning. The DPM worked well, but was another device going for a ride and it added additional complexity to the discharging process. I think that today, with our individual cell charging and the fact that every pack is fully balanced after each charge, that the DPM is no longer required. But if you feel comfortable with it, by all means continue to use it.

BALANCE PRO 6S CHARGER

The Skyvolt/BalancePro 6S charger at left and a typical large capacity 5 cell Skyvolt Li-poly battery pack at the right. Note the large and heavy connectors and that there is no LCD screen.

As already mentioned, the SKYVOLT, later renamed, BALANCE Pro 6S, charger was the first successful balancing charger for RC aircraft. The node connector used was big and heavy. The balance charge cable wiring was also heavy to handle up to the 10-amp charge current. The end result was that the BALANCE PRO battery packs were intended for the larger model aircraft and certainly had no place in a parking lot flyer. The choice was made not to continue with this particular charger and battery wiring. Adapter cables will not be offered to allow the new CellPro 10S to charge the older SKYVOLT and BALANCE PRO packs. You are advised to keep using the 6S charger and packs until the packs no longer provide adequate service and then just retire them.

SUMMARY

The FMA Direct CellPro 10S is certainly the state-of-the-art (2008) in lithium battery charging. If you haven’t as yet bought a lithium battery charger, you should consider the 10S for your first and only charger. If you already own a CellPro 4A, there is still rationale for purchasing the new CellPro 10S charger. The higher charge current, larger number of cells, the ability to charge two packs simultaneously, to charge at up to a 3C rate in twenty minutes and to establish pre-set charging conditions make this charger one of the best offerings to date.

The only hesitation I might have is for the modeler who knows he won’t be flying large planes and will never require more than 4 cells. If that is your case, the CellPro 4A (Catalog No. LIPOCH4S04-A123) at $74.95 makes sense.

But if you want the best and want it all, the new CellPro 10S (Catalog No. LC10S10ADC) at $189.95 (plus the optional $19.95 PC interface cable) makes even more sense. In my case, this is now my primary lithium battery charger.

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